Faculty Profile

Pega Hrnjak

Mechanical Science and Engineering
 Pega Hrnjak
Pega Hrnjak
Research Professor, Director Air Conditioning and Refrigeration Center
2121 Mechanical Engineering Lab
105 S. Mathews
Urbana Illinois 61801
(217) 244-6377

Primary Research Area

  • Fluid Mechanics

Academic Positions

  • Director, Air Conditioning and Refrigeration Center (ACRC), Department of Mechanical Science and Engineering, UIUC, Jan. 2015-date

Other Professional Employment

  • Creative Thermal Solutions. Inc., President 2003-date

Research Areas

  • Energy
  • Environment
  • Fluid Mechanics
  • Manufacturing
  • Security and Defense
  • Thermo Heat and Transfer
  • Transportation

Selected Articles in Journals

  • Xu, J. and P.Hrnjak, "Flow visualization and experimental measurement of compressor oil separator" SAE International Journal of Passenger Car. Mechanical Systems, JPCM-2018-0021, 2018
  • Khovalyg, D., P. Hrnjak, and A. Jacobi. "Heat flux variation between neighboring channels in compact minichannel heat exchangers." Applied Thermal Engineering, 2018. Applied Thermal Engineering, 135, pp. 418-434
  • Davies W.A., Y. Kang, P. Hrnjak, A. M. Jacobi, "Method for evaluating the effect of inclination on the performance of large flattened-tube steam condensers with visualization of flow regimes", 2018/2/21, Applied Thermal Engineering
  • Li, H. and P. Hrnjak. "Effect of Refrigerant Thermophysical Properties on Flow Reversal in Microchannel Evaporators." International Journal of Heat and Mass Transfer, vol. 117, February 2018, pp. 1135-1146.
  • Li, W. and P. Hrnjak. "Experimentally Validated Model of Heat Pump Water Heater with a Water Tank in Heating-up Transients." International Journal of Refrigeration, 2018, 88, pp. 420-431
  • Xiao, J. and P. Hrnjak. "Pressure Drop of R134a, R32 and R1233zd(E) in Diabatic Conditions during Condensation from Superheated Vapor." International Journal of Heat and Mass Transfer, July 2018, v. 122, 442-450
  • Yang, C-M. and P. Hrnjak. "Effect of Straight Micro Fins on Heat Transfer and Pressure Drop of R410A during Evaporation in Round Tubes." International Journal of Heat and Mass Transfer, vol. 117, February 2018, pp. 924-939.
  • Li, Y. and P. Hrnjak. "Control of Flash Gas Bypass MAC System with Emphasis on Start-ups and Transients." International Journal of Refrigeration, vol. 84, December 2017, pp. 1-12.
  • Li, H. and P. Hrnjak. "Effect of Channel Geometry on Flow Reversal in Microchannel Evaporators." International Journal of Heat and Mass Transfer, vol. 115, no. A, December 2017, pp. 1-10.
  • Li, H. and P. Hrnjak. "Effect of Periodic Reverse Flow on the Heat Transfer Performance of Microchannel Evaporators." International Journal of Refrigeration, vol. 84, December 2017, pp. 309-320.
  • Hrnjak, P., P. Zhang, and C. Rennels. "Effect of Louver Angle on Performance of Heat Exchanger with Serpentine Fins and Flat Tubes in Frosting: Importance of Experiments in Periodic Frosting." International Journal of Refrigeration, vol. 84, December 2017, pp. 321-335.
  • Li, H. and P. Hrnjak. "Measurement of Heat Transfer Coefficient and Pressure Drop during Evaporation of R134a in New Type Facility with One Pass Flow-through Microchannel Tube." International Journal of Heat and Mass Transfer, vol. 115, December 2017, pp. 502-512.
  • Meyer, M. and P. Hrnjak. "Flow Regimes during Condensation in Superheated Zone." International Journal of Refrigeration, vol. 84, December 2017, pp. 336-343.
  • Li, J. and P. Hrnjak. "Visualization and Quantification of Separation of Liquid-vapor Two-phase Flow in a Vertical Header at Low Inlet Quality." International Journal of Refrigeration, November 2017, doi: 10.1016/j.ijrefrig.2017.09.018.
  • Jin, S. and P. Hrnjak. "A New Method to Simultaneously Measure Local Heat Transfer and Visualize Flow Boiling in Plate Heat Exchanger." International Journal of Heat and Mass Transfer, vol. 113, October 2017, pp. 635-646.
  • Kang, Y., W. A. Davies, P. Hrnjak, and A. Jacobi. "Effect of Inclination on Pressure Drop and Flow Regimes in Large Flattened-tube Steam Condensers." Applied Thermal Engineering, vol. 123, August 2017, pp. 498-513.
  • Xu, J. and P. Hrnjak. "Quantification of Flow and Retention of Oil in Compressor Discharge Pipe." International Journal of Refrigeration, vol. 80, August 2017, pp. 252-263.
  • Xiao, J. and P. Hrnjak. "A Heat Transfer Model for Condensation Accounting for Non-equilibrium Effects," International Journal of Heat and Mass Transfer, vol. 111, August 2017, pp. 201-210.
  • Li, J. and P. Hrnjak. "Separation in Condensers as a Way to Improve Efficiency." International Journal of Refrigeration, vol. 79, July 2017, pp. 1-9.
  • Zhu, L. and P. Hrnjak. "Thermosiphon with Vapor Separation: Experimental Comparison to Conventional Type." Applied Thermal Engineering, vol. 121, July 2017, pp. 879-886.
  • Li, J. and P. Hrnjak. "Improvement of Condenser Performance by Phase Separation Confirmed Experimentally and by Modeling." International Journal of Refrigeration, vol. 78, June 2017, pp. 60-69.
  • Li, H. and P. Hrnjak. "Visualization and Measurement of Reverse Flow in an Actual Channel of a Microchannel Evaporator." International Journal of Heat and Mass Transfer, vol. 108, no. B, May 2017, pp. 2346-2354.
  • Xiao, J. and P. Hrnjak. "A New Flow Regime Map and Void Fraction Model Based on the Flow Characterization of Condensation." International Journal of Heat and Mass Transfer, vol. 108, May 2017, pp. 443-452.
  • Stevanovic, V. D. and P. Hrnjak. "Numerical Simulation of Three-dimensional Two-phase Flow and Prediction of Oil Retention in an Evaporator of the Automotive Air-conditioning System." Applied Thermal Engineering, vol. 117, May 2017, pp. 468-480.
  • Jin, S. and P. Hrnjak. "Effect of End Plates on Heat Transfer of Plate Heat Exchanger." International Journal of Heat and Mass Transfer, vol. 108 no. A, May 2017, pp. 740-748.
  • Li, H. and P. Hrnjak. "Modeling of Bubble Dynamics in Single Diabatic Microchannel." International Journal of Heat and Mass Transfer, vol. 107, April 2017, pp. 96-104.
  • Xiao, J. and P. Hrnjak. "Heat Transfer and Pressure Drop of Condensation from Superheated Vapor to Subcooled Liquid." International Journal of Heat and Mass Transfer, vol. 103, December 2016, pp. 1327-1334.
  • Wang, X., K. Tang, and P. Hrnjak. "Evaporator Performance Enhancement by Pulsation width Modulation (PWM)." Applied Thermal Engineering, vol. 99, April 2016, pp. 825-833.
  • Jin, S. and P. Hrnjak. "Refrigerant and Lubricant Charge in Air-condition Heat Exchangers: Experimentally Validated Model." International Journal of Refrigeration, vol. 67, April 2016, pp. 395-407.
  • Feng, L. and P. Hrnjak. "Modeling of a Reversible Air-conditioning, Heat Pump System for Electric Vehicles." SAE International Journal of Passenger Cars - Mechanical Systems, vol. 9, no. 1, April 2016, pp. 68-74.
  • Khovalyg, D., P. Hrnjak, and A. M. Jacobi. "Interactions between Parallel Unevenly Heated Minichannels during Flow Boiling of R134a.." Heat Transfer Engineering, vol. 37, no. 11, January 2016, pp. 921-937.
  • Li, H. and P. Hrnjak. "An Experimentally Validated Model for Microchannel Heat Exchanger Incorporating Lubricant Effect." International Journal of Refrigeration vol. 59, November 2015, pp. 259-268.
  • Zou, Y. and P. Hrnjak. "Comparison and Generalization of R410A and R134a Distribution in the Microchannel Heat Exchanger with the Vertical Header." Science and Technology for the Built Environment, vol. 21, no. 5, July 2015, pp. 555-563.
  • Sethi, A. and P. Hrnjak. "Modeling of Oil Retention and Pressure Drop in Vertical Suction Risers." Science and Technology for the Built Environment, vol. 21, no. 7, April 2015, pp. 1033-1046.
  • Khovalyg, D., P. Hrnjak, and A. M. Jacobi. "Transient Pressure Drop Cross-correlation During Flow Boiling of R134a in Parallel Minichannels." Science and Technology for the Built Environment, vol. 21, no. 5, April 2015, pp. 545-554.
  • Li, H. and P. Hrnjak. "An Infrared Thermography-based Method for Quantification of Liquid Refrigerant Distribution in Parallel Flow Microchannel Heat Exchanger." SAE International Journal of Materials and Manufacturing, vol. 8, no. 3, April 2015, pp. 603-608.
  • Li, H. and P. Hrnjak. "Quantification of Liquid Refrigerant Distribution in Parallel Flow Microchannel Heat Exchanger using Infrared Thermography." Applied Thermal Engineering, vol. 78, March 2015, pp. 410-418.
  • Pottker, G. and P. Hrnjak. "Experimental Investigation of the Effect of Condenser Subcooling in R134a and R1234yf Air-conditioning Systems with and without Internal Heat Exchanger." International Journal of Refrigeration, vol. 50, February 2015, pp. 104-113.
  • Pottker, G. and P. Hrnjak. "Effect of the Condenser Subcooling on the Performance of Vapor Compression Systems." International Journal of Refrigeration, vol. 50, February 2015, pp. 156-164.
  • Agarwal, R. and P. Hrnjak. "Condensation in Two-phase and Desuperheating Zone for R1234ze(E), R134a and R32 in Horizontal Smooth Tubes." International Journal of Refrigeration, vol. 50, February 2015, pp. 172-183.
  • Pottker, G. and P. Hrnjak. "Ejector in R410A Vapor Compression Systems with Experimental Quantification of Two Major Mechanisms of Performance Improvement: Work Recovery and Liquid Feeding." International Journal of Refrigeration, vol. 50, February 2015, pp. 184-192.
  • Ren, T. and P. Hrnjak. "Pressure Drop in Round Cylindrical Headers of Parallel Flow MCHXs: Pressure Loss Coefficients for Single-phase Flow." International Journal of Refrigeration, vol. 49, January 2015, pp. 119-134.
  • Agarwal, R. and P. Hrnjak. "Effect of Sensible Heat, Condensation in Superheated and Subcooled Region Incorporated in Unified Model for Heat Rejection in Condensers in Horizontal Round Smooth Tubes." Applied Thermal Engineering, vol. 71, no. 1, October 2014, pp. 378-388.
  • Zou, Y. and P. Hrnjak. "Effects of Fluid Properties on Two-phase Flow and Refrigerant Distribution in the Vertical Header of a Reversible Microchannel Heat Exchanger -- Comparing R245fa, R134a, R410A, and R32." Applied Thermal Engineering, vol. 70, no. 1, September 2014, pp. 966-976.
  • Zou, Y. and P. Hrnjak. "Single-phase and Two-phase Flow Pressure Drop in the Vertical Header of Microchannel Heat Exchanger." International Journal of Refrigeration, vol. 44, August 2014, pp. 12-22.
  • Sethi, A. and P. Hrnjak. "Oil Retention and Pressure Drop of R1234yf and R134a with POE ISO 32 in Suction Lines." HVAC and R Research, vol. 20, no. 6, May 2014, pp. 703-720.
  • Jin, S. and P. Hrnjak. "An Experimentally Validated Model for Predicting Refrigerant and Lubricant Inventory in MAC Heat Exchangers." SAE International Journal of Passenger Cars -- Mechanical Systems, vol. 7, no. 2, April 2014, pp. 769-780.
  • Zou, Y. and P. Hrnjak. "Effect of Oil on R134a Distribution in the Microchannel Heat Exchanger with Vertical Header." International Journal of Refrigeration, vol. 40, April 2014, pp. 201-210.
  • Tuo, H. and P. Hrnjak. "Vapor-liquid Separation in a Vertical Impact T-junction for Vapor Compression Systems with Flash Gas Bypass." International Journal of Refrigeration, vol. 40, April 2014, pp. 189-200.
  • Tuo, H. and P. Hrnjak. "Visualization and Measurement of Periodic Reverse Flow and Boiling Fluctuations in a Microchannel Evaporator of an Air-conditioning System." International Journal of Heat and Mass Transfer, vol. 71, April 2014, pp. 639-652.
  • Ren, T. and P. Hrnjak. "Pressure Drop in D-shaped Cylindrical Headers of Parallel Flow MCHXs: Pressure Loss Coefficients for Single-phase Flow." Applied Thermal Engineering, vol. 65, no. 1-2, April 2014, pp. 111-123.
  • Tuo, H. and P. Hrnjak. "Enhancement of Vapor-liquid Separation in Vertical Impact T-junctions for Vapor Compression Systems with Flash Gas Bypass." International Journal of Refrigeration, vol. 40, April 2014, pp. 43-50.
  • Zou, Y., H. Tuo, and P. Hrnjak. "Modeling Refrigerant Maldistribution in Microchannel Heat Exchangers with Vertical Headers Based on Experimentally Developed Distribution Results." Applied Thermal Engineering, vol. 64, no. 1-2, March 2014, pp. 172-181.
  • Tuo, H. and P. Hrnjak. "Effect of Venting the Periodic Reverse Vapor Flow on the Performance of a Microchannel Evaporator in Air-conditioning Systems." International Journal of Heat and Mass Transfer, vol. 69, February 2014, pp. 66-76.
  • Zou, Y., H. Tuo, and P. Hrnjak. "R-410A Maldistribution Impact on the Performance of Microchannel Evaporator." ASHRAE Transactions, vol. 120, no. 1, January 2014, pp. 406-415.
  • Zou, Y. and P. Hrnjak. "Refrigerant Distribution in the Vertical Header of the Microchannel Heat Exchanger - Measurement and Visualization of R410A Flow." International Journal of Refrigeration, vol. 36, no. 8, December 2013, pp. 2196-2208.
  • Tuo, H. and P. Hrnjak. "New Approach to Improve Performance by Venting Periodic Reverse Vapor Flow in Microchannel Evaporator." International Journal of Refrigeration, vol. 36, no. 8, December 2013, pp. 2187-2195.
  • Tuo, H. and P. Hrnjak. "Effect of the Header Pressure Drop Induced Flow Maldistribution on the Microchannel Evaporator Performance." International Journal of Refrigeration, vol. 36, December 2013, pp. 2176-2186.
  • Petersen, M., C. Bowers, S. Elbel, and P. Hrnjak. "Development of High-efficiency Carbon Dioxide Commercial Heat Pump Water Heater." HVAC&R Research, vol. 19, no. 7, August 2013, pp. 823-835.
  • Zou, Y. and P. Hrnjak. "Experiment and Visualization on R134a Upward Flow in the Vertical Header of Microchannel Heat Exchanger and its Effect on Distribution." International Journal of Heat and Mass Transfer, vol. 62, no. 1, July 2013, pp. 124-134.
  • Wang, X., P. Hrnjak, S. Elbel, A. M. Jacobi, and M. G. He. "Heat Transfer Performance for a Falling-film on Horizontal Flat Tubes." Journal of Heat Transfer, vol. 135, no. 7, June 2013, pp. 1-12.
  • Tuo, H. and P. Hrnjak. "Periodical Reverse Flow and Boiling Fluctuations in a Microchannel Evaporator of an Air-conditioning System." International Journal of Refrigeration, vol. 36, no. 4, June 2013, pp. 1263-1275.
  • Tuo, H. and P. Hrnjak. "Periodic Reverse Flow and Boiling Fluctuations in a Microchannel Evaporator of an R134a Mobile Air-conditioning System." SAE International Journal of Materials and Manufacturing, vol. 6, no. 3, April 2013, pp. 540-548.
  • Li, H. and P. Hrnjak. "Effect of Lubricant on Two-phase Refrigerant Distribution in Microchannel Evaporator." SAE International Journal of Materials and Manufacturing, vol. 6, no. 3, April 2013, pp. 567-575.
  • Jin, S. and P. Hrnjak. "Refrigerant and Lubricant Distribution in MAC System." SAE International Journal of Passenger Cars -- Mechanical Systems, vol. 6, no. 2, April 2013, pp. 1013-1020.
  • Zhao, H., S. Elbel, and P. Hrnjak. "Controlled Atmosphere Brazing of Aluminum Heat Exchangers." Welding Journal, vol. 92, no. 2, February 2013, pp. 44-46.
  • Kondou, C. and P. Hrnjak. "Heat Rejection in Condensers Close to Critical Point-de-superheating, Condensation in Superheated Region, and Condensation of Two-phase Fluid." Heat Transfer Engineering, vol. 34, no. 14, February 2013, pp. 1180-1190.
  • Wang, X., M. A. Rahman, A. M. Jacobi, and P. Hrnjak. "Dynamic Wetting Behavior and Water Drops on Microgrooved Surfaces." Heat Transfer Engineering, vol. 34, no. 13, January 2013, pp. 1088-1098.
  • Wang, X. F., P. Hrnjak, S. Elbel, A. M. Jacobi, and M. G. He. "Heat Transfer Performance for a Falling-film on Horizontal Flat Tubes." Journal of Heat Transfer, vol. 135, no. 7, January 2013, pp. 1-12.
  • Tuo, H. and P. Hrnjak. ￿Flash Gas Bypass in Mobile Air-conditioning System with R134a.￿ International Journal of Refrigeration, vol. 35, no. 7, November 2012, pp. 1869-1877.
  • Kondou, C. and P. Hrnjak. "Condensation From Superheated Vapor Flow of R744 And R410A at Subcritical Pressures in a Horizontal Smooth Tube." International Journal of Heat and Mass Transfer, vol. 55. no. 11-12, May 2012, pp. 2779-2791.
  • Tuo, H., A. Bielskus, and P. Hrnjak. ￿Experimentally Validated Model of Refrigerant Distribution in a Parallel Microchannel Evaporator.￿ SAE International Journal of Materials and Manufacturing, vol. 5, no. 2, April 2012, pp. 365-374.
  • Wang, X., P. Hrnjak, S. Elbel, A. M. Jacobi, and M. He. "Flow Modes and Mode Transitions for Falling Films on Flat Tubes." Journal of Heat Transfer, vol. 134, no. 2, February 2012, 9 pages.
  • Tuo, H., and P. Hrnjak. "Experimental Study of Refrigerant Two-phase Separation in a Compact Vertical T-Junction." ASHRAE Transactions, vol. 118, no. 1, January 2012, pp. 672-680.
  • Tuo, H., A. Bielskus, and P. Hrnjak. "An Experimentally Validated Model of Refrigerant Distribution in a Parallel Microchannel Evaporator." ASHRAE Transactions, vol. 118, no. 1, January 2012, pp. 375-383.
  • Li, B., S. Peuker, P. Hrnjak, and A. G. Alleyne. "Refrigerant Mass Migration Modeling and Simulation for Air Conditioning Systems." Applied Thermal Engineering, vol. 31, no. 10, July 2011, pp. 1770-1779.
  • Kondou, C. and P. Hrnjak. ￿Heat Rejection from R744 Flow Under Uniform Temperature Cooling in a Horizontal Smooth Tube Around the Critical Point.￿ International Journal of Refrigeration, vol. 34, no. 3, May 2011, pp. 719-731.
  • Tuo, H., A. Bielskus, and P. Hrnjak. ￿Effect of Flash Gas Bypass on the Performance of R134a Mobile Air-Conditioning System with Microchannel Evaporator.￿ SAE International Journal of Materials and Manufacturing, vol. 4, no. 1, April 2011, pp. 231-239.
  • Li, B., S. Peuker, P. Hrnjak, and A. Alleyne. ￿Evaluation of Transient Refrigerant Migration Modeling Approach on Automotive Air-Conditioning Systems.￿ SAE International Journal of Materials and Manufacturing, vol. 4, no. 1, April 2011, pp. 864-874.
  • Oh, J. T., A. S. Pamitran, K. I. Choi, and P. Hrnjak. ￿Experimental Investigation on Two-phase Flow Boiling Heat Transfer of Five Refrigerants in Horizontal Small Tubes of 0.5, 1.5 and 3.0mm Inner Diameters.￿ International Journal of Heat and Mass Transfer, vol. 54, no. 9-10, April 2011, pp. 2080-2088.
  • Park, C. Y. and P. Hrnjak. ￿Pure NH3 and CO2 Heat Transfer and Pressure Drop in Horizontal Smooth Tubes for NH3 Two-stage and NH3/CO2 Cascade Refrigeration Systems: A Review.￿ International Journal of Air-conditioning and Refrigeration, vol. 18, no. 2, 2010, pp. 85-100.
  • Zhang, P. and P. Hrnjak. "Air-side Performance of a Parallel-flow Parallel-fin (PF2) Heat Exchanger in Sequential Frosting." International Journal of Refrigeration, vol. 33, no. 6, September 2010, pp. 1118-1128.
  • Hrnjak, P. and S. H. Hong. ￿Effect of Return Bend and Entrance on Heat Transfer in Thermally Developing Laminar Flow in Round Pipes of Some Heat Transfer Fluids with High Prandtl Numbers.￿ Journal of Heat Transfer, vol. 132, no. 6, June 2010, pp. 1-12.
  • Pamitran, A. S., K. I. Choi, J. T. Oh, and P. Hrnjak. "Characteristics of Two-phase Flow Pattern Transitions and Pressure Drop of Five Refrigerants in Horizontal Circular Small Tubes." International Journal of Refrigeration, vol. 33, no. 3, May 2010, pp. 578-588.
  • Zhang, P. and P. Hrnjak. ￿Effect of Some Geometric Parameters on Performance of PF2 Heat Exchangers in Periodic Frosting.￿ International Journal of Refrigeration, vol. 33, no. 2, March 2010, pp. 334-346.
  • Hrnjak, P. "Issues in Two-phase Flow Distribution in Microchannel Heat Exchangers." KGH -- Air-conditioning, Heating and Refrigeration, (in Serbian: Problematika raspodele dvofaznih tokova u mikrokanalnim razmenjivacima toplote), vol. 39, no. 1, 2010, pp. 63-74.
  • Hrnjak, P., J. Manzione, D. Adams, D. Garski, and S. Collier. "EXITOSA CONVERSIÓN A R744 EN UNA UNIDAD DE CONTROL MEDIOAMBIENTAL." Frio-Calor-Aire Acondicionado, (Based on #125 conference publication), September 2009.
  • Park, C. Y. and P. Hrnjak. "CO2 Flow Condensation Heat Transfer and Pressure Drop in Multi-port Microchannels at Low Temperatures." International Journal of Refrigeration, vol. 32, no. 6, September 2009, pp. 1129-1139.
  • Park, C. Y. and P. Hrnjak. "Flow Boiling Heat Transfer, Pressure Drop, and Flow Pattern for CO2 in a 3.5mm Horizontal Smooth Tube." Journal of Heat Transfer, vol. 131, no. 9, September 2009, 12 pages.
  • Zhang, P. and P. Hrnjak. "Air-side Performance Evaluation of Three Types of Heat Exchangers in Dry, Wet and Periodic Frosting Conditions." International Journal of Refrigeration, vol. 32, no. 5, August 2009, pp. 911-921.
  • Elbel, S. and P. Hrnjak. "REFRIGERACI￿ CON EYECTOR EN APLICACIONES DE AIRE ACONDICIONADO VISI￿ GENERAL DE LA EVOLUCI￿ DE DESARROLLOS." Frio-Calor-Aire Acondicionado, (based on #123 conference publication), July/August 2009.
  • Peuker, S. and P. Hrnjak. "Transient Refrigerant Migration and Oil Distribution of an R134a Automotive A/C System." SAE International Journal of Passenger Cars -- Mechanical Systems, vol. 2, no. 1, April 2009, pp. 714-724.
  • Wujek, S. S. and P. Hrnjak. "Using Density to Calculate the Oil Circulation Ratio of a PAG Oil in R134A." SAE International Journal of Materials and Manufacturing, vol. 1, no. 1, April 2009, pp. 362-368.
  • Kim, Y. J., J. Jang, P. Hrnjak, and M. S. Kim. "Condensation Heat Transfer of Carbon Dioxide Inside Horizontal and Vertical Pressure Smooth and Microfin Tubes at Low Temperatures." Journal of Heat Transfer, vol. 131, issue 2, February 2009, 10 pages.
  • Park, C. Y. and P. Hrnjak. "CONDENSACI￿, TRANSMISI￿ DE CALOR Y CA￿A DE PRESI￿ DEL NH3 EN EL INTERIOR DE UN TUBO LISO." Frio-Calor-Aire Acondicionado, (Based on #40), January 2009.
  • Park, C. Y. and P. Hrnjak. "Flow Condensation Heat Transfer and Pressure Drop in Multi-Port Microchannels at Low Temperatures." International Journal of Refrigeration, vol. 32, no. 6, 2009, pp. 1129-1139.
  • Pamitran, A. S., K. I. Choi, J. T. Oh, and P. Hrnjak. "Experimental Investigation of Flow Boiling Heat Transfer of R-410A and R-134a in Horizontal Small Tubes." Korean Journal of Air-Conditioning and Refrigeration Engineering, vol. 21, no. 12, 2009, pp. 1141~1146.
  • Choi, K. I., A. S. Pamitran, J. T. Oh, P. Hrnjak, and C. Y. Park. "Effect on Flow Boiling Heat Transfer of Minichannel Diameter for R-410A." 설비공학논문집 제21권 제12호, 12, 2009, pp. 663-670.
  • Kim, Y. J., J. Jang, P. Hrnjak, and M. S. Kim. ￿Adiabatic Horizontal and Vertical Pressure Drop of Carbon Dioxide Inside Smooth and Microfin Tubes at Low Temperatures.￿ Journal of Heat Transfer, vol. 130, no. 11, November 2008, pp. 1-10.
  • Park, C. Y. and P. Hrnjak. ￿Experimental and Numerical Study on Microchannel and Round-Tube Condensers in a R410A Residential Air-Conditioning System.￿ International Journal of Refrigeration, vol. 31, no. 5, August 2008, pp. 822-831.
  • Hrnjak, P. and A. D. Litch. "Microchannel Heat Exchangers for Charge Minimization in Air-cooled Ammonia Condensers and Chillers." International Journal of Refrigeration, vol. 31, no. 4, June 2008, pp. 658-668.
  • Park, C. Y. and P. Hrnjak. ￿NH3 In-Tube Condensation Heat Transfer and Pressure Drop in a Smooth Tube.￿ International Journal of Refrigeration, vol. 31, no. 4, June 2008, pp. 643-651.
  • Hrnjak, P. and A. D. Litch. ￿Microchannel Heat Exchangers for Charge Minimization in Air-cooled Ammonia Condensers and Chillers.￿ International Journal of Refrigeration, vol. 31, no. 4, June 2008, pp. 658-668.
  • Elbel, S. W. and P. Hrnjak. ￿Experimental Validation of a Prototype Ejector Designed to Reduce Throttling Losses Encountered in Transcritical R744 System Operation.￿ International Journal of Refrigeration, vol. 31, no. 3, May 2008, pp. 411-422.
  • Field, B. S. and P. Hrnjak. "Adiabatic Two-phase Pressure Drop of Refrigerants in Small Channels." Heat Transfer Engineering, vol. 28, no. 8-9, August 2007, pp. 704-712.
  • Park, C. Y. and P. Hrnjak. ￿Effect of Heat Conduction Through the Fins of a Microchannel Serpentine Gas Cooler of Transcritical CO2 System.￿ International Journal of Refrigeration, vol. 30, no. 3, May 2007, pp. 389-397.
  • Hrnjak, P. and X. Tu. ￿Single-phase Pressure Drop in Microchannels.￿ International Journal of Heat and Fluid Flow, vol. 28, no. 1, February 2007, pp. 2-14.
  • Park, C. Y. and P. Hrnjak. "CO2 and R410A Flow Boiling Heat Transfer, Pressure Drop, and Flow Pattern at Low Temperatures in a Horizontal Smooth Tube." International Journal of Refrigeration, vol. 30, no. 1, January 2007, pp. 166-178.
  • Xia, Y, Y. Zhong, P. Hrnjak, and A. M. Jacobi. ￿Frost, Defrost, and Refrost and Its Impact on the Air-side Thermal-hydraulic Performance of Louvered-fin, Flat Tube Heat Exchangers.￿ International Journal of Refrigeration, vol. 29, no. 7, November 2006, pp. 1066-1079.
  • Ni￿V. G., E. W. Jassim, P. Hrnjak, and T. A. Newell. ￿Flow-regime-based Model for Pressure Drop Predictions in Microchannels.￿ International Journal of HVAC&R Research, vol. 12, no. 1, January 2006, pp. 17-34.
  • Hrnjak, P. "Carbon Dioxide Systems." HVAC&R Research, vol. 12, no. 1, January 2006, pp. 1-2.
  • Tu, X., P. Hrnjak, and C. W. Bullard. "Refrigerant 134a Liquid Flow through Micro-scale Short Tube Orifices with/without Phase Change." Experimental Heat Transfer and Fluid Flow, vol. 30, no. 3, January 2006, pp. 253-262.
  • McEnaney, R. and P. Hrnjak. ￿Clutch Cycling Mode of Compressor Capacity Control of Transcritical R744 Systems Compared to R134a Systems.￿ Society of Automotive Engineering Journal of Passenger Cars -￿ Mechanical Systems.￿ May 2005, 2005-01-2033.
  • Park, C. Y. and P. Hrnjak. ￿Flow Boiling Heat Transfer of CO2 at Low Temperatures in a Horizontal Smooth Tube.￿ ASME Journal of Heat Transfer, vol. 127, no. 12, March 2005, pp. 1305-1312.
  • Xia, Y., P. Hrnjak, and A. M. Jacobi. ￿The Air-side Thermal-hydraulic Performance of Louvered-fin, Flat-tube Heat Exchangers with Sequential Frost-growth Cycles.￿ ASHRAE Transactions, vol. 111, no. 1, February 2005, pp. 487-495.
  • Elbel, S. and P. Hrnjak. ￿Flash Gas Bypass for Improving the Performance of Transcritical R744 Systems that Use Microchannel Evaporators.￿ International Journal of Refrigeration, vol. 27, no. 7, November 2004, pp. 724-735.
  • Hrnjak, P. ￿Developing Adiabatic Two-phase Flow in Headers ￿- Distribution Issue in Parallel Flow Microchannel Heat Exchangers.￿ Heat Transfer Engineering, vol. 25, no. 3, April 2004, pp. 61-68.
  • Hrnjak, P. ￿Flow Distribution Issues in Parallel Flow Heat Exchangers.￿ ASHRAE Transactions, vol. 110, no. 1, January 2004, pp. 301-306.
  • Hrnjak, P. ￿Microchannel Heat Exchangers.￿ KGH, Belgrade, Serbia (in Serbocroation), 2004.
  • Richter, M. R., S. M. Song, J. M. Yin, M. H. Kim, C. W. Bullard, and P. Hrnjak. ￿Experimental Results of Transcritical CO2 Heat Pump for Residential Application.￿ Energy, vol. 28, no. 10, August 2003, pp. 1005-1019.
  • ElSherbini, A. I., A. M. Jacobi, and P. Hrnjak. ￿Experimental Investigation of Thermal Contact Resistance in Plain-fin-and-tube Evaporators with Collarless Fins.￿ International Journal of Refrigeration, vol. 26, no. 5, August 2003, pp. 527-536.
  • Tu, X. and P. Hrnjak. "Pressure Drop and Visualization of R134a Two-phase Flow in a Rectangular Microchannel." Transactions of ASHRAE, vol. 109, no. 1, January 2003, pp. 703-710.
  • Giannavola, S. M., J. M. Yin, C. W. Bullard, and P. Hrnjak. "Contribution of Heat Exchangers in Improved Performance of New Generation Automotive Air-conditioning System with R744." Transactions of ASHRAE, vol. 109, no. 1, January 2003, pp. 542-554.
  • Nino, V. G., P. Hrnjak, and T. A. Newell. "Two-phase Flow Visualization of R134a in a Multiport Microchannel Tube." Heat Transfer Engineering, vol. 24, no. 1, January 2003, pp. 41-52.
  • Yin, J. M., C. W. Bullard, and P. Hrnjak. "Single-phase Pressure Drop Measurements in a Microchannel Heat Exchanger." Journal of Heat Transfer Engineering, vol. 23, no. 4, July 2002, pp. 3-12.
  • Song, S., C. W. Bullard, and P. Hrnjak. "Frost Deposition and Refrigerant Distribution in Microchannel Heat Exchangers." Transactions of ASHRAE, vol. 108, no. 2, June 2002, pp. 944-953.
  • Bullard, C. W., J. M. Yin, and P. Hrnjak. "Compact Counterflow Gas Cooler for R744." Transactions of ASHRAE, vol. 108, no. 1, January 2002, pp. 487-491.
  • Bullard, C. W. and P. Hrnjak. "Research in Transcritical R744 at ACRC, University of Illinois at Urbana-Champaign." J. Soc. Air Conditioning and Refrig. Engrs. of Korea, vol. 31, no. 7, 2002, pp. 32-52.
  • Hrnjak, P., M. A. Shannon, T. M. Leicht, and N. R. Miller. "Detection of Liquid Mass Fraction at the Evaporator Exit of Refrigeration Systems." International Journal of Thermal Sciences, vol. 40, no. 8, September 2001, pp. 773-786.
  • Yin, J. M., C. W. Bullard, and P. Hrnjak. "R-744 Gas Cooler Model Development and Validation." International Journal of Refrigeration, vol. 24, no. 7, July 2001, pp. 692-701.
  • Singh, G. M., P. Hrnjak, and C. W. Bullard. "Flow of Refrigerant R134a through Orifice Tubes." International Journal of HVAC&R Research, vol. 7, no. 3, July 2001, pp. 245-262.
  • Hrnjak, P. and Y. Mao. "Defrost Issues in Indirectly Refrigerated Display Cases." ASHRAE Transactions, vol. 107, no. 2, June 2001, pp. 466-472.
  • Boewe, D. E., C. W. Bullard, J. M. Yin, and P. Hrnjak. "Contribution of Internal Heat Exchanger to Transcritical R-744 Cycle Performance." International Journal of HVAC&R Research, vol. 7, no. 2, April 2001, pp. 155-168.
  • Shannon, M. A., T. M. Leicht, P. Hrnjak, N. R. Miller, and F. A. Kahn. "Thin-film Resistance Sensor for Measuring Liquid Mass Fraction in Super-heated Refrigerant." Sensors and Actuators A, vol. 88, no. 2, February 2001, pp. 164-177.
  • Fang, X., C. W. Bullard, and P. Hrnjak. "Modeling and Analysis of Gas Coolers." ASHRAE Transactions, vol. 107, no. 1, January 2001, pp. 4-13.
  • Fang, X., C. W. Bullard, and P. Hrnjak. "Heat Transfer and Pressure Drop of Gas Coolers." ASHRAE Transactions, vol. 107, no. 1, January 2001, pp. 255-266.
  • McEnaney, R. P. and P. Hrnjak. "Control Strategies for Transcritical R744 Systems." Journal of Passenger Cars, vol. 109, no. 6, 2001, pp. 1711-1720.
  • Drozdek, J., J. Chappel, C. Cusano, P. Hrnjak, N. R. Miller, and T. A. Newell. "Methods for Detection of Lubrication Failure Applied to a Swashplate Compressor." Journal of Passenger Cars, vol. 109, no. 6, 2001, pp. 1553-1557.
  • Stoecker, W. F., P. Hrnjak, and C. A. Infante Ferreira. "Application of Ammonia and CO2 in Supermarkets." Koude and Luchtbehandeling, vol. 94, no. 8, 2001, pp. 17-20.
  • Rodarte, E., G. Singh, N .R. Miller, and P. Hrnjak. "Sound Attenuation In Tubes Due to Visco-thermal Effects." Journal of Sound and Vibration, vol. 231, no. 5, April 2000, pp. 1221-1242.
  • Rodarte, E., G. Singh, N. R. Miller, and P. Hrnjak. "Refrigerant Expansion Noise Propagation through Downstream Tube Walls." Journal of Passenger Cars, vol. 108, no. 6, 1999, pp. 2224-2234.
  • Rodarte, E., N. Miller, and P. Hrnjak. "Acoustic Resonance in Plate Heat Exchangers." International Journal of Refrigeration, vol. 21, no. 8, December 1998, pp. 626-638.
  • Peixoto, R. A. and P. Hrnjak. "Elimina￿ de CFCs na Refrigera￿ de Supermercados." Abrava, Sao Paolo, Brazil, March/April 1998, pp.50-58.
  • Vujic, S., M. Markoski, and P. Hrnjak. "On Generalization of Test Results for Air Coolers with Moisture Extraction." KGH, 4, Belgrade, Yugoslavia (in Serbocroatian), 1983.

Articles in Conference Proceedings

  • Li, J. and P. Hrnjak. "Phase Separation in Vertical Header of Microchannel Condensers -- A Mechanistic Model." ASME Conference, FEDSM 2018.
  • Xu, J. and P. Hrnjak. "Flow Visualization and Experimental Measurement of Compressor Oil Separator." SAE Congress, 2018, technical paper 18HX-0052.
  • Feng, L. and P. Hrnjak. "Performance Characteristics of a Mobile Heat Pump System at Low Ambient Temperature." SAE Congress, 2018, technical paper 18HX-0054.
  • Feng, L. and P. Hrnjak. "Application of Intermediate Vapor Bypass to Mobile Heat Pump System: Extending Operating Range to Lower Ambient Temperature with Low Pressure Low GWP Fluid." SAE Congress, 2018, technical paper 18HX-0049.
  • Li, Jun and Pega Hrnjak. "Optimization of Microchannel Condenser with Phase Separation in the Header." 2018 ASHRAE Winter Conference, 2018, paper 23363, CH-18-C044.
  • Davies, W. A., Y. Kang, P. Hrnjak, and A. Jacobi. "Effect of Inclination on Heat Transfer in Large Flattened-tube Steam Condensers." Proceedings of the ASME 2017 International Mechanical Engineering Congress and Exposition, IMECE2017, Tampa, FL, 3-9 November 2017.
  • Hrnjak, P. "Situation of Carbon Dioxide as Refrigerant and What Can We Expect." 10th International Conference on Compressors and their Systems, City University, London, 11-13 September 2017.
  • Xu, J. and P. Hrnjak. "Oil Flow at the Scroll Compressor Discharge: Visualization and CFD Simulation." 10th International Conference on Compressors and their Systems, City University, London, 11-13 September 2017.
  • Hrnjak, P. "Challenges for Al Microchannel Heat Exchangers and their Solutions." 5th International Congress on Aluminum Heat Exchanger Technologies for HVAC&R, Dusseldorf, Germany, 16-17 May 2017.
  • Zhao, H., S. Elbel, and P. Hrnjak. "Joining Dissimilar Materials in Heat Exchanger Manufacturing Process." 5th International Congress on Aluminum Heat Exchanger Technologies for HVAC&R, Dusseldorf, Germany, 16-17 May 2017.
  • Hrnjak, P. "The￿Future￿of￿CO2￿Refrigeration￿and￿Thermal￿Technology." The￿8th￿International￿Conference￿on￿Compressors￿and￿Refrigeration, ICCR 2017 Xi￿an, 20-22 July 2017.
  • Hrnjak, P. "Efficient Vely Low-charged Ammonia Systems." Ammonia and CO2 Refrigeration Technologies, Ohrid, Macedonia, 11-13 May 2017.
  • Hrnjak, P. "A New Approach to Predict Void Fraction, Flow Regime and Heat Transfer Accounting for Non-Equilibrium in Condensers with Superheated Inlets." TPTPR Seoul, Korea, 23-26 April 2017.
  • Feng, L. and P. Hrnjak. "Refrigerant Charge Imbalance in a Mobile Reversible Air Conditioning Heat Pump System." SAE World Congress Experience, WCX 2017, Detroit, MI, 4-6 April 2017, SAE technical paper 2017-01-0177.
  • Li, J., L. Feng, and P. Hrnjak. "Experimentally Validated Effects of Separation of Liquid and Vapor on Performance of Condenser and System." WCX 17: SAE World Congress Experience, Detroit, MI, 4-6 April 2017, SAE technical paper 2017-01-0162.
  • Hrnjak, P. "Actual Condensation in Refrigeration and Air Conditioning." The 47th￿International Congress and Exhibition￿on Heating, Refrigeration and Air-Conditioning, Belgrade, 30 November 2016.
  • Hrnjak, P. "Oil in Circulation and its Retention at the Compressor Discharge." The 47th￿International Congress and Exhibition￿on Heating, Refrigeration and Air-Conditioning, Belgrade, 30 November 2016.
  • Hrnjak, P. "Тrends in Ammonia Industrial Refrigeration." The 47th￿International Congress and Exhibition￿on Heating, Refrigeration and Air-Conditioning, Belgrade, 30 November 2016.
  • Elbel, S. and P. Hrnjak. "Natural Refrigerants for Light Commercial Applications: A Fair Comparison of the Pros & Cons of CO2 and Propane." Gustav Lorentzen Natural Working Fluids Conference, Edinburgh, United Kingdom, 21-24 August 2016, paper 1099, pp. 618-625.
  • Elbel, S., M. Duggan, T. LaGrotta, S. Raj, and P. Hrnjak. "Accelerated Fatigue Testing of Aluminum Refrigeration Press Fittings for HVAC&R Applications." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2438.
  • Elbel, S., M. Visek, and P. Hrnjak. "A Fair Comparison of CO2 and Propane used in Light Commercial Applications Featuring Natural Refrigerants." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2429.
  • Wong, M. Y., G. D. Hardy, A. M. Jacobi, and P. Hrnjak. "Numerical Simulation (CFD) to Explore Optimal Vortex Generator Array Configurations in Air-cooled Condensers." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2555.
  • Wenzel, M., S. Elbel, and P. Hrnjak. "Design, Build-up, and Commissioning of 350 kW Refrigeration Test Facility for Experimental Investigation of Large Cold Chain Equipment." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2580.
  • Musser, A., P. Hrnjak, and S. Elbel. "Internal Heat Exchanger Performance Quantification and Comparison Testing Methods Including Exploration of the Effects of Location of Measurements and Oil in Circulation." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2453.
  • Zou, Y. and P. Hrnjak. "CFD Simulation of R134a and R410A Two-phase Flow in the Vertical Header of Microchannel Heat Exchanger." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2367.
  • Zou, Y., H. Li, and P. Hrnjak. "Simulation of a R410A Residential Air-conditioning System with Round-tube and/or Microchannel Evaporators and Condensers under both Dry and Wet Air Conditions." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2303.
  • Zou, Y., Hl. Li, K. Tang, and P. Hrnjak. "Round-tube and Microchannel Heat Exchanger Modeling at Wet Air Condition." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2474.
  • Visek, M., S. Elbel, and P. Hrnjak. "Conversion of Cold Beverage Dispenser's Refrigeration System to R744 Refrigerant." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2556.
  • Zhao, H., S. Raghunandanan, S. Elbel, and P. Hrnjak. "A Study of Microchannel Heat Exchanger Performance Associated with Manufacturing Process." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2545.
  • Wujek, S., W. Staats, S. Elbel, J. Koplow, H. Kariya, and P. Hrnjak. "Method for Determining Air Side Convective Heat Transfer Coefficient using Infrared Thermography." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2587.
  • Visek, M., S. Elbel, P. Hrnjak, B. Hoaglan, C. Tang, and D. Smith. "Conversion of Platelet Incubator Refrigeration System to R600a and Performance Optimization." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2615.
  • Li, H. and P. Hrnjak. "Heat Transfer and Pressure Drop during Evaporation of R134a in Microchannel Tubes." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2133.
  • Liu, X. and P. Hrnjak. "Oil Effects on Distribution of Refrigerant In MAC Heat Exchangers." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2198.
  • Liu, X. and P. Hrnjak. "Oil Effects on Performance of Automobile A/C System." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2199.
  • Li, Jun and P. Hrnjak. "Separation of Liquid and Vapor in Header of MCHE." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 22-14 July 2016, paper 2248.
  • Jiu, X and P. Hrnjak. "Oil Flow Measurement at the Compressor Discharge." 23rd International Compressor Engineering Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 1612.
  • Xu, J. and P. Hrnjak. "Visualization and Simulation of Oil Flow in a Scroll Compressor Plenum." 23rd International Compressor Engineering Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 1613.
  • Kang, Y., W. A. Davies, P. Hrnjak, and A. M. Jacobi. "Effect of Inclination on Condensation Pressure Drop in Large Flattened-tube Steam Condensers." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2250.
  • Davies, W. A., Y. Kang, P. Hrnjak, and A. M. Jacobi. "Heat Transfer and Visualization in Large Flattened-tube Condensers with Variable Inclination." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2299.
  • Jin, S. and P. Hrnjak. "Effect of End Plates on Heat Transfer of Plate Heat Exchanger." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2337.
  • Jin, S. and P. Hrnjak. "A Method to Combine Local Heat Transfer and Flow Visualization of Flow Boiling in Frame-and-plate Heat Exchanger." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2338.
  • Li, H. and P. Hrnjak. "Effect of Channel Geometries on Flow Reversal in Microchannel Evaporators." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2471.
  • Li, H. and P. Hrnjak. "Experimental Study on Microchannel and Round Tube Plate Fin Evaporators in a Residential Air Conditioning System." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2472.
  • Feng, L. and P. Hrnjak. "Experimental and Numerical Study of a Mobile Reversible Air Conditioning-Heat Pump System." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2569.
  • Li, W. and P. Hrnjak. "Single Phase Pressure Drop and Flow Distribution in Brazed Plate Heat Exchangers." 16th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 11-14 July 2016, paper 2609.
  • Xu, J. and P. Hrnjak. "Refrigerant Oil Flow at Compressor Discharge." SAE 2016 World Congress and Exhibition, Detroit, MI, 12-14 April 2016, paper 1612.
  • Feng, L. and P. Hrnjak. "Experimental Study of an Air Conditioning Heat Pump System for Electric Vehicles." SAE 2016 World Congress and Exhibition, Detroit, MI, 12-14 April 2016, SAE technical paper 2016-01-0257.
  • Li, J. and P. Hrnjak. "The Analysis of Phase Separation in Vertical Headers of Microchannel HEs." SAE 2016 World Congress and Exhibition, Detroit, MI, 12-14 April 2016, SAE technical paper 2016-01-0253.
  • Li, H. and P. Hrnjak. "Visualization and Analysis of Periodic Reverse Flow in an Automobile Microchannel Evaporator." SAE 2016 World Congress and Exhibition, Detroit, MI, 12-14 April 2016, SAE technical paper 2016-01-0252.
  • Davies, W. A., Y. Kang, P. Hrnjak, and A. M. Jacobi. "Heat Transfer and Visualization in Large Flattened-tube Condensers with Variable Inclination." International Refrigeration and Air Conditioning Conference, 2016 July, paper 2299.
  • Xu, J. and P. Hrnjak. "Visualization and Simulation of Oil Flow in a Scroll Compressor Plenum." International Compressor Engineering Conference, 2016, paper 1613.
  • Xiao, J. and P. Hrnjak. "A New Flow Map and Flow Characterization of Condensation in Smooth Round Tube from Superheated Vapor." International Refrigeration and Air Conditioning Conference, 2016, paper 2077.
  • Xiao, J. and P. Hrnjak. "Heat Transfer of Condensation in Smooth Round Tube from Superheated Vapor." International Refrigeration and Air Conditioning Conference, 2016, paper 2078.
  • Hrnjak, P. "New Developments in Microchannel Heat Exchangers." ASHRAE Conference, Orlando, FL, 2016.
  • Xu, J. and P. Hrnjak. "Refrigerant-oil Flow at the Compressor Discharge." 2016, SAE technical paper 2016-01-0247.
  • Fuentes Y. P., P. Hrnjak, and S. Elbel. "High-efficiency, Low-cost Glass Door Merchandisers using Transcritical Carbon Dioxide." 24th IIR International Congress of Refrigeration, ICR 2015, Japan, 16-22 August 2015, pp. 2757-2764.
  • Fuentes, Y. P., P. Hrnjak, and S. Elbel. "Low-charge Propane Refrigeration System Technology for Single and Multi-door Bottle Coolers." 24th IIR International Congress of Refrigeration, ICR 2015, Japan, 16-22 August 2015, pp. 2749-2756.
  • Wujek, S., P. Hrnjak, and S. Elbel. "Waste Heat Driven Cooling by Vapor Jet Ejector." 24th IIR International Congress of Refrigeration, ICR 2015, Japan, 16-22 August 2015, pp. 1958-1965.
  • Zou, Y. and P. Hrnjak. "Distribution Function for Reversible Microchannel Heat Exchanger with Vertical Headers -- Considering the Effects of Inlet Conditions, Geometries and Fluid Properties." 24th IIR International Congress of Refrigeration, ICR 2015, Japan, 16-22 August 2015, pp. 1748-1755.
  • Wujek, S., and P. Hrnjak. "Flow Development in the Discharge of a Compressor." 24th IIR International Congress of Refrigeration, ICR 2015, Japan, 16-22 August 2015, pp. 1589-1596.
  • Khovalyg, D., P. Hrnjak, and A. M. Jacobi. "Thermodynamic Analysis of the Transition between Slug and Annular Flow in Minichannels." Proceedings of the ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels, San Francisco, CA, 6-9 July 2015.
  • Zou, Y. and P. Hrnjak. "Effect of Pressure Drop in the Header on Refrigerant Distribution in an Outdoor Reversible Microchannel Heat Exchanger." SAE 2015 World Congress and Exhibition, Detroit, MI, 21-23 April 2015, SAE Technical Paper 2015-01-0361.
  • Li, J. and P. Hrnjak.. "Phase Separation in Second Header of MAC Condenser." SAE 2015 World Congress and Exhibition, Detroit, MI, 21-23 April 2015, SAE Technical Paper 2015-01-1694.
  • Zhao H., S. Elbel, and P. Hrnjak. "An Investigation on Thermal Integrity of Brazed Heat Transfer Devices." 6th International Brazing and Soldering Conference, Long Beach, CA, 19-22 April 2015.
  • Zhao, H. S. Elbel, P. Hrnjak. "Low Temperature Controlled Atmosphere Brazing of Aluminum Matrix Composite." 6th International Brazing and Soldering Conference, Long Beach, CA, 19-22 April 2015.
  • Zou, Y. and P. Hrnjak. "Measuring and Predicting Two-phase Pressure Drop in the Vertical Header with Protruded Microchannel Tubes (AT-15-C026)." ASHRAE Conference, Atlanta, GA, 2015.
  • Zou, Y. and P. Hrnjak. "Comparing Distribution of R32 (Low GWP), R410A, R134a and R245fa in the Vertical Header of a Reversible Microchannel Heat Exchanger: Affecting HX Performance (AT-15-C025)." ASHRAE Conference, Atlanta, GA, 2015.
  • Dzinic, N., P. Hrnjak. "Transient Behavior of FGB Systems for Reversible Systems." 46th Congress KGH, Belgrade, 2015.
  • Hrnjak, P. and S. Kim. "In-tube Evaporation of CO2: Visualization and Effect of Oil." IIR Ammonia Refrigeration Conference, Ohrid--Macedonia, 2015.
  • P. S. Hrnjak. "New Developments in Microchannel Heat Exchangers." ICR Yokohama, 2015.
  • Li, H. and P. Hrnjak. "An Infrared Thermography-based Method for Quantification of Liquid Refrigerant Distribution in Parallel Flow Microchannel Heat Exchanger." SAE 2015 World Congress & Exhibition, 2015, SAE Technical Paper 2015-01-0357.
  • Khovalyg, D., P. Hrnjak, A. Baranenko, and A. M. Jacobi. "Interactions between Parallel Minichannels during Flow Boiling of R134A." Proceedings of the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels, Chicago, IL, 3-7 August 2014.
  • Ren, T., A. Chavoshi, G. Ding, and P. Hrnjak. "Single-phase Pressure Drop in Round Cylindrical Headers of Parallel Flow MCHXs." Proceedings of the 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2542.
  • Meyer, M. and P. Hrnjak. "Pressure Drop in Condensing Superheated Zone." Proceedings of the 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2551.
  • Zhao, H., S. Elbel, and P. Hrnjak. "Influence of Surface Morphology on Wetting Behaviors of Liquid Metal during Aluminum Heat Exchanger Fabrication." Proceedings of the 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2461.
  • Wang, X., K. Tang, and P. Hrnjak. "Effect of Pulsation Width Modulation (PWM) on the Performance of an Evaporator." Proceedings of the 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2585.
  • Xu, L. and P. Hrnjak. "Potential of Controlling Subcooling In Residential A/C System." Proceedings of the 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2387.
  • Padilla Fuentes, Y., S. Elbel, and P. Hrnjak. "Extremely Low Refrigerant Charge Beverage Display Cooler Technology using Propane." Proceedings of the 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2458.
  • Zou, Y. and P. Hrnjak. "Single-phase Flow Pressure Drop of R134a Vapor and Liquid in the Vertical Header of Multi-Pass Microchannel Heat Exchanger." Proceedings of the 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2212.
  • Bowers, C. D., D. Wrocklage, S. Elbel, and P. Hrnjak. "Improvements in Refrigerant Flow Distribution using an Expansion Valve with Integrated Distributor." Proceedings of the 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2363.
  • Elbel, S., Y. Padilla Fuentes, C. Bowers, and P. Hrnjak. "Successful Design, Implementation, and Validation of Transcritical R744 Technology for Beverage Display Coolers." Proceedings of the 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2192.
  • Musser, A. and P. Hrnjak. "Mobile Heat Pump Exploration using R445A and R744." Proceedings of the 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2509.
  • Jiang, L. and P. Hrnjak. "Refrigerant Charge Reduction In Small Commercial Refrigeration Systems." Proceedings of the 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2467.
  • Li, H. and P. Hrnjak. "An Experimentally Validated Model for Microchannel Heat Exchanger Incorporating Lubricant Effect." Proceedings of the 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2148.
  • Zimmermann, A. and P. Hrnjak. "Visualization of the Opening Process of a Discharge Reed Valve in the Presence of Oil." Proceedings of the 22nd International Compressor Conference at Purdue University, West Lafayette, IN, 14-17 July 2014, paper 1569.
  • Li, H. and P. Hrnjak. "Quantification of Liquid Refrigerant Distribution in Parallel Flow Microchannel Heat Exchanger Using Infrared Thermography." Proceedings of the 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2147.
  • Khovalyg, D., P. Hrnjak, and A. Jacobi. "Transient Pressure Drop Correlation between Parallel Minichannels during Flow Boiling of R134a." Proceedings of the 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2171.
  • Zimmermann, A. and P. Hrnjak. "Source Identification and In Situ Quantification of Oil-refrigerant Mist Generation by Discharge Valve Opening Process." Proceedings of the 22nd International Compressor Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 1563.
  • Jin, S. and P. Hrnjak. "Refrigerant and Lubricant Charge in AC Heat Exchangers: Experimentally Validated Model." Proceedings of the 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2398.
  • Shah, T. and P. Hrnjak. "Linked Modelling of Heat Pump Water Heater Vapor Compression System and Water Tank." 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2431.
  • Zou, Y. and P. Hrnjak. "Comparison and Generalization of R410A and R134a Distribution in the Microchannel Heat Exchanger with the Vertical Header." Proceedings of the 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2122.
  • Bowers, C. D., G. Baker, S. Elbel, and P. Hrnjak. "Accelerated Thermal Cycling Test for Heat Exchangers used in Reversible Heat Pump." Proceedings of the 15th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2014, paper 2369.
  • Li, H. and P. Hrnjak. "Lubricant Effect on Performance of R134a MAC Microchannel Evaporators." SAE 2014 World Congress and Exhibition, Detroit, MI, vol. 1, 8-10 April 2014.
  • Zou, Y., H. Li, and P. Hrnjak. "Lubricant Impact on R134a Distribution and Microchannel Heat Exchanger Performance." SAE World Congress Exhibition, Detroit, MI, vol. 1, 8-10 April 2014, paper 2014-01-0706.
  • Li, H. and P. Hrnjak. "OCR Effects on Performance of R134a MAC Microchannel Evaporators." SAE World Congress, Detroit, MI, 2014 April, paper 2014-01-0692.
  • Jin, S. and P. Hrnjak. "An Experimentally Validated Model for Predicting Refrigerant and Lubricant Inventory in MAC Heat Exchangers." SAE World Congress, Detroit, MI, 2014 April, paper 2014-01-0694.
  • Li, H. and P. Hrnjak. "Oil Effects on Distribution in the Inlet Header." SAE World Congress, Detroit, MI, 2014 April, paper 2014-01-0701.
  • Hrnjak, P. "Strategies and Results in Building Ultra Low-charged Ammonia Systems." IIAR Conference, Nashville, TN, 23-26 March 2014.
  • Zou, Y., H. Tuo, and P. Hrnjak. "R-410A Maldistribution Impact on the Performance of Microchannel Evaporator." 2014 ASHRAE Winter Conference, New York, NY, vol. 120, no. 1, 18-22 January 2014, pp. 406-415.
  • Khovalyg, D., P. Hrnjak, and A. M. Jacobi. "Interactions between Parallel Unevenly Heated Minichannels during Flow Boiling of R134a." Proceedings of the International Conference in Nanochannels, Microchannels and Minichannels, Chicago, IL, 3-7 August 2014.
  • Zhao, H., S. Elbel, and P. Hrnjak. "Wetting Behaviors of Al-based Filler Metals on Aluminum Matrix Composites." International Conference on Brazing, Soldering and Special Joining Technologies, Beijing, China, 9-13 June 2014.
  • Dzinic, N., P. Hrnjak. "Application of FGB Concept in Reversible Cooling & AC Systems." 46th Conference KGH, Belgrade, 2014.
  • Hrnjak, P. "Refrigerant and Oil Charge Distribution in Refrigeration Systems." 46th Conference KGH, Belgrade, 2014.
  • Hrnjak, P. "Major Shift in Industrial Refrigeration." 46th Conference KGH, Belgrade, 2014.
  • Elbel, S., Fuentes, Y. P., Bowers, C., Hrnjak, P. "Successful Conversion and Validation of Glass Door Merchandisers using Transcritical R744." 11th IIR Gustav Lorentzen Conference on Natural Refrigerants: Natural Refrigerants and Environmental Protection, GL, 2014, pp. 421-429.
  • Elbel, S., Y. P. Fuentes, and P. S. Hrnjak. "Extremely Low Refrigerant Charge Beverage Display Cooler Technology using Propane." 11th IIR Gustav Lorentzen Conference on Natural Refrigerants: Natural Refrigerants and Environmental Protection, GL, 2014, pp. 193-201.
  • Hrnjak, P. and S. Kim. "Oil Effects on In-tube Boiling of CO2." 11th IIR Gustav Lorentzen Conference on Natural Refrigerants: Natural Refrigerants and Environmental Protection, GL, 2014, pp. 510-518.
  • Hrnjak, P. "Effect of Oil on Evaporative Heat Transfer in R744." 44th KGH Congress, Belgrade, 4-6 December 2013.
  • Hrnjak, P. "Refrigerants: Now and in the Making," 44th KGH Congress, Belgrade, 4-6 December 2013.
  • Hrnjak, P. "Refrigerant Charge Reduction: Strategies and Opportunities, 2013," ISCERA Conference, Yaesu, 21-24 October 2013.
  • Zimmermann, A. and P. Hrnjak. "Oil Flow at Discharge Valve in a Scroll Compressor." Proceedings of 8th International Conference on Compressors and Their Systems, London, 9-10 September 2013, pp. 311-320.
  • Zimmermann, A. and P. Hrnjak. "Assessment of Reed Valve Dynamic Behavior in a Scroll Compressor through Visualization." Proceedings of International Conference on Compressors and their Systems, London, 9-10 September 2013, pp. 277-284..
  • Hrnjak, P. and S. Kim. "Oil Effects on In-tube Evaporation of CO2 by Altering Flow Regime and Properties." Proceedings of the ASME 2013 Heat Transfer Summer Conference, Minneapolis, MN, vol. 2, 14-19 July 2013.
  • Hrnjak, P. and S. Kim. "Two-phase Refrigerant Maldistribution in the Vertical Header and Its Effect on the Heat Exchanger Performance as Evaporator in Heat Pump Mode." Proceedings of the ASME 2013 Summer Heat Transfer Conference, Minneapolis, MN, 14-19 July 2013.
  • Hrnjak, P. and C. Kondou. "Refrigerant Side Heat Transfer in Condensers with Round Tubes." Proceedings of the 4th IIR International Conference on Thermophysical Properties and Transfer Processes of Refrigerants, Delft, 17-19 June 2013.
  • Zou, Y. and P. Hrnjak. "Measurement and Visualization of R134a Distribution in the Vertical Header of the Microchannel Heat Exchanger." SAE 2013 World Congress and Exhibition, Detroit, MI, vol. 2, 16-18 April 2013, paper 2013-01-1498.
  • Li, H. and P. Hrnjak. "Effect of Lubricant on Two-phase Refrigerant Distribution in Microchannel Evaporator." SAE 2013 World Congress and Exhibition, Detroit, MI, vol. 2, 16-18 April 2013, paper 2013-01-1508.
  • Tuo, H. and P. Hrnjak. "Periodic Reverse Flow and Boiling Fluctuations in a Microchannel Evaporator of an R134a Mobile Air-conditioning System." SAE 2013 World Congress and Exhibition, Detroit, MI, vol. 2, 16-18 April 2013, paper 2013-01-1500.
  • Jin, S. and P. Hrnjak. "Refrigerant and Lubricant Distribution in MAC System." SAE World Congress & Exhibition, 2013, paper 2013-01-1496.
  • Hrnjak, P. "Pioneering Applications of Refrigeration Technologies." Proceedings of Institute of Refrigeration, 2012-13. pp. 5-24.
  • Hrnjak, P. "Air Cooled Low Charged Chillers with Ammonia ￿ Efficient and Ecological Option for Cooling." Proceedings of the 43rd International Congress on Heating, Refrigerating and Air￿conditioning, Belgrade, Serbia, 5-7 December 2012.
  • Hrnjak, P. "Charge Minimization of Various Fluids in Refrigeration and A/C Systems." Proceedings of the 43rd International Congress on Heating, Refrigerating and Air Conditioning, Belgrade, Serbia, 5-7 December 2012.
  • Zou, Y., H. Tuo, and P. Hrnjak. ￿Two-phase Refrigerant Maldistribution in the Vertical Header and Its Effect on the Heat Exchanger Performance as Evaporator in Heat Pump Mode.￿ Proceedings of the ASME 2012 International Mechanical Engineering Congress & Exposition, Houston, TX, 9-15 November 2012, pp. 1823-1832.
  • Hrnjak, P. "Low Refrigerant Charge with a Focus on Microchannel Heat Exchangers." Proceedings of ASHRAE/NIST Refrigerants Conference, Gaithersburg, MD, 29-30 October 2012, pp. 272-283.
  • Brown, I., M. W. Critchley, J. Yin, S. Memory, S. Elbel, C. Bowers, M. Petersen, P. Hrnjak, and G. Sizov. ￿Design and Evaluation of Interior Permanent Magnet Compressor Motors for Commercial Transcritical CO2 (R-744) Heat Pump Water Heaters.￿ 4th Annual IEEE Energy Conversion Congress and Exposition, ECCE 2012, Raleigh, NC, 15-20 September 2012, pp. 2790-2797.
  • Wujek, S. S., and P. Hrnjak. ￿Modeling Mist to Annular Flow Development in the Discharge of a Compressor.￿ Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 16-19 July 2012, paper 2507.
  • Wujek, S. S. and P. S. Hrnjak. ￿Measurement of Mist to Annular Flow Development in the Discharge of a Compressor,￿ Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 16-19 July, 2012, paper 2506.
  • Musser, A., D. Rhyner, G. Miller-Gaines, and P. Hrnjak. ￿Flow Re-circulatory Air Curtain Efficiencies." Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 2-12 July, paper 3500.
  • Zhao, H., S. Elbel, and P. Hrnjak. ￿Capillary Flow of Liquid Metal Occurring in Microchannel Heat Exchanger Fabrication.￿ Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 16-19 July 2012, paper 2498.
  • Zhao, H., S. Elbel, and P. Hrnjak. ￿Transport Phenomena Involved in Controlled Atmosphere Brazing of Microchannel Al Heat Exchanger.￿ Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 2012 July, paper 2406.
  • P￿er, G. and P. Hrnjak. ￿Designated vs Non-designated Areas for Condenser Subcooling.￿ Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 16-19 July 2012, paper 2522.
  • Kim, S. and P. Hrnjak. ￿Effect of Oil on Flow Boiling Heat Transfer and Flow Patterns of CO2 in 11.2 mm Horizontal Smooth and Enhanced Tube.￿ Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 16-19 July 2012, paper 2519.
  • Zou, Y. and P. Hrnjak. ￿Measurement and Visualization of R410A Distribution in the Vertical Header of the Microchannel Heat Exchanger.￿ Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 16-19 July 2012, paper 2465.
  • Zimmermann, A. J. P., P. Hrnjak, and S. S. Wujek. ￿Developing Mist-annular Flow of R134a/PAG 46 Oil on Inclined Tubes at Compressor Discharge.￿ Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 16-19 July 2012, paper 2401.
  • Fuentes, Y. and P. Hrnjak. "Charge Reduction Potentials of Several Refrigerants based on Experimentally Validated Micro-channel Heat Exchangers Performance and Charge Model." Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 16-19 July 2012, paper 2292.
  • Bowers, C. D., H. Mai, S. Elbel, and P. Hrnjak. ￿Refrigerant Distribution Effects on the Performance of Microchannel Evaporators.￿ Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 16-19 July 2012, paper 2173.
  • Petersen, M., C. D. Bowers, S. Elbel, and P. Hrnjak. ￿Development of High-efficiency Carbon Dioxide Commercial Heat Pump Water Heater.￿ HVAC&R Research, Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, vol. 19, 16-19 July 2012, pp. 823-835, paper 2168.
  • Elbel, S., C. Bowers, M. Reichle, J. M. Cristiani, and P. Hrnjak. ￿Vapor Jet Ejector Used to Generate Free Waste Heat Driven Cooling In Military Environmental Cooling Units.￿ Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 16-19 July 2012, paper 2164.
  • Elbel, S., C. Bowers, H. Zhao, S. Park, and P. Hrnjak. ￿Development Of Microclimate Cooling Systems for Increased Thermal Comfort of Individuals.￿ Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 16-19 July 2012, paper 2149.
  • Hrnjak, P. and C. Kondou. ￿Effect of Microfins on Heat Rejection in Desuperheating, Condensation in Superheated Region and Two-phase Zone.￿ Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 16-19 July 2012, paper 2566.
  • P￿er, G. and P. Hrnjak. ￿Effect of Condenser Subcooling of the Performance of Vapor Compression Systems: Experimental and Numerical Investigation.￿ Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 16-19 July 2012, paper 2512.
  • Ramakrishnan, A. and P. Hrnjak. ￿Oil Retention and Pressure Drop of R134a, R1234yf and R410A with POE 100 in Suction Lines.￿ Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 16-19 July 2012, paper 2508.
  • Kondou, C. and P. Hrnjak. "Heat Rejection in Condensers: Desuperheating, Condensation in Superheated Region and Two-phase Zone." Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 16-19 July 2012, paper 2503.
  • Tuo, H. and P. Hrnjak. ￿Flash Gas Bypass Method for Improving Performance of an A/C System with a Microchannel Evaporator.￿ Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 16-19 July 2012, paper 2502.
  • Hrnjak, P., P. Zhang, and C. Rennels. ￿Effect of Louver Angle on Performance of Heat Exchanger with Serpentine Fins and Flat Tubes in Periodic Frosting.￿ Proceedings of the 14th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 16-19 July 2012, paper 2501.
  • Musser, A., D. Rhyner, G. Miller-Gaines, and P. Hrnjak. "Energy Transfer-based Test Method Development and Evaluation of Horizontal Air Flow Re-circulatory Air Curtain Efficiencies." International High Performance Buildings Conference at Purdue, West Lafayette, IN, 16-19 July 2012, paper 3500.
  • Zhao, H., S. Elbel, and P. Hrnjak. "Controlled Atmosphere Brazing of Microchannel Heat Exchangers for Mini-cooling Systems." 5th International Brazing and Soldering Conference, IBSC 2012, Las Vegas, NV, 22-25 April 2012, pp. 183-187.
  • Tuo, H. and P. Hrnjak. "Experimental Study of Refrigerant Two-phase Separation in a Compact Vertical T-junction." 2012 ASHRAE Winter Conference, Chicago, IL, vol. 118, no. 1, 21-25 January 2012, pp. 672-680.
  • Tuo, H. A. Bielskus, and P. Hrnjak. "An Experimentally Validated Modeling of Refrigerant Distribution in a Parallel Microchannel Evaporator." 2012 ASHRAE Winter Conference, Chicago, IL, vol. 118, no. 1, 21-25 January 2012, pp. 375-383.
  • Bowers, C., M. Petersen, S. Elbel, and P. Hrnjak. "Next Generation Commercial Heat Pump Water Heater using Carbon Dioxide using Different Improvement Approaches." 10th IIR Gustav Lorentzen Conference on Natural Refrigerants, Delft, The Netherlands, 2012.
  • Elbel, S., M. Reichle, C. Bowers, and P. Hrnjak. "Integration of a Two-phase Ejector into a Compact, Lightweight Unitary-type Air-conditioner using R744 for Energy Efficient Operation in Hot Climates." IIR Gustav Lorentzen Conference on Natural Refrigerants, Delft, The Netherlands, 2012.
  • Hrnjak, P. "Technologies Needed to Advance the Position of Major Natural Refrigerants: HC, NH3 or CO2." IIR Gustav Lorentzen Conference on Natural Refrigerants, Delft, The Netherlands, 2012.
  • Padilla Y. and P. Hrnjak. "Experimentally Validated Microchanel Heat Exchanger Performance and Charge Predictions used to Compare Charge Reduction Potentials of Some Refrigerants." 10th IIR Gustav Lorentzen Conference on Natural Refrigerants, Delft, The Netherlands, 2012.
  • Wang, X., P. Hrnjak, S. Elbel, A. M. Jacobi, and M. G. He. "Heat Transfer Performance for a Falling-film on Horizontal Flat Tubes." Proceedings of the ASME 2011 International Mechanical Engineering Congress and Exposition, Denver, CO, vol. 10, nos. A and B, 11-17 November 2011, pp. 43-50.
  • Field, B. and P. Hrnjak. "A Mechanistic Model of Two-phase Pressure Drop in Microchannels." Proceedings of the ASME 2011 International Mechanical Engineering Congress and Exposition, Denver, CO, vol. 6, nos. A and B, 11-17 November 2011, pp. 411-419.
  • Bowers C. D., S. Elbel, M. Petersen, and P. Hrnjak. "Performance Improvements in Commercial Heat Pump Water Heaters using Carbon Dioxide." The 23rd IIR International Congress of Refrigeration, no. 389, Prague, Czech Republic, 21-26 August 2011.
  • Elbel, S., C. D. Bowers, H. Zhao, S. Park, and P. Hrnjak. "Development and Analysis of Miniature Vapor Compression Cooling Technology." The 23rd IIR International Congress of Refrigeration, no. 389, Prague, Czech Republic, 21-26 August 2011.
  • Kondou, C. and P. Hrnjak. ￿Condensation in Presence of Superheated Vapor for Near-Critical CO2 and R410A in Horizontal Smooth Tubes.￿ (Keynote). The 23rd IIR International Congress of Refrigeration, no. 389, Prague, Czech Republic, 21-26 August 2011.
  • Hrnjak, P. and Kondo, C. ￿Heat Rejection in Condensers Close to Critical Point - Desuperheating, Condensation in Superheated Region and Condensation of Two-phase Fluid.￿ Proceedings of the HEFAT2011, 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, 11￿13 July 2011.
  • Hrnjak, P. ￿New Opportunities for All Microchannel Heat Exchangers.￿ 2nd International Congress Aluminum Brazing Technologies for HVAC&R, D￿orf, 2011 May.
  • Hrnjak, P. ￿Low Charged Hermetic Ammonia Chillers are Excellent Opportunity for Air Conditioning and Indirect Refrigeration.￿ IIR Ammonia Refrigeration Conference, Ohrid--Macedonia, 2011 April.
  • Li, B., S. Peuker, P. Hrnjak, and A. Alleyne. ￿Evaluation of Transient Refrigerant Migration Modeling Approach on Automotive Air Conditioning Systems.￿ SAE 2011 World Congress & Exhibition, April 2011, paper 2011-01-0649.
  • Tu, H., A. Bielskus, and P. Hrnjak. ￿Effect of Flash Gas Bypass on the Performance of R134a Mobile Air-conditioning System with Microchannel Evaporator.￿ SAE 2011 World Congress & Exhibition, 12 April 2011, paper 2011-01-0139.
  • Zhao, H., S. Elbel, and P. Hrnjak. ￿The Potential of Open Cell Aluminum Foam as Fin Structures for CAB Brazed Heat Exchangers.￿ AFC-Holcroft￿s 14th Annual Aluminum Brazing Invitational Seminar, Sheraton Hotel, Novi, Michigan, 27-29 October 2010.
  • Kondou, C. and P. Hrnjak. "R744 Flow in a Horizontal Smooth Tube around the Critical Point under the Uniform Temperature Cooling - Condensation in Presence of Superheated Vapor." JSRAE Annual Conference 2010, Kanazawa Japan, 14-18 September 2010, no. B233. (Award winning)
  • Wang, X., P. Hrnjak, S. Elbel, A. M. Jacobi, and M. He. ￿Flow Patterns and Mode Transitions for Falling-films on Flat Tubes.￿ Proceedings of the 13th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 12-15 July 2010, paper 2461.
  • Bowers, C. D. and P. Hrnjak. ￿Determination of Void Fraction in Separated Two-phase Flows Using Optical Techniques.￿ Proceedings of the 13th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 12-15 July 2010, paper 2293.
  • Kondou, C. and P. Hrnjak. ￿Heat Rejection from R744 Near the Critical Point.￿ Proceedings of the 13th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 12-15 July 2010, paper 2424.
  • Pehlivanoglu, N., S. Kim, and P. Hrnjak. ￿Effect of Oil on Heat Transfer and Pressure Drop of R744 in 6.1 mm Horizontal Smooth Tube.￿ Proceedings of the 13th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 12-15 July 2010, paper 2438.
  • Kim, S., N. Pehlivanoglu, and P. Hrnjak. ￿R744 Flow Boiling Heat Transfer with and without Oil at Low Temperatures in 11.2 mm Horizontal Smooth Tube.￿ Proceedings of the 13th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 12-15 July 2010, paper 2459.
  • Wujek, S., S. Peuker, H. Mai, J. Bower, M. Koffler, and P. Hrnjak. ￿Method for Measuring Oil Contained in Air Conditioning Components.￿ Proceedings of the 13th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 12-15 July 2010, paper 2173.
  • Wujek, S. and P. Hrnjak. ￿Method for Quantitatively Analyzing Flow Phenomena in Annular-mist Two-phase Flows.￿ Proceedings of the 13th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 12-15 July 2010, paper 2174.
  • Zoellick, K. F. and P. Hrnjak. ￿Oil Retention and Pressure Drop in Horizontal and Vertical Suction Lines with R410A/POE.￿ Proceedings of the 13th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 12-15 July 2010, paper 2327.
  • Pottker, G., B. Guo, and P. Hrnjak. ￿Experimental Investigation of an R410A Vapor Compression System Working with an Ejector.￿ Proceedings of the 13th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 12-15 July 2010, paper 2473.
  • Bowers, C. D., S. S. Wujek, and P. Hrnjak. "Quantification of Refrigerant Distribution and Effectiveness in Microchannel Heat Exchangers Using Infrared Thermography." Proceedings of the 13th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 12-15 July 2010, paper 2117.
  • Zhao, H., S. Elbel, and P. Hrnjak.￿Transport Phenomena Involved in Controlled Atmosphere Brazing of Microchannel Aluminum Heat Exchanger.￿ Proceedings of the 13th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 12-15 July 2010, paper 2406.
  • Li, B., S. Peuker, A. G. Alleyne, and P. Hrnjak. ￿Refrigerant Migration Modeling during Shut-down and Start-up Cycling Transients.￿ Proceedings of the 13th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 12-15 July, 2010, paper 2317.
  • Peuker, S. and P. Hrnjak. ￿Experimental Techniques to Determine Oil Distribution in Automotive A/C Systems.￿ Proceedings of the 13th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 12-15 July 2010, paper 2107.
  • Elbel, S. and P. Hrnjak. ￿Design, Build-up, and Performance Investigation of a 35 kW (10 Ton) Military Environmental Control Unit Using Transcritical R744 Technology.￿ Proceedings of the 13th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 12-15 July 2010, paper 2205.
  • Hrnjak, P. "Operation of R-744 Environmental Control Units at High Ambient Temperatures." ASHRAE 2010 Annual Conference, Albuquerque, NM, 26-30 June 2010.
  • Bowers, C. and P. Hrnjak. "Effects of Oil and Saturation Temperature on Developing Two-phase Flow of R134a in an Air-conditioning System." 2010 ASHRAE Annual Conference, Albuquerque, NM, vol. 116, no. 2, 26-30 June 2010, pp. 290-299.
  • Hrnjak, P. "The Search for Natural Refrigerants and Sustainable Solutions Greatly Improves the Art and Science of Refrigeration." IIR Conference Sustainable Refrigeration and Heat Pump Technology, KTH, Stockholm, 13-16 June 2010.
  • Kondou, C. and P. Hrnjak. "Excellent Heat Rejection from CO2 Near the Critical Point--Opportunity for High Efficiency." IIR Conference Sustainable Refrigeration and Heat Pump Technology, KTH Stockholm 13-16 June 2010.
  • Hrnjak, P. "Developments in Charge Reduction and Microchannel Technology Mass Flux as a way to Affect Void Fraction Charge." 2nd IIR Workshop on Refrigerant Charge Reduction, KTH, Stockholm, 16-17 June 2010.
  • Elbel, S., J. A. Manzione, S. J. Collier, and P. Hrnjak. "Compact, Lighweights Unitary-type Air Conditioner using Transcritical R744 Designed for Energy Efficient Operation in Hot Climates." 9th IIR Gustav Lorentzen Conference on Natural Working Fluids, Sydney, 12-14 April 2010.
  • Hrnjak, P. "Ultra Low Charged Air-cooled Ammonia Chillers." 9th IIR Gustav Lorentzen Conference on Natural Working Fluids, Sydney, 12-14 April 2010.
  • Park, Y. C. and P. Hrnjak. "A Study on the Improving Seasonal Energy Efficiency of an A/C System." 2nd International Conference on Computer and Automation Engineering, ICCAE 2010, Singapore, vol. 5, 26-28 February 2010, pp. 313-316.
  • Hrnjak, P. "Thermodynamic Possibilities and Technological Opportunities for Improving the Science of Refrigeration in Search for Low Global Warming Thermal Systems." International Symposium on Next-generation Air Conditioning and Refrigeration Technology, Tokyo, Japan, 17￿19 February 2010.
  • Hrnjak, P. ￿Developments in Charge Reduction and Microchannel Technology - Mass Flux as a Way to Affect Void Fraction Charge.￿ IIR Conference Sustainable Refrigeration and Heat Pump Technology, KTH Stockholm, 2010.
  • Hrnjak, P. ￿Two-phase Distribution Issues in Microchannel HXs.￿ ECI International Conference Enhanced Compact and Ultra-Compact Heat Exchangers: from Microscale Phenomena to Industrial Applications, Heredia, Costa Rica, 13-18 September 2009.
  • Hrnjak, P. ￿Competition between Synthetic and Natural Refrigerants: Contributions to the Art and Science of Thermal Systems.￿ 3rd IIR Conference on Thermophysical Properties and Transfer Processes of Refrigerants; Boulder, CO, 23-26 June 2009.
  • Hrnjak, P. ￿New Opportunities for All Microchannel Heat Exchangers.￿ 1st International Congress Aluminum Brazing Technologies for HVAC&R, D￿orf, 16-17 June 2009.
  • Pamitran, A. S., J. Ardiyansyah, T. Oh, and P. Hrnjak. ￿Flow Boiling Heat Transfer Characteristics in Horizontal Minichannels with R-410A." 3rd IIR Conference on Thermophysical Properties and Transfer Processes of Refrigerants, Boulder, CO, 23-26 June 2009.
  • Park, C. Y., and P. Hrnjak. ￿CO2 Condensation Heat Transfer and Pressure Drop in Multi-Port Microchannels.￿ 3rd IIR Conference on Thermophysical Properties and Transfer Processes of Refrigerants, Boulder, CO, 23-26 June 2009.
  • Seeton, C. and P. Hrnjak. ￿Interfacial Tension of CO2-POE and CO2-PVE Mixtures.￿ 3rd IIR Conference on Thermophysical Properties and Transfer Processes of Refrigerants, Boulder, CO, 23-26 June 2009.
  • Seeton, C. and P. Hrnjak. ￿Measurements of Solubility, Liquid Density, and Liquid Viscosity for CO2 Lubricant Mixtures.￿ 3rd IIR Conference on Thermophysical Properties and Transfer Processes of Refrigerants, Boulder, CO, 23-26 June 2009.
  • Hrnjak, P. "New Opportunities for Al Microchannel Heat Exchangers.￿ 1st International Congress Aluminum Brazing Technologies for HVAC&R, D￿orf, 16-17 June 2009.
  • Hrnjak, P. ￿Low Charge Chillers based on Microchannel Heat Exchangers: Opportunity for Expanding Use of Ammonia.￿ Ammonia Refrigeration Conference, Ohrid--Macedonia, 2009 May.
  • Pamitran, A. S., K.-I. Choi, J.-T. Oh, H.-K. Oh, and P. Hrnjak. "Boiling Heat Transfer and Pressure Drop of R-410A and R-134A in Horizontal Minichannels." 4th Asian Conference on Refrigeration and Air-Conditioning, ACRA 2009, Taipei, Taiwan, 20-22 May 2009, pp. 202-207.
  • Rifaldi, M., A. S. Pamitran, K.-I.Choi, J.-T. Oh, and P. Hrnjak. "Two-phase Flow Boiling Heat Transfer of R-22 and R-410A in Horizontal Microchannels." 4th Asian Conference on Refrigeration and Air-Conditioning, ACRA 2009, Taipei, Taiwan, 20-22 May 2009, pp. 196-201. pp. 196-201.
  • Hrnjak, P. ￿Carbon Dioxide in Light of New Low GWP Fluids.￿ 3rd Korean Congress of Refrigeration, Seoul, 19 March 2009.
  • Hrnjak, P. ￿Trends in CO2 as Refrigerant, Reaching out for a Greener Tomorrow.￿ International Conference ACRECONF 20, 21 February 2009.
  • Hrnjak, P. ￿Refrigerant Charge Reduction: Strategies and Experience.￿ IIR 1st Workshop on Refrigerant Charge Reduction, Cemagref Antony, France, 2009.
  • Hrnjak, P. ￿Carbon Dioxide is Becoming Stronger Contender.￿ IIR￿KGH Conference, Belgrade, 2008 December.
  • Hrnjak, P. "Carbon Dioxide as Refrigerant Challenges, the Role and the Prospective." 6th International Conference on Compressors and Refrigeration, Xi'an, China, 25-28 September 2008.
  • Hrnjak, P., J. Manzione, D. Adams, D. Garski, and S. Collier. "Successful Conversion of R134a ECU Air Conditioner to R744." 8th IIF/IIR Gustav Lorentzen Conference on Natural Working Fluids, Copenhagen/Denmark, Session T3, CDP10-T3-02, 7-10 September 2008.
  • Elbel, S. and P. Hrnjak. "Ejector Refrigeration: An Overview of Historical and Present Developments with an Emphasis on Air-conditioning Applications." Proceedings of the 12th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2008, paper 2350.
  • Peuker, S. and P. Hrnjak. ￿Refrigerant Mass and Oil Migration during Start-up Transient.￿ Proceedings of the 12th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2008, paper 2169.
  • Bowers, C. D. and P. Hrnjak. ￿Developing Two-phase R134a Flow after an Expansion Valve in an 8.7mm Tube.￿ Proceedings of the 12th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2008, paper 2398.
  • Zhang, P. and P. Hrnjak. ￿Air-side Performance of a Parallel Fin Parallel Flow (PF2 ) Heat Exchanger in Sequential Frosting.￿ Proceedings of the 12th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17 July 2008, paper 2275.
  • Peuker, J. M. and P. Hrnjak. ￿Investigation to Improve Efficiency of Transcritical R744 Two-stage Vapor Compression Systems.￿ Proceedings of the 12th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 14-17, July 2008, paper 2171.
  • Pamitran, A. S., K. I. Choi, and J. T. Oh, P. Hrnjak. "Flow Boiling Heat Transfer of R410A in 0.5mm and 0.3mm Diameter Horizontal Tube." Summer Annual Conference SAREK, The Society of Air-Conditioning and Refrigeration Engineers of Korea, 25 June 2008.
  • Peuker, S. and P. Hrnjak. ￿Experiences from Experimental Investigation of an R744 Dual Evaporator Automotive A/C System.￿ 2008 World Congress, Detroit, MI, 14-17 April 2008, SAE Technical Papers.
  • Wujek, S. S. and P. Hrnjak. "Using Density to Calculate the Oil Circulation Ratio of a PAG Oil in R134a." 2008 World Congress, Detroit, MI, 14-17 April 2008, SAE Technical Papers.
  • Bowers, C. D. and P. Hrnjak. ￿Developing Flow Map for Two-phase R134a after Expansion Device.￿ 2008 World Congress, Detroit, MI, 14-17 April 2008, SAE Technical Papers.
  • Hrnjak, P. "Carbon Dioxide as Refrigerant in New Circumstances." 38th International Congress on Heating, Refrigeration and Air Conditioning, Belgrade, Serbia, 2007 December.
  • Hrnjak, P. "Carbon Dioxide, State-of-the-Art and Perspectives." (Keynote Lecture), AICARR-PADUA, Italy, 4 December 2007.
  • Field, B. and P. Hrnjak. ￿Visualization of Two-phase Refrigerant and Refrigerant-oil Flow in a Microchannel.￿ Proceedings of ASME International Mechanical Engineering Congress and Exposition, Seattle, WA, vol. 8, 11-15 November 2007, pp. 1647-1656.
  • Bowers, C. D. and P. Hrnjak. ￿Using Change Point Analysis for Image Processing of Developing Adiabatic Two-phase Flow after Expansion Valve.￿ Proceedings of the 5th Joint ASME/JSME Fluids Engineering Summer Conference, San Diego, CA, FEDSM 2007, vol. 2 FORA, no. A, 30 July-2 August 2007, pp. 169-174.
  • Wujek, S. S., P. Hrnjak, and C. J. Seeton. ￿Online Measurement Techniques for Determining Oil Circulation Rate.￿ Proceedings of the 5th Joint ASME/JSME Fluids Engineering Summer Conference, San Diego, CA, 30 July-2 August, 2007, FEDSM 2007 2 FORA, no. A, pp. 181-186.
  • Wujek, S. S., P. Hrnjak, and C. J. Seeton. "Online Measurement Techniques for Determining Oil Circulation Rate.￿ Proceedings of the 5th Joint ASME/JSME Fluids Engineering Summer Conference, San Diego, CA, vol. 2 FORA, no. A, 30 July-2 August 2007, pp. 181-186.
  • Hrnjak, P. and C. Y. Park. ￿In-tube Heat Transfer and Pressure Drop Characteristics of Pure NH3 and CO2 in Refrigeration Systems.￿ IIR International Conference: Ammonia Refrigeration Technology for Today and Tomorrow, Ohrid, Republic of Macedonia, 2007 April.
  • Elbel, S. and P. Hrnjak. ￿Experimental Validation of a CO2 Prototype Ejector with Integrated High-side Control.￿ VDA Meeting, Saalfelden, Austria, 2007.
  • Park, C. Y. and P. Hrnjak. ￿CO2 Flow Boiling Heat Transfer and Flow Pattern at Low Temperatures in Horizontal Smooth Tubes.￿ Proceedings of ASME International Mechanical Engineering Conference and Exposition, Chicago, IL, 5-10 November 2006.
  • Park, C. Y. and P. Hrnjak. ￿CO2 Flow Boiling Heat Transfer and Flow Pattern at Low Temperatures in Horizontal Smooth Tubes.￿ 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5-10 November 2006.
  • Zhang, P. and P. Hrnjak. ￿Air-side Performance Evaluation of Three Types of Heat Exchangers in Dry, Wet, and Periodic Frosting Conditions.￿ Proceedings of the 11th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 17-20 July 2006, paper R177.
  • Adams, D. C., J. D. Burr, P. Hrnjak, and T. A. Newell. ￿Void Fraction of CO2 and Ammonia in Multiport Aluminum Microchannel Tubes.￿ Proceedings of the 11th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 17-20 July 2006, paper R175.
  • Adams, D. C., J. D. Burr, P. Hrnjak, and T. A. Newell. ￿Two-phase Pressure Drop of CO2, Ammonia and R245fa in Multiport Aluminum Microchannel Tubes.￿ Proceedings of the 11th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 17-20 July 2006, paper R174.
  • Park, C. Y. and P. Hrnjak. ￿CO2 and R410A Flow Boiling Heat Transfer and Pressure Drop at Low Temperatures in a Horizontal Smooth Tube.￿ Proceedings of the 11th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 17-20 July 2006, paper R173.
  • Seeton, C. J. and P. Hrnjak. ￿Thermophysical Properties of CO2 Lubricant Mixtures and Their Affect on 2-Phase Flow in Small Channels (Less than 1mm).￿ Proceedings of the 11th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 17-20 July 2006, paper R170.
  • Peuker, S. and P. Hrnjak. ￿R744 Two Evaporator System for US Army HMMWV.￿ Proceedings of the 11th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 17-20 July 2006, paper R166.
  • Elbel, S. and P. Hrnjak. ￿A Thermodynamic Property Chart as a Visual Aid to Illustrate the Interference between Expansion Work Recovery and Internal Heat Exchange.￿ Proceedings of the 11th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 17-20 July 2006, paper R165.
  • Wujek, S. S. and P. Hrnjak. "Effects of Oil on a Transcritical Carbon Dioxide Air Conditioning System ￿ some experiences -.￿ Proceedings of the 11th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 17-20 July 2006, paper R164.
  • Bowers, C. D., P. Hrnjak, and T. A. Newell. ￿Two-phase Refrigerant Distribution in a Micro-channel Manifold.￿ Proceedings of the 11th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 17-20 July 2006, paper R161.
  • Field, B. S. and P. Hrnjak. ￿Pressure Drop of Two-phase Refrigerant Oil Mixtures in a Small Channel.￿ Proceedings of the 11th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 17-20 July 2006, paper R148.
  • Field, B. and P. Hrnjak. "Adiabatic Two-phase Pressure Drop of Refrigerants in Small Channels." Proceedings of the 4th International Conference on Nanochannels, Microchannels and Minichannels, ICNMM2006, Limerick, Ireland, vol. 2006, no. B, 19-21 June 2006, pp. 1173-1180.
  • Elbel, S. and P. Hrnjak. ￿Experimental Validation and Design Study of a Transcritical CO2 Prototype Ejector System.￿ 7th IIR Gustav Lorentzen Conference on Natural Working Fluids, Trondheim, Norway, 28-31 May 2006.
  • Hrnjak, P. and X. Tu. ￿Single-phase Pressure Drop in Microchannels.￿ (Keynote Lecture), ECI Proceedings of the International Conference on Heat Transfer and Fluid Flow in Microscale, Castelvecchio Pascoli, Italy, 25-30 September 2005.
  • Park, C. Y. and P. Hrnjak. ￿Evaporation of CO2 in a Horizontal Smooth Tube.￿ Proceedings of IIR Conference Thermophysical Properties and Processes of Refrigerants, Vicenza, Italy, 31 August-2 September 2005, .pp 225-236.
  • DeAngelis, J. and P. Hrnjak. ￿Development of Transcritical R744 Systems for Small Commercial Applications.￿ Proceedings of IIR Conference Refrigeration Science and Technology, Vicenza, Italy, 31 August-2 September 2005.
  • Hrnjak, P. ￿Major Issues in Transcritical CO2 Systems.￿ (Keynote Lecture), Proceedings of the Fifth International Conference on Compressors and Refrigeration, Dalian City, The People￿s Republic of China, 18-21 July 2005.
  • Hrnjak, P. ￿Transcritical CO2 Systems.￿ Proceedings of the Fundamentals and Applications of the Heating, Ventilating and Air Conditioning (HVAC&R) Systems Conference, Kaist, Korea, 5-7 July 2005.
  • Hrnjak, P. ￿Charge Minimization in Ammonia Refrigeration Systems.￿ Proceedings of the International Institute of Refrigeration Conference on Ammonia Refrigerating Systems, Renewal and Improvement, Ohrid, Macedonia, 2005 May.
  • Memory, S., J-M. Yin, S. Collier, M. Gunter, P. Hrnjak, S. Peuker, S. Elbel, J. Manzione, N. Schultz, and J. Dolney. ￿Using R744 (CO2) to Cool an Up-armored M1114 HMMWV.￿ Proceedings of the Vehicle Thermal Management Systems Conference and Exhibition, Toronto, ON, Canada, 10-12 May 2005, SAE Technical Papers.
  • McEnaney, R. and P. Hrnjak. ￿Clutch Cycling Mode of Compressor Capacity Control of Transcritical R744 Systems Compared to R134a Systems.￿ Proceedings of the Vehicle Thermal Management Systems Conference and Exhibition, Toronto, ON, Canada, 10-12 May 2005, SAE Technical Papers.
  • Xia, Y., P. Hrnjak, and A. M. Jacobi. ￿Air-side Thermal-hydraulic Performance of Louvered-fin, Flat-tube Heat Exchangers with Sequential Frost-growth Cycles.￿ American Society of Heating, Refrigerating and Air-Conditioning Engineers, ASHRAE Winter Meeting, Orlando, FL, vol. 111, no. 1, 5-9 February 2005, pp. 487-495.
  • Hrnjak, P. "Charge Reduction in Ammonia Systems." (Keynote Lecture), IIR Conference, Ohrid, 2005.
  • Hrnjak, P. "Microchannel Heat Exchangers." (Keynote Lecture), 35th International Conference KGH, Beograd, 1 December 2004.
  • Xia, Y., P. Hrnjak, and A. M. Jacobi. ￿An Empirical Study of Frost Accumulation Effects on Louvered-fin, Microchannel Heat Exchangers.￿ Proceedings of the 10th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 12-15 July 2004, paper R054.
  • Park, C. Y. and P. Hrnjak. ￿Effect of Gas Cooler Size on Its Performance and Entire R744 A/C System.￿ International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 12-15 July 2004, paper R165.
  • Elbel, S. and P. Hrnjak. ￿Effect of Internal Heat Exchanger on Performance of Transcritical CO2 Systems with Ejector.￿ Proceedings of the 10th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, IN, 12-15 July 2004, paper R166.
  • Hrnjak, P. ￿Challenges and Results of Mobile Air Conditioning Cooling and Energy Efficiency Performance Exploration Project.￿ Proceedings of the 15th Annual Earth Technologies Forum and Mobile Air Conditioning Summit, Washington DC, 13-15 April 2004.
  • Hrnjak, P. "Flow Distribution Issues in Parallel Flow Heat Exchangers." ASHRAE Transactions, Anaheim, CA, vol. 110, no. 1, 25 January 2004, pp. 301-306.
  • Hrnjak, P. "Flow Distribution Issues in Parallel Flow Heat Exchangers." 2004 Winter Meeting - American Society of Heating, Refrigerating and Air-Conditioning Engineers, Anaheim, CA, 24-28 January 2004, pp. 263-268, Technical and Symposium Papers.
  • Hoehne, M. and P. Hrnjak. ￿Charge Minimization in Hydrocarbon Systems.￿ Proceedings of the IIR Conference, Gustav Lorentzen in Glasgow, 2004.
  • Li, X., J. Che, and P. Hrnjak. ￿Performance Improvement of a R134a Mobile A/C System by using Internal Heat Exchangers.￿ Proceedings of the SAE, 2004.
  • Hrnjak, P. "Refrigeration and its Environmental Impact." Keynote Lecture, CISBE-ASHRAE Worldwide Gathering of the Building Services Industry Conference, Edinburgh, 24-26 September 2003.
  • Hrnjak, P. ￿Developing Adiabatic Two-phase Flow in Headers ￿ Distribution Issue in Parallel Flow Microchannel Heat Exchangers.￿ Proceedings of the First International Conference on Microchannels and Minichannels, Rochester, NY, vol. 1, no. 3, 24-25 April 2003, pp. 207-214.
  • Nelson, S. and P. Hrnjak. ￿Effect of Internal Heat Exchanger on Performance of R134a Systems.￿ Proceedings of the Vehicle Thermal Management Systems Conference, VTMS , Brighton, United Kingdom, 18-21 May 2003, pp. 17-27.
  • Tu, X. and P. Hrnjak. ￿Experimental Investigation of Single-phase Flow Pressure Drop through Rectangular Microchannels.￿ Proceedings of the First International Conference on Microchannels and Minichannels, Rochester, NY, vol. 1, 24-25 April 2003, pp. 257-267.
  • Tu, X and P. Hrnjak. "Pressure Drop and Visualization of R-134a Two-phase Flow in a Rectangular Microchannel." ASHRAE 2003 Winter Meeting, Chicago, IL, vol. 109, no. 1, 26-29 January 2003, pp. 693-700, Technical and Symposium Papers.
  • Giannavola, M., J. Yin, C. W. Bullard, and P. Hrnjak. "Contribution of Heat Exchangers in Improved Performance of New Generation Automotive Air-conditioning System with R-744." ASHRAE 2003 Winter Meeting, Chicago, IL, vol. 109, no. 1, 26-29 January 2003, pp. 537-549, Technical and Symposium Papers.
  • Hrnjak, P. ￿Two-phase Flow Distribution in Headers of Parallel Flow Heat Exchangers and its Effect on Performance.￿ Proceedings of the HEFAT 2003, Victoria Falls.
  • Jang, J., and P. Hrnjak. ￿Flow Regimes and Heat Transfer in Condensation of Carbon Dioxide at Low Temperatures.￿ Proceedings of the HEFAT 2003, Victoria Falls.
  • Li, X., J. Che, and P. Hrnjak. ￿Effect of Internal Heat Exchanger on Performance of Mobile R134a Systems.￿ Proceedings of the IIR World Congress, Washington DC, 2003.
  • Zilly, J., J. Jang, and P. Hrnjak. ￿Condensation of Carbon Dioxide at Low Temperatures in Micro-finned Horizontal Tubes.￿ Proceedings of the International Institute of Refrigeration, Washington D.C, 2003.
  • Tu, X. and P. Hrnjak. ￿Pressure Drop Characteristics of R134A Two-phase Flow in Rectangular Microchannels.￿ Proceedings of ASME International Mechanical Engineering Congress and Exposition, New Orleans, LA, vol. 4, no. 4, 17-22 November 2002, pp. 211-220.
  • Song, S. M., P. Hrnjak, M. H. Kim, and C. W. Bullard. ￿Effect of Humidity and Inclination Angle on Microchannel Heat Exchanger Performance.￿ Proceedings of the 8th International Refrigeration and Air Conditioning Conference, Purdue University, West Lafayette, IN, 2002 July.
  • Ilic, S. M., P. Hrnjak, and C. W. Bullard. ￿Experimental Comparison of Continuous vs. Pulsed Flow Modulation in Vapor Compression Systems.￿ Proceedings of the 8th International Refrigeration Conference, West Lafayette, IN, 2002 July.
  • Nino, V., P. Hrnjak, and T. A. Newell. ￿Analysis of Void Fraction in Microchannels.￿ Proceedings of the 8th International Refrigeration and Air Conditioning Conference, Purdue University, West Lafayette, IN, 2002 July.
  • Tompkins, D. M., T. Yoo, P. Hrnjak, T. A. Newell, and K. Cho. ￿Flow Distribution and Pressure Drop in Micro-channel Manifolds.￿ Proceedings of the 8th International Refrigeration Conference, Purdue University, West Lafayette, IN, 2002 July.
  • Tu, X., P. Hrnjak, and C. W. Bullard. ￿Flow of R134A through Micro-Orifices.￿ Proceedings of the 8th International Refrigeration and Air Conditioning Conference, Purdue University, West Lafayette, IN, 2002 July.
  • Park, C. Y. and P. Hrnjak. ￿R-410A Air Conditioning System with Microchannel Condenser." Proceedings of the 8th International Refrigeration Conference, Purdue University, West Lafayette, IN, 2002 July.
  • Song, S., C. W. Bullard, and P. Hrnjak. "Frost Deposition and Refrigerant Distribution in Microchannel Heat Exchangers." ASHRAE Transactions 2002, Honolulu, HI, vol. 108, no. 2, 22-26 June 2002, pp. 944-953.
  • Mathur, G. D. and P. Hrnjak. "Visualization of the Effects of Spiral Angle on the Enhancement of In-tube Flow Boiling in Microfin Tubes: Discussion." ASHRAE Transactions 2002, Honolulu, HI, vol. 108, no. 2, 22-26 June 2002, pp. 516.
  • Rasmussen, B. P., A. Alleyne, C. W. Bullard, P. Hrnjak, and N. R. Miller. ￿A Control-oriented Modeling and Analysis of Automotive Transcritical A/C System Dynamics.￿ Proceedings of the American Control Conference, Anchorage, Alaska, vol. 4, 8-10 May 2002, pp. 3111-3116.
  • Newell, T. A., P. Hrnjak, C. Monroe, V. Nino, D. M. Tompkins, T. Yoo. ￿Microchannel Heat Exchanger Characteristics in Air Conditioning and Refrigeration Systems,￿ Proceedings of the 5th International HVAC&R Technology Symposium, Istanbul, Turkey, 29 April-1 May 2002.
  • Hrnjak, P. and S. H. Hong. ￿Heat Transfer in Single Phase Secondary Refrigerants at Low Temperatures.￿ Proceedings of Heat Transfer, Fluid Mechanics and Thermodynamics, Kruger Park, South Africa, vol. 1, part 2, 2002 April, pp. 1121-1126.
  • Tu, X. and P. Hrnjak. ￿Liquid Superheat during Flow Boiling in Microchannels.￿ Proceedings of Heat Transfer, Fluid Mechanics and Thermodynamics, Kruger Park, South Africa, vol. 1, part 2, 2002 April, pp. 1060-1065.
  • Rasmussen, B. P., A. Musser, A. Alleyne, C. W. Bullard, P. Hrnjak, and N. R. Miller. ￿A Control-oriented Model of Transcritical Air-conditioning System Dynamics.￿ Proceedings of the SAE World Congress, Detroit, MI, 4-7 March 2002, SAE Technical Papers.
  • Fei, P., D. J. Cantrak, and P. Hrnjak. ￿Refrigerant Distribution in the Inlet Header of Plate Evaporators.￿ Proceedings of the SAE World Congress, Detroit, MI, 4-7 March 2002, SAE Technical Papers.
  • Hrnjak, P. ￿Some Issues in R744 Heat Exchangers.￿ Proceedings of the VDA Winter Meeting, Saalfinden, Austria, 2002 January.
  • Singh, G. M., P. Hrnjak, C. W. Bullard. "Flow of Refrigerant 134a through Orifice Tubes." 2002 ASHRAE Winter Meeting, Atlantic City, NJ, vol. 108, no. 1, 13-16 January 2002, pp. 145.
  • Bullard, C. W., J. M. Yin, P. Hrnjak, and M. Heidenreich. "Compact Counterflow Gas Cooler for R-744." 2002 ASHRAE Winter Meeting, Atlantic City, NJ, vol. 108, no. 1, 13-16 January 2002, pp. 487-491.
  • Hrnjak, P. ￿New Options in Increasing Energy Efficiency in Commercial Refrigeration ￿ Microchannel Heat Exchangers.￿ Proceedings of the FREE2002, Milano, Italy, 2002, pp. 1-18.
  • Verma, P., D. M. Carlson, Y. Wu, P. Hrnjak, and C. W. Bullard. ￿Experimentally Validated Model for Frosting of Plain-fin-round-tube Heat Exchangers.￿ Proceedings of IIR Conference New Technologies in Commercial Refrigeration, Urbana, IL, 2002, pp. 158-168.
  • Verma, P., C. W. Bullard, and P. Hrnjak. ￿Design Strategies for Reducing Performance Degradation due to Frosting of Display Case Heat Exchangers.￿ Proceedings of IIR Conference New Technologies in Commercial Refrigeration, Urbana, IL, 2002, pp. 227-237.
  • Hrnjak, P. ￿Microchannel Heat Exchangers as a Design Option for Charge Minimization on NH3 and HC Systems.￿ Proceedings of IIR Conference Zero Leakage - Minimal Charge, Stockholm, 2002, pp. 111-118.
  • Jang, J. and P. Hrnjak. ￿Condensation of Carbon Dioxide at Low Temperatures.￿ Proceedings of the International Institute of Refrigeration Conference on Natural Refrigerants, Guangchou, China, 2002, pp. 64-74.
  • Bullard, C. W. and P. Hrnjak. ￿Advanced Technologies for Auto A/C Components.￿ Proceedings of the 7th International Energy Agency Heat Pump Conference, Beijing, China, 2002.
  • Richter, M. R., C. W. Bullard, and P. Hrnjak. ￿Effect of Comfort Constraints on Cycle Efficiencies.￿ Proceedings of the ASME International Mechanical Engineering Congress and Exposition, New York, NY, vol. 41, 11-16 November 2001, pp. 275-286.
  • Ni￿V., W. Payne, P. Hrnjak, T. A. Newell, and C. A. Infante Ferreira. ￿Two-phase Pressure Drop in Microchannels.￿ Proceedings of the International Institute of Refrigeration Conference, Paderborn, Germany, 2001 October, pp. 225-233.
  • Hong, S. H. and P. Hrnjak. ￿Heat Transfer in Thermally Developing Laminar Flow in Pipes of Some Secondary Refrigerants and Effect of Return Bend.￿ Proceedings of the International Institute of Refrigeration Conference, Paderborn, Germany, 2001 October, pp. 455-462.
  • Hrnjak, P. ￿Transcritical CO2 Cycles in Automotive and Residential Systems: State of the Art, Advances, Potentials.￿ Proceedings of the KOSEF/ACRC Joint Symposium, UIUC, Urbana, IL, 2001 July.
  • Boewe, D. E., C. W. Bullard, J. M. Yin, and P. Hrnjak. "Contribution of Internal Heat Exchanger to Transcritical R-744 Cycle Performance." 2001 ASHRAE Annual Meeting, Cincinnati, OH, vol. 107, no. 2, 24-27 June 2001, pp. 189-203.
  • Hrnjak, P., Y. Mao, K. Elovitz, and J. Behr. "Defrost Issues in Indirectly Refrigerated Display Cases." 2001 ASHRAE Annual Meeting,,Cincinnati, OH, vol. 107, no. 2, 24-27 June 2001, pp. 466-472.
  • Fang, X., C. W. Bullard, and P. Hrnjak. "Modeling and Analysis of Gas Coolers." ASHRAE Transactions -- 2001 Winter Meeting, Atlanta, GA, vol. 107, no. 2, 27-31 January 2001, pp. 4-13.
  • Fang, X., C. W. Bullard, and P. Hrnjak. "Heat Transfer and Pressure Drop of Gas Coolers." ASHRAE 2001 Winter Meeting, Atlanta, GA, 27-31 January 2001, pp. 255-266.
  • Hrnjak, P. and A. D. Litch. ￿Charge Reduction in Ammonia Chiller using Air-cooled Condensers with Aluminum Microchannel Tubes.￿ Proceedings of International Institute of Ammonia Refrigeration, Long Beach, CA, 2001, pp. 235-267.
  • Hrnjak, P. ￿Heat Transfer Issues in Laminar Flow of Single-phase Secondary Refrigerants through the Pipes.￿ Proceedings IEA Annex 26: Natural Working Fluids, Stockholm, Sweden, 2000 October.
  • Chappell, J., J. Drozdek, C. Cusano, P. Hrnjak, N. R. Miller, and T. A. Newell. ￿The State of Compressor Lubrication as Measured by Contact Resistance during Two Transient Tests.￿ Proceedings of the International Compressor Engineering Conference, Purdue University, West Lafayette, IN, 25-28 July 2000, pp. 353-360, paper 1407.
  • Richter, M. R., S. M. Song, J. M. Yin, M-H. Kim, C. W. Bullard, and P. Hrnjak. ￿Transcritical CO2 Heat Pump for a Residential Application.￿ Proceedings of the IIR Gustav Lorenzen Conference on Natural Refrigerants, Purdue University, West Lafayette, IN, 2000 July, pp. 9-16.
  • Litch, A. D. and P. Hrnjak. ￿Low-charge Air-cooled Ammonia Chiller with Aluminum Microchannel Condenser.￿ Proceedings of the IIR Gustav Lorenzen Conference on Natural Refrigerants, Purdue University, West Lafayette, IN, 2000 July, pp. 543-551.
  • Yin, J. M., C. W. Bullard, and P. Hrnjak. ￿Design Strategies for R744 Gas Coolers.￿ Proceedings of the IIR Gustav Lorenzen Conference on Natural Refrigerants, Purdue University, West Lafayette, IN, 2000 July, pp. 315-322.
  • Yin, J. M., C. W. Bullard, and P. Hrnjak. ￿Performance of Transcritical and Subcritical R410A Residential A/C and H/P System.￿ Proceedings of the International Refrigeration and Air Conditioning Conference, Purdue University, West Lafayette, IN, 2000 July, pp. 169-176.
  • Bullard, C. W., J. M. Yin, and P. Hrnjak. ￿Transcritical CO2 Mobile Heat Pump and A/C System Experimental and Model Results.￿ Proceedings of the SAE Phoenix Meeting, Phoenix, AZ, 2000 June.
  • Solberg, J., N. R. Miller, and P. Hrnjak. ￿A Sensor for Estimating the Liquid Mass Fraction of the Refrigerant Exiting an Evaporator.￿ Proceedings of the SAE World Congress, Detroit, MI, 6-9 March 2000, SAE paper 2000-01-0976.
  • Drozdek, J., J. Chappel, C. Cusano, P. Hrnjak, N. R. Miller, and T. A. Newell. ￿Methods for Detection of Lubrication Failure Applied to a Swashplate Compressor.￿ Proceedings of the SAE World Congress, Detroit, MI, 6-9 March 2000, SAE paper 2000-01-0974.
  • McEnaney, R. P. and P. Hrnjak. ￿Control Strategies for Transcritical R744 Systems.￿ Proceedings of the SAE World Congress, Detroit, MI, 6-9 March 2000, SAE paper 2000-01-1272.
  • Beaver, A., P. Hrnjak, J. Yin, and C. W. Bullard. ￿Effects of Distribution in Headers of Micro-channel Evaporators on Transcritical CO2 Heat Pump Performance.￿ Proceedings of the ASME Advanced Energy Systems Division, Orlando, FL, AES-vol. 40, 2000, pp. 55-64.
  • Kim, M.-H. , J. M. Yin, C. W. Bullard, and P. S. Hrnjak. ￿Development of a Micro-channel Evaporator Model for a CO2 Mobile Air Conditioner.￿ Proceedings of the ASME Advanced Energy Systems Division, Orlando, FL, AES-vol. 40, 2000, pp. 47-54.
  • Giannavola, M. S., R. Murphy, J. M. Yin, M-H. Kim, C. W. Bullard, and P. Hrnjak. "Experimental Investigations of an Automotive Heat Pump Prototype for Military, SUV and Compact Cars." Proceedings of the IIR Gustav Lorenzen Conference on Natural Refrigerants, Purdue University, West Lafayette, IN, 2000, pp. 115-122.
  • Shannon, M. A., M. L. Philpott, N. R. Miller, C. W. Bullard, D. J. Beebe, A. M. Jacobi, P. Hrnjak, T. Saif, N. Aluru, H. Sehitoglu, A. Rockett, and J. Economy. ￿Integrated Mesoscopic Cooler Circuits (IMCCS).￿ Proceedings of the International Mechanical Engineering Congress and Exposition, Nashville, TN, 15-20 November 1999, pp. 75-81.
  • Beaver, A., J. M. Yin, C. W. Bullard, and P. Hrnjak. ￿Experimental and Model Study of the Heat Pump/Air Conditioning Systems based on Transcritical Cycle with R744.￿ Proceedings of XXth International Congress of Refrigeration, Sydney Australia, 1999 September.
  • Mao, Y. and P. Hrnjak. ￿Defrost Issues of Display Cabinets with DX Evaporators and Heat Exchangers with Secondary Refrigerants.￿ Proceedings of XXth International Congress of Refrigeration, Sydney, Australia 1999 September.
  • Park, Y. C., J. M. Yin, C. W. Bullard, and P. Hrnjak. ￿Experimental and Model Analysis of Control and Operating Parameters of Transcritical CO2 Mobile Air Conditioning System.￿ Proceedings of the VTMS Conference, London, United Kingdom, 1999 May, pp. 163-170.
  • Boewe, D. E., J. M. Yin, Y. C. Park, C. W. Bullard, and P. Hrnjak. ￿The Role of Suction Line Heat Exchanger in Transcritical R744 Mobile Air Conditioning Systems--Experimental and Model Analysis.￿ Proceedings of the SAE Conference, Detroit, MI, 1-4 March 1999, SAE paper 1999-01-0583.
  • Rodarte, E., G. Singh, N. R. Miller, and P. Hrnjak. ￿Noise Generation from Expansion Devices in Refrigerant.￿ Proceedings of the SAE Conference, Detroit, MI, 1-4 March 1999, SAE paper 1999-01-0866.
  • McEnaney, R. P., Y. C. Park, J. M. Yin, and P. Hrnjak. ￿Performance of the Prototype of a Transcritical R744 Mobile Air Conditioning System.￿ Proceedings of the SAE Conference, Detroit, MI, 1-4 March 1999, SAE paper 1999-01-0872.
  • Rodarte, E., G. Singh, N. R. Miller, and P. Hrnjak. ￿Refrigerant Expansion Noise Propagation through Downstream Tube Walls.￿ Proceedings of the SAE Conference, Detroit, MI, 1999 March, SAE paper 1999-01-1197.
  • Park, Y. C., R. McEnaney, D. E. Boewe, J. M. Yin, and P. Hrnjak. ￿Steady State and Cycling Performance of a Typical R134a Mobile Air Conditioning System.￿ Proceedings of the SAE Conference, Detroit, MI, 1-4 March 1999, SAE paper 1999-01-1190.
  • Mao, Y., W. Terrell, and P. Hrnjak. ￿Heat Exchanger Frosting Patterns with Evaporating R404A and Single Phase Secondary Refrigerant.￿ Proceedings of the International Refrigeration and Air Conditioning Conference, Purdue University, West Lafayette, IN, 1998 July, pp. 277-282.
  • McEnaney, R. P., D. E. Boewe, J. M. Yin, Y. C. Park, C. W. Bullard, and P. Hrnjak. ￿Experimental Comparison of Mobile Air Conditioning Systems when Operated with Transcritical CO2 Versus Conventional R134a.￿ Proceedings of the International Refrigeration and Air Conditioning Conference, Purdue University, West Lafayette, IN, 1998 July, pp. 145-150.
  • Yin, J., Y. Park, D. Boewe, R. McEnaney, A. Beaver, C. W. Bullard, and P. Hrnjak. ￿Experimental and Model Comparison of Transcritical CO2 Versus R134a and R410 System Performance.￿ Proceedings of IIR Conference, Oslo, Norway, 1998 June, pp. 376-385.
  • Mao, Y., W. Terrell, and P. Hrnjak. ￿Performance of a Display Case at Low Temperatures Refrigerated with R404a and Secondary Coolants.￿ Proceedings of the International Institute of Refrigeration, Refrigeration Science and Technology, Cambridge, United Kingdom, 1998 April, pp. 181-188.
  • Rodarte, E., N. R. Miller, and P. Hrnjak. ￿Use of Stereolithography as a Design Tool for Developing Quiet Plate Mobile Air Conditioning Evaporators.￿ Proceedings of the SAE International and Exposition Conference, Detroit, MI, 23-26 February 1998, SAE paper 980287.
  • Terrell, Jr., W., Y. Mao, and P. Hrnjak. ￿Tests of Supermarket Display Cases when Operating with Secondary Refrigerants,￿ Proceedings of International Conference on Ozone Protecting Technologies, Baltimore, MD, 1997 November, pp. 176-186.
  • Peixoto, R. and P. Hrnjak. ￿CFC Replacement in Supermarket Refrigeration.￿ Proceedings of the CIAR, Santiago, Chile, 1997 October, pp. 127-132.
  • Hrnjak, P. ￿Benefits and Penalties Associated with the Use of Secondary Loops.￿ Proceedings of NIST-ASHRAE Conference, Gaithersburg, MD, 1997 October, pp. 85-95.
  • Hrnjak, P. ￿Secondary Loops--Is it the Only Option for Some Natural Refrigerants?￿ Proceedings IEA Annex 22: Natural Working Fluids for Compression Refrigeration Systems, Gatlinburg, TN, 1997 October, pp. 197-206.
  • Hrnjak, P. ￿Thermal Contact Resistance in Plate Finned Tube Heat Exchangers--The Model to Predict Contact Pressure and Its Response to Variation of Influential Parameters.￿ Proceedings of XIXth International Congress of Refrigeration, The Hague, Holland, vol. IIIa, 1995 August, pp. 91-98.
  • Peixoto, R., F. Johnson, J. Meyers, and P. Hrnjak. ￿Analise Experimental de Trocadores de Calor Tubo Capilar-Linha de Succao Utilizando HFC-134a (Experimental Analysis of the Suction Line/Capillary Tube Heat Exchanger When Using R134a).￿ Proceedings of 5th Thermal Sciences Brazilian Meeting, Sao Paolo, Brazil, 1994 December, pp. 455-458.
  • Markoski, M. and P. Hrnjak. ￿Thermodynamic Analysis of Air Dehumidification.￿ Proceedings of the Saopstenja Masinskog Fakulteta, Belgrade, Yugoslavia (in Serbocroatian), 1992 January, pp. 23-27.
  • Markoski, M. and P. Hrnjak. ￿The Influence of Tube Row Position on the Heat Transfer Coefficient in the Bundle of Bimetallic Cu Al Tubes Experimental Investigations.￿ Proceedings of XVIIIth International Congress of Refrigeration, Montreal, Canada, vol. III, 1991 August, pp. 1321￿1324.
  • Markoski, M., Z. Stajic, and P. S. Hrnjak. ￿Experimental Study of Heat Transfer between Inside Evaporating and Outside Condensing R12 on Integral External Spirally Finned Tubes.￿ Proceedings of the XVIIIth International Congress of Refrigeration, Montreal, Canada, vol. III, 1991 August, pp. 1312-1315.
  • Markoski, M. and P. S. Hrnjak. ￿Thermodynamic Analysis of Air Drying Process on the Cold Surface.￿ Proceedings of XVIIIth International Congress of Refrigeration, Montreal, Canada, Vol. II, 1991 August, pp. 830-835.
  • Markoski, M., P. S. Hrnjak, and Z. Stajic. ￿Development Philosophy for Thermal Apparatus.￿ Proceedings of XXI Congress of Yugoslav Society of Heating, Refrigeration and Air Conditioning Engineers, Belgrade, Yugoslavia (in Serbocroatian), 1990 November, pp. 263-266.
  • Sheffield, J. W. and P. S. Hrnjak. ￿Contact Resistance in Plate Finned Tubed Heat Exchangers.￿ Proceedings of the 9th International Heat Transfer Conference, Jerusalem, Israel, 1990 August.
  • Markoski, M. and P. S. Hrnjak. ￿Exergetic Efficiency for Conversion of Concentrational into Thermal Nonequilibrium in Thermodynamics Analysis and Improvement of Energy Systems." Pergamon Press, Ruxian, C. and Moran, M. J., eds., Oxford, United Kingdom, 1989, pp. 583￿589.
  • Markoski, M. and P. S. Hrnjak. ￿Determination of Exergetic Efficiency for Evaporation of Water in Evaporative Condensers.￿ Proceedings of XVIIth International Congress of Refrigeration, Vienna, Austria, vol. B, 1987, pp. 35-39.
  • Hrnjak, P. S. ￿Mathematical Model for Dynamic Behavior of Evaporator-Thermoexpansion Valve Loop Influence of the Bulb.￿ Proceedings of XIIIth Congress of Yugoslav Society of Heating, Refrigeration and Air Conditioning Engineers, Klimatizacija Grejanje Hladjenje, Belgrade, Yugoslavia, 1985 November.
  • Vujic, S., M. Markoski, P. S. Hrnjak, and N. Ilic. ￿Thermal Characteristic of Specially Designed Copper Aluminum Finned Tubes.￿ Proceedings of the INTERKLIMA, Zagreb, Yugoslavia (in Serbocroatian), 1985 June, pp. 233￿244.
  • Hrnjak, P. S. ￿Steady State Mathematical Model for Evaporator-Thermostatic Expansion Valve Loop.￿ Proceedings of the INTERKLIMA, Zagreb, Yugoslavia (in Serbocroatian), 1984 June, pp. 267-276.
  • Vujic, S., M. Markoski, P. S. Hrnjak, and M. Vranic. ￿Calorimetric Installation for Testing Monoblock and Split Type Air Conditioning Equipment at Refrigeration Laboratory in Belgrade.￿ Proceedings of the INTERKLIMA, Zagreb, Yugoslavia (in Serbocroatian). 1981 June, pp. 403-409.

Research Honors

  • 2014 Fellow ASME, American Society of Mechanical Engineers
  • 2013 Fellow SAE, Society of Automotive Engineers
  • 2012 Academician - Academy of Engineering Sciences AINS Serbia
  • 2012 J&E Hall Medal, IoR (Institute of Refrigeration, London f. 1899) This single annual award recognizes the most noteworthy practical contribution to the science of refrigeration.
  • 2011 Gustav Lorentzen Medal, IIR (International Institute of Refrigeration, Paris f. 1908). The prize is awarded every four years to one person with outstanding and original achievements in academic or industrial research, innovation or development, in all fields of refrigeration, thus promoting creativity and renewal.
  • Fellow ASHRAE, American Society of Heating, Refrigeration and Air Conditioning Engineers
  • 2008 The Ritter von Rittinger award. The highest international award in the air conditioning, heat pump and refrigeration field by IEA. This award highlights outstanding contributions to the advancement of international collaboration in research, policy development and applications for energy-efficient heat pumping technologies. It is awarded every three years. The Rittinger award is named for Peter Ritter von Rittinger who is credited with the design and installation of the first energy-conserving heat pump system at a salt works in Upper Austria in 1855.
  • 2004-2005 Environmental Excellence in Weapon System Acquisition (EEWSA) Award - US Army. The award is the Army￿s highest honor for outstanding environmental stewardship during the acquisition of weapon systems that will support the nation￿s military objectives.