University of Illinois at Urbana-Champaign
The Grainger College of Engineering
Mechanical Science & Engineering

Stefan Elbel

Stefan Elbel
Stefan Elbel
Research Assistant Professor
(217) 244-1531
2121 Mechanical Engineering Lab
Co-Director, ACRC
(217) 244-1531
2121 Mechanical Engineering Lab

Education

  • Ph.D. in Mechanical Engineering, University of Illinois at Urbana-Champaign, 2007
  • M.Sc. in Mechanical Engineering, University of Illinois at Urbana-Champaign, 2003
  • Diplom-Ingenieur (FH) in Automotive Engineering/Mechatronics, Esslingen University of Applied Sciences (Germany), 2000

Academic Positions

  • Co-Director, Air Conditioning and Refrigeration Center (ACRC), University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering, 2022 - date (0%)
  • Research Assistant Professor, University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering, 2018 - date (2018: 51%, 2019: 65%, 2020 - date: 83.2%)

Short Courses

  • An update on the transition to flammable refrigerants: Refrigerant gas leak detectors, Short course presentation at Purdue University, West Lafayette, IN, USA, July 10, 2022
  • Ejector design for vapor compression systems: 1. Ejector working principles and background; 2. Ejector implementation and application; 3. Current and future challenges in ejector research; Multiple short course presentations at Purdue University, West Lafayette, IN, USA, July 10, 2022
  • Flame-free fittings for flammable refrigerants, Short course at Purdue University, West Lafayette, IN, USA, July 8, 2018
  • Training course on transcritical CO2 technology, Short course for practicing engineers organized by Creative Thermal Solutions, Inc., Urbana, IL September 20-21, 2016
  • Training course on economical design of efficient bottle coolers utilizing carbon dioxide, Short course for practicing engineers organized by Creative Thermal Solutions, Inc., Urbana, IL September 22-25, 2015
  • Latest technology trends in low-charge hydrocarbon refrigeration, Short course for practicing engineers organized by Creative Thermal Solutions, Inc., Urbana, IL January 22-23, 2015
  • Training course on economical design of efficient bottle coolers utilizing carbon dioxide, Short course for practicing engineers organized by Creative Thermal Solutions, Inc., Urbana, IL June 24-27, 2014
  • Economical design of efficient bottle coolers utilizing CO2, Short course for practicing engineers organized by Creative Thermal Solutions, Inc., Urbana, IL June 11-14, 2013
  • CO2 as the refrigerant in bottle coolers, Short course for practicing engineers organized by Creative Thermal Solutions, Inc., Urbana, IL July 6-12, 2012
  • Experience with transcritical CO2 systems and their efficiency improvements, Short course in supermarket refrigeration organized by Creative Thermal Solutions, Inc. and the Air Conditioning and Refrigeration Center at the University of Illinois at Urbana-Champaign, Urbana, IL, USA, February 23-24, 2010
  • Update on natural refrigerants: military environmental control units, Short course (together with J.A. Manzione/US. Army) at Purdue University, West Lafayette, IN, USA, July 12-13, 2008

Other Undergraduate Advising Activities

  • Advisor of winning 2007 University of Illinois Solar Decathlon Thermal Comfort Team

Research Statement

Dr. Elbel is interested in experimental and numerical research in the areas of thermodynamics, fluid mechanics, and heat transfer. His focus is on energy conversion systems with specialization in vapor compression technology using synthetic and natural refrigerants. He conducts both fundamental and applied research on components and systems used in mobile, residential, commercial, and industrial heating and cooling applications.

Dr. Elbel has been researching transcritical carbon dioxide cooling and heating cycles for a large variety of applications for more than 15 years. He has worked extensively on designing and improving refrigerant ejector systems to increase the energy efficiency of vapor compression cycles. His interest in expansion work recovery has been extended to vortex tubes that offer attractive improvement potentials at very low cost. He is also working on waste heat recovery systems that allow the efficient generation of waste heat driven cooling as a promising alternative to absorption cooling systems.

Research Interests

  • Fundamental and applied research on components and systems used in mobile, residential, commercial, and industrial heating and cooling applications to support future decarbonization goals
  • Energy conversion systems with specialization in sustainable vapor compression technology using synthetic and natural low-GWP refrigerants
  • Experimental and numerical research in thermodynamics, fluid mechanics, and heat transfer

Research Areas

  • Energy
  • Environment
  • Fluid Mechanics
  • Security and Defense
  • Transportation

Selected Articles in Journals

  • Kang M., Elbel S., 2023, "Novel regenerator design for caloric cycles using artificial neural network – genetic algorithm method and additive manufacturing," Energy Reports (accepted manuscript)
  • Che M., Elbel S., 2022, "Comparison of local and averaged air-side heat transfer coefficients on fin-and-tube heat exchangers obtained with experimental and numerical methods," J. Therm. Sci. Eng. Appl., 14(7): 071013
  • Zhang Y., Elbel S., 2021, "Synchronized measurements of noise characteristics and flow regimes near the thermal expansion valve using R134a refrigerant," Int. J. Refrig., 132:119-132
  • Che M., Elbel S., 2021, "Experimental quantification of air-side row-by-row heat transfer coefficients on fin-and-tube heat exchangers," Int. J. Refrig., 131:657-665
  • Haider M., Elbel S., 2021, "Development of ejector performance map for predicting fixed-geometry two-phase ejector performance for wide range of operating conditions," Int. J. Refrig., 128:232-241
  • Che M., Elbel S., 2021, "Experimental study of local air-side heat transfer coefficient on real-scale heat exchanger fins by employing an absorption-based mass transfer method," Appl. Therm. Eng., 189:116718
  • Mahvi A.J., Boyina K., Musser A., Elbel S., Miljkovic N., 2021, "Superhydrophobic heat exchangers delay frost formation and enhance efficiency of electric vehicle heat pumps," Int. J. Heat Mass Tran., 172:121162
  • King W.P., Amos J., Azer M., Baker D., Bashir R., Best C., Bethke E., Boppart S.A., Bralts E., Dietkus R., Durack G., Elbel S., Elliott G., Fava J., Goldenfeld N., Goldstein M.H., Hayes C., Herndon N., Jamison S., Johnson B., Johnson H., Johnson M., Kolaczynski J., Lee T., Maslov S., McGregor D., Milner D., Moller R., Mosley J., Musser A., Newberger M., O’Bryan L., O’Leary J., Pagano A., Philpott M., Pianfetti B., Pille A., Pizzuto L., Rubessa M., Rylowicz S., Shipley C., Stewart B., Switzky R., Tawfick S., Wheeler M., White K., Wood E., Wood C., Wooldridge A.R., 2020, "Emergency ventilator for COVID-19," PLoS One, 15(12): e0244963
  • Zhang Y., Elbel S., 2020, "Visualization study of the relationship between the orientation of tube and the flow regimes near the expansion valve," SAE Int. J. Adv. & Curr. Prac. in Mobility, Technical Paper 2020-01-1256
  • Gullo P., Kærn M.R., Haida M., Smolka J., Elbel S., 2020, "A review on current status of capacity control techniques for two-phase ejectors," Int. J. Refrig., 119:64-79
  • Lawrence N., Elbel S., 2020, "Servicing and installing equipment using flammable refrigerants: assessment of field-made mechanical joints (ASHRAE RP-1808)," Science and Technology for the Built Environment, 26(5):621-630
  • Zhu J., Elbel S., 2020, "Experimental investigation of the influence of vortex control on transcritical R744 ejector and cycle performance," Appl. Therm. Eng., 164:114418
  • Zhu J., Elbel S., 2020, "CFD simulation of vortex flashing R134a flow expanded through convergent-divergent nozzles," Int. J. Refrig., 112:56-68
  • Zhu J., Elbel S., 2019, "Measurement of static pressure profiles of vortex flashing R134a flow expanded through convergent-divergent nozzles," Int. J. Refrig., 108:258-270
  • Che M., Elbel S., 2019, "An experimental method to quantify local air-side heat transfer coefficient through mass transfer measurements utilizing color change coatings," Int. J. Heat Mass Tran., 114:118624
  • Lawrence N., Elbel S., 2019, "Experimental investigation on control methods and strategies for off-design operation of the transcritical R744 two-phase ejector cycle," Int. J. Refrig., 106:570-582
  • Lawrence N., Elbel S., 2018, "Numerical investigation of the effect of microchannel evaporator design and operation on the improvement potential of ejector refrigeration cycles," Energy, 164:21-34
  • Zhu J., Botticella F., Elbel S., 2018, "Experimental investigation and theoretical analysis of oil circulation rates in ejector cooling cycles," Energy, 157:718-733
  • Zhu J., Elbel S., 2018, "Experimental investigation of a novel expansion device control mechanism: vortex control of initially subcooled flashing R134a flow expanded through convergent-divergent nozzles," Int. J. Refrig., 85:167-183
  • Zhu J., Elbel S., 2017, "Influence of geometric parameters on two-phase flow vortex control," SAE Int. J. Passeng. Cars - Mech. Syst. 10(1):121-127
  • Zhu J., Elbel S., 2016, "A new control mechanism for two-phase ejector in vapor compression cycles for automotive applications using adjustable motive nozzle inlet swirl," SAE Int. J. Passeng. Cars - Mech. Syst. 9(1):44-51
  • Lawrence N., Elbel S., 2016, "Experimental investigation on the effect of evaporator design and application of work recovery on the performance of two-phase ejector liquid recirculation cycles with R410A," Appl. Therm. Eng., 100:398-411
  • Elbel S., Lawrence N., 2016, "Review of recent developments in advanced ejector technology," Int. J. Refrig., 62:1-18
  • Lawrence N., S. Elbel, 2015, "Mathematical modeling and thermodynamic investigation of the use of two-phase ejectors for work recovery and liquid recirculation in refrigeration cycles," Int. J. Refrig., 58:41-52
  • Lawrence N., Elbel S., 2015, "Analysis of two-phase ejector performance metrics and comparison of R134a and CO2 ejector performance," Science and Technology for the Built Environment (formerly HVAC&R Res.), 21:515-525
  • Brown I.P., Sizov G., Critchley M., Yin J., Memory S., Elbel S., Bowers C., Petersen M., Hrnjak P., 2014, "Design and evaluation of interior permanent magnet compressor motors for commercial transcritical CO2 (R-744) heat pump water heaters," IEEE T. Ind. Appl., 51(1):576-586
  • Bowers C.D., Wrocklage D., Elbel S., Hrnjak P., 2014, "Evaluation of seasonal performance improvements in a 3-Ton air-conditioning heat pump system using a novel design of integrated electronic expansion valves and distributors," ASHRAE Tran., 120(1):1-8
  • Lawrence N., Elbel S., 2014, "Experimental investigation of an alternate two-phase ejector cycle with low-pressure refrigerants R134a and R1234yf," Int. J. Refrig., 38(2): 310-322
  • Petersen M., Bowers C., Elbel S., Hrnjak P., 2013, "Development of high efficiency carbon dioxide commercial heat pump water heater," HVAC&R Res., 19(7): 823-835
  • Wang X.F., Hrnjak P.S., Elbel S., Jacobi A.M., He M.G., 2013, "Heat transfer performance for a falling-film on horizontal flat tubes," J. Heat Transf., 135(7): 072901
  • Zhao H., Elbel S., Hrnjak P., 2013, "Controlled atmosphere brazing of aluminum heat exchangers," Weld J., 92(2): 44-46
  • Lawrence N., Elbel S., 2013, "Theoretical and practical comparison of two-phase ejector refrigeration cycles including first and second law analysis," Int. J. Refrig., 36(4): 1220-1232
  • Wang X.F., Hrnjak P.S., Elbel S., Jacobi A.M., He M., 2012, "Flow modes and mode transitions for falling films on flat tubes," J. Heat Transf., 134(2): 021801
  • Elbel S., 2011, "Historical and present developments of ejector refrigeration systems with emphasis on transcritical carbon dioxide air-conditioning applications," Int. J. Refrig., 34(7): 1545-1561
  • Elbel S., Hrnjak P., 2008, "Experimental validation of a prototype ejector designed to reduce throttling losses encountered in transcritical R744 system operation," Int. J. Refrig., 31(3): 411-422
  • Elbel S., Hrnjak P., 2004, "Flash gas bypass for improving the performance of transcritical R744 systems that use microchannel evaporators," Int. J. Refrig., 27(7): 724-735

Articles in Conference Proceedings

Refereed Conference Papers and Presentations

  • Inampudi S.T., Elbel S., 2022, "Experimental investigation into the effect of charge optimization with different heat exchanger configurations and compressor modulation strategies on the seasonal performance in a R410A chiller," 16th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics and the Editorial Board of Applied Thermal Engineering - HEFAT-ATE 2022, Online Conference, August 8 - 10, Paper 131
  • Zhao H., Wang Y., Elbel S., Hrnjak P., 2021, "Inspection of brazed aluminum microchannel heat exchangers by x-ray imaging," International Brazing and Soldering Conference (IBSC), Denver, CO, USA, October 3-6
  • Kang M., Elbel S., 2021, "Improving performance of solid-state cooling cycles using two-phase zeotropic heat transfer fluids," 9th IIR International Conference on Caloric Cooling and Applications of Caloric Materials (THERMAG IX), University of Maryland, College Park, MD, USA, June 7-11, Paper 103 (online participation)
  • Kang M., Elbel S., 2021, "Optimization of regenerator design with respect to geometric and operational parameters for solid-state caloric cooling using 1-D transient system model," 9th IIR International Conference on Caloric Cooling and Applications of Caloric Materials (THERMAG IX), University of Maryland, College Park, MD, USA, June 7-11, Paper 102 (online participation)
  • Zhao H., Elbel S., Hrnjak P., 2021, "Impact of substrate surface features on brazing of microchannel heat exchangers," 1st Digital International Congress 2021 on Aluminium Brazing and Aluminium Heat Exchanger Technologies for HVAC&R, May 4-5
  • Che M., Elbel S., 2019, "Quantification of local air-side heat transfer coefficient using color-change coatings," 14th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics - HEFAT 2019, Wicklow, Ireland, July 22-24, Paper 151
  • Che M., Elbel S., 2019, "Measurement of local air-side heat transfer coefficient through absorption-based optical method," 9th International Conference on Compressors and Refrigeration, Xi’an, China, July 10-12, Paper 1122
  • Zhang Y., Elbel S., 2019, "Simultaneous measurement of flow-induced noise and two-phase flow regimes in expansion devices," 9th International Conference on Compressors and Refrigeration, Xi’an, China, July 10-12, Paper 1121
  • Zhao H., Elbel S., Hrnjak P., 2018, "Joining of aluminum and stainless steel for heat exchanger applications," 7th International Brazing and Soldering Conference, New Orleans, LA, USA, April 15-18
  • Zhu J., Elbel S., Botticella F., 2018, "Measurement of oil in circulation in transcritical R744 systems using two-phase ejector," 6th International on Cryogenics and Refrigeration, Shanghai, China, April 12-14
  • Zhu J., Elbel S., 2018, "Application of vortex control to a transcritical R744 ejector cycle," 6th International on Cryogenics and Refrigeration, Shanghai, China, April 12-14, Paper PB-R-135
  • Zhao H., Elbel S., Hrnjak P., 2017, "Joining dissimilar materials in heat exchanger manufacturing process," 5th International Congress and Exhibition on Aluminum Heat Exchanger Technologies for HVAC&R, Düsseldorf, Germany, May 16-17
  • Zhao H., Elbel S., Hrnjak P., 2016, "Influence of surface morphology on wetting behaviors of Zn-Al filler metal on aluminum matrix composite," LÖT 2016 - 11th International Conference on Brazing, High Temperature Brazing and Diffusion Bonding, Aachen, Germany, June 7-9
  • Zhao H., Elbel S., Hrnjak P., 2015, "An investigation on thermal integrity of brazed heat transfer devices," Proceedings of the 6th International Brazing and Soldering Conference (IBSC), Long Beach, CA, April 19-22
  • Zhao H., Elbel S., Hrnjak P., 2015, "Low temperature controlled atmosphere brazing of aluminum matrix composite," Proceedings of the 6th International Brazing and Soldering Conference (IBSC), Long Beach, CA, April 19-22
  • Zhao H., Elbel S., Hrnjak P., 2014, "Wetting behaviors of Al based filler metals on aluminum matrix composites," International Conference on Brazing, Soldering and Special Joining Technologies, Beijing, China, June 9-13
  • Bowers C., Wrocklage D., Elbel S., Hrnjak P., 2014, "Evaluation of seasonal performance improvements in a 3-ton residential heat pump system using a novel design of integrated electronic expansion valves and distributors," poster presentation at the 11th IEA Heat Pump Conference, Montreal, QC, Canada, May 12-16
  • Zhao H., Elbel S., Hrnjak P., 2012, "Controlled atmosphere brazing of microchannel heat exchangers for mini-cooling systems," Proceedings of the 5th International Brazing and Soldering Conference (IBSC), Las Vegas, NV, April 22-25, pp. 183-187
  • Elbel S., 2009, "Historical and present developments of ejector refrigeration systems with emphasis on transcritical carbon dioxide air-conditioning applications," International Seminar on Ejector/Jet-pump Technology and Application, EUROTHERM Seminar 85, Louvain-la-Neuve, Belgium, September 6-9, Paper 5 (invited keynote)

Pending Articles

  • Kang, M., Elbel S., 2022, "Applying position and time dependent Nusselt number and friction factor into 1D model to improve regenerator design for solid-state caloric cooling cycles," Manuscript submitted to Appl. Therm. Eng. (under review)
  • Haider, M., Elbel S., 2023, "Performance improvement of the simultaneous solvers using gradient methods for the non-convex and ill-conditioned vapor compression systems," Manuscript submitted to Appl. Therm. Eng. (under review)

Magazine Articles

  • Hwang Y., Greenfield B., Kranz B., Hoaglan B., Repice C., Vaisman I., Oliver J., Nawaz K., Elbel S., 2022, "Transporting and storing COVID-19 vaccines," ASHRAE Journal, February issue

Presentations

  • Elbel S., 2023, "Multi-temperature refrigerated container using advanced transcritical R744 technology," Presentation at ASHRAE 2023 Winter Conference, Atlanta, GA, USA, Feb 4-8, AHR Expo Session 2
  • Elbel S., 2022, "A new storage heat pump concept for applications requiring large temperature lifts," Presentation at China Heat Pump Conference (2022) (Hybrid), Hangzhou, Zhejiang Province, China, October 24-27 (invited presentation)
  • Elbel S., 2022, "Ejector refrigeration with focus on expansion work recovery," Presentation at the International Symposium on Compact Solar Desalination and Cold Storage Systems held at IIT Madras (Hybrid), Chennai, Tamil Nadu, India, October 3 (invited presentation)
  • Elbel S., 2022, "Two-phase refrigerant ejector: an expansion device capable of recovering work," Presentation at ASHRAE 2022 Winter Conference, Las Vegas, NV, USA, January 29 - February 2, Seminar 13
  • Elbel S., 2021, "Refrigerant charge reduction to mitigate risks associated with flammable refrigerants," Presentation at ASHRAE 2021 Virtual Winter Conference, Feb 9-11, Seminar 24
  • Elbel S., 2020, "Energy savings in commercial air conditioning by use of a low-charge ammonia chiller," Presentation at online conference on natural refrigerants: The Future of Air Conditioning organized by Danish Technological Institute and ATMOsphere, https://atmo.org, June 23-24
  • Elbel S., 2020, "Two-phase ejectors to improve efficiency of applications using low-GWP refrigerants," Presentation at ASHRAE 2020 Winter Conference, Orlando, FL, USA, Feb 1-5, AHR Expo Session 6
  • Elbel S., 2019, "Verification of a new absorption-based experimental method to quantify local air-side heat transfer coefficient on fundamental geometries," 12th International High Energy Materials Conference & Exhibit (HEMCE) held at IIT Madras, Chennai, Tamil Nadu, India, December 16-18 (invited keynote)
  • Elbel S., 2019, "Quantification of local air-side heat transfer through an absorption-based color change coating," Presentation at ASHRAE 2019 Annual Conference, Kansas City, MO, USA, June 22-26, Seminar 60
  • Elbel S., 2019, "Why and when expansion work recovery makes sense," Presentation at the HighEFF Annual Consortium Meeting, Trondheim, Norway, May 8-9
  • Elbel S., 2018, "Ejectors to improve refrigeration system performance through expansion work recovery," 5th International Conference on Refrigeration Technology, Zhuhai, China, December 5-7 (invited keynote)
  • Elbel S., 2018, "Evaluation of field-made mechanical joints for systems with flammable refrigerants (ASHRAE RP-1808)," AHRTI Flammable Refrigerants Research & Planning Conference held at Underwriters Laboratories (UL), Northbrook, IL, October 8-9
  • Elbel S., 2018, "Quantification of local air-side heat transfer through a novel optical method," Presentation at ASHRAE 2018 Annual Conference, Houston, TX, USA, June 23-27
  • Elbel S., 2018, "Thermodynamic considerations on reversible air-conditioning and heat pump systems for use in vehicles (in German)," 15th Karlsruher Kfz-Klima-Symposium, Karlsruhe, Germany, March 22 (invited presentation)
  • Elbel S., 2017, "Recent advances in transcritical CO2 ejector refrigeration and air-conditioning systems," International Symposium on Natural Working Fluid CO2 Refrigeration and Heat Pump Technology, Tianjin, China, September 17-18 (invited keynote)
  • Elbel S., 2017, "Opportunities for utilizing two-phase ejectors to increase efficiency of commercial refrigeration systems using natural refrigerants," Presentation at ASHRAE 2017 Annual Conference, Long Beach, CA, USA, June 24-28
  • Elbel S., 2017, "Modeling, design and efficiency of two-phase ejectors to increase COP of transport refrigeration systems," Presentation at ASHRAE 2017 Annual Conference, Long Beach, CA, USA, June 24-28
  • Elbel S., 2016, "Natural, low-GWP refrigerants for light commercial refrigeration: examples of successfully converted applications using R290, R600a and R744," Presentation at ASHRAE 2016 Annual Conference, St. Louis, MO, USA, June 26-29
  • Elbel S., Tang C., 2016, "Conversion of platelet incubator to hydrocarbon refrigerant," ATMOsphere America, Chicago, IL, USA, June 16-17
  • Elbel S., 2016, "Improvement of cooling capacity and COP through the use of two-phase ejectors in transcritical CO2 automotive air-conditioning systems (in German)," 14th Karlsruher Kfz-Klima-Symposium, Karlsruhe, Germany, June 2 (invited presentation)
  • Zhu J., Elbel S., 2015, "Fresh look at vortex tubes and their potential use as expansion device in automotive vapor compression systems," SAE 2015 Thermal Management Systems Symposium, Troy, MI, USA, September 29 - October 1
  • Elbel S., 2013, "Successful Design and Implementation of Transcritical CO2 Technology for Beverage Display Coolers," Presentation at ASHRAE 2013 Annual Conference, Denver, CO, June 23-26
  • Elbel S., Lawrence N., 2012, "Investigation of automotive ejector air-conditioning cycles," Presentation at SAE 2012 Thermal Management Systems Symposium, Scottsdale, AZ, October 31 - November 1
  • Bowers C., Elbel S., Reichle M., 2012, "Research, development, and demonstration of co-generation ejector and modified organic Rankine cycle environmental control systems," Interagency Advanced Power Group, Mechanical Working Group Meeting, Arlington, VA, USA, May 1-3
  • Zhao H., Elbel S., Hrnjak P., 2010, "Development of novel compact heat exchanger using aluminum brazing technology," AWS 37th International Brazing and Soldering Symposium, Atlanta, GA, November 3
  • Zhao H., Elbel S., Hrnjak P., 2010, "The potential of open cell aluminum foams as fin structures for CAB brazed heat exchangers," AFC-Holcroft’s 14th Annual Aluminum Brazing Invitational Seminar, Novi, MI, USA, October 27-29
  • Elbel S., 2010, "Electrically driven automotive air-conditioning systems: potentials, challenges and major differences in comparison to conventional technology (in German)," 11th Karlsruher Kfz-Klima-Symposium, Karlsruhe, Germany, September 16 (invited presentation)
  • Elbel S., 2008, "Next generation ECU," Presentation given at the c-dig Meeting at CETIAT/CETHIL, Lyon, France, November 3-4
  • Elbel S., Hrnjak P., 2007, "Experimental validation of a prototype ejector with integrated high-side pressure control designed to reduce throttling losses encountered in transcritical CO2 system operation," Presentation given at the VDA Alternative Refrigerant Winter Meeting at Saalfelden, Austria, February 14-15, www.vda-wintermeeting.de
  • Elbel S., Hrnjak P., 2006, "Experiments and modeling of ejector systems," Presentation given at the c-dig Meeting at Purdue University, West Lafayette, IN, USA, March 16-17
  • Elbel S., Hrnjak P., 2006, "Development of a prototype refrigerant ejector used as expansion device in a transcritical CO2 system," Presentation given at the VDA Alternative Refrigerant Winter Meeting at Saalfelden, Austria, February 15-16, www.vda-wintermeeting.de
  • Elbel S., Hrnjak P., 2004, "Flash gas bypass in transcritical R744 systems using microchannel evaporators," Presentation given at the c-dig Meeting at the University of Illinois at Urbana-Champaign, Urbana, IL, USA, October 7-8

Professional Societies

  • Society of Automotive Engineers (SAE); Member of Interior Climate Control Committee (Jan. 2008 - present); Member of Steering Committee of Cooperative Research Program on Next Generation Thermal Management Refrigerant (Nov. 2020 - present)
  • International Institute of Refrigeration (IIR); US Representative of IIR Commission D2 (June 2019 - present); Treasurer of IIR U.S. National Committee (Jan. 2020 - present)
  • International Institute of Ammonia Refrigeration (IIAR)
  • Deutscher Kaelte- und Klimatechnischer Verein (DKV)
  • American Society of Mechanical Engineers (ASME)
  • American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE); Research Administration Committee (RAC) Member / Research Liaison for Technical Committees of Section 6 (July 2020 - present); TC 10.6: Program Subcommittee Chair and Voting Member (July 2018 - present); TC 1.3: Voting Member (Jan. 2019 - present); Member of ASHRAE’s COVID-19 Task Force: Practical Guidance for Vaccine Refrigerated Transportation and Storage (Jan. - May 2021)

Teaching Honors

  • List of Teachers Ranked as Excellent, University of Illinois at Urbana-Champaign (Fall 2017)
  • List of Teachers Ranked as Excellent, University of Illinois at Urbana-Champaign (Fall 2015)
  • List of Teachers Ranked as Excellent, University of Illinois at Urbana-Champaign (Fall 2014)
  • List of Teachers Ranked as Excellent, University of Illinois at Urbana-Champaign (Spring 2012)

Research Honors

  • Advisor of recipient of David Hinde Memorial Award (2023)
  • Advisor of recipient of David Hinde Memorial Award (2022)
  • HEFAT-ATE Conference Best Paper Award (2022)
  • Advisor of recipient of Purdue Conference Best Paper Award (2021)
  • Recognition of COVID-19 Related Research by Grainger College of Engineering (2021)
  • International Journal of Refrigeration Best Paper Award (2019)
  • HEFAT Conference Best Paper Award (2019)
  • Eurammon Natural Refrigeration Award (2009)
  • IIR Willis H. Carrier Young Researcher's Award (2007)
  • IIR Gustav Lorentzen Conference Best Paper Award (2006)
  • US Army Award for Environmental Excellence (2005)

Public Service Honors

  • Recognition Award from the Society of Automotive Engineers (2005)

Other Honors

  • Behr GmbH & Co Award of Excellence (2000)
  • Award of Excellence from Verein der Förderer der Fachhochschule Esslingen (2000)
  • Dr.-Ing. H.C.F. Porsche AG Award of Excellence (2000)

Recent Courses Taught

  • ME 401 - Refrigeration and Cryogenics
  • ME 402 - Design of Thermal Systems

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