There is significant worldwide interest in using substances that are naturally occurring in the biosphere as refrigerants, which are considered benign to the environment and are termed “natural working fluids”. Among these substances, CO2 has been investigated extensively as a potential substitute for HFCs in HVAC&R applications. When considering the utilization of CO2 for this application, the low critical temperature and the transcritical operation of CO2 cycles necessitate advanced cycle architectures to achieve competitive system performance with respect to conventional HFC systems. In this seminar, an overview of refrigerants and an outlook on future developments on HFOs and HFC/HFO blends are provided. In addition, the implications of using CO2 as the working fluid are discussed, and a newly designed multi-stage two-evaporating temperature transcritical CO2 experimental setup with the purpose of conducting systematic comparisons of different cycle architectures will be described. Finally, general insights on the numerical simulations of the experimental system will also be given for completeness.  

Dr. Davide Ziviani is a Post-Doc Research Associate of the Center for High Performance Buildings (CHPB) at the Ray W. Herrick Laboratories working with Prof. Eckhard A. Groll and Prof. James E. Braun. He has extensive expertise in the modeling and testing of thermal systems and their components, including positive displacement compressors and expanders, organic Rankine cycles for waste heat recovery, as well as advanced vapor compression cycles for residential and commercial applications. 

Dr. Ziviani received his Doctoral degree in Electromechanical Engineering from the University of Ghent in Belgium, and Master’s and Bachelor’s degrees in Mechanical Engineering from the University of Ferrara in Italy. Dr. Ziviani is involved with ASHRAE and IIR, and serves as a member of the editorial committee of the Knowledge Center on Organic Rankine Cycle (KCORC) technology.