S4E12

Abstract

Phase-change heat exchangers, such as condensers, are necessary components in refrigeration cycles and power generation cycles. Liquid condensed on the wall of a condenser is an extra thermal resistance and therefore detrimental to heat transfer. Separation of liquid from vapor can increase the heat transfer rate for a condenser. I will discuss two novel designs that used this fundamental mechanism to improve condensers, namely separation and extraction. Both designs have phase separation in the header of the condenser only based on gravity, so there was little cost on manufacturing. For the separation design, experiments on an R134a vehicular air conditioning system first confirmed that a separation condenser prototype increased the condensate flow rate by 7.4% and the Coefficient of Performance (COP) of the system by 6.6%. Then, with a detailed study for the two-phase flow in the header, a condenser model was built, and the condenser was optimized using that model. The optimized condenser was found to increase the condensate flow rate by 17.8% and the system COP by 10.2%. For the extraction design, experiments on an un-optimized condenser showed an increase of 4.7% in the condensate flow rate and 5.2% in the system COP. The effect of extraction flow rate on the condenser performance and the separation efficiency in the header were also quantified experimentally.

Introduction of speaker

Jun is a Postdoctoral Research Fellow advised by Professor Anish Tuteja in the Department of Materials Science and Engineering at the University of Michigan. He received his Ph.D. and M.S. degrees from the University of Illinois (UIUC) and his B.S. degree from Shanghai Jiao Tong University, China, all in mechanical engineering. At UIUC, he was working at the Air Conditioning and Refrigeration Center, advised by Professor Pega Hrnjak. His research areas are thermal fluids, energy systems, surfaces/interfaces, and polymers. He has been honored with the David Hinde Award, Mavis Future Faculty Fellow, and James O. Smith Outstanding TA award from UIUC, the Graduate Student Grant-in-Aid Fellowship from the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), etc.