Experimental evaluation of a mini-VCS for electronic cooling applications: R1234yf vs R134a

This paper compares the performance of R1234yf and R134a used as working fluids in a mini Vapour Cycle System (VCS) for electronic thermal management of aeronautical packaging. The water cooled miniature scale refrigeration system implements a new concept oil-free linear compressor prototype. The compressor operates at constant speed whileits capacity can be varied by controlling the piston stroke. The experimental measurements were carried out at constant evaporation temperature of 15°C and varying the condensation levels permitted to compare the performance of the mini VCS, operating with R134a and R1234yf, in terms of cooling capacity and COP. Furthermore, particular attention was dedicated to the cold plate design, which had to meet the requirements established by the aeronautical standards. The cold plate was equipped with 15 thermocouples in order to analyze the wall temperatures distribution. In this way, it was possible to directly compare the flow boiling heat transfer behaviors of the two fluids under the same operating conditions.