Experimental analysis of a window air conditioner with R-22 and zeotropic mixture of R-32/125/134a

This study is the result of the cooperative research and development agreement (CRADA) between Oak Ridge National Laboratory and E.I. Du Pont De Nemours and Company, Inc., (CRADA No. 92-0161) for testing the use of heat exchangers as the evaporator and condenser in an air-conditioning rig. Heat exchangers at typical realistic operating conditions were tested with R-22 and with its potential replacement, a ternary mixture of R-32(30%)/R-125(10%)/R-134a(60%). A test rig was built that provided for operation of the low-temperature exchanger (evaporator) with flooded coils. The test results indicated that the performance of the evaporator heat exchanger using ternary mixture, in terms of cooling capacity, would be around 7.4% less than the performance using R-22. The cooling capacity for both refrigerants improved with flooded evaporator operation by 8.6% for R-22 and by 15% for ternary mixture. Compared with R-22 operation, operation with ternary mixture results in slightly higher compressor discharge pressure, lower compressor discharge temperature, slightly lower compressor power consumption, and a higher compressor high-low pressure ratio. Temperature glide for ternary mixture, for both evaporator and condenser, was clearly evident, but not as pronounced as expected because of the pressure drop (and thus the temperature drop) along the coils. Further improvement of the performance of ternary mixture is possible if the evaporator is arranged in a counter-cross-flow configuration to take advantage of the temperature glide. Current evaporator designs are mostly concurrent-cross-flow, which is more appropriate for single-component refrigerants or azeotropic refrigerant mixtures