3925 -- System Performance Comparison of R507 with R502 PDF

R-507 is an azeotropic of HFC-125/HFC-143a (50%/50%) and is a long-term, zero ozone depletion potential (ODP) replacement for CFC-containing low-temperature refrigerant R502. A series of system performance tests has been completed comparing R507 with R502. The tests were carried out under controlled conditions in a well-instrumented alternative refrigerants test facility, using an open drive reciprocating compressor and counterflow tube-in-tube heat exchangers. Measurements were conducted at two different condensing temperatures; 54.4degC (130.0degF) and 43.3degC (110.0degF). The refrigerant evaporating temperature was varied over a range of -30.0degC to -15.0degC (-22degF to 5.0degF). The degree of liquid subcooling at the condenser outlet was varied between 6.0degC and 18degC (10.8degF and 32.4degF). Test data were used to compare important compressor performance characteristics including shaft power, pressure ratio and compressor discharge temperature. System performance characteristics were also measured, including evaporator capacity, refrigerant mass flow, and cooling coefficient of performance (COP). The effect of additional liquid subcooling on the evaporator capacity and COP was also evaluated. The relative evaporator capacity of R507 compared to R502 was found to range from 0.95 to 1.05, depending on the operating conditions and the amount of liquid subcooling present. For all the conditions tested, R507 was less energy efficient than R502. The relative COP of R507 ranged from 0.87 to 0.97.

KEYWORDS: year 1995, performance, comparing, refrigerants, replacing, R507, R502, azeotropic, testing, reciprocating compressors, counter flow heat exchangers, tube in tube heat exchangers, measuring, subcooling, condensers, properties, coefficient of performance, evaporators, efficiency