The development of a performance-enhancing additive for vapor-compression heat pumps

This paper describes the testing results of a vapor-compression heat pump operating with HFC-134a refrigerant and a performance-enhancing additive. Preliminary bench-top testing of this additive, when added to polyolester (POE) lubricant and HFC-134a refrigerant, showed surprising enhancements to system COP. To further investigate this finding, we designed and fabricated a vapor-compression heat pump test stand for the 3-5 ton range. We investigated the effect of different concentrations of this additive on various system performance parameters such as cooling capacity, compressor power requirement, pressure ratio, compressor pressure difference, compressor isentropic efficiency, refrigerant flow rate, and heat exchanger performance. We investigated various heat source and heat sink conditions to simulate air-conditioning and heat pump operating conditions. To investigate the effect of this additive on compressor lubrication and life, we performed compressor life tests (with scroll and reciprocating compressors), and we had lubrication wear tests performed with various concentrations of the additive in the POE lubricant.