Investigation of reduced density low-GWP refrigerants in existing compressor technologies

The rise in global temperatures has led to international mandates to begin a phase-out to refrigerants that have a low-GWP. However, these newer refrigerants have a loss in thermodynamic efficiency, meaning that components such as the compressor will have to improve to overcome this loss in efficiency. While there are several losses compressors experience during operation, greater leakage areas are one of the largest contributors to compressor performance. The lower the operating pressures are inside the compressor, the greater the leakage will be. This work presents results from an 80-ton hot gas bypass load stand used to test a scroll compressor designed for R-410A- a high pressure refrigerant- and a spool compressor designed for R-134a, a medium pressure fluid. Several medium and low pressure refrigerants including R-1234yf, R-1234ze(E), R-444A, and R-456A were tested in each compressor, and the performance was measured. Results show that performance metrics such as the specific power, specific mass flow rate, and the COP are dependent on the working fluid, while the isentropic and volumetric efficiencies are driven by the compressor used. The refrigerants tested in the scroll compressor showed losses in efficiencies of approximately 10% from R-410A, while the spool compressor had minimal losses in efficiency, and in some cases slightly higher isentropic efficiencies. R-410A had the highest COPs, while R-444A experienced significant losses in the overall compressor performance.