Experimental study of a small-scale refrigeration system with high efficiency by ultra-fast centrifugal compressor

Improving compressor efficiency in the refrigeration, air-conditioning, and heat pump (RACHP) sector—which accounts for nearly 20 % of global electricity consumption—is essential for energy conservation and emissions reduction. Centrifugal compressors inherently possess the potential for higher efficiency compared to volumetric compressors. However, traditionally, their application has been limited to large-scale refrigeration systems, while small-scale refrigeration systems continue to rely on volumetric compressors. The miniaturization of centrifugal compressors as a replacement for volumetric compressors is expected to significantly enhance the energy efficiency of small-scale refrigeration systems. To evaluate the feasibility of this approach and address the research gaps concerning the performance and cycle characteristics of centrifugal compressors in small-scale refrigeration systems, a 45 kW cooling capacity test rig was developed in this study. The test rig employs a high-speed, small-scale, oil-free R134a centrifugal compressor. Extensive experimental investigations were carried out. The findings demonstrate that the system surpasses conventional volumetric compressor refrigeration systems, reaching a peak cooling capacity of 44.54 kW with a system COP of 2.84, whereas the optimal system COP of 3.36 is achieved at a cooling capacity of 28.54 kW. The compressor COP reaches 5.65, representing an 40.2 % improvement over the average value of traditional systems. Moreover, an energy-saving assessment conducted in the context of thermal management for lithium battery energy storage systems indicates that the proposed system could save approximately 122.78 GW h of electricity and reduce CO2 emissions by 58,567 tons annually.