Linear Compressor, Experimental Comparison, Oil-Lubricated, Oil-Free
Compared to other types of positive displacement compressors, linear compressors show many advantages due to low friction, low power losses and compactness. Relatively little information is available in the literature with respect to linear compressor performance comparisons between oil-lubricated and oil-free linear compressors. Currently, there are two commercial linear compressors available in the market that are used in residential refrigerator/freezers. One of them uses synthetic POE oil while the other is oil-free. Both compressors operate over a wide range of capacity modulation instead of switching on and off, which results in smaller temperature variations and smaller vibration. The oil-free compressor has a special surface coating and a single bearing lubricated by the refrigerant gas itself. This paper presents experimental comparisons between the oil-lubricated and oil-free linear compressors for a domestic refrigerator/freezer. A hot-gas bypass test stand is used for testing the two compressors. During all tests, the following compressor measurements were recorded: compressor mass flow rate, suction and discharge temperatures, suction and discharge pressures, intermediate pressure and temperature, and compressor power consumption. Using these measurements, the two compressors were characterized and compared in terms of dimensionless performance parameters.