Influence of break-in on the leakage through reed-type valves of low-capacity refrigeration compressors
Abstract Valve leakage can significantly decrease the efficiency of reciprocating compressors adopted in household refrigeration systems, especially in low-capacity and oil-free compressors. These leakages occur through the valves due to geometric irregularities resulting from the manufacturing and assembly processes, which form leakage paths between the reeds and seats. Valve leakage is generally measured using completely new valve systems, which may not represent the actual leakage in valves after break-in. The aim of this study was to assess the influence of break-in on the leakage through reed-type valves of low-capacity refrigeration compressors. The leakage was measured for the suction and discharge valves of a R600a compressor before and after the valves were subjected to a break-in period. The valve leakage was characterized by the geometric parameter edge gap, defined as the gap between the reed and seat at the internal border of the valve orifice. The results indicate that the edge gap, and consequently leakage, is reduced with break-in. The leakage was reduced by up to 76% for the suction valve and by up to 95% for the discharge valve after break-in, while the edge gap was reduced by up to 50% for the suction valve and by up to 73% for the discharge valve. It should be mentioned that the reed and seat surfaces of the suction valve had their maximum roughness reduced by 40% and 29%, respectively, after break-in, suggesting that the edge gap is related to the surface finishing.