OPTIMUM PISTON-BORE FIT FOR MAXIMUM COMPRESSOR EFFICIENCY

摘要

Among many other parameters affecting energy efficiency of small refrigerating compressors the piston-bore fit plays a very important role. Small refrigerating compressors use almost exclusively plunger type ring-less pistons. It is the oil film between the piston and the cylinder wall, which seals gas during compression and re-expansion. If the clearance between the piston and the cylinder is too big, significant blow-by and loss of volumetric efficiency of the compressor can be expected. It the clearance between the piston and the cylinder is too small, one can expect high viscous friction and increased energy input to run the compressor. The aim of this paper is to show there is an optimum piston-cylinder clearance that provides maximum energy efficiency of the compressor, and that even a very simplified approach can predict this optimal piston-bore fit with satisfactory accuracy. Because COP of a refrigerating compressor depends on many other mechanical, electrical, and thermodynamic parameters, the prediction of the magnitude of COP is beyond the scope of this paper.