Performance Evaluation of the Energy Efficiency of Crank-Driven Compressor and Linear Compressor for a Household Refrigerator

Since conventional crank-driven compressor had many difficulties to increase efficiency due to mechanical loss, new kind of compressor has been paid much of attention by the compressor manufacturers. The free piston compressor mechanism has been one of those kinds. The compressor manufacturers developed an energy efficient free piston linear resonance compressor for a household refrigerator. In this study, we investigate the energy efficiency of two different types of compressors for a household refrigerator. One of these is conventional crank-driven compressor which is a positive-displacement compressor that has the piston driven by a crankshaft to discharge gas at high pressure. The other is linear compressor which has no crank mechanism and its piston is oscillated by linear motor and helical coil spring. The energy efficiency is tested with a compressor calorimeter. Experimental results show that the new linear compressor has the power consumption reductions about 10% as compared with the brushless direct-current (BLDC) reciprocating compressor. The linear compressor demonstrates excellent energy efficiency by reducing the friction loss since it does not produce any side load between the cylinder and the piston. Due to use of the moving magnet type linear oscillating motor, its motor efficiency goes more than 90%. Additionally, the compressor stroke to piston diameter ratio of the oscillating piston in the free piston linear compressor can be adjusted in order to modulate the cooling capacity of compressor for better system efficiency.