Performance investigation of a linear compressor in refrigeration system with its natural frequency realtime monitored.

Linear compressors are receiving a great deal of attention for high efficiency, compacted structure and a variable cooling capacity. However, for its unique free-piston structure, the linear compressor is hypersensitive to the gas load changing in refrigeration system. In this paper, a phasor model which employs vectors to express the voltage, current and velocity respectively in frequency domain for estimating the natural frequency of a linear compressor is proposed. Besides, the performance of a linear compressor is also investigated in the refrigerator testing conditions (GB/T 9098-2008) using R600a with a natural frequency real-time monitor program running simultaneously. The COP and cooling capacity at top dead centre (TDC) position is tested under different operating frequency, as well as the natural frequency. The maximum COP reaches 1.98 with 254.1W cooling capacity at 58Hz. The natural frequency tested is 58Hz within ±0.5Hz variation when operating frequency rises from 52Hz to 62Hz. It also observed that the natural frequency goes down rapidly with the stroke increasing till TDC after pumping and the natural frequency reaches a minimum value at TDC.