Linear compressor

Abstract: Linear compressor has no crank mechanism compared with conventional reciprocating compressor. This allows higher efficiency, oil-free operation, lower cost and smaller size when linear compressors are used for vapour compression refrigeration (VCR) system. Typically, a linear compressor consists of a linear motor (connected to a piston) and suspension springs, operated at resonant frequency. This paper presents a review of linear compressors for refrigeration system. Different designs and modelling of linear compressors for both domestic refrigeration and electronics cooling (miniature VCR system) are discussed. Key characteristics of linear compressor are also described, including motor type, compressor loss, piston sensing and control, piston drift and resonance. The challenges associated with the linear compressors are also discussed to provide a comprehensive review of the technology for research and development in future.

Abstract: A comprehensive model of a miniature-scale linear compressor for electronics cooling is presented. Linear compressors are appealing for refrigeration applications in electronics cooling. A small number of moving components translate to less theoretical frictional losses and the possibility that this technology could scale to smaller physical sizes better than conventional compressors. The model developed here incorporates all of the major components of the linear compressor including dynamics associated with the piston motion. The results of the compressor model were validated using experimental data from a prototype linear compressor. The prototype compressor has an overall displacement of approximately 3 cm 3 , an average stroke of 0.6 cm. The prototype compressor was custom built for this work and utilizes custom parts with the exception of the mechanical springs and the linear motor. The model results showed good agreement when validated against the experimental results. The piston stroke is predicted within 1.3% MAE. The volumetric and overall isentropic efficiencies are predicted within 24% and 31%, MAE respectively.

Abstract: Linear compressors with a free piston driven by a linear motor have attracted wide attention in cooling apparatuses such as refrigerators due to their high efficiency. The method of using triacs as a linear motor drive is not satisfactory for improving the efficiency of linear compressors. In this paper, the performance of linear compressors using a pulsewidth modulation inverter is investigated, with emphasis on the efficiency and power factor along with variations of both mechanical and electrical resonant frequencies. The strategy for improving the efficiency of the linear compressor is suggested by controlling the average value of the product of the piston stroke and motor current to 0. The performance of both the stroke and efficiency controls of the linear compressor is verified through experiments under various gas pressure conditions.

Abstract: LG Electronics developed an energy efficient resonant free piston linear compressor for a household refrigerator. This linear compressor has no crank mechanism and its piston IS oscillated by linear motor and helical coil spring. This compressor demonstrated excellent energy efficiency from the following reasons. • Due to the simple mechanism, its mechanical loss is much less than conventional crank driven compressors • Using the moving magnet type linear oscillating motor, its motor efficiency goes more than 90% • With simple electronics, cooling capacity could be modulated to get better system efficiency LG linear compressor IS 20~ 30% more efficient than most efficient current crank driven compressors.