تجزیه و تحلیل حساسیت از مدل جامع برای کمپرسور خطی در مقیاس کوچک برای خنک کننده الکترونیک

A comprehensive model of a linear compressor for electronics cooling was previously presented by Bradshaw et al. (2011). The current study expands upon this work by first developing methods for predicting the resonant frequency of a linear compressor and for controlling its piston stroke. Key parameters governing compressor performance – leakage gap, eccentricity, and piston geometry – are explored using a sensitivity analysis. It is demonstrated that for optimum performance, the leakage gap and frictional parameters should be minimized. In addition, the ratio of piston stroke to diameter should not exceed a value of one to minimize friction and leakage losses, but should be large enough to preclude the need for an oversized motor. An improved linear compressor design is proposed for an electronics cooling application, with a predicted cooling capacity of 200 W a cylindrical compressor package size of diameter 50.3 mm and length 102 mm.

A comprehensive simulation model for a miniature-scale linear compressor was recently developed by Bradshaw et al. (2011). The model was also validated against experiments conducted on a prototype linear compressor constructed for the purpose. It was found that the overall performance metrics predicted by the compressor model are highly sensitive to the leakage gap g, eccentricity ɛ, dry friction coefficient f, and motor efficiency ηmotor. Fig. 1 depicts the major components and design parameters of a linear compressor. The geometry of the piston is directly related to both the friction and leakage of a compressor. Therefore, for a fixed displaced volume, some piston diameter and stroke combinations will provide higher efficiency than others. The impact of changes to these parameters proves useful when designing a linear compressor, and warrants further investigation. Full-size image (21 K) Fig. 1. Schematic diagram of linear compressor at Top Dead Center (TDC, top) and Bottom Dead Center (BDC, bottom) with primary linear compressor components and design parameters highlighted. Figure options A linear compressor has two major practical limitations, which restrict its implementation in practical systems. Both the resonant frequency and stroke are sensitive to changes in geometry and operating conditions (Cadman and Cohen, 1969; Park et al., 2004; Pollak et al., 1979; Unger and Novotny, 2002). This poses a challenge not only to compressor design but also to modeling efforts. The ability to predict and control these two parameters provides a useful tool for linear compressor design efforts. A method for calculating the resonant frequency of a linear compressor is developed here. An approach to numerical control is also provided that ensures compressor operation at the desired stroke. A series of sensitivity studies are presented, which highlight the sensitivity to leakage gap and eccentricity as well as piston geometry. Finally, an improved compressor design is formulated for an electronics cooling application using results from the model.

The sensitivity of the performance of a linear compressor to changes in its geometric parameters is analyzed, leading to insights in the design methodology of linear compressors. These insights allow for a further refinement of the design prototype presented in Bradshaw et al. (2011). Methods for predicting the resonant frequency of a linear compressor as well as for numerical control of the stroke of the device are presented. In addition, a loss analysis is presented which quantifies the work lost due to friction and leakage. The sensitivity studies conducted showed that the linear compressor is highly sensitive to changes in the leakage gap between the piston and cylinder as well as the spring eccentricity; both parameters should be minimized for optimal performance. Therefore, it is important to quantify and control these parameters in any compressor design that is mass-produced to maximize performance. The present work also illustrates the ability of the linear compressor to be readily scaled to smaller capacities. Other types of positive-displacement compressors suffer from performance limitations upon miniaturization due to manufacturing tolerances. The small number of moving parts in the proposed linear compressor design, along with its insensitivity to dead volume, make it an ideal technology for electronics cooling applications. The ability to handle larger amounts of dead volume without performance degradation could also allow this technology to be used to control the capacity of the refrigeration system. Capacity control is a critical need for high-performance refrigeration systems in electronics cooling and should be further investigated. The results from the sensitivity analysis are used to inform the scalable design procedure for a linear compressor, and an improved linear compressor design for electronics cooling is presented with an overall package size of 50.3 mm diameter by 102 mm length and a predicted refrigeration capacity of 200 W.