The power density of electronic devices has increased to a level that requires new technology for heat rejection. An alternative to conventional heat rejection techniques is refrigeration. However, current refrigeration technologies cannot meet the packaging constraints, or perform well at the operating conditions encountered by electronics cooling applications. The compressor is critical to the performance of a vapor compression refrigeration system. However, current compressor technology is not well suited for electronics cooling applications. This points to a need for new compressor technology developed specifically for electronics cooling. In this work, a linear compressor applied to electronics cooling is studied. Linear compressors are appealing for vapor compression refrigeration applications in electronics cooling. A small number of moving components translates to lower frictional losses. Also the potential for this technology to be scaled to smaller physical sizes is better than for conventional compressors. To test the feasibility of a linear compressor applied to electronics cooling, a comprehensive model of a miniature-scale linear compressor for electronics cooling has been developed. The model developed here incorporates all of the major components of the linear compressor including the dynamics associated with piston motion. The results of the compressor model were validated using experimental data from a prototype linear compressor custom-built for this study as well as a commercially available linear compress from a domestic refrigerator/freezer. The model results showed good agreement with the experimental results. The resonant frequency of the prototype compressor is predicted with 0.5% Mean Absolute Error (MAE) compared with experimental data. The mass flow rate of the prototype linear compressor is predicted with 16.8% MAE compared with experimental data. The commercial linear compressor mass flow rate, power, and overall isentropic efficiency are predicted to within 4.9%, 6.1%, and 5.2%, MAE, respectively. A sensitivity study using the model is also presented. This study examined the sensitivity to changes in compressor geometry. The study has identified the leakage gap and piston eccentricity as important parameters to consider when designing a linear compressor. The piston diameter and stroke is also shown to play an important role in overall performance. This study also shows that linear compressor technology scales well to smaller sizes. In addition, the unique ability to provide efficient capacity control is shown. This ability allows a single compressor to cool an electronic device over a wide variety of power input levels with only small changes in overall efficiency. Using this knowledge, an updated prototype compressor design is presented. This updated design provides 200 W of cooling capacity in an overall cylindrical package size of 50.3 mm diameter and 102 mm length.
linear compressor, electronics cooling, comprehensive model
Vibrations and Nonlinear Dynamics, High Performance Buildings, Thermal Systems and Air Quality
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