Design and Evaluation of a MEMS-Based Stirling Microcooler

A new Stirling microrefrigeration system composed of arrays of silicon MEMS cooling elements has been designed and evaluated. The cooling elements are to be fabricated in a stacked array on a silicon wafer. A regenerator is placed between the compression (hot side) and expansion (cold side) diaphragms, which are driven electrostatically. Air at a pressure of 2 bar is the working fluid and is sealed in the system. Under operating conditions, the hot and cold diaphragms oscillate sinusoidally and out of phase such that heat is extracted to the expansion space and released from the compression space. Parametric study of the design shows the effects of phase lag between the hot space and cold space, swept volume ratio between the hot space and cold space, and dead volume ratio on the cooling power. Losses due to regenerator nonidealities are estimated and the effects of the operating frequency and the regenerator porosity on the cooler performance are explored. The optimal porosity for the best system coefficient of performance (COP) is identified.