NUMERICAL MODELING OF A MICRO-SCALE STIRLING COOLER

Micro-scale coolers have a wide range of potential application areas, such as cooling for chip- and board-level electronics, sensors and radio frequency systems. Miniature devices operating on the Stirling cycle are an attractive potential choice due to the high efficiencies realized for macro-scale Stirling machines. A new micro-scale Stirling cooler system composed of arrays of silicon MEMS cooling elements has been designed. In this paper, we use computational tools to analyze the porosity-dependence of the pressure and heat transfer performance in the regenerator. For laminar flow in the micro-scale regenerator, the optimal porosity is in a range of 0.85 similar to 0.9 based on maximizing the system coefficient of performance (COP). The system's thermal performance was then predicted considering compressible flow and heat transfer with a large deformed mesh in COMSOL. The Arbitrary Lagrangian-Eulerian (ALE) technique was used to handle the deformed geometry and the moving boundary. To overcome the computational complexity brought about by the fine pillar structure in the regenerator, a porous medium model was used to replace the pillars in the model, allowing for numerical predictions of full-element geometry. Parametric studies of the design demonstrate the effect of the operating frequency on the cooling capacity and the COP of the system.