Silicon Spaced Wafer Stack Thermoacoustic Refrigerator Design and Testing

Abstract

The design of a new, small-scale thermoacoustic refrigerator stack and heat exchanger test platform is presented. A special silicon (Si) stack is fabricated to encourage anisotropic heat conduction — good heat conduction along the plane of the Si wafer (normal to the direction of acoustic propagation) and poor conduction across it (along the direction of acoustic propagation). This is accomplished by separating two wafer pieces with an insulator in between. The aim of this paper is to quantify the performance of this stack arrangement. The apparatus utilizes a modified piston engine with a motor running the piston (max 300 Hz) as an acoustic source. Comparison of results show that the a slight performance degradation for the Si stack compared with that of the ceramic stack. It is believed that advantages gain by suppressing heat conduction along the stack is offset by increased losses due to viscous effect and flow streaming within the Si stack.