Thermal performance of heat exchangers for thermoacoustic refrigerators

Abstract

Heat exchangers in thermoacoustic refrigerators extract heat from the refrigerated volume and reject it to the surroundings. Eight essential heat-transfer processes coupled in the energy migration from the cold-side heat exchanger through the stack to the hot-side heat exchanger were identified, and a simplified computational model describing them was developed. Geometrical and operational parameters as well as thermophysical properties of the heat exchangners, the stack plate, and the working medium were organized into dimensionless groups. Heat transfer in the transverse direction, resulting from temperature differences between the inlet and outlet temperatures of the transport fluid in the heat exchangers, was accounted for in the simulations. Two types of boundary conditions between the thermoacoustic working fluid and the heat exchangers were considered: (1) constant temperature of the thermoacoustic working fluid over the heat exchangers with constant temperature difference along and across the stack and (2) constant heat flux from the thermoacoustic working fluid to the heat exchanger. Nonlinear temperature distributions and heat fluxes near the edge of the stack plate were observed. Effects of different parameters on the thermal performance of the heat exchangers were investigated. [Work supported by the Office of Naval Research.]