An alternative stack arrangement for thermoacoustic heat pumps and refrigerators

Abstract

One major setback of thermoacoustic engines—when comparing them with “conventional” heat-engines or refrigerators—is their low power density. In this work a new attempt for achieving higher power densities was undertaken. The stack of a thermoacoustic engine, which usually consists of parallel plates much longer than the acoustic displacement amplitude, was substituted by parallel-plate segments, which were only a fraction of the displacement amplitude long and randomly orientated to each other. This alternative stack arrangement was expected to benefit from improved heat transfer characteristics and an anisotropic thermal conductivity. A simplified numerical model confirmed these expectations. Experiments with a thermoacoustic heat pump were carried out. The experimental results qualitatively agreed with the numerical model. At most, the power density was raised by approximately 50%. The coefficient of performance—defined as useful heat output divided by work input—increased by approximately one-third.