Measurements of thermal field at stack extremities of a standing wave thermoacoustic heat pump

Abstract

In this paper, we experimentally measure the temperature fields at different locations on the stack plate and in the surrounding working fluid in a standing wave thermoacoustic device. The temperature measurements at the stack extremities and at the neighboring gas show axial heat transfer at the stack extremities, as opposed to the hypothesis of a perfectly isolated stack used in the linear thermoacoustic theory. Four different mechanisms of heat transfer are identified at the stack extremities in the present study. This information is necessary for the optimization of the performances of practical thermoacoustic engines. For the selected operating conditions, temperature measurements along the stack reveal a linear behavior along the stack and the corresponding gas residing near the stack. Temperature gradient along the working fluid is higher than that of along the stack, as opposed to the equal temperature gradient assumed by the linear theory. This information might be incorporated into the linear thermoacoustic theory to accurately predict the temperature difference generated across the stack ends.