Development and study of stack for thermoacoustic refrigerator

Abstract

In this article, an analysis has been made of the processes occurring in gas pockets of stack -the internal heat exchanging apparatus of the thermoacoustic device that operates on standing-wave cycle. The results of investigatory tests of the stack of a mock-up thermoacoustic refrigerator (TAR) operating on standingwave cycle are reported. The special features of the stack design are described. The parameters influencing the performance of the stack are analyzed. The results of the investigatory tests are depicted in graphic form.Periodic (cyclic) gas compression and expansion processes in acoustic wave, combined with processes of heat exchange with external sources, govern classical processes that occur in thermoacoustic cycle. These processes are used both in heat engines, which convert the heat of external sources into acoustic energy, and in heat pumps, which coverts acoustic energy into heat. Let us examine the processes that occur in the stack of a thermoacoustic refrigerator operating in standing wave where energy conversion occurs inside a built-in apparatus (stack).One of the factors holding up application of thermoacoustic devices (TD) is low specific density of heat flows via-à-vis flows typical for conventional heat pumps and refrigerators operating on inverse Stirling cycle.This work reports the results of the investigations aimed at formulating recommendations for selection of geometric makeup of the packing of the stack that ensures adequate densities of heat flows as well as the results of the study of the influence of various TD parameters on the performance of the stack.Qualitative Analysis of Processes. The most comprehensive analysis of the processes occurring in TD was reported in [1]. In this work were also offered recommendations on selection of geometric dimensions of gaps in heat exchangers of TD in standing wave. As we find from these recommendations, the dimensions of gas gaps (pockets) in the stack are comparable with those of thermal boundary layer, whereas the dimensions of gas gaps in the regenerator are far smaller than those of the thermal boundary layer.In classical standing wave, pressure and volume velocity fluctuations occur in antiphase (reverse phase), i.e., the shift angle is 180°. In this case, the variation in the temperature of the gas portion occurs exactly in the phase with pressure variation. In standing acoustic wave, the gas portion lying far from the solid surface (at a distance far exceeding the distance of the thermal boundary layer) is subjected to adiabatic compression and expansion processes, whereupon an equilibrium temperature T 0 equaling the local temperature of the solid surface is established in the gas portion.For the other limiting case, i.e., for a gas potion lying in the immediate vicinity of the solid surface (at a distance far less than the distance of the thermal boundary layer), the compression and expansion process occurs in the isothermal