Abstract
Heat exchangers (HXs) constitute key components of thermoacoustic devices and play an important role in determining the overall engine performance. In oscillatory flow conditions, however, standard heat transfer correlations for steady flows cannot be directly applied to thermoacoustic HXs, for which reliable and univocal design criteria are still lacking. This work is concerned with the initial stage of a research aimed at studying the thermal performance of thermoacoustic HXs. The paper reports a detailed discussion of the design and fabrication of the experimental set-up, measurement methodology and test-HXs characterized by two different pore geometries, namely a circular pore geometry and a rectangular (i.e., straight fins) pore geometry. The test rig is constituted by a standing wave engine where the test HXs play the role of ambient HXs. The experiment is conceived to allow the variation of a range of testing conditions such as drive ratio, operation frequency, acoustic particle velocity, etc. The procedure for estimating the gas side heat transfer coefficient for the two involved geometries is described. Some preliminary experimental results concerning the HX with straight fins are also shown. The present research could help in achieving a deeper understanding of the heat transfer processes affecting HXs under oscillating flow regime and in developing design optimization procedures.
Highlights
This paper addresses the issues of heat transfer in heat exchangers working under oscillatory flow conditions, which are typically found in thermoacoustic devices
Thermoacoustic engines are a new class of energy conversion devices whose operation relies on the interaction between heat and sound in close proximity of solid surfaces, a phenomenon identified as “thermoacoustic effect” [1,2]
Standard heat transfer correlations for steady flows cannot be directly applied to thermoacoustic Heat exchangers (HXs), for which reliable and unambiguous design criteria are still lacking
Summary
This paper addresses the issues of heat transfer in heat exchangers working under oscillatory flow conditions, which are typically found in thermoacoustic devices. Thermoacoustic engines are a new class of energy conversion devices (prime movers, refrigerators and heat pumps) whose operation relies on the interaction between heat and sound in close proximity of solid surfaces, a phenomenon identified as “thermoacoustic effect” [1,2] Since in these devices the synchronization among the compression, expansion and heat transfer phases of the thermodynamic gas cycle is naturally accomplished by an acoustic wave, a number of technological benefits directly result. There is the complete absence of moving mechanical parts (pistons, sliding seals, etc.) which leads to engineering simplicity, reliability, longevity and low maintenance costs They are intrinsically low cost devices, being constituted basically by a small number of standard components made of inexpensive and common materials. This could help in developing optimization procedures of their performance in the design phase
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