Experimental study and analysis of a thermoacoustically driven thermoacoustic refrigerator

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Sådhanå (2020) 45:213 https://doi.org/10.1007/s12046-020-01452-9

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Experimental study and analysis of a thermoacoustically driven thermoacoustic refrigerator A B DESAI1,* , K P DESAI1, H B NAIK1 and M D ATREY2 1

Department of Mechanical Engineering, Sardar Vallbhbhai National Institute of Technology, Surat 395007, India 2 Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India e-mail: [email protected] MS received 25 November 2019; revised 7 April 2020; accepted 1 July 2020 Abstract. Experimental investigations are performed on a half-wavelength standing wave type thermoacoustically driven thermoacoustic refrigerator also known as TADTAR. Present TADTAR device conceived to be a quarter wavelength standing wave type thermoacoustic engine (TAE) coupled to a quarter wavelength standing wave thermoacoustic refrigerator (TAR). A TAE generates acoustic work using heat, and this produced acoustic work is directly fed to TAR where a useful cooling effect is developed. The study here aims to project the enhancement in the performance of a TADTAR system by using better geometric choices and operating conditions. In the present work, by keeping the engine part unaltered, parametric variations on the refrigerator side are performed. Two geometric parameters namely resonator length and TAR stack position and one operating parameter, working gas, have been varied at three distinct choices. The performance of TADTAR is examined for three output parameters of TADTAR namely frequency of oscillations, pressure amplitude, and temperature difference across TAR stack. The present study should be useful for assisting select these parameters for starting the designing of a TADTAR. It also helps in concluding in a more generalized way the dependence of the above-said output of TADTAR on the varying parameters. This paper shows that longer resonator and He-Ar mixture as working gas among the choices is better for a TADTAR system for achieving better performance. It also highlights the potential existence of a unique position for a stack length for a TADTAR to attain maximum performance in terms of the temperature difference across the TAR stack. The present paper reports the maximum temperature difference of 16.3 K across the TAR stack. Keywords. Thermoacoustic refrigeration; standing wave; TADTAR; mixture working gas; stack position; resonator length.

1. Introduction Thermoacoustics, as the name suggests, involves the study of heat and acoustic interactions. In thermoacoustics, heat may be supplied to produce acoustic work, or acoustic work may be absorbed to realize the useful cooling effect. There are mainly two types of devices working on the principle of thermoacoustics. One is a thermoacoustic engine (TAE) which uses the heat to produce acoustic work and the other is a thermoacoustic refrigerator (TAR) which absorbs acoustic work to produce cooling effect across refrigerator stack. Usually, these thermoacoustic devices are of quar