Thermoacoustic refrigeration was developed during the past two decades as anew, environmentally safe refrigeration technology. The operation of thermoacoustic refrigerators employs acoustic power to pump heat. Nowadays, as commercial applications are sought, it is important to be able to obtain fast and simple engineering estimates for the design and optimization of prototypes. This paper provides such estimates by implementing the simplified linear model of thermoacoustics - the short stack boundary layer approximation - into a systematic design and optimization algorithm. The proposed algorithm serves as an easy-to-follow guideline for the design of thermoacoustic refrigerators. Performance calculations applying the algorithm developed in this paper, predict values of 40–50% of Carnot's efficiency for the thermoacoustic core, the heart of a thermoacoustic refrigerator. One reason that these efficiencies have not yet been achieved in devices built to date, is the poor performance of the heat exchangers in thermoacoustic refrigerators. This issue and other remaining challenges for future research are also addressed in the paper. Solving these problems in the near future, we believe, will bring an environmentally safe refrigeration technology a step closer to commercial use.

Design optimization of thermoacoustic refrigerators

An experimental study of heat transfer from a cylinder in low-amplitude zero-mean oscillatory flows

Kertas kerja ini memperkenalkan teknologi terbaru dalam kuasa bendalir iaitu termoakustik, fenomenon yang disebabkan oleh interaksi pepejal-bendalir. Secara umumnya, termoakustik boleh dibahagi kepada dua kategori. Kategori pertama ialah enjin haba, di mana kuasa akustik dapat dijana hasil daripada gelombang yang wujud disebabkan oleh perbezaan suhu yang merentas suatu susunan plat. Keadaan sebaliknya untuk pam haba, di mana pemindahan haba berlaku merentas suatu susunan plat dengan kuasa akustik masukan dalam bentuk gelombang akustik. Teori asas termoakustik dan beberapa parameter reka bentuk sistem termoakustik yang diguna penyelidik masa kini dibincangkan disini. Analisis dengan menggunakan teori tersebut juga dilakukan. Perbincangan ini adalah sebagai dorongan untuk penyelidikan dalam bidang termoakustik khususnya secara eksperimen dan analisis berangka. 
				
				Kata kunci: Termoakustik, parameter reka bentuk, analisis
				
				This paper is an attempt at introducing the latest technology in fluid power, thermoacoustics, a phenomenon due to solid-fluid interactions. Thermoacoustics can be generally characterised by the following two categories. The first, the oscillations induced by temperature difference across a stack of plates can generate acoustic power consistent of a prime mover. While the reverse, that of heat transfers across a stack of plates powered by acoustic waves is typical of a heat pump learnt in the engineering introductory course. Basic thermoacoustic theory and some simple thermoacoustic design parameters that are currently being used are discussed. Analysis using these theories is shown. Discussions through this paper will show the way for initial and continuing research into thermoacoustics, particularly in the experimental and numerical fields. 
				
				Key words: Thermoacoustics, design parameters, analysis

Thermoacoustic Heat Engine

https://iopscience.iop.org/article/10.1088/1757-899X/539/1/012037/pdf

Experimental study of thermoacoustic cooling with parallel-plate stack in different distances

Thermoacoustic refrigeration is a fast advancing new refrigeration technology. Performance calculations indicate remarkable values for the thermoacoustic core of a thermoacoustic refrigerator. The thermoacoustic core is responsible for pumping heat from a cold to a hot temperature reservoir. However, the systems necessary to support the thermoacoustic core, such as heat exchangers and acoustic drivers are the weak points of this refrigeration technology. Particularly, heat exchangers were designed so far without any optimization. A reason for this is the lack of knowledge of the flow structures and heat transfer phenomena at the interface between the thermoacoustic core and the heat exchangers. For the purpose of gaining better insight, the authors built a thermoacoustic refrigerator model and applied visualization techniques, such as smoke injection and holographic interferometry, to visualize the flow and temperature fields at the interface.

M. Wetzel

Papers

Design issues of a thermoacoustic refrigerator and its heat exchangers