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Thermoacoustic refrigerator uses acoustic power to transport heat from a low-temperature source to a high-temperature source. The increasing interest in thermoacoustic technology is caused due to its simplicity, reliability as well as application of environmentally friendly working fluids. A typical thermoacoustic refrigerator consists of a resonator, a stack of parallel plates, two heat exchangers and a source of acoustic wave. The article presents the influence of the stack position in the resonance tube and the acoustic frequency on the performance of thermoacoustic refrigerator with a standing wave driven by a loudspeaker, which is measured in terms of the temperature difference between the stack edges. The results from experiments, conducted for the stack with the plate spacing 0.3 mm and the length 50 mm, acoustic frequencies varying between 100 and 400 Hz and air as a working fluid are consistent with the theory presented in this paper. The experiments confirmed that the temperature difference for the stack with determined plate spacing depends on the acoustic frequency and the stack position. The maximum values were achieved for resonance frequencies and the stack position between the pressure and velocity node.

Thermoacoustic refrigerators use acoustic power to transport heat from a low-temperature reservoir to a high-temperature reservoir through a stack in a resonance tube. These devices nowadays can be considered as an alternative cooling technology as they use environmentally friendly working fluids and have few moving components. This paper presents the design procedure of a small thermoacoustic refrigerator with nominal cooling power of 10 W. It explains the design choices with the reasons for using specific parameters. The design strategy applies simplified linear model of thermoacoustic in order to find optimum length and position of the stack. The model of the device was simulated by using a specialized tool DELTAEC. The simulation was performed under different temperatures of the cold heat exchanger varying from 250 to 295 K, and under different drive ratios varying from 0.006 to 0.016. The simulation results show that the cooling power of the refrigerator increases with the increase in the drive ratio and with the increase in the temperature of the cold heat exchanger. It was also found that the EER and the EERC coefficients of the device majorly depend on the temperature difference between the heat exchangers and only slightly depend on the drive ratio. The model achieved maximum cooling power of 55 W at the drive ratio of 0.016 and at the temperature difference between the heat exchangers of 5 K, which corresponded to EER of 2.03 and EERC of 0.034.

Abstract. Thermoacoustic refrigerator is a new and emerging technology capable of transporting heat from a low-temperature source to a hightemperature source by utilizing the acoustic power input. These devices, operating without hazardous refrigerants and owning no moving components, show advantages of high reliability and environmental friendliness. However, simple to fabricate, the designing of thermoacoustic refrigerators is very challenging. This paper illustrates the impact of significant factors on the performance of the thermoacoustic refrigerator which was measured in terms of the temperature difference generated across the stack ends. The experimental device driven by a commercial loudspeaker and air at atmospheric pressure as a working fluid was examined under various resonator length and operating frequencies. The results indicate that appropriate resonator's length and operating frequency lead to an increase in the temperature difference created across the stack. The maximum values were achieved for operating frequency equalled to 200 and 300 Hz whereas resonator length corresponded to the half-length of the acoustic wave for these frequencies. The results of experiment also confirm that relationship between these parameters is strongly affected by the stack spacing, which in this research was equalled to 0.4 mm.

Thermoacoustic devices are the systems which use acoustic power to transport heat through a stack in a resonance tube. The stack is one of the most important parts of the thermoacoustic systems. It can have different geometries, like parallel plates, circular pores, or pin arrays. However, the fabrication of stacks with regular geometries is sometimes impractical due to material and assembly costs. These problems can be solved by using stack fabricated with random and easily accessible porous materials. In this paper an experimental investigation on the thermoacoustic effect in easily accessible porous materials is presented. The measurements with the stacks were made in a standing wave device filled with air at atmospheric pressure. The reported results confirm that some of the materials with high porosity can be an alternative to a traditional stack geometries and materials.