关键词: 压力波制冷机, 激波衰减, 振荡管, 制冷效率, 流动, 气体, 传热

Abstract: The pressure wave refrigerator represents a simple arrangement for gas cooling by its decompression and has many applications in chemical processes and energy transformation. The mechanism of the cooling effect of oscillatory tube is the conversion of the pressure energy of gas to heat through the movement of pressure waves, which are moving shock wave and unsteady expansion wave. In the present paper, the regular pattern of incident shock wave attenuation and its influence on the performance of pressure wave refrigerator are investigated by means of a single-tube set up. In the experiments, the expansion ratio is from 2.0 to 6.0, the relative length of the oscillatory tube L/d is from 87 to 737, and the exciting frequency is from 10 Hz to 240 Hz. The experimental results show that the relative strength of incident shock wave is reduced with the increase of relative position in length x/L because the energy of the reflected shock wave is exhausted by the viscosity and friction of the gas inside the tube. The other reason is the result of the gas in the tube pressurized and heated by the shock wave. The shock wave strength is also influenced by transmission and reflection effects resulted from the reflected shock wave. When the tube is relatively short, the relative strength of incident shock wave is less reduced as the tube length decreases, while the strength of the reflected shock wave at the closed end of the tube increases. The maximum refrigeration efficiency η_max of the refrigerator increases with the tube length, but the value of η_max is not affected obviously when the tube length increases to some value. The recommended optimal tube length L/d is 300-435 for the tube in this experiment. It helps to improve the performance of the pressure wave refrigerator under variable work condition when the amplitude of the refrigeration efficiency fluctuation is reduced as the length increases. The relative strength of the incident shock wave attenuation is concerned with the gas Reynolds number and Mach number in the front of the incident shock wave and the ratio of length to diameter. The attenuation formula is obtained by the dimensional analysis and experimental data, and the results are in good agreement with the experimental data. The maximum error is 5.70%.

Key words: pressure wave refrigerator, shock wave attenuation, oscillatory tube, refrigeration efficiency, flow, gas, heat transfer