A thermoacoustic refrigerator is a device that transfers heat from a low temperature reservoir to a high temperature reservoir by utilizing acoustic wave. Due to using no moving parts, no exotic and poisonous materials, Thermoacoustic refrigerators have been considered by many researchers. In this paper, the OpenFOAM package is used to simulate a thermoacoustic refrigerator. The unsteady compressible Navier-Stokes equations and equation of state are solved with PIMPLE algorithm. The effects of driver pressure ratio, frequency and heat exchangers temperature differencing for air and helium have been studied. Length of heat exchangers and stack remains constant throughout the analysis process. The results are shown that the coefficient of performance (COP) is decreased and cooling power is increased due to rise of driver pressure ratio. Helium cooling power is greater than air, but their COP is equal because of its need greater input power. The cooling power for both air and helium are increased with enhance of temperature difference of heat exchangers. Also, COP of air refrigerator is decreased, but COP of helium refrigerator is increased. The longer device length, smaller COP and cooling power are the resultants of driver’s frequency reducing. When frequency is increased, the length of cold heat exchanger will be greater than gas particle displacement of air. Therefore, cold heat exchanger absorbs heat from the air instead of heat transfer to it and COP will be zero.