Thermoacoustics is an emerging technology which generates the cooling power from acoustic energy, provides a significant alternative to the ozone destructing vapour compression refrigerators since there is no production of exotic materials. The performance of the thermoacoustic heat engine (TAHE) is mainly affected by its geometrical and operational parameters. Though it is a well known fact, an attempt was made in the present study to analyse the performance of TAHE using CFD simulation with variation in stack and resonator length under identical simulation conditions with different working fluids namely air, argon and nitrogen. It was found that the frequency of TAHE decreases with increase in stack and resonator length and also in the variation of fluid medium from nitrogen to air and then to argon. The simulation software DeltaEC is also used for predicting the performance of TAHE, in which the results obtained from DeltaEC are compared with CFD results.