This study presents an investigation of transient local entropy generation rate in Pulsating turbulent How through ail externally heated pipe. The flow inlet to the pipe pulsates at a constant period and amplitude, only the velocity oscillates. The simulations are extended to include different Pulsating flow cases (sinusoidal flow, step flow, and saw-clown flow) and for varying periods. The flow and temperature fields are computed numerically with the help of the Fluent computational fluid dynamics (CFD) code, and a computer program developed by us by using( the results of the calculations performed for the flow and temperature fields. In all investigated cases, the irreversibility clue to the heat transfer dominates. With the increase of flow period, the highest levels of the total entropy generation rates increase logarithmically in the case of sinusoidal and saw-down flow cases whereas they are almost constant and the highest total local entropy is also generated in the step case flow. The Merit number oscillates periodically in the pulsating flow cases along the flow time. The results of this study indicate that flow Pulsation has an adverse effect oil the ratio of the useful energy transfer rate to the irreversibility rate.