Due to compact size, high power density, low cost and short construction time, the Small Modular Reactors (SMRs) are considered as one of the candidate reactors, in which the power generation system is important with a compact heat exchanger for modular construction. Therefore, the effect of plate structure and nature of the working fluid on the thermal performance of Plate Heat Exchanger (PHE) are analyzed for the design of compact and efficient heat exchanger. The heat transfer rate, temperature counters, velocity vectors and pressure drop have been optimized and investigated using FLUENT. The Nusselt number has been calculated for the corrugated and flat PHE to validate the convective heat transfer. The numerical results are agreed well with correlation within deviation of ~ 5-7%. The performance of heat exchanger can be improved by controlling the mass flow rate and temperature of working fluid. The corrugation PHE increases the heat transfer rate 20 % and effectiveness 23 %, respectively, as compare to flat PHE when the working fluid is water. In the case of air, heat transfer rate and effectiveness are about 10 % and 9 %, respectively. The results show that the corrugated PHE is more effective than the flat PHE because corrugation pattern enhances the turbulence of fluids, which further increase heat transfer rate and coefficient. The selection of the working fluid and structure of the plate must be considered carefully for efficient and compact design of heat exchanger.