This paper aims to determine the flow characteristics and thermal performance of plate heat exchangers. The study is divided into two parts. In the first part, four different shapes of corrugated boundaries have been recommended, rectangular, trapezoidal, triangular, and sinusoidal shapes. In addition, an artificial roughness has been introduced to improve heat transfer within corrugated channel. In the second part, a corrugated wall was used at the inlet channel. Numerical results are presented as Nusselt number (Nu) and friction factor (C f ) using the commercial software ansys-fluent where the Reynolds number is ranged between 3000 and 12,000. The results of this investigation reveal that the overall thermal performance improves greatly by 50% due to the use of the sinusoidal artificial roughness and added undulations in the inlet channel. It is also observed that the latter case with the ratio A″/ λ ″ = 0.05 is the optimal design for the plate heat exchanger.