Plate heat exchangers are commonly used in a variety of industries, and flow distribution among different channels affects their performance and is often assumed to be uniform. In this work, Computational Fluid Dynamics (CFD) simulations were conducted to examine the impact of flow maldistribution on the hydraulic performance of a plate heat exchanger. The parameters varied were inlet mass flow rate, and header configuration. The relevance of nonuniformity on heat exchanger efficiency was supported by the CFD results. The findings indicate that the most important factor in non-uniformity is header geometry. Tapered and nontapered headers with unequal diameters were studied. In our study, the non-uniformity of the flow was higher with the tapered header. A plate heat exchanger's channels have more uniform flow when an unequal ratio of the inlet to outlet header diameters is used instead of the same header diameter for both inlet and outlet. The findings from this research could have an impact on how heat exchanger header geometry is optimally designed to minimize flow maldistribution in U-type plate heat exchangers.