Computational Fluid Dynamics (CFD) and heat transfer simulations are conducted for a cross flow heat exchanger. The heat exchanger consists of a linear pipe carrying a heated fluid. The thermal interactions between the heated fluid having a laminar flow and the walls of the pipe have been studied under the influence of an external environment of water having a turbulent flow, in a direction normal to the pipe. A RANS model with a k-ε variant was used to model the behavior of different material pipes which were observed under the varying conditions of turbulence, velocity, pressure and vorticity. When subjected to the same conditions, plots of the temperature gradient, isothermal contours, heat transfer coefficient against Reynolds number and thermal conductivity modelled against the various graphene coating thicknesses studied have shown that out of Copper and Stainless Steel the former has shown the most significant increase in thermal conductivity on the addition of a Graphene coating. Furthermore, to check for optimum efficiency, the same study was conducted with an internal coating of a Graphene layer for the aforementioned materials. It has been observed that an outer coating was not only more economically feasible, but also showed better thermal performance compared to an inner coating of graphene for copper, however it did improve the thermal performance of Stainless Steel significantly. © 2021