A Numerical Study on Cross Flow Heat Exchanger with Different Reynolds (Re) Numbers

Abstract

Heat exchangers are highly popular in engineering and industrial applications. Numerical studies on heat exchangers to investigate the performance of heat transfer have been carried out widely by Computational Fluid Dynamics (CFD) in recent years. In this study, a circular pipe with hot water in cross flow is investigated in different Reynolds (Re) numbers. Flow is turbulent flow and the Re number varies from 3165 to 4643 in the circular pipe. The air is at a temperature of 303 K and the water is at 333 K. Variation of flow characteristics and thermal performance is observed according to an increase in Re numbers such as Wall Shear Stress (WSS), Skin Friction Coefficient (Cf), Nusselt Number (Nu), heat transfer coefficient (h) and surface temperature of the circular pipe. Results show that there are no significant changes for the WSS and Cf values in the specified range of the Re number. However, when the thermal performance is evaluated, the temperature of the surface of the circular pipe, heat transfer coefficient, and Nu number values are increased by an increase in the Re number. Here, the increase is approximately 2% for the specified range of Re number, and it is shown that it can be increased by the flow conditions. The maximum Nu number is 4482.37 at the Re number of 4643. As a result, the Re number is highly effective in controlling the heat transfer performance of a heat exchanger