Modelling of Heat Exchangers with Computational Fluid Dynamics

Heat transfer is one of the major aspects of machineries, devices and industrial processes for maintaining their functionality and also for achieving better product quality. Hence, different types of heat exchangers are used in these applications with the purpose of removal of extra process/device heat to maintain them in desirable working temperatures. However, the size of a heat exchanger is a key consideration for any type of process or device as it decides the size of the machine/device or of the processing plant. This study aims to study the design of a heat exchanger theoretically and then to use computational fluid dynamics to optimize its performance. For design purposes, a counter flow heat exchanger was considered and its length was calculated with the LMTD method while the pressure drop and energy consumption were also calculated with the Kern method. Then, a computational model of the same heat exchanger was developed with ANSYS and then this was extended to six different models by changing its parameters for the optimization purposes. Also, these models were used to analyse the heat transfer behaviour, mass flow rates, pressures drops, and flow vortices of the shell and tube flows inside the heat exchanger. Theoretical and CFD results showed only a 1.05% difference in terms of the cooling performance of the hot fluid. The axial pressure drop showed positive correlations with both the overall heat transfer coefficient and pumping power. Overall, CFD modelling gave a promising outlook for design and optimization of heat exchangers.