Study of Heat Transfer to Different Graetz Numbers in Square Tube Heat Exchangers with Passive Improvements using Cfx ®

Heat exchangers are devices that allow heat to be transferred fromone fluid to another. There are techniques to improve the heat transfer rate, which can be active or passive. This article numerically studies the behavior of heat transfer in improved exchangers using the ANSYS® package. A simple, twisted, spiral, and twisted spiral square tube geometric model was developed, then its meshing was carried out in the Meshing® module. Next, a mesh independence study was performed where the mesh was refined. Subsequently, the CFX® module was entered for the simulation configuration with three parameters: inlet temperature, wall temperature and different speeds at the inlet of the exchanger. Comparing the heat transfer coefficient at different Graetz numbers (Gz) for each geometry verifies the positive effect of passive improvements on the convective heat transfer coefficient;as the case of the double passive improvement that has increases between 112 and 137%.