Study of The Thermal Performance of a Shell and Tube Heat Exchanger

Heat exchangers are used in various industries to exchange thermal energy between hot and cold streams. Thereby, heat exchangers are an invaluable tool for processes integration to minimize the need for external sources of energy. There are numerous types of heat exchangers, but shell and tube heat exchangers (STHXs) are by far the most ubiquitous type in the market. Baffles are an integral part of the STHX design, used in order to increase the thermal efficiency, and support the tube bundle from flow-induced vibrations. The existence of baffles entails several adjustable design parameters that can affect the pressure drop and heat transfer rate drastically. The number of baffles, baffle cut, baffle spacing, and baffle orientation are just a few key parameters that can be fine tuned for optimization purposes. Evidently, the experimental modification of all these variables is tedious and costly, and a computational approach must be used. In this project, Ansys Fluent is employed as a computational fluid dynamic (CFD) code to perform an in-depth investigation of various design elements of baffles. Also, experimental data on an available STHX is collected and compared with our modeling results to ensure the validity of our model. The number of baffles is changed from zero to ten, and the resulting pressure drop (the main drawback) and heat transfer rate (the main benefit) of each case are compared. It was found that four baffles are the optimum number of baffles, whereas only three baffles were present in the experimental unit. We then considered three baffle cut orientations: up-down, left-right, and clockwise but the changes in performance were marginal. We concluded the baffle cut orientation is not a notable design variable, and the default up-down orientation is acceptable. Finally, the baffle cut was modified that resulted in significant enhancement of the thermal performance of the device. Overall, CFD enabled us to improve the thermal efficiency of an STHX by ten percent, and, at the same time, decrease its pressure drop to one third. This approach has been proven effective and can be scaled up to large industrial STHXs.