CFD analysis of heat transfer in a helical coil heat exchanger using fluent

Abstract

Heat exchangers are the important engineering systems with wide variety of applications including powerplants, nuclear reactors, refrigeration and air-conditioning systems, heat recovery systems, chemical processing and food industries. Helical coil configuration is very effective for heat exchangers and chemical reactors as they can accommodate a large heat transfer area in a small space, with high heat transfer coefficients. This project deals with the analysis of the helical coiled heat exchanger with various correlations given by different papers for specific conditions. Although various configurations are available, the basic and most common design consists of a series of stacked helically coiled tubes placed in a helical outer cover. The inner tube ends are connected to manifolds, which act as fluid entry and exit locations. And the outer tube is provided with inlet and outlet manifolds so that cooling fluid can be passed through it. The tube bundle is constructed of a number of tubes stacked atop each other and the entire bundle is placed inside a helical casing. The complex fluid-dynamic inside curved pipe heat exchangers gives them important advantages over the performance of straight tubes in terms of area/volume ratio and enhancing of heat transfer and mass transfer coefficient. Convective heat transfer between a surface and the surrounding fluid in a heat exchanger has been a major issue and a topic of study for a long time. The analysis of these various correlations with certain defined data is presented in this project. In this study, an attempt has been made to analyze the effect of counter-flow on the total heat transfer from a helical tube. The temperature contours, velocity vectors, surface nusselt number, total heat transfer rate from the wall of the tube was calculated and plotted using ANSYS 13.0. Copper was chosen as the metal for the construction of the helical tube. The fluid flowing through the inner tube and outer casing was taken as water.