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

Abstract

Enhancing the heat transfer by the use of helical coils has been studied and researched by many researchers, because the fluid dynamics inside the pipes of a helical coil heat exchanger offer certain advantages over the straight tubes, shell and tube type heat exchanger, in terms of better heat transfer and mass transfer coefficients. Various configurations of coil structure are possible, and the configuration in which there is a series of vertically stacked helically coiled tubes is the most common type. The end of the tubes act as the inlet and outlet manifolds, which serve the purpose for the entry and exit of hot as well as cold fluid. This configuration offers a high compact structure and a high overall heat transfer coefficient, hence helical coil heat exchangers are widely used in industrial applications such as power sector, nuclear power generation, food processing plants, heat recovery systems, refrigeration, food industry, industrial HVACs etc. Convective heat transfer between a surface and the surrounding fluid in a heat exchanger has been a major issue and a topic of study in the recent years. In this particular study, an attempt has been made to analyze the effect of two different flows (parallel and counter-flow) on the total heat transfer from a helical tube, where the cold fluid flows in the outer pipe and the hot fluid flowing in the inner pipes of the tube in tube helical coiled heat exchanger. Different dimensions of the pipes, helix are taken into consideration while running the analysis. The surface Nusselt number, the contours of temperature and energy, velocity vectors and the total heat transfer rate from the wall of the tube were calculated and plotted using ANSYS FLUENT 13.0 where the governing equations of mass, momentum and heat transfer were solved simultaneously, using the k-e two equations turbulence model.