Performance of Turbulence Models on Heat Transfer and Pressure Drop with a 25° Continuous Helical Baffled Heat Exchanger

Abstract

The objective of the present work is to study the influence of three turbulence models and find out the suitability of the k-ω SST turbulence model. The thermal performance of a heat exchanger with single continuous helical baffle is studied numerically and experimentally. A commercial CFD package (Ansys-Fluent),based on the finite volume method, is used to predict the performance of 25° continuous helical baffled Heat Exchanger using 3 turbulence models viz. k-ε Realizable, k-ε RNG and k-ω SST. The experiments are carried out in counter-flow mode with cold fluid (ambient water) on the shell side and hot fluid (hot water) on the tube side. In the experimentation, the variation of the shell side heat transfer coefficient and of the pressure drop with shell side mass flow rate is tested. For the validation of the numerical model, the numerical results are compared with the experimental results and with the published literature. The experimental heat transfer coefficient exhibits a deviation from the correlated values in the range of 1.5% to 5.3%, whereas pressure drop shows deviation in the range of 4.22 to 6.67%. The results indicate that all the three turbulence models are in good agreement with the experimental findings. The k-ε Realizable model is the best turbulence model for the prediction of heat transfer and k-ω SST is the best turbulence model for prediction of pressure drop. For the overall performance, k-ω SST model is suitable for the prediction of both heat transfer and pressure drop and it helps in capturing the swirling flows in helical baffle heat exchangers.