Unsteady Flow Modelling in Plate-Fin Heat Exchanger Channels

A methodology using Computational Fluid Dynamics (CFD) was developed to predict the flow and heat transfer performance of a single two dimensional sinusoidal channel of a Heat Exchanger (HE) at a Reynolds number (Re) range of 5 ≤ Re ≤ 500. The impact of different modelling assumptions was thoroughly evaluated which has not has been done in detail before. Two computational domains were used: a single period sinusoidal channel for fully periodic flow predictions and finite length channel consisting of 6 sinusoidal channel periods. Mesh and time independence was achieved for both domains whilst results with periodic domain were compared to numerical results in the literature. Laminar, k-ε and k-ω SST predictions were assessed throughout the Reynolds range with unsteady flow onset detected at Re ≈ 200 using laminar and k-ω SST models. The impact of different accuracy numerical discretisation schemes is assessed throughout the Re range and it was found that second order accuracy schemes should be used to fully capture the unsteady flow. Comparison between open-source CFD package OpenFOAM and Ansys was Fluent was performed and agreement was ‘ found.