Heat transfer enhancement on the liquid side of an industrially designed flat-tube heat exchanger with passive inserts - Numerical investigation

In order to investigate the heat transfer in such a channel, the incompressible Navier-Stokes and energy equations are solved directly on a very fine computational mesh. These quasi-DNS simulations are carried out at three Reynolds numbers, spanning the threshold where laminar-turbulent regime transition is believed to occur based on previous experiments. Results suggest that turbulence does contribute to heat transfer enhancement at the highest Reynolds number. However, the boundary layer modification, which is the main heat transfer enhancement mechanism, is identically in action in both, laminar and turbulent, regimes. Results also show that the non-symmetric distribution of passive inserts is disadvantageous, particularly in the event of laminar-turbulence regime transition.