The LES and DNS simulations of heat transfer and fluid flow in a plate-fin heat exchanger with vortex generators

Unsteady three-dimensional DNS and LES simulations for resolutions up to about 1.2 million points were performed to investigate the fluid flow and heat transfer in a plate-fin heat exchanger with vortex generators. The Prandtl and Reynolds numbers are 0.71 and 2000, respectively. An incompressible finite volume code, based on a fractional step technique with a non-staggered grid arrangement and a multigrid pressure Poisson solver, was used. From these simulations, the heat transfer and fluid flow were studied using instantaneous and time-averaged quantities such as the contours of velocity components, pressure, vorticity, turbulent stresses, temperature fluctuations and Nusselt number. This study shows that the temperature fluctuations, the turbulent kinetic energy, and the unsteadiness effects are stronger in the regions where the longitudinal vortices are more active. In this study, the effects of spatial resolution and the angle of incidence of the vortex generators are also investigated. A comparison between DNS and LES simulations for the present study shows that the predicted structures of fluid flow and temperature fields are similar for both methods.