Detached eddy simulation of flow and heat transfer in swirl tubes

Abstract

Detached Eddy Simulations (DES) are carried out to predict the flow structure and the heat transfer of swirling flows in tubes. Such swirl tubes are a promising method for heat transfer enhancement compared to the flow in a smooth tube. However, the physics in such a swirl tube is far from being fully understood. The numerical results in terms of velocity and Nusselt number are compared to own experimental data. DES and experiments agree well for the mean velocity profile and the numerics give insight in the turbulent vortex structure in a swirl tube. The axial velocity is characterized by a backflow in the tube center due to the induced strong swirl. The occurrence of this backflow region depends on the swirl strength and its influence on the heat transfer is still under research. Therefore, we simulate swirl tubes with different swirl numbers for the same mass flow and consequently same Reynolds number. Furthermore, we showa speed-up comparison for the parallelization with OpenFOAMand provide details about the computational performance of a DES on the new Cray XC40.