NUMERICAL STUDY OF THE VELOCITY FIELD IN A VORTEX FLOW HEAT EXCHANGER-MIXER

摘要

Simulation of flows in a model of vortex heat exchanger-mixer has been performed using the CFD-ACE code from CFDRC. Numerical and experimental velocity profiles show good agreement in the main vortex flow with all inlet conditions studied. Some differences appear on calculated profiles characterising the secondary flow due to the fact that the classical k - ε turbulent model used cannot model transient effects occurring. Nevertheless, visualisation of the calculated secondary flow point out its dependency on Reynolds numbers with variation of number and location of vortices which appear near peripheral walls. This secondary flow dynamics is governing the spatial residence time distribution of fluid particles flowing through the geometry: with Reynolds number increasing, the zone containing the longest residence time is moving from near both side walls with laminar inlet condition to the half span plane, that is far from the heated side walls, with Re=60000. Some particular dynamical conditions appearing with Re=30000 lead to a regular residence time.