Steady and Unsteady Forced Convective Heat Transfer Analysis in 180 Degree Bend

Abstract

Numerical studies on fluid flow and heat transfer through a two-dimensional 180-degree sharp bend are performed using an in-house code based on streamline upwind Petrov-Galerkin finite element method. A new geometric parameter called inlet height to outlet height ratio (IOR) is defined to assess the heat transfer performance. Parametric analyses are carried out by varying the Reynolds number (Re) from 100 to 900 for five IORs (1:2, 1:1.5, 1:1, 1.5:1, 2:1). The fluid flow changes from steady to unsteady for all IORs with increasing Re. The critical Reynolds number range is identified for each IOR and is found to be lower for IOR < 1 or IOR > 1 when compared with IOR 1:1, thus enhancing the heat transfer due to unsteadiness. IOR also influences the rate of generation of the vortices and the vortex interactions, which emphasize the enhancement in heat transfer. Nusselt number (Nu) and thermal performance factor (TPF) for the domain are calculated and it is observed that though there is an increase of 20%–40% in Nu for IOR 2:1 configuration with respect to IOR 1:1, the TPF predicts that IOR 1:1.5 is an overall good domain for heat transfer and pressure drop considerations.