Numerical Computations on Heat Transfer Characteristics from the Cavity Bottom in Parallel Plates Swept by Viscoelastic Fluid

Abstract

A two dimensional numerical study on flow and heat transfer of viscoelastic fluid in a cavity has been performed in order to investigate how effective the heat transfer augmentation technology is by using the Barus effect in the region of low Reynolds and Weissenberg numbers on the bottom wall of the cavity between ribs mounted in the parallel plates. In this paper, the heat transfer characteristics on the bottom of the cavity were focused on. The cavity length and the rib height were changed in three steps, respectively, while the wide flow path width and the solid wall temperature were kept constant. The solvent Reynolds number based on the rib height was set at 100. From the results, it is found that the flow penetration into the cavity effectively occurs just at the inlet of the cavity in the cases of viscoelastic fluids, while a large recirculating region is formed there for the cases of water. The local Nusslt number takes peaks at the position corresponding to the peak positions of velocity gradients on the bottom wall. It is also found that the mean Nusselt number increases with rib height and cavity length. However, the increase rate on the cavity length becomes smaller in a large cavity length region. This indicates there exists the optimum geometric condition and that the present technology has an advantage for making the heat exchanger compact in comparison with that using a water flow.