Numerical Simulation of Heat Transfer Enhancement in Laminar Flow of Viscoelastic Fluids through a Rectangular Channel

摘要

A finite-volume method is applied to the three-dimensional simulation of heat transfer of a viscoelastic fluid in laminar flow through a rectangular channel with an aspect ratio of 2 and constant heat flux at the channel walls. The objectives of the present work are twofold: (a) to compare the numerical results with the heat transfer experimental data of Hartnett and Kostic [l]; (b) to analyze the influence of the secondary flow on the heat transfer enhancement on account of the non-zero second normal-stress difference. The rheology of the viscoelastic fluid is represented by the Phan-Thien-Tanner constitutive equation with non-zero second normal-stress difference. The simulations show the strong effect of secondary flows on the correct prediction of experimental results. The predictions confirm the enhancement of local and mean Nusselt numbers, as found experimentally by Hartnett and Kostic [1], and show that free convection has a major influence in the experimental heat transfer results for Newtonian fluid, but less so as fluid elasticity is increased.