Mixed convection heat transfer in a lid-driven enclosure with a double-pipe heat exchanger

Abstract

The numerical investigation of mixed convection in a heat exchanger with double-pipe, where the upper lid is given a constant velocity, is presented in this paper. The governing equations, as well as the boundary conditions, define the physical problem. The boundary conditions and governing equations are translated into non-dimensional form and solved by means of a finite-element methodology based on the Galerkin weighted residual. The investigation is conducted for three different governing parameters; namely, Prandtl number (Pr), Richardson number (Ri) and Reynolds number (Re). The outcomes are presented in terms of streamlines, isotherms and average heat transfer rate. Computations are done for a range of Ri (0.01 ≤ Ri ≤ 10), Re (50 ≤ Re ≤ 500), and Pr (1 ≤ Pr ≤ 10) for different dimensionless time (τ = 0.1, 0.5, 1). It is found that the influence of Ri on streamlines, isothermal lines, and heat transfer rate is significant and the maximum heat transfer is gained when values of Ri and Re are higher and Pr is lower. It is also found that the flow strength increases substantially with time and multiple vortices emerge as the convection rate increases.