EFFECT OF WALL HEAT-CONDUCTION ON LAMINAR MIXED CONVECTION IN THE THERMAL ENTRANCE REGION OF HORIZONTAL RECTANGULAR CHANNELS

This paper presents a numerical study of the effect of peripheral wall heat conduction on laminar mixed convection in the thermal entrance region of horizontal rectangular channels. In addition to the Rayleigh number Ra and the channel aspect ratio (width-to-height) gamma, the wall heat conduction parameter K = k(w)t/(k(f)D(e)) plays an important role in heat transfer. A numerical method of solution utilizing the vorticity-velocity formulation is developed to solve the system of governing partial differential equations coupled with the boundary condition equation considering peripheral wall heat conduction. Local friction factor ratio and Nusselt number variations are shown for Pr = 0.7, Ra = 10(4), 3 x 10(4), and 10(5), gamma = 0.2, 0.5, 1, 2 and 5, K = 0.01, 0.1 and 1. The effect of peripheral wall heat conduction on Nusselt number is found to be significant when the value of gamma is less than 1. The asymptotic solutions for z --> infinity are compared with the existing numerical results and good agreement is indicated.