Effect of Gr/Re on Mixed Convection an d Comb in ed Mixed Convection-Radiation Hea t Transfer Within a Vertical Channel with Variable Wall Temperature

Th e present paper invest igates, numerically, the effect of the Grashof number to a Reynolds number rat io (Gr/ Re), on fluid flow and heat t ransfer wit hin a vert ical channel for two cases: Mixed (nat ural-forced) convect ion and combined mixed convect ion-radiat ion. The flow in the channel is assumed to be two-dimensional, laminar and steady . The wall tem peratu re is defined as a linear function of t he channel height . When dealing with the combined mixed convectionradiation case, radiat ional propert ies have been taken into account , both for the walls and the fluid. The fluid has a Prandtl number of 0.71 and it is radiat ionally assumed as a participat ing medium. A comparison between the two cases at a constant Gr/Re is reported , so as to invest igate the influence of radiation, as one of t he heat tra nsfer modes, more clearly. To solve the governing equations (i.e., mass cont inuity, momentum and energy) the Finite Volume method is employed and the SIM PLE algorithm is ado pted to couple the velocity and pressure fields. T he radiat ive t ransfer equation is solved using the Discrete Ordinates Met hod, by ado pting its 5.1 order quadrat ure scheme. The results for both cases are present ed as the profiles of axial velocity across the channel width, axial cente rline velocity, bulk temperatu re and pressure versus channel height .