Numerical Study of Mixed Convection in an Isosceles Trapezoidal Cavity with Several Outlets: Application for Primary Air Draft in ASUTO Charcoal Stove

Mixed convection of heat and mass transfer in an isosceles trapezoidal cavity has been studied numerically. Constant heat flux is imposed through four outlets and the grid is insulated. The inclined walls are maintained in natural convection while the lower horizontal wall is adiabatic. These conditions reflect the air draft zone of the ASUTO charcoal stove. The governing two-di- mensional flow equations have been solved by using the finite difference method and Thomas’s algorithm. The investigations are conducted for different values of Richardson (Ri), Reynolds number (Re) and inclination angles of sidewalls. The results are presented in terms of streamlines, isotherms, moisture contours. It was found that for Reynolds number (Re) equal to 100, the flow pattern is strongly dependent on the inclination angle and Richardson number. Thus, for high Richardson number (Ri) values (10, 100), the dominance of natural convection over the flow structure decreases with the decreasing of the inclination angle of sidewalls of the cavity. For Ri = 1, an optimum air draft corresponds to an inclination angle in the vicinity of 22° while for Ri = 10 or 100 (in dominance of natural convection), the optimum inclination angle for air draft is in the vicinity of 15°.