Numerical Study of Mixed Convection in an Isosceles Trapezoidal Cavity for the Optimization of ASUTO Charcoal Stove

Mixed convection of heat and mass transfer in an isosceles trapezoidal cavity has been studied numerically. Constant heat flux is imposed at the top grid with four outlets. 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-dimensional 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 values ​​(10,1000), 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 in natural convection (𝑅𝑖 = 10 or 100), the optimum inclination angle for air draft is in the vicinity of 15°.