Heat transfer by convection, conduction and radiation in solar chimney systems for ventilation of dwellings

Abstract

Numerical study by conjugate heat transfer is carried out of solar chimney systems for heating and ventilation of dwellings. Conservation equations are solved by finite difference-control volume numerical method. The governing parameters were: the Rayleigh numbers from 5 × 10 8 to 10 11, the Prandtl number, Pr = 0.7, constant for air, the chimney aspect ratio, A = H/L from 6 to 15, the air channel width l′/ L = 0.2 to 0.5, the air entrance port size, h/L = 0.167–0.667, the wall thickness l/ L = 0.25–0.4, the conductivity ratio k r from 5 to 50 and the surface emissivity, ε from 0 to 1. The Nusselt number, the dimensionless volume flow rate V ˙ and radiation heat flux ratio q r/ q tot are calculated as a function of the governing parameters, and streamlines and isotherms are produced. The results show that the surface radiation modifies the flow and temperature fields, affects the Nusselt number and the volume flow rate, both in a positive way, and improves the ventilation performance of the chimneys.