Numerical study on mixed buoyancy-wind driving induced flow in a solar chimney for building ventilation

In a solar chimney, the buoyancy induced flow of air generates ventilation of the building where the chimney is attached. When atmospheric wind blows over the upper part of a solar chimney, a mixed buoyancy-wind driving induced flow appears, and then the thermal behaviour of the chimney changes drastically. Assuming that the chimney is devoid of any protective device at its upper part, numerical results for the pressure difference coefficients, average Nusselt number and the induced mass flow rate are obtained for values of Rayleigh number varying from 107 to 1012 (symmetrically, isothermal heating condition) and 1011 to 1015 (symmetrically, uniform heat flux heating condition), with wind speeds from 0 to 10 m/s. A correlation for the non-dimensional mass flow rate is presented, which is valid for the complete range of relevant parameters regarded, with an average deviation about 6%.