Numerical Analysis of the Impact of Incoming Cold Airstream on a Room Shaped to Passive Solar Chimney Coupled with Earth-Air Heat Exchanger

Numerical results are presented for a morphology fitted to a passive solar chimney attached to a room coupled with an earth-air heat exchanger. The effects of the variable thermophysical properties of air are included in the modelling. The considered operating mode is room cooling (summer ventilation) by means of an incoming airstream drawn from the soil at a temperature lower than that of the ambient. Buoyancy is assumed to be the only driving force acting on the fluid. A wide range of irradiance over the solar chimney walls, from 10 to 1000 W/m2 (Rayleigh number based on the glazing wall from 1.77 × 1011 to 1.77 × 1014), is analyzed. The impact of the incoming airstream temperature on the overall dynamic and thermal behavior of the system is studied. The induced mass-flow rate and average Nusselt number are presented as a function of relevant parameters for evaluating the passive device performance. The results reveal a strong influence of temperature and the position of the incoming cool airstream on room cooling. Some opposite effects on the relevant parameters are detected, but a sizeable increase in ventilation within the room for the middle and upper positions of the incoming duct is highlighted.