Solar chimney: modelling and verification

In this article, the first part of a research project about the modelling of a solar chimney is presented. In this first part, the average ventilation flows measured in an experimentalinstallation have been compared to the results obtained by CFD (Computational Fluid Dynamics) simulations.In order to do so, a solar chimney with a cross-section of 0.78 m x 0.156 m, height 3.6 m, has been constructed.The chimney consists of a glass surface oriented towardsthe south. The internal (absorber) surface is made of a copper plate, which has been painted black in order to increase the solar absorption. The chimney is connectedto a room measuring 5 m x 2.5 m x 2.5 m, from where it extracts air.The modelling of natural ventilation openings is usually done by specifying the discharge coefficient, which relatesthe air velocity of the ventilation flow with a pressuredifference. In the case of modelling a solar chimney,the effect of buoyancy caused by the hot chimney surfaces should be taken into account as well as the dischargecoefficients dependence of the external wind.The data acquisition system used in this first part of the project measures the ventilation flow, the absorber and glass temperatures and the pressure difference between the chimney inlet and outlet.The comparison of the results obtained by measurements with those obtained by CFD simulations show that computationaltools are accurate enough to predict the behaviourof natural buoyancy in this kind of installations. In a later stage of the project the relationship between the external wind field and the pressure difference will be investigated and a mathematical model to predict the absorber and glass temperatures will be developed.