Numerical analysis for performance evaluation of a passive roofing system cooled by water evaporation

The performance of a special passive building component is investigated. it consists of a ventilated roof where the lower surface of the channel in which flows the external air is mantained wet. For thermal performance evaluation purposes have been carried out numerical analysis of the flow thermal and water vapour concentration fields within the duct. As results the temperature and specific heat fluxes distributions on the wet lower surface are shown, moreover, to evaluate the overall performance of the component the averaged values of thermal fluxes are presented. The effect of pressure due to different wind regimes are investigated along with the behaviour of the roofing system subject to different climatic conditions. For the evaluation of mass and thermal fluxes the influence of buoyancy term has been taken into account. In order to obtain an estimate of the thermal cooling flux on the wet surface suitable procedures were coded and linked to a commercial program for computational fluid dynamics. A recently presented approach to solve the coupled heat and mass transfer problem has been adopted.