Water drop size numerical optimization for hydrosolar roof

Abstract

Air-conditioning systems of buildings and other industrial facilities commonly use water as a heat drain to remove heat from refrigerant condensers. Classical solutions to reduce the temperature of this service water are air cooled heat exchangers or mechanical draught cooling towers. The Hydrosolar Roof optimized in this paper, working as a heat focus in the thermodynamic cycle of a heat pump, achieves the same objectives without fan energy consump tion. This system consists of an extended framework on the roof of the building with some thermal plates installed over it. Some of the plates are made of a high reflective material, and the others are made of absorbent material. The Hydrosolar Roof uses the design of the reflective and absorbent parts of the device, made of flat plates, to form a sloping channel. Solar radiation is collected by this channel and, due to local heating in this zone, natural convection through it is produced. The natural induced air flow is irrigated with water sprays, placed below the plates at the inlet of the channel, generating a cross flow between air and water. In this way, water is cooled by direct contact with a reduced amount of vaporization, and most of the water is recovered at a reduced temperature. This work shows the numerical study to obtain an optimum for the sprayed water drop size. The two-dimensional version of the CFD code Fluent was applied to predict both atmospheric air and sprayed water main variables in a real geometry and under different thermodynamic conditions.