P.D. Dan and R..M. Aynsley (Australia)
energy, environment, cooling, experiments, modelling, simulation.
The potential of cooling using the roof assembly of the building as an air-heat exchanger has been investigated. At night, the roof surface naturally acts as a cooler, emitting long-wave radiation to the sky. With air flowing underneath it, heat is extracted from the air to the sky. The degree of cooling achievable is dependent on the atmospheric conditions at the site. Experiments of this type of cooling have been conducted in Townsville, a warm and humid location in northern Australia, using metallic roofing sheets as nocturnal radiators. Mathematical models have also been established and validated previously. In this paper, the cooling models are used to predict the cooling potential for other warm and humid locations in Australia and USA: Cairns, Darwin, Atlanta and Miami. Climate data, three-hourly, are obtained from the local Bureau of Meteorology. The simulation covers three different roof areas, ranging from one piece of roofing surface, which has been used in the experiments, to that equivalent to three pieces being arranged in series. Results indicate that with a larger roof area, temperature of the cooled air approaches the minimum possible temperature, which is the surface temperature of a roof with no airflow underneath as working fluid.
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