Abstract

The unglazed transpired solar collector is now a well-recognised solar air heater for heating outside air directly. Example applications include pre-heating ventilation air and heating air for crop drying. The outside air in question is sucked straight from ambient, uniformly through the whole surface of a perforated blackened plate (the absorber plate) exposed to the sun. An important parameter fixing the collector’s efficiency is the heat exchange effectiveness, ε. Once ε is known, finding the collector efficiency is straightforward. The effectiveness depends on the wind speed, the suction velocity, and the plate geometry. This paper is about determining this effectiveness by computational fluid mechanics (CFD), for conditions of no wind. Because of symmetry, the computational domain needed only to extend over a representative element, which included one hole and the region immediately adjacent to it extending to half the distance between holes. Simulations were carried out over a wide range of conditions, and the results are incorporated into a correlation model. Because of the no-wind assumptions, the model is of limited direct use, but when combined with experimental data, the model can permit a wider-ranging correlation equation to be obtained.

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