RP-237 -- Research on Wind-Related Heat Losses from Solar Collectors PDF

An ASHRAE-sponsored research program has been carried out to investigate various aspects of the wind-related heat loss from a flat plate solar collector. The program encompasses three distinct parts, each of which deals with a specific problem area. In the first part, attention was focused on collectors which are mounted flush with respect to the host surface (e.g., the roof of a building) and which face into the wind. In such an installation, the collector is framed by the host surface which, therefore, acts as a co-planar adiabatic extension of the upper cover plate of the collector. This extension, although thermally inactive, may have a significant influence on the velocity distribution in the air passing over the collector and, in this way, may also influence the collector heat transfer coefficients.

The experiments performed here have demonstrated that co-planar adiabatic extensions which frame a flat plate collector function effectively to reduce the collector heat transfer coefficient. On the basis of a large number of experiments encompassing a variety of frame configurations and Reynolds numbers, a simple correlation equation was evolved which can be used to estimate the reduction in the heat transfer coefficient.