Heat Transfer and Friction Loss Performance of Perforated Heat Exchanger Surfaces

A scale-up modeling technique has been developed to examine the effects of perforation geometry on the heat transfer and friction loss performance of compact heat exchangers having plate-perforated rectangular fin surfaces. The test cores, each consisting of a number of aluminum plates separated by wooden spacers to form parallel flow channels, were tested in a subsonic wind tunnel. The effects of the Reynolds number, plate surface porosity, core frontal porosity, and slot geometry on the heat transfer rate, friction loss, and noise intensity are determined. It is found that under certain circumstances plate perforation will produce significant improvement in heat transfer for the same pressure drop and pumping power. These studies are directed to the design of air-cooled condensers for Rankine cycle automotive engines, marine power propulsion systems, and the dry cooling towers of extra-high capacity electric power plants.