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This paper presents an investigation of the effect of fouling by considering a tube and plate fin geometry for which performance characteristics are well defined. By matching a particular heat exchanger to a given fan it can be shown that the air-side heat transfer coefficient increases as the air-side passages become progressively blocked, reaching a maximum close to the fully blocked condition. For moderate fouling this increase largely compensates for the change in mean temperature difference brought about by the variation in air flow rate, giving an overall performance very close to that for the clean condition.

This paper presents an analysis and critical appraisal of a ‘lumped-capacity’ method for the determination of the average air-side heat transfer coefficient of a finned-tube heat exchanger geometry. A simple transient heat transfer experiment is described in which a small finned heat exchanger sample was tested in a wind tunnel. The heat exchanger sample consisted of three rows of staggered flat copper rods within an array of continuous fins of the same material. Analysis and supporting experimental results, demonstrate the validity of an assumed pseudo-constant fin efficiency thereby justifying the employment of a modified lumped-capacity approach for finned geometries.