Experimental Investigation into the Temperature and Heat Transfer Distribution around Air-Cooled Cylinders

This paper describes an experimental investigation into the surface heat transfer coefficient of finned metal cylinders in a free air stream. Ten cylinders were tested with four different fin pitches and five different fin lengths. The cylinders and their fins were designed to be representative of those found on a motorcycle engine with an external cylinder diameter of 100mm and fin lengths of 10 to 50mm. The fins of each cylinder were gravity die cast in aluminium alloy. Each cylinder was electrically heated and mounted in a wind tunnel which subjected it to a range of air speeds between 2 and 20 m/s.

The surface heat transfer coefficient, h, was found primarily to be a function of the air speed and the fin separation, with fin length having a lesser effect.

In addition to the determination of an overall heat transfer coefficient, the distribution of cooling around the circumference of each cylinder was also studied. Not surprisingly, the cooling was found to be greatest on the front of the cylinder, which is the side first impinged by the air stream. The cooling of the rear of the cylinder was better than might have been expected and this is quantified.