A six row pin-fin array was constructed with a spanwise spacing of 2.5 diameters, streamwise spacing of 1.5 diameters and a height to diameter ratio of 1. The streamwise stagger of alternate rows was continuously varied from fully in-line to fully staggered. Tests were carried out at Reynolds numbers of 2.7 × 104 and 2.3 × 104, corresponding to maximum velocities, in the low subsonic range, of 21 m/s and 18 m/s respectively. These results showed that the array averaged heat transfer was greatest from a fully staggered array and had a minimum at a stagger slightly greater than fully in-line. However, with increasing stagger, the array-averaged friction factor grew at a greater rate than the heat transfer. The ensuing analysis of the total array performance, considering both the magnitude of heat transfer and the losses within the array, showed that the fully in-line array had the highest ratio of heat transfer enhancement to friction factor enhancement. Therefore, if pressure loss was a design criterion, the fully in-line array was preferable. However, if pressure loss was not a constraint, then the staggered array was preferable.

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