Forced-convective steady-state heat transfers from shrouded vertical fin arrays, aligned parallel to an undisturbed air-stream

Abstract

An experimental investigation of the steady-state rates of heat loss from an array of vertical rectangular fins of 3 mm thickness and 250 mm length, when in the presence of an almost adiabatic horizontal shroud, situated adjacent to and above the horizontal fin tips, is reported. With the fin's horizontal base at a uniform temperature of 40 ± 0·1° C above that of the ambient environment, the optimal fin separation—corresponding to the maximum rate of heat loss—is deduced. As the ratio of the shroud height above the vertical fins to the fin height decreases from unity to zero, this optimal value decreases by approximately 17%. The frictional characteristics of the air flow through the fin array have also been studied in the Reynolds number range of 4·0 × 10 4 to 2·0 × 10 5. Large streamwise pressure drops and high heat-transfer rates resulted when the fins were closely spaced and no clearance gap was present above the vertical fins. In reasing the shroud clearance resulted in smaller overall pressure drops and decreasing heat-transfer rates from the heat exchanger.