Performances of heat exchangers with tapered fins

The steady-state rates of deliberate heat dissipation from an array of vertical duralumin fins, under natural convection conditions, have been measured when their base (which was either horizontal, with the fins protruding upwards, or vertical) was maintained at a uniform temperature of 40 K above that of the ambient environment. The 500-mm long tapered fins were each 1·6 mm at their tips and 4·4 mm thick at their base, and protruded 60 mm perpendicularly outwards from their 500 mm x 190 mm rectangular base. The optimal peak-to-peak pitch, S'opt of the fins, corresponding to the maximum steady-state rate of heat loss to the ambient air, was 14 mm ± 1 mm. This was smaller than that obtained under similar imposed conditions, with an array of rectangular fins, identical in dimensions except for their uniform fin thickness, and was almost invariant with respect to the orientation of the fin array for [theta] = 40 K. The steady-state rates of heat dissipation from these two types of exchanger were compared. For the horizontally-based finned systems, slight decreases in the rates of heat dissipation were observed for the tapered-fin arrays compared with those for the rectangular-fin arrays. However, for the orientation with vertical fins protruding outwards from the vertical base, increases in the rates of heat dissipation were observed with the tapered-fin arrays for 8 mm