Thermal performance of metallic and non-metallic natural convection heat-exchanger fins

The steady-state rates of heat dissipation from an array of vertical rectangular heatexchanger fins to the ambient air had been measured experimentally under natural convection conditions, when their horizontal base was maintained at an uniform temperature of 40 K above that of the ambient environment which was kept uniformly at 20°C The fins were 3 mm thick and 500 mm long, and protruded 60 mm perpendicularly from the 500 mm X 190 mm horizontal rectangular base. The fins were fabricated with duralumin (kf = 160 Wm−1 K−1), stainless steel (kf = 15 Wm−1 K−1) and fibre plastic (kf = 0.2 Wm−1K−1) respectively. The optimal fin separation corresponding to the maximum rate of heat loss from the fin array was increased from 14.5 mm to 18 mm, and the maximum rate of heat dissipation was only slightly reduced by 12% when stainless steel fins were used instead of duralumin fins. There was no optimal fin separation observed when fibre plastic was used to fabricate the fin array. and the maximum heat dissipation rate was less than 1/3 of that obtained from the duralumin fins. In addition, the heat dissipation increased and approached a steady value when the number of fins was reduced for the fibre plastic fin array. It is suggested that natural convection heat-exchanger fins are no longer effective to enhance heat dissipation when they are fabricated with material of thermal conductivity less than unity (which is normally used as the separating value between thermal conductor and thermal insulator).