AN EXPERIMENTAL INVESTIGATION OF ANNULAR FINS UNDER FORCED CONVECTION

Abstract

Heat transfer characteristics under forced convection are investigated experimentally by varying parameters like surface area, base-to-ambient temperature difference and Reynolds number. To investigate the performance of fins experimentally, fins made of aluminium (high thermal conductivity) are taken. For varying the surface area fin with 11 mm diameter without circumferential fins, fin with 31 mm diameter and annular fins of 31 mm diameter are taken as specimens. Base to ambient temperature difference is varied with the aid of dimmerstat ranging from 25W to 45W. Reynolds number is also varied by varying the velocities of air. Velocities are varied by the aid of fan. Then these fins are tested under different load conditions, different Reynolds number by varying the surface area of fins increase the rate of heat transfer. With the variation of relevant parameters under forced convection heat transfer rates are analyzed experimentally. Experiments are conducted by using the annular fins, fin with diameter 11mm without circumferential fins and fin with diameter 31mm at different Reynolds number and loads under forced convection and comparison is made between fins. Experimental results shows that forced convection heat transfer rate from fins depend on surface areas, base ambient temperature difference and Reynolds number. The base temperature for annular fins is reduced by 30% when compared to fin with diameter 11mm due to increase in surface area about 40%. The base temperature for annular fins is reduced by 10% when compared to fin with diameter of 31mm due to decrease in surface area about 41%. It is also observed that at higher heat load i.e., 45W, the overall fin efficiency of annular fins is increased by 44% and 8% compared to fin with diameter of 11mm and 31mm respectively. At higher Reynolds number range 800-2000, heat transfer rate increases in annular fins due to more number of air molecules get in contact with the heated surface. ---------------------------------------------------------------------***--------------------------------------------------------------------INTRODUCTION Heat generation is the result of many engineering system. But due to unwanted heat overheating and failure of the system occure so the heat generated with in the system should be dissipated to surrounding in order to maintain the system working effectively and reliably. To overcome from this problem, thermal systems with effective emitters as fins is considerable, to achive the desired rate of heat dissipation. The heat dissipation from system to atmosphere can be obtain by using of convection and radiation heat transfer. As we know that the heat transfer rate can be increased by increasing the surface area or heat transfer coefficient.