Experimental investigation of natural convection from variable cross-section fin arrays on horizontal surface

In order for the electronic circuits to operate efficiently, it is necessary to move away the thermal energy, which occurs in consequence of the operation of systems, from the system. Otherwise, the efficiency of the systems will remain low or that energy will even cause the burning of the systems. Fin arrays are used in the cooling of these systems. Fin arrays provide the removal of the energy from the environment by increasing the surface area of heat transfer. Natural convection heat transfer from the fin array which has different ratio of tip to base fin spacing on a horizontal base has been experimentally investigated at a wide range of Rayleigh numbers for different fin heights. Base fin spacing, fin length and fin thickness were kept fixed at 12, 100 and 3 mm respectively, while the ratio of tip to base fin spacing was varied from 0.25 to 1 and fin height was varied from 15 to 40 mm. For the same fin heights and Rayleigh number, the better performance was obtained from the fin arrays configuration which were tested in this study compared with rectangular fin arrays. The results of the analysis show that there are some important geometrical factors affecting the design of fin arrays. It has been found that for a given Rayleigh number, Nusselt number based on fin height takes maximum values as a function of the ratio of tip to base fin spacing and fin height. Taking into consideration these factors, an optimum ratio that yields the highest Nusselt number has been determined. The results obtained from experimental study show that the ratio of tip to base fin spacing which yields the maximum heat transfer is between C=0.50 and C=0.75. Results also show that optimum ratio depends on especially the fin height and Rayleigh number. Keywords: Natural convection, variable cross-section fins, fin height, fin spacing, optimal vacancy rate