This paper provides further insight in heat transfer from horizontal-base pin fin heat-sinks in free convection of air. The main objective is to assess the effect of base size, and this with regard to the effects of fin height and fin population density studied in a previous work (Sahray, D., et al., 2010, “Study and Optimization of Horizontal-Base Pin-Fin Heat Sinks in Natural Convection and Radiation,” ASME J. Heat Transfer, 132(012503), pp. 1–13). To this end, experimental and numerical investigations are performed with sinks of different base sizes. The sinks are made of aluminum, with no contact resistance between the base and the fins, and are heated using foil electrical heaters. In the corresponding numerical study, the sinks and their environment are modeled using the FLUENT 6.3 software. In the experiments, sink bases of $100×100 mm2$ and $200×200 mm2$ are used, while in the numerical study sinks of $50×50 mm2$ are investigated, too. In addition to the sinks with exposed, free edges (Sahray, D., et al., 2010, “Study and Optimization of Horizontal-Base Pin-Fin Heat Sinks in Natural Convection and Radiation,” ASME J. Heat Transfer, 132(012503), pp. 1–13), the same sinks are explored also with their edges blocked. This is done in order to exclude the edge effect, thus making it possible to estimate heat transfer from a sink of an “infinite” base size. Heat-transfer enhancement due to the fins is assessed quantitatively and analyzed for various base sizes and fin heights. The effect of fin location in the array on its contribution to the heat-transfer rate from the sink is analyzed. By decoupling convection from radiation, a dimensional analysis of the results for natural convection is attempted. Interdependence of the base size and fin height effects on the heat transfer is demonstrated. A correlation that encompasses all the cases studied herein is obtained, in which the Nusselt number depends on the Rayleigh number, which uses the “clear” spacing between fins as the characteristic length, and on the dimensions of the fins and the base.

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