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Research Papers: Natural and Mixed Convection

Scale-Up and Generalization of Horizontal-Base Pin-Fin Heat Sinks in Natural Convection and Radiation

[+] Author and Article Information
D. Sahray, G. Ziskind, R. Letan

Department of Mechanical Engineering, Heat Transfer Laboratory, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105, Israel

J. Heat Transfer 132(11), 112502 (Aug 13, 2010) (10 pages) doi:10.1115/1.4002032 History: Received March 23, 2010; Revised May 27, 2010; Published August 13, 2010; Online August 13, 2010

Abstract

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., , 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., , 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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Figures

Figure 1

Examples of pin-fin heat-sinks used in the present study: (a) 100 mm sink with dimensions and (b) 200 mm sink

Figure 2

Free and blocked edges

Figure 3

Summary of the experimental results for the sinks of Table 1 at various heat inputs, L=100 mm and blocked edges

Figure 4

Additional experimental results and validation of the numerical results at H=30 mm: (a) comparison for 100 mm and 200 mm sinks with free and blocked edges and (b) comparison for 100 mm and 200 mm sinks at the same heat input per unit base area

Figure 5

Normalized numerical results and optimum for different fin arrays: (a) 100 mm sinks with blocked edges (results for free edges are reproduced (1)), (b) 200 mm sinks with free edges, and (c) 200 mm sinks with blocked edges

Figure 6

Contribution of different rows and individual fins to the total heat output of a sink with 81 fins, of L=100 mm and H=10 mm: (a) different rows and (b) individual fins

Figure 7

Simulated transient flow fields of the sink with 81 fins, of L=100 and H=10 mm: (a) free edges and (b) blocked edges

Figure 8

Nusselt number versus Rayleigh number for different base sizes and fin heights with free edges: (a) H=10 mm, (b) H=20 mm, and (c) H=30 mm

Figure 9

Generalized results and overall correlation: (a) blocked edges and (b) free edges

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