Natural Convection From Finned Heat Sinks

A CFD (computational fluid dynamics) analysis is performed on the finned heat sinks. For convenience, a commercial CFD code, Flotherm, is utilized in the analysis. Though the code can handle the radiation heat transfer, the present analysis is limited to the natural convection with the base of the heat sink at a constant temperature. The continuous fin configuration is first considered due to the importance of its applications. Several experimental data are available for the vertically straight-fin heat sink and a useful correlation is also developed. For given overall fin dimensions of 15″ × 10.341″ × 2.2″, the correlations are first employed to determine the optimal fin spacing. This optimal fin spacing of 0.439 in is then used to develop the baseline CFD model. The dimensions of the baseline CFD model are as follows: Fin width (in): 10.341. Heat sink length (in): 15. Fin spacing (in): 0.439. Fin height (in): 2.0. Fin thickness (in): 0.1. Fin base plate thickness (in): 0.2. Fin numbers: 20. The baseline model with various fin spacing is analyzed and the results (heat loss from the finned heat sink) compare well with those obtained through the correlations. The analysis is extended to the staggered and in-line fin configurations because of their practical applications. Three different fin lengths, including 1″, 3″ and 5″ fin length for the staggered fin array are examined. The results indicate that the effectiveness of heat transfer is increased as the fin length increasing. The continuous fin configuration is the most efficient, and is followed by the staggered fins and then by the in-line fins.