CFD Optimization of free Convective Cooling of Finned Heat Sinks: Effect of Fin Spacing

In this work, the conjugate free convective-heat transfer over a single fin in a vertical heat sink is analyzed using CFD for optimizing fin spacing. The study includes characterization of temperature and stream function contours for different fin spacing and corresponding Rayleigh number. The flow characteristics and heat dissipation under different spacing are theoretically interpreted. Cooling is assessed based on fin effectiveness and subsequently overall cooling effectiveness defined as fin effectiveness divided by the spacing. Simulations predict increase of heat dissipated and fin effectiveness with increase in spacing, due to enhanced flow circulation. However, the overall cooling effectiveness decreases due to lesser heat transfer area available per unit length of heat sink. Hence an optimal spacing requires a trade off between the magnitude of natural convection and the heat transfer area available per unit length of heat sink wall, which increases and decreases with increase in the fin spacing respectively.