In this paper pin-fin cooling by mixed convection has been considered. The system consisting of a pin-fin heat sink and a chimney is presented for increasing heat transfer and draft force. The flow regime is laminar. The results is applied to problems in which the size of the overall system is constrained. For a given heat dissipation and total system size optimal values of the pin-fin diameter and heat sink porosity are obtained. It is shown that the optimum occur for systems with and without chimney. The pin-fin array is modeled as a Forchheimer-flow porous medium (Non Darcy-flow). The results of optimization are compared with existing data in literature. Also it is shown that the results obtained from Forchheimer-flow porous model agree much better with the experimental results compared with the natural convection Darcy model.
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