CFD models of circular pin fin heat sinks have beendeveloped. The heat sinks are situated in bypass flow in a duct with constant dimensions. The air velocity was constant,the flow was turbulent, and for turbulence modeling the Chen-Kim k-ε model was used. The influence of increasing fin height in the flow direction, and uneven distribution of the fins in the lengthwise and the spanwise direction are studied.

In the case of increasing fin height, it was shown that an increase in the heat transfer coefficient can be achieved without an increase in pressure drop when compared at equal mean fin height.

In the case of uneven distribution of the fins it was shown that the heat transfer coefficient could be increased by an uneven distribution of the fins in the lengthwise direction, using smaller fin spacing at the trailing edge of the heat sink. Results also showed that some cases of unevenly distributed fins in the spanwise direction could achieve an increase inthe heat transfer coefficient. These cases had smaller fin spacing at the center of the heat sink, and the fin height was close to the duct height. The pressure drop was almost thesame as for heat sinks with even distribution of the fins.