How Orientation Affects Heat Sink Performance?

The orientation of pin fin heat sink has been found to exert only a minor influence on the heat transfer. It was reported that the thermal transport from pin arrays inclined by 15° to 30° from the vertical was identical to that of the vertical array. Additionally, heat transfer from an optimal array was 15 percent higher than for the vertical when the base plate was horizontal with the fins pointing upward and only 5 percent lower than the vertical when the base plate was horizontal with the fins pointing downward. (Source: Kraus and Bar-Cohen, Design and Analysis of Heat Sinks)