On the numerical simulation of fins in natural convection

In the numerical study of heat sinks it is known from open literature that a sufficient amount of fluid domain should be added at each side of the heat sink. However, the question in this context is: what can be defined as sufficiently far away from the heat sink? This work studies how the size and location of the fluid domain affects the calculated heat transfer coefficient. The purpose of this study is showing the large uncertainties that are implied by adding an insufficient amount of fluid domain. Three fin row types are studied: a rectangular, an interrupted rectangular and an inverted triangular fin row. First, the influence of adding fluid domain to the sides of the heat sink is studied. A large decrease of the heat transfer coefficient on both sides and bottom is observed. Next, the influence of adding fluid domain on both the top and the sides is studied. For the rectangular fins the impact on the lumped heat transfer coefficient is +12% compared to the case without any fluid domain added. While for the inverted triangular fin shape no net effect is observed on the lumped heat transfer coefficient.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016