. This heat transfer coefficient is an average heat transfer coefficient over all the available fin surfaces. If a fluid domain is added to e.g. the sides of the fin row, the heat transfer coefficient of the frontal fins will also be taken into account. Therefore is in fact a lumped heat transfer coefficient. . This is the heat transfer coefficient only for the left, right and bottom side of the fin, independent of which mesh (Table 2) being studied. This heat transfer coefficient is an area-averaged value of and . All the results with their percentage difference compared to the base case (Mesh-Ref) are reported in Table A.1 in the Appendix. First of all, the largest influence of the domain is observed when the rectangular fin shape is compared to the inverted triangular one. The results for the interrupted rectangular fin shape are very similar to those for the rectangular fin shape. Locally the flow resistance in the middle of the interrupted fin is decreased due to the interruption. However, as a single chimney pattern is observed in both the rectangular case and the interrupted case, no extra fluid will be drawn to the middle of the interrupted fin. Furthermore, the region where the fin is interrupted has a symmetric boundary condition, this makes it more difficult for air to penetrate from above the heat sink. As can be seen from Figures 5 to 8, an increase in the height of the fluid domain on top of the fin from 50 mm to 100 mm does not have any significant influence on the heat transfer coefficients (the uncertainty on the fine grid is 1.77%, as shown in Table 3 and discussed in and Uncertainty and/or wider fluid domains result in no further Section ‘Mesh analysis’). Higher significant changes to the heat transfer coefficient. The results for a 200 mm high fluid domain are reported in Table A.1 and depicted in Figures 5 to 8, however, they will not be discussed further in this work as the boundary conditions for this grid are slightly different. When the fluid
. This heat transfer coefficient is an average heat transfer coefficient over all the available fin surfaces. If a fluid domain is added to e.g. the sides of the fin row, the heat transfer coefficient of the frontal fins will also be taken into account. Therefore is in fact a lumped heat transfer coefficient. . This is the heat transfer coefficient only for the left, right and bottom side of the fin, independent of which mesh (Table 2) being studied. This heat transfer coefficient is an area-averaged value of and . All the results with their percentage difference compared to the base case (Mesh-Ref) are reported in Table A.1 in the Appendix. First of all, the largest influence of the domain is observed when the rectangular fin shape is compared to the inverted triangular one. The results for the interrupted rectangular fin shape are very similar to those for the rectangular fin shape. Locally the flow resistance in the middle of the interrupted fin is decreased due to the interruption. However, as a single chimney pattern is observed in both the rectangular case and the interrupted case, no extra fluid will be drawn to the middle of the interrupted fin. Furthermore, the region where the fin is interrupted has a symmetric boundary condition, this makes it more difficult for air to penetrate from above the heat sink. As can be seen from Figures 5 to 8, an increase in the height of the fluid domain on top of the fin from 50 mm to 100 mm does not have any significant influence on the heat transfer coefficients (the uncertainty on the fine grid is 1.77%, as shown in Table 3 and discussed in Section ‘Mesh and Uncertainty analysis’). Higher and/or wider fluid domains result in no further significant changes to the heat transfer coefficient. The results for a 200 mm high fluid domain are reported in Table A.1 and depicted in Figures 5 to 8, however, they will not be discussed further in this work as the boundary conditions for this grid are slightly different. When the fluid
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