Question 2 You are to design a finned heat sink for a computer mother board, which comprises of vertically mounted rectangular parallel plates on a porous base, as shown in figure

2. The height of each fin is 40 mm, and the temperature of the fins are constant at 80 °C. The heat from the fins induces an air flow (due to free convection) from the surroundings through the porous base and through the parallel plates, where they exit at the top. The surrounding temperature is constant at 80 °C. The base is square, with a width of 50 mm. Neglect heat transfer Air flow (via free convection) Fins Neglect heat transfer 50 mm Porous base Neglect heat transfer Figure 2: Free convection in between parallel plates. 40 mm Neglecting the heat transfer from the bottom of the base, and through the extreme left and right side of the fins, i.e., the only heat transfer is due to the convection in between the parallel plates (as shown in figure 2), calculate the minimum number of fins (plates) required if the required heat transfer rate is 18 W. [10 marks] You may assume that the thickness of the fins is negligible.