Consider the enclosure and heat sink of Problem 7.30. The heat sink is rotated 90° so that the air is no longer directed between the fins, but normal to one of the (L b + L f ) X W2 surfaces. Estimate the required air velocity if the height of the enclosure is Le = 10 mm. Neglect heat transfer from the enclosure surfaces and assume isothermal fins, no heat transfer in the gaps between the fins and negligible heat transfer from the downstream (L_b + L_f) x w₂ surface. Include heat transfer from the (L_b + L_f) x w₁ sides and the fin tips.