Problem

Reconsider the heat sink in Prob. 20-56. In order to enhance heat transfer, a shroud (a th...

Reconsider the heat sink in Prob. 20-56. In order to enhance heat transfer, a shroud (a thin rectangular metal plate) whose surface area is equal to the base area of the heat sink is placed very close to the tips of the fins such that the interim spaces are converted into rectangular channels. The base temperature of the heat sink in this case was measured to be 108°C. Noting that the shroud loses heat to the ambient air from both sides, determine the average natural convection heat transfer coefficient in this shrouded case. (For complete details, see Cengel and Zing, 1987.)