1. The air conditioning duct in a house is 60 m long. The duct cross section is a rectangle with a..

1. The air conditioning duct in a house is 60 m long. The
duct cross section is a rectangle with a height of 35 cm and width of 75 cm.
The duct is bare and exposed to air at 18 C. Find the total rate of heat loss
if the average surface temperature of the duct metal is 35 C.

2. A block of steel is uniformly heated from inside to
maintain its temperature at 100 C. The block is a rectangular parallelepiped.
The base of the block is a 3 cm by 3 cm square and the height of the block is 6
cm. We place this block in air at 25 C. Find the rate of heat loss from this
block by natural convection.