Problem

A 10-in-thick. 30-ft·long, and 10-ft·high wall is to be constructed using 9-in-long solid...

A 10-in-thick. 30-ft·long, and 10-ft·high wall is to be constructed using 9-in-long solid bricks (k - 0.40 Btu/h ft· Fi of cross section 7 in × 7 in, or identical size bricks with nine Square air holes (k = 0.015 Btu/h·ft·°F) that are 9 in long and have a cross section of 1.5 in × 1.5 in. There is a 0.5-in-thick plaster layer (k = 0.10 Btu/h·ft·°F) between two adjacent bricks on all four sides and on both sides of the wall. The house is maintained at 80°F and the ambient temperature outside is 35°F. Taking the heat transfer coefficients at the inner and outer surfaces of the wall to be 1.5 and 6 Btu/h·ft2-°F, respectively, determine the rate of heat transfer through the wall constructed of (a) solid bricks and (b) bricks with air holes.