Solve Problem 15.23 if instead of the surface temperatures being known, the air temperatur...

Solve Problem 15.23 if instead of the surface temperatures being known, the air temperatures outside and inside are 30 and 75°F, respectively, and the convective heat-transfer coefficients are 7 and 2 Btu/h ft2 °F, respectively.

Problem 15.23

The outside walls of a house are constructed of a 4-in. layer of brick, 1/2 in. of celotex, an air space in: thick, and 1/4 in. of wood panelling. If the outside surface of the brick is at 30°F and the inner surface of the panelling at 75°F, what is the heat flux if

a. the air space is assumed to transfer heat by conduction only?

---

b. the equivalent conductance of the air space is 1.8 Btu/h ft2 °F?

---

c. the air space is filled with glass wool?