A typical section of a building wall is shown in Fig. P17–58. This section extends in and...

A typical section of a building wall is shown in Fig. P17–58. This section extends in and out of the page and is repeated in the vertical direction. The wall support members are made of steel (k = 50 W/m·K). The support members are 8 cm (t₂₃) × 0.5 cm (L_B). The remainder of the inner wall space is filled with insulation (k = 0.03 W/m·K) and measures 8 cm (t₂₃) × 60 cm (L_B). The inner wall is made of gypsum board (k = 0.5 W/m·K) that is 1 cm thick (t₁₂) and the outer wall is made of brick (k = 1.0 W/m·K) that is 10 cm thick (t₃₄). What is the average heat flux through this wall when T₁ = 20°C and T₄ = 35°C?

FIGURE P17–58: