5 A composite slab is made of three layers 15 cm, 10 cm and 12 cm thickness. The first layer is of material with thermal conductivity 1.45 for 60% of the area and the rest is of material with conductivity of 2.5 W/m. K. The second layer is made of material with thermal conductivity of 12.5 W/m. K for 50% area and a material with thermal conductivity of 18.5 W/m. K is used for the other 50%. The third layer is of single material of thermal conductivity 0.76 Wm. K. The slab is exposed on one side to warm air at 26°C and to cold air at -20°C on the other side. The convection coefficients are 15 and 20 W/m². K on the inside and outside, respectively. Determine the heat flow and interface temperatures of the composite slab. Assume a total area of 1 m². Use the data and equivalent circuit shown in Figure Q1 (c). h-15 Wm. K k-2.5 Wm.K k-0.76 W/m.K k-12.5Wmk B: Area -40% CAma-50% EArea = 100% -20 Wm.K k=1.45 Wim.K A: Area -60% T-26°C 18.5Wm. K DArea 50% 2 3 0.15 m 0.10 m 0.12 m T--20°C