Question 1 (30 pts) A composite wall is made up of 3 layers (A, B, C) of thicknesses 25 cm, 10 cm and 15 cm with thermal conductivities of 1.7, kn and 9.5 W/mK. The outside surface is exposed to air at 20°C with convection coefficient of 15 W/m²K and the inside is exposed to gases at 1200°C with a convection coefficient of 28 W/m² K and the inside surface is at 1080°C. Assuming unit area for the composite wall, Determine 1. the unknown thermal conductivity, 2. Other 3 surface temperatures, 3. Resistances of each layer A = Im! 4. Overall heat transfer coefficient (U=1/Riotal) 5. Temperature gradient for the first layer only (dT/dX) [hints: 1. find Q first 2. Then find kn K = 1-1 Wim k 27 h:28 Whe TS 6200 Air h=15 Wink T 9a3e5 CALC (-) RC CON MA