Consider the composite solid shown. Solid A is a thermally conductive material that is 0.5-cm thick and has a thermal conductivity, KA = 50 W=m · K. The back side of solid A (x = 0) is thermally insulated. Electrical current is applied to solid A such that 20 W per cm3 is generated as heat. Solid B is 0.2-cm thick and has a thermal conductivity of KB = 20 W/m • K. The surface of solid B is exposed to air. The surface temperature, Ts, of solid B is 80°C. The bulk air temperature is constant at 30°C. The process is at steady state. 

a. What is the heat-transfer rate per unit area (flux) at x = L2? What is the temperature Ti at x = Li, the boundary between solid A and solid B? 

b. What is the required convective heat-transfer coefficient, h, for the flowing air? 

c. What is the temperature T0 at x = 0, the insulating side of solid A?

solid A kA = 50 W/m-K solid B ke- 20 Wim-K bulk gas film . gas T, = 80C T= 30C insulated boundary x= L2 = 0.7 cm x = L, = 0.5 cm