Transient heating of a concrete wall. a wall made of concrete 0.305 m thick is insulated on the rear side. the wall at a uniforin temperature of 10°c (283.2 k) is exposed on the front side to a gas at 843°c (1116.2 k). the convection coefficient is 28.4 w/m².k, the thermal diffusivity is 1.74 x 10" mº/h, and the thermal conductivity is 0.935 w/ m k . (a) calculate the time for the temperature at the insulated face to reach 232°c (505.2 k). (b) calculate the temperature at a point 0.152 m below the surface at this same time.