A new fire resistant insulation is to be tested. A specimen of the insulation is placed in front of a test furnace. The specimen is 140 mm thick, and is initially at 25°C. The furnace gases are at 900°C, and the convective heat transfer coefficient on the exposed side of the specimen is 50 W/m2 °C. Based on previous testing in the lab, the R-value for this insulation is 22, its density is 100 kg/m3 and its specific heat is 1000 J/kg°C.
a) Estimate how long it takes for the exposed surface of this insulation to reach a temperature of 550°C. What will be the temperature of the unexposed surface of the insulation at this time?
b) What will be the temperature at a depth of 25 mm from the exposed surface of the insulation after 5 minutes of testing?