- Your answer is partially correct. A stainless steel (AISI 304) tube used to transport a chilled pharmaceutical has an inner diameter of 36 mm and a wall thickness of 2 mm. The pharmaceutical and ambient air are at temperatures of 2°C and 23°C, respectively, while the corresponding inner and outer convection coefficients are 400 W/m2.K and 8 W/m2.K, respectively. Evaluate the properties of the stainless steel at T =280 K. (a) What is the heat gain per unit tube length? q'uninsulated = 20.42 W/m (b) What is the heat gain per unit length if a 10-mm-thick layer of calcium silicate insulation (kins = 0.05 W/m.K) is applied to the tube? l'insulated = i 9.5 W/m