The heat-transfer rate to the jacket of an agitated polymerization kettle is 7.4 kW/m² when the polymerization temperature is 50°C and the water in the jacket is at 20°C. The kettle is made of stainless steel with a wall 12 mm thick, and there is a thin layerof polymer (k = 0.16 W/m-°C) left on the wall from previous runs. 

(a) What is the temperature drop across the metal wall? 

(b) How thick would the polymer deposit have to be to account for the rest of the temperature difference? 

(c) By what factor I could the heat flux be increased by using a stainless-clad reactor with a 3-mm stainless-steel layer bonded to a 9-mm mild-steel shell?