Asphere of 200 mm diameter made of cast iron initially at uniform temperature of 400 °c is quenched into oil. the oil bath temperature of 40 °c. if the temperature of the sphere is 100 °c after 5 minutes, find the heat transfer coefficient on the surface of the sphere. take cp (cast ron) 0.32 kj/kg °c, p neglect internal thermal resistance [ans. 134 kw/m2 °c] 3 (cast ron) -7000 kg/m