A rigid iron tank with a mean surface area of 5 m2 and a wall thickness of 5 mm contains 50 kg of steam at 150 C and 200 kPa. An electric heater with a voltage of 240V is used to maintain the steam temperature constant. If the tank is surrounded by air at 25 C, for which the convective heat transfer coefficient is 300 W/m2 .K. Determine a. The temperature of the outside surface of the tank (assume the inner wall temperature of the tank is the same as that of steam, and neglect heat losses by radiation) [Ans. 147.7 C] b. The required current of the electric heater [Ans. 767 A]