Water at a rate of 0.32 L/s and a temperature of 27°C enters a No. 18 BWG 1.6 cm condenser tube made of nickel chromium steel (k = 26 W/m K). The tube is 3 m long, and its outside is heated by steam condensing at 50°C. Under these conditions the average heat transfer coefficient on the water side is 10 kW/m² K, and the heat transfer coefficient on the steam side can be taken as 11.3 kW/m² K. On the interior of the tube, however, there is a scale having a thermal conductance equivalent to 5.6 kW/m² K. 

(a) Calculate the overall heat transfer coefficient U per square meter of exterior surface area. 

(b) Calculate the exit temperature of the water.