The condenser of a large power plant is to remove 500 MW of heat from steam condensing at 30°C (hfg = 2431 kJ/kg). The cooling is to be accomplished by cooling water (cp = 4180 J/kg(°C) from a nearby river, which enters the tubes at 18°C and leaves at 26°C. The tubes of the heat exchanger have an internal diameter of 2 cm, and the overall heat transfer coefficient is 3500 W/m2(°C. Determine the total length of the tubes required in the condenser. What type of heat exchanger is suitable for this task?