Lubricating oil at 150°F is to be cooled to 105°F by water available at 70°F in a double-pipe, counter-current flow, heat exchanger. The oil and water flow rates are 225 and 195 lbm/hr respectively, and the specific heat of the oil is 0.46Btu/lbm°F. The overall heat transfer coefficient is 58 Btu/hrft2°F based on the outside area:
(a) Determine the required heat transfer area,
(b) If this exchanger is used to cool this same oil entering the exchanger at 210°F at a rate of 225 lbm/hr, what is the exit temperature of the oil if the water inlet temperature and flow rate are kept constant?