1. A 60 m concentric tube heat exchanger for cooling lubricating oil consists of a thin-walled inner tube of unknown diameter carrying water and an outer tube of 45 mm diameter carrying the oil. Mass flow rates of oil and water are both 0.1 kg/s, oil enters the exchanger at 100C, and water enters the exchanger at 30C. The exchanger operates in countercurrent flow with an overall heat transfer coefficient of 55 W/m K and the tabulated average properties given below. (a) If the outlet temperature of the water is 50C, determine Property Water the total rate of heat transfer and the outlet temperature of P (kg/m3) 1000 the oil. Cp (J/kg K) 4200 (b) Determine the diameter of the inner tube. (c) If the flow was changed to co-current flow, what would be the diameter of the inner tube needed to achieve the same heat transfer rate and outlet temperatures? Comment on how your answer differs from part (b). Oil 800 1900