A concentric tube heat exchanger is comprised of a thin wall inner tube of 25.4 mm diameter and an outer tube of 47 mm diameter. The heat exchanger is used for cooling lubricating oil. The exchanger operates in counterflow, the inner tube carrying water and the outer tube carrying the oil with an overall heat transfer coefficient of 65 W/m2K. The following figure illustrates the heat exchanger. Properties of water are in Table A.6, oil properties in Table A.5.
a) If the oil outlet temperature is 55oC, determine the total heat transfer and the water outlet temperature.
b) Determine the length required for the tube heat exchanger.