A concentric tube heat exchanger is used for cooling lubricating oil. The exchanger is comprised of a thin walled tube of 35mm diameter carrying cooling water and an outer tube of 45mm diameter carrying the oil. The fluids enter the exchanger countercurrent to each other and the fluids have the following average properties: The water enters the heat exchanger at 0.7kg/s at 20C and the oil at 0.65kg/s at 102C. (i) Calculate the Re number for the flows of the oil and water. State whether the flows are laminar or turbulent. (ii) If the oil leaves at 70C, calculate the total heat transfer in the exchanger and obtain the water outlet temperature. (iii) Using the Dittus-Boelter formula: Nu=0.023Re0.8Pr0.4 calculate the heat transfer coefficients for the water and oil. What is the overall heat transfer coefficient (U) for the exchanger? (iv) Determine the log-mean temperature difference and use this to calculate the length of the exchanger