A simple heat exchanger consisting of two concentric flow passages is used for heating 1110 kg/h of oil (CP= 2.1 kJ/kg-K) from a temperature of 27°C to 49°C. The oil flows through the inner pipe made...

A simple heat exchanger consisting of two concentric flow passages is used for heating 1110 kg/h of oil (CP= 2.1 kJ/kg-K) from a temperature of 27°C to 49°C. The oil flows through the inner pipe made of copper (O.D. = 2.86 cm, I.D. = 2.54 cm) and the surface heat transfer coefficient on the oil side is 635 W/m2-K. The oil is heated by hot water (CP= 4.18 kJ/kg-K) supplied at the rate of 390 kg/h and at an inlet temperature of 93°C. The water side heat transfer coefficient is 1270 W/m2- K. Take the thermal conductivity of copper to be 350 W/m-K and the fouling factors on the oil and water sides to be 0.0001 and 0.0004 m2-K/W. What is the length of the heat exchanger for (a) parallel flow, (b) counter flow