Problem 1:

A double tube heat exchanger is constructed of Schedule 40 carbon steel tube. The inner tube is 1/2-inch nominal diameter, while the outer tube is 1-inch nominal diameter. The exchanger is operated against the current. The cold fluid is liquid water and it circulates outside the internal tube at a rate of 1.5 kg/s, entering at 20 oC and leaving at 50 oC. The hot fluid is liquid ethylene glycol that circulates inside the tube at a rate of 3 kg/s. The ethylene glycol enters the exchanger at 85 oC. Making use of the correlations for estimation of Nu proposed by Taler and Taler , calculate:

1.Using the energy balance in the exchanger, obtain the ethylene glycol outlet temperature assuming that there are no heat losses or gains with the surroundings of the exchanger. 2.Using the correlations for Nu estimation proposed by Taler and Taler, calculate the necessary tube length in the exchanger. 3.Calculate the necessary area (in m2) of the exchanger referenced to the external wall of the inner tube (Ao) Note: DO NOT neglect the tube wall conduction term in calculating the overall coefficient of heat transfer. The tube used has no negligible thickness as it is Schedule 40