Effectiveness, ntu for heat exchangers. problem 4.9-4, p351. outlet temperature and effectiveness of an exchanger. hot oil at a flow rate of 3.00 kg/s (cp = 1.92 kj/kg×k) enters an existing counterflow exchanger at 400 k and is cooled by water entering at 325 k (under pressure) and flowing at a rate of 0.70 kg/s. the overall u = 350 w/m2 ×k and a = 12.9 m2. calculate the heat transfer rate and the exit oil temperature.

Athin walled concentric tube exchanger is used to cool engine oil from 160°c to 60°c with water that is available at 25°c acting as a coolant. the oil and water flow rates are each at 2 kg/s, and the diameter of the inner tube is 0.5 m and the corresponding value of the overall heat transfer coefficient is 250 w/m2. oc. how long must the heat exchanger be to accomplish the desired cooling? cpwater=4.187 kj/kg-candcpengine el=2.035 kj/kg·°c, oil . 120]