Air at 1 atm and 10c flows over a bank of tubes (15 rows high and 10 rows deep) at an upstream velocity of 7 m/sec. tube surfaces are maintained at 65c. tubes are 2.54 cm in diameter and arranged in-line. st = 3.175 cm, sl = 3.81 cm. calculate total heat transfer per unit length & the exit air 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]