A12.49-cm diameter plunger of 7.5 cm length moves inside a 12.50-cm diameter horizontal cylinder at a velocity of 6 m/s. if there is a film of sae 30 oil separating the plunger from the cylinder, what is the power required to maintain the motion?

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]