Air is heated as it flows subsonically through a duct. when the amount of heat transfer reaches 67 kj/kg, the flow is observed to be choked and the velocity and the static pressure are measured to be 680 m/s and 261 kpa. disregarding frictional losses, determine the velocity, static temperature, and static pressure at the duct inlet. take the properties of air to be k = 1.4, cp = 1.005 kj/kg·k, and r = 0.287 kj/kg·k.

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]