Oranges with a diameter of about 3 inches are to be cooled from room temperature of 25°C to a surface temperature of 3°C using an air-convection environment with h = 45 W/m2-K and T[infinity] = -5°C. Assuming that the oranges have the properties of water at 10°C, calculate the time required for the cooling. What is the center temperature at that instant?

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]