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# hw4 -  = 888 kg/m 3 k = 0.145 W/mºC p c = 1880 J/kgºC...

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ME 324 HW #4 18.04.2011 1. A sphere with a diameter of 20 mm and a surface temperature of 60ºC is immersed in a fluid at a temperature of 30ºC and a velocity of 2.5 m/s. Calculate the heat transfer rate when the fluid is (1) water and (2) air at atmospheric pressure. 2. Suppose an experiment is conducted as follows: Water at 20ºC enters a smooth tube of 6 mm in (inner) diameter and 3 m in length. The mean velocity is measured to be 0.3 m/s. A constant heat flux is imposed and the total heat flux to the tube is 400 W. The outside tube wall is thermally insulated from the atmosphere. (1) Calculate the exit bulk temperature of water. (2) Find the heat transfer coefficient at the exit. (3) Estimate the wall temperature at the exit. 3. Engine oil at 20ºC enters a 2.0-mm-diameter tube at a velocity of 1.2m/s. The tube wall temperature is constant at 60ºC and the tube is 1.0 m long. Calculate the exit oil temperature. Use the following properties of oil:
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Unformatted text preview:  = 888 kg/m 3 , k = 0.145 W/mºC, p c = 1880 J/kgºC and  = 0.0009 m 2 /s. 4. Water at 20ºC enters a 1-cm-diameter tube at a velocity of 2 m/s. The tube wall temperature is constant at 50ºC and the tube is 3.0 m long. Calculate the exit water temperature. Use the following properties of water: = 997 kg/m 3 , k = 0.61 W/mºC, p c = 4180 J/kgºC and  = 0.00086 Ns/m 2 . 5. Air at 300 K and 50 kPa flows over the upper side of a 1-m-square plate. The upper plate is maintained at a constant temperature of 400 K. (1) If air flows at a velocity of 50 m/s, calculate the heat lost by the upper plate. (2) If air flows at a velocity of 1 m/s, calculate the heat lost by the upper plate. (3) If no air flows over the horizontal plate, calculate the heat lost by the upper plate. (4) If the emissivity of the upper plate is 0.2 and the temperature of the surroundings is 300 K, what will be the heat loss of the upper plate by radiation?...
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