Homework 8

# Homework 8 - 3 Water enters a 2.5 cm internal diameter thin...

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Homework # 8 1. In our classes about packed beds, (18 and 19), we found the T o using a simplified thermal energy balance, as well as the thermal energy generated per pellet. We made the assumption that the k of the uranium oxide and graphite were the same (2 W/m 2 -K). Now assume that graphite is 5.7 W/m-K. What are the temperatures at the surface of the pellet as well as at the surface between the uranium oxide and the graphite? What is the maximum temperature? 2. Consider laminar flow in a parallel plate channel. The axis is in the center of the channel, and the width between the two plates is 2y O . Velocity and temperature profiles have the form: with units of m/s and o C respectively. Find the mean velocity and mean temperature, and plot the velocity and temperature distributions. Comment on the plots.
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Unformatted text preview: 3. Water enters a 2.5 cm internal diameter thin copper tube of a heat exchanger at 15 o C at a rate of 0.3 kg/s, and is heated by steam condensing outside at 120 o C. If the average heat transfer coefficient is 800 W/m 2-C, what is the length of the tube required in order to heat the water to 115 o C. 4. Consider the flow of oil at 20 o C in a 30-cm-diameter pipeline at an average velocity of 2 m/s. A 200-m long section of the pipeline passes through icy waters of a lake at 0 o C. Measurements indicate that the surface temperature of the pipe is 0 o C. Disregarding the thermal resistance of the pipe material, find: a) the temperature of the oil when the pipe leaves the lake b) the rate of heat transfer from the oil c) the pumping power required to overcome the pressure losses...
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