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# hw3 - an equation in Table 3.4(ANSWER 26.8ºC 3 A straight...

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ME 322 HW #3 04.03.2008 1. An uninsulated, thin-walled pipe of 100-mm diameter is used to transport water to equipment that operates outdoors and uses the water as a coolant. During particularly harsh winter conditions, the pipe wall achieves a temperature of -15ºC and a cylinder layer of ice forms on the inner surface of the wall. If the mean water temperature is 3ºC and a convection coefficient of 2000 W/m 2 K is maintained at the inner surface of the ice, which is at 0ºC, what is the thickness of the ice layer? (ANSWER: 5 mm) 2. A 1.6-mm-diameter stainless-steel rod of thermal conductivity of 22 W/m ºC protrudes from a wall maintained at 49ºC. The rod is 12.5 mm long and the convection coefficient is 570 W/m 2 ºC. The environment temperature is 25ºC. Calculate the temperature of the tip of the rod. (Hint: Use
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Unformatted text preview: an equation in Table 3.4.) (ANSWER: 26.8ºC) 3. A straight fin having a triangle profile has a length of 5 cm and a thickness of 4 mm and is constructed of a material having k = 23 W/m ºC. The fin is exposed to surroundings with a convection coefficient of 20 W/m 2 ºC and a temperature of 40ºC. The base of the fin is maintained at 200ºC. Calculate (1) the fin effectiveness, (2) the fin efficiency and (3) the heat lost from the fin per unit depth of fin. (ANSWER: 17.2; 220.0 W/m; 69%) 4. Consider a circumferential aluminum fin having a thickness of 1.0 mm to be installed on a 2.5-cm-diameter aluminum tube. The fin length is 1.25 cm. The convection environment is at 20ºC, and h = 125 W/m 2 ºC. Calculate the heat transfer for each fin for a tube wall temperature of 200 ºC. (ANSWER: 60.1 W)...
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