cen58933_ch10

# Answers a 3678 kw b 1496 kgs 1062c what is the effect

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Unformatted text preview: ube as a function of the temperature of the saturated R-134a vapor as the temperature varies from 25°C to 50°C, and discuss the results. Special Topic: Heat Pipes 10–61C A heat pipe with water as the working fluid is said to have an effective thermal conductivity of 100,000 W/m · °C, which is more than 100,000 times the conductivity of water. How can this happen? P = 4.25 kPa n = 100 tubes 10–55 10–60C What is a heat pipe? How does it operate? Does it have any moving parts? Saturated steam N = 10 long and have an outer diameter of 3 cm. If the tube surfaces are at 20°C, determine (a) the rate of heat transfer from the steam to the cooling water and (b) the rate of condensation of steam in the condenser. Answers: (a) 3678 kW, (b) 1.496 kg/s 10–62C What is the effect of a small amount of noncondensable gas such as air on the performance of a heat pipe? 10–63C Why do water-based heat pipes used in the cooling of electronic equipment operate below atmospheric pressure? 10–64C What happens when the wick of a heat pipe is too coarse or too fine? 10–65C Does the orientation of a heat pipe affect its performance? Does it matter if the evaporator end of the heat pipe is up or down? Explain. FIGURE P10–54 10–66C How can the liquid in a heat pipe move up against gravity without a pump? For heat pipes that work against gravity, is it better to have coarse or fine wicks? Why? cen58933_ch10.qxd 9/4/2002 12:38 PM Page 558 558 HEAT TRANSFER 10–67C What are the important considerations in the design and manufacture of heat pipes? coefficient, (b) the rate of heat transfer, and (c) the rate of condensation of ammonia. 10–68C What is the major cause for the premature degradation of the performance of some heat pipes? 10–74 Saturated isobutane vapor in a binary geothermal power plant is to be condensed outside an array of eight horizontal tubes. Determine the ratio of the condensation rate for the cases of the tubes being arranged in a horizontal tier versus Answer: 1.68 in a vertical tier of horizontal tubes. 10–69 A 4...
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## This note was uploaded on 01/28/2010 for the course HEAT ENG taught by Professor Ghaz during the Spring '10 term at University of Guelph.

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