Unformatted text preview: 0-cm-long cylindrical heat pipe having a diameter
of 0.5 cm is dissipating heat at a rate of 150 W, with a temperature difference of 4°C across the heat pipe. If we were
to use a 40-cm-long copper rod (k 386 W/m · °C and
8950 kg/m3) instead to remove heat at the same rate, determine
the diameter and the mass of the copper rod that needs to be installed.
10–70 Repeat Problem 10–69 for an aluminum rod instead of
10–71E A plate that supports 10 power transistors, each dissipating 35 W, is to be cooled with 1-ft-long heat pipes having
a diameter of 1 in. Using Table 10–6, determine how many
pipes need to be attached to this plate.
pipe 10–75E The condenser of a steam power plant operates at a
pressure of 0.95 psia. The condenser consists of 144 horizontal
tubes arranged in a 12 12 square array. The tubes are 15 ft
long and have an outer diameter of 1.2 in. If the outer surfaces
of the tubes are maintained at 80°F, 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.
10–76E Repeat Problem 10–75E for a tube diameter of 2 in. 10–77 Water is boiled at 100°C electrically by a 80-cm-long,
2-mm-diameter horizontal resistance wire made of chemically
etched stainless steel. Determine (a) the rate of heat transfer to
the water and the rate of evaporation of water if the temperature of the wire is 115°C and (b) the maximum rate of evaporation in the nucleate boiling regime.
Answers: (a) 2387 W, 3.81 kg/h, (b) 1280 kW/m2 Transistor Steam Water
100°C FIGURE P10–71E
115°C Review Problems
10–72 Steam at 40°C condenses on the outside of a 3-cm diameter thin horizontal copper tube by cooling water that enters
the tube at 25°C at an average velocity of 2 m/s and leaves at
35°C. Determine the rate of condensation of steam, the average
overall heat transfer coefficient between the steam and the
cooling water, and the tube length.
water 35°C 25°C FIGURE P10–72
10–73 Saturated ammonia vapor at 25°C condenses on the...
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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.
- Spring '10