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Unformatted text preview: tainer that has a mass of 75 lbm
when empty is filled with liquid water. Initially, both the steel
tank and the water are at 120°F. Now heat is transferred, and
the entire system cools to the surrounding air temperature
of 70°F. Determine the total entropy generated during this
7–168 Air enters the evaporator section of a window air
conditioner at 100 kPa and 27°C with a volume flow rate of
6 m3/min. The refrigerant-134a at 120 kPa with a quality of 0.3
enters the evaporator at a rate of 2 kg/min and leaves as saturated vapor at the same pressure. Determine the exit temperature of the air and the rate of entropy generation for this
process, assuming (a) the outer surfaces of the air conditioner
are insulated and (b) heat is transferred to the evaporator of the
air conditioner from the surrounding medium at 32°C at a rate
of 30 kJ/min.
Answers: (a) 15.5°C, 0.00188 kW/K, (b)
27°C 6°C 18°C 11.2°C, 0.00222 kW/K R-134a
Q 120 kPa
x = 0.3 AIR
vapor FIGURE P7–164
7–165 A well-insulated 4-m 4-m 5-m room initia...
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- Spring '09