Unformatted text preview: e entropy change of air and (b) the work done.
450 kPa 7–68 Air is compressed steadily by a 5-kW compressor
from 100 kPa and 17°C to 600 kPa and 167°C at a rate of
1.6 kg/min. During this process, some heat transfer takes place
between the compressor and the surrounding medium at 17°C.
Determine the rate of entropy change of air during this process.
Answer: FIGURE P7–73 0.0025 kW/K
17°C 600 kPa
167°C 7–74 Reconsider Prob. 7–73. Using EES (or other)
software, investigate the effect of the final pressure on the final mass in the tank as the pressure varies from
450 kPa to 150 kPa, and plot the results. AIR
5 kW 100 kPa
17°C FIGURE P7–68
7–69 An insulated rigid tank is divided into two equal parts
by a partition. Initially, one part contains 5 kmol of an ideal gas
at 400 kPa and 50°C, and the other side is evacuated. The partition is now removed, and the gas fills the entire tank. Determine the total entropy change during this process.
Answer: 28.81 kJ/K 7–70 Air is compressed in a...
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