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Answer: 7–65 0.0617 kJ/K Reconsider Prob. 7–64. Using EES (or other)
software, investigate the effect of varying the cen54261_ch07.qxd 11/18/03 9:58 AM Page 338 338
FUNDAMENTALS OF THERMAL-FLUID SCIENCES polytropic exponent from 1 to 1.4 on the entropy change of the
nitrogen. Show the processes on a common P-υ diagram.
7–66E A mass of 15 lbm of helium undergoes a process
from an initial state of 50 ft3/lbm and 80°F to a final state of
10 ft3/lbm and 200°F. Determine the entropy change of helium
during this process, assuming (a) the process is reversible and
(b) the process is irreversible. 7–73 An insulated rigid tank contains 4 kg of argon gas at
450 kPa and 30°C. A valve is now opened, and argon is allowed to escape until the pressure inside drops to 150 kPa.
Assuming the argon remaining inside the tank has undergone a
reversible, adiabatic process, determine the final mass in the
tank. Answer: 2.07 kg 7–67 Air is compressed in a piston-cylinder device from
90 kPa and 20°C to 400 kPa in a reversible isothermal process.
Determine (a) th...
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