02.15 Closed and Steady-State Open Systems

Ideal gas compression

Adiabatic Compression of an Ideal Gas (LearnChemE.com, 6min) calculate adiabatic temperature for compression of an ideal gas, both reversibly and irreversibly.

Comprehension Questions:
1. 10 mol/s of air is compressed adiabatically and reversibly from 298K and 1bar to 5 bar.
(a) Compute the exit temperature (K). (Hint: check out Eqn. 2.51.)
(b) Compute the power requirement (kW) for this compressor.
(c) Suppose the compressor was only 75% efficient, where efficiency≡Wrev/Wact for compression. Is the temperature of the irreversible compressor higher or lower than that of the reversible compressor? Explain.
(d) Calculate the temperature exiting a 75% efficient compressor.
2. Air is expanded adiabatically and reversibly (through a turbine) from 298K and 5 bar to 1 bar.
(a) Is the outlet temperature higher or lower than 298K?
(b) Suppose the air was expanded through a 50% efficient turbine. Would the temperature be higher or lower than the reversible turbine? Explain.

Adiabatic, Reversible, Ideal gas

Reversible Adiabatic Compression of Ideal Gas (LearnChemE.com, 5min) calculate the final conditions for adiabatic, reversible compression of an ideal gas. Here, we derive an important equation that should be memorized: (T2/T1)=(P2/P1)^(R/Cp).