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Nitrogen can be liquefied using a Joule-Thomson expansioni process. This is done by rapidlyl and adiabatically expandign cold nitrogen gas from high pressure to a low pressure. If nitrogen at 135 K and 20 MPa undergoes a Joule-Thomson expansion to 0.4 MPa,

a. Estimate the fraction of vapor and liquid present after the expansion, and the emperature of this mixture using the pressure-enthalpy diagram for nitrogen.

b. Repeat the calculation assuming nitrogen to be an ideal gas with Cp* = 29.3 J/molK

Answer :

t is desired to produced liquefied methane as illustrated in problem 1; however, theconditions are now changed so that the gas is initially available at 1 bar and 200 K, and leaving the cooler will be at 100 bar and 200 K. The flash drum is adiabatic, oerates at 1 bar, and each compressor stage canbe assumed to operate reversibly and adiabatically. A three-stage compressor will be used with the first stage compressing the gas fro 1 bar to 5 bar, each stage the gas will be isobarically cooled to 200 K.

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