Problem 14.04 Heat Effect Upon Mixing of Methane and Dodecane at Elevated Temperature and Pressure Using SRK

1600 kg/hr of methane is mixed with 170 kg/hr of dodecane. The inlet temperature of both streams is 160 °C, and each enter at a pressure of 2 MPa. The mixing process is isobaric. What is the temperature of the combined stream? Use the SRK EOS with no binary interaction parameters.


This is a straightforward calculation. The energy of both streams is combined; and the outlet pressure is known. The calculation only requires calculating the inlet energy of both streams, adding it up, and finding the mole fractions of the outlet.

from thermo import ChemicalConstantsPackage, SRKMIX, FlashVL, CEOSLiquid, CEOSGas
from chemicals import ws_to_zs, mixing_simple

constants, correlations = ChemicalConstantsPackage.from_IDs(['methane', 'dodecane'])
eos_kwargs = dict(Tcs=constants.Tcs, Pcs=constants.Pcs, omegas=constants.omegas)
liquid = CEOSLiquid(SRKMIX, HeatCapacityGases=correlations.HeatCapacityGases, eos_kwargs=eos_kwargs)
gas = CEOSGas(SRKMIX, HeatCapacityGases=correlations.HeatCapacityGases, eos_kwargs=eos_kwargs)
flasher = FlashVL(constants, correlations, liquid=liquid, gas=gas)

P1 = P2 = 2e6
T1 = 160+273.15

ws = [1600, 170]
zs = ws_to_zs(ws=ws, MWs=constants.MWs)

methane_H = flasher.flash(T=T1, P=P1, zs=[1, 0]).H()
dodecane_H = flasher.flash(T=T1, P=P1, zs=[0, 1]).H()
H = zs[0]*methane_H + zs[1]*dodecane_H

res = flasher.flash(P=P2, H=H, zs=zs)
print(f'The outlet temperature is {res.T-273.15:.4f} °C')
The outlet temperature is 150.2259 °C