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how to get Sutherland and JANAF coefficients of air?

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Old   September 18, 2018, 14:55
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  #61
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Hello guys,

I used the code made by arvindpj (post #57) by running it on python 3.6 and cantera 2.4 but it does'nt work. I have attached the error message;

does anyone have a clue?

Cheers.
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File Type: png Issue for the JANAF coefficient.PNG (8.8 KB, 30 views)
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Old   September 18, 2018, 15:15
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  #62
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Here is my new "Old NASA Thermo Generator"
Give it a try.
Code:
###########################
#Old NASA Thermo Generator#
#      Oskar Zuranski     #
#   Warsaw, Poland,2018   #
###########################

import sys
import cantera as ct
import numpy as np
import math
from numpy.linalg import inv

#######################################################################
# USER EDITABLE PART
#######################################################################

gas = ct.Solution('gri30.cti','gri30_mix')
#gas = ct.Solution('Dagaut_Ori.cti')
#gas = ct.Solution('curran.cti')

q = 'C2H2:1'

p = 101325
Tlow = 300.0
Tcommon = 1000.0
Thigh = 5000.0
step = 100

#######################################################################
# END OF USER EDITABLE PART
#######################################################################

#######################################################################
# LOW TEMPERATURE RANGE
#######################################################################

# reference temperature for standard enthalpy/entropy
Tref = 298.15

#create gas
gas.TPX = Tlow, p, q

# create empty temperature table for low temperature range
templist = [0 for x in range(step+1)]
np.float64(templist)

#set temperatures in temperature table for low temperature range
for i in range (step+1):
    templist[i] = Tlow+i*((Tcommon-Tlow)/step)
    
#create X matrix
tab = [[0 for x in range(5)] for y in range(5)]
np.float64(tab)

#set X matrix coefficients
for a in range(5):
    for b in range(5):
        for i in range (step+1):
            tab[a][b] += templist[i]**(b+a)

#create Y matrix
tab2 = [0 for x in range(5)]
np.float64(tab2)

#set Y matrix coefficients
for a in range(5):
    for i in range(step+1):
        gas.TPX = templist[i], gas.P, gas.X
        tab2[a] += gas.cp_mole/ct.gas_constant*templist[i]**a

# invert X matrix
inverse = inv(tab)

# multiply X^-1*Y
low_temp_range = np.matmul(inverse,tab2)
print 'Low temperature range coefficients:'

print 'a1 = ',low_temp_range[0]
print 'a2 = ',low_temp_range[1]
print 'a3 = ',low_temp_range[2]
print 'a4 = ',low_temp_range[3]
print 'a5 = ',low_temp_range[4]



gas.TPX = Tref, gas.P, gas.X

hOffset = gas.enthalpy_mole/ct.gas_constant - (low_temp_range[0]*Tref+low_temp_range[1]/2.0*Tref**2+low_temp_range[2]/3.0*Tref**3+low_temp_range[3]/4.0*Tref**4+low_temp_range[4]/5.0*Tref**5)
sOffset = gas.entropy_mole/ct.gas_constant - (low_temp_range[0]*np.log(Tref)+low_temp_range[1]*Tref+low_temp_range[2]/2.0*Tref**2+low_temp_range[3]/3.0*Tref**3+low_temp_range[4]/4.0*Tref**4)

print 'a6 = ', hOffset
print 'a7 = ', sOffset
print ''

#######################################################################
# HIGH TEMPERATURE RANGE
#######################################################################
gas.TPX = Tcommon, gas.P, gas.X

hbak = gas.enthalpy_mole/ct.gas_constant
sbak = gas.entropy_mole/ct.gas_constant

# clear tabs
templist = [0 for x in range(step+1)]
tab = [[0 for x in range(5)] for y in range(5)]
tab2 = [0 for x in range(5)]

#set temperatures in temperature table for high temperature range
for i in range (step+1):
    templist[i] = Tcommon+i*((Thigh-Tcommon)/step)

#set X matrix coefficients
for a in range(5):
    for b in range(5):
        for i in range (step+1):
            tab[a][b] += templist[i]**(b+a)


#set Y matrix coefficients
for a in range(5):
    for i in range(step+1):
        gas.TPX = templist[i], gas.P, gas.X
        tab2[a] += gas.cp_mole/ct.gas_constant*templist[i]**a
        
# inverse X matrix
inverse = inv(tab)

# multiply X^-1*Y
high_temp_range = np.matmul(inverse,tab2)

print 'High temperature range coefficients:'

print 'a1 = ', high_temp_range[0]
print 'a2 = ', high_temp_range[1]
print 'a3 = ', high_temp_range[2]
print 'a4 = ', high_temp_range[3]
print 'a5 = ', high_temp_range[4]



hOffset = hbak - (high_temp_range[0]*Tcommon+high_temp_range[1]/2.0*Tcommon**2+high_temp_range[2]/3.0*Tcommon**3+high_temp_range[3]/4.0*Tcommon**4+high_temp_range[4]/5.0*Tcommon**5)
sOffset = sbak - (high_temp_range[0]*np.log(Tcommon)+high_temp_range[1]*Tcommon+high_temp_range[2]/2.0*Tcommon**2+high_temp_range[3]/3.0*Tcommon**3+high_temp_range[4]/4.0*Tcommon**4)

print 'a6 = ', hOffset
print 'a7 = ', sOffset
print ''
print 'M = ', gas.mean_molecular_weight, '[g/mol]'
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Old   September 18, 2018, 15:25
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  #63
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Arvind Jay
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Try this:

Code:
from cantera import *
import numpy as np
import sys

gas = Solution('gri30.cti')
#q = 'CH4:1'
#q = 'O2:7, H2O:95, N2:719, CO:14, CO2:158, NO:4'  #Mole fraction
#gas.TPX = 273.16,101325,q


Pin = 101325 #Pa
Tin = 1200 #K
qmass = 'N2:.76, CO2:.13, H2O:.11'
gas.TPY = Tin,Pin,qmass

gasmass = gas.Y
gasmole = gas.X
gasnames = gas.species_names

n=0

print gas()

print "Temperature:\t", gas.T, "K"
print "Pressure:\t", gas.P, "Pa"

print ""
print "Molar fractions:"
for i in range(gas.n_species):
    if gasmole[i]!=0:
        n+=1    
        if gasmole[i]>=0.1: print n, gasnames[i], "\t{0:.10f}".format(100.0*gasmole[i]), "%"
        else:
            print n, gasnames[i], "\t {0:.10f}".format(100.0*gasmole[i]), "%"

n=0
print ""
print "Mass fractions:"
for i in range(gas.n_species):
    if gasmass[i]!=0:
        n+=1    
        if gasmass[i]>=0.1: print n, gasnames[i], "\t{0:.10f}".format(100.0*gasmass[i]), "%"
        else:
            print n, gasnames[i], "\t {0:.10f}".format(100.0*gasmass[i]), "%"    

#kg/m^3\t{0:.15f}".format(gasmole[i]), "mol/m^3"
print ""
print "Mean molar mass:"
print "M  =", gas.mean_molecular_weight, "kg/kmol"

print ""
print "Density:"
print "rho =", gas.density, "kg/m^3"
print "rho =", gas.density_mole, "kmol/m^3"

print ""
print "Specific gas constant:"
print "R  =",gas_constant/gas.mean_molecular_weight, "J/kg/K"  #CHheck units ??????????

print ""
print "Molar heat capacities:"
print "Cp =", gas.cp_mole/1000.0, "J/mol/K"
print "Cv =", gas.cv_mole/1000.0, "J/mol/K"


print ""
print "Mass heat capacities:"
print "Cp =", gas.cp_mass, "J/kg/K"
print "Cv =", gas.cv_mass, "J/kg/K"

print ""
print "Heat capacity ratio"
print "kappa =", gas.cp_mole/gas.cv_mole
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Old   September 19, 2018, 06:27
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  #64
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Thanks a lot guys,

It works for both scripts you gave me.

For the script to calculate the Janaf coefficients, the results seem to be quite close from those coefficients in OpenFOAM 5 by choosing the nitrogen (except for a2, a3 and a4 for the lower interval where the gap is high).

Cheers.

Last edited by john myce; September 19, 2018 at 11:30.
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Old   October 18, 2022, 10:17
Default How the low_enthalpy_offset and high_enthalpy_offset are calculated
  #65
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Mieszko Młody
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Hi,


I am trying to understand how the low_enthalpy_offset and high_enthalpy_offset are calculated ?



what is gas.enthalpy_mass() ?


Thank you.


Mieszko
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