def fit_shomate_species(symbol, T, Cp, H0, S0):
"""Derives the shomate species from fitting the heat capacity (J/mol/K) and temperature (K) data and including the formation of enthalpy (kJ/mol) and entropy (J/mol/K)."""
T_low = min(T)
T_high = max(T)
t = np.array(T)/1000.
[a, pcov] = curve_fit(_shomate_Cp, t, np.array(Cp))
a = list(a)
a.extend([0., 0., 0.])
shomate_instance = shomate(symbol = symbol, T_low = T_low, T_high = T_high, a = np.array(a))
a6 = H0 - shomate_instance.get_HoRT(c.T0)*c.R('kJ/mol/K')*c.T0
a7 = S0 - shomate_instance.get_SoR(c.T0)*c.R('J/mol/K')
shomate_instance.a[5] = a6
shomate_instance.a[6] = a7
return shomate_instance
def plot_thermo(self, T_low=None, T_high=None, units=None):
"""
Plots the heat capacity, enthalpy and entropy in the temperature range specified.
The units for the plots can be specified by using R
"""
import matplotlib.pyplot as plt
if T_low == None:
print "T_low not specified. Using self.T_low attribuate."
T_low = self.T_low
if T_high == None:
print "T_low not specified. Using self.T_high attribuate."
T_high = self.T_high
T = np.linspace(T_low, T_high)
Cp = self.get_CpoR(T)
H = self.get_HoRT(T)
S = self.get_SoR(T)
if units is not None:
Cp = Cp * c.R(units)
H = H * c.R(units) * T
S = S * c.R(units)
plt.figure()
plt.subplot(311)
plt.plot(T, Cp, 'r-')
if units is None:
plt.ylabel('Cp/R')
else:
plt.ylabel('Cp (%s)' % units)
plt.xlabel('T (K)')
plt.title('Plots for %s using NASA polynomials.' % self.symbol)
plt.subplot(312)
plt.plot(T, H, 'b-')
if units is None:
plt.ylabel('H/RT')
else:
plt.ylabel('H (%s)' % units.replace('/K', ''))
plt.xlabel('T (K)')
#Entropy graph
plt.subplot(313)
plt.plot(T, S, 'k-')
if units is None:
plt.ylabel('S/R')
else:
plt.ylabel('S (%s)' % units)
plt.xlabel('T (K)')
def read_fund_csv(symbol, csv_path, print_graph = False):
"""Reads a csv file for data that will be fed into function fit_shomate_species."""
import matplotlib.pyplot as plt
H0_S0_read = False
T = []
Cp = []
print "Reading from file: %s" % csv_path
with open(csv_path, 'r') as csv_file:
for line in csv_file:
if line[0] != '!':
#Split data and remove unnecessary characters
data = line.split(',')
T.append(float(data[0]))
Cp.append(float(data[1]))
if len(data) > 2 and not H0_S0_read:
H0 = float(data[2])
S0 = float(data[3])
H0_S0_read = True
shomate = fit_shomate_species(symbol, T, Cp, H0, S0)
if print_graph:
T_range = np.linspace(shomate.T_low, shomate.T_high)
Cp_fit = shomate.get_CpoR(T_range)*c.R('J/mol/K')
H_fit = shomate.get_HoRT(T_range)*T_range*c.R('kJ/mol/K')
S_fit = shomate.get_SoR(T_range)*c.R('J/mol/K')
plt.figure()
plt.subplot(311)
plt.plot(T, Cp, 'ro', T_range, Cp_fit, 'b-')
plt.legend(['NIST Data', 'Fit'])
plt.xlabel('Temperature (K)')
plt.ylabel('Cp (J/mol/K)')
plt.subplot(312)
plt.plot(T_range, H_fit)
plt.xlabel('Temperature (K)')
plt.ylabel('H (kJ/mol/K)')
plt.subplot(313)
plt.plot(T_range, S_fit)
plt.xlabel('Temperature (K)')
plt.ylabel('S (J/mol/K)')
return shomate
def _get_single_SoR(self, T, verbose = True):
"""Calculates the dimensionless entropy (i.e. S/R) given a temperature."""
t = T/1000.
T_arr = np.array([np.log(t), t, t ** 2 / 2., t ** 3 / 3., -0.5 * ( 1 / t ) ** 2, 0., 1., 0.])
if verbose:
if T < self.T_low:
print "Warning. Input temperature (%f) lower than T_low (%f) for species %s" % (T, self.T_low, self.symbol)
elif T > self.T_high:
print "Warning. Input temperature (%f) higher than T_high (%f) for species %s" % (T, self.T_high, self.symbol)
return np.dot(T_arr, self.a)/c.R('J/mol/K')
def _get_single_CpoR(self, T, verbose = True):
"""Calculates the heat capacity at constant pressure (i.e. Cp/R) given a temperature."""
t = T/1000.
T_arr = np.array([1, t, t ** 2, t ** 3, (1/t) ** 2, 0, 0, 0])
if verbose:
if T < self.T_low:
print "Warning. Input temperature (%f) lower than T_low (%f) for species %s" % (T, self.T_low, self.symbol)
elif T > self.T_high:
print "Warning. Input temperature (%f) higher than T_high (%f) for species %s" % (T, self.T_high, self.symbol)
return np.dot(T_arr, self.a)/c.R('J/mol/K')
def _get_single_HoRT(self, T, H_correction = False, verbose = True):
"""Calculates the dimensionless enthalpy (i.e. H/RT) given a temperature."""
t = T/1000.
if H_correction:
T_arr = np.array([t, t ** 2 / 2, t ** 3 / 3, t ** 4 / 4, -1/t, 1., 0., 1.])
else:
T_arr = np.array([t, t ** 2 / 2, t ** 3 / 3, t ** 4 / 4, -1/t, 1., 0., 0.])
if verbose:
if T < self.T_low:
print "Warning. Input temperature (%f) lower than T_low (%f) for species %s" % (T, self.T_low, self.symbol)
elif T > self.T_high:
print "Warning. Input temperature (%f) higher than T_high (%f) for species %s" % (T, self.T_high, self.symbol)
return np.dot(T_arr, self.a)/(c.R('kJ/mol/K')*T)