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Update gas viscosity function
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@wigging
wigging committed Jan 1, 2023
1 parent a7c8e33 commit 332ac68
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186 changes: 85 additions & 101 deletions chemics/gas_viscosity.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2,97 +2,41 @@
import os
import pandas as pd

__all__ = ['mu_gas', 'mu_graham', 'mu_herning']


def _mu(df, formula, temp, cas, full):
"""
Helper for the `mu_gas` function to determine gas viscosity.
Parameters
----------
df : dataframe
Dataframe from inorganic or organic data
formula : str
Molecular formula for the gas
temp : float
Gas temperature
cas : str
CAS number
full : bool
Flag to print more information
Returns
-------
mu_gas : float
Viscosity of gas [micropoise]
mu_gas, cas, tmin, tmax, a, b, c, d : tuple
Additional values returned only if full=True.
"""

if cas:
# new dataframe based only on row for cas number
df = df[df['CAS No.'] == str(cas)]

cas = df.loc[formula]['CAS No.']
tmin = df.loc[formula]['temperature, Tmin (K)']
tmax = df.loc[formula]['temperature, Tmax (K)']
a = df.loc[formula]['A']
b = df.loc[formula]['B']
c = df.loc[formula]['C']
d = df.loc[formula]['D']

if temp < tmin or temp > tmax:
raise ValueError('Temperature out of range. Applicable values are '
f'{tmin} - {tmax} K for {formula} gas.')

mu = a + b * temp + c * (temp**2) + d * (temp**3)

if full:
return mu, cas, tmin, tmax, a, b, c, d
else:
return mu


def mu_gas(formula, temp, cas=None, full=False):
def mu_gas(formula, temp, cas=None, disp=False):
"""
Viscosity of gas as a function of temperature. Results calculated from
coefficients in Yaws' Critical Property Data for Chemical Engineers and
Chemists [1]_. CAS (Chemical Abstracts Service) number may be required for
some species.
Gas viscosity as a function of temperature using coefficients in Yaws'
Critical Property Data for Chemical Engineers and Chemists [1]_. CAS
(Chemical Abstracts Service) number may be required for some species.
Parameters
----------
formula : str
Molecular formula of the gas.
temp : float
Temperature of the gas [K]
Gas temperature [K].
cas : str, optional
CAS number of the gas, required for some species [-]
full : bool, optional
When set to :code:`False` (default) just gas viscosity is returned.
When set to :code:`True` then return gas viscosity and other
information.
Returns
-------
mu_gas : float
Viscosity of gas [micropoise]
mu_gas, cas, tmin, tmax, a, b, c, d : tuple
Additional values are only returned when keyword :code:`full=True`.
| mu_gas - Viscosity of gas [micropoise]
| cas - CAS number [-]
| tmin, tmax - Temperature range at which results are applicable [K]
| a, b, c, d - Values for regression coefficients [-]
CAS number of the gas, required for some species.
disp : bool
Display information about the calculation such as the CAS number,
applicable temperature range in Kelvin, and values for regression
coefficients.
Raises
------
KeyError
If provided CAS number is not found.
ValueError
If gas formula is not found in csv data file.
If multiple substances found for given formula.
KeyError
If gas chemical formula not found.
ValueError
If gas temperature is not in range between tmin and tmax.
If given temperataure is out of range for calculation.
Returns
-------
mu : float
Gas viscosity [microPoise].
Examples
--------
Expand All @@ -108,8 +52,17 @@ def mu_gas(formula, temp, cas=None, full=False):
>>> mu_gas('N2', 773)
363.82
>>> mu_gas('N2', 773, full=True)
(363.82, '7727-37-9', 63.15, 1970.0, 4.46, 0.63, -0.00026, 5.41e-08)
>>> mu_gas('N2', 773, disp=True)
Formula N2
CAS 7727-37-9
Min Temp. (K) 63.15
Max Temp. (K) 1970.0
A 4.46555763078484
B 0.638137789753159
C -0.0002659562785407
D 5.41126875437814e-08
μ (microPoise) 363.8235847080749
363.8235847080749
References
----------
Expand All @@ -118,33 +71,64 @@ def mu_gas(formula, temp, cas=None, full=False):
2014.
"""
abs_path = os.path.dirname(os.path.abspath(__file__))

data_inorganic = abs_path + '/data/mu-gas-inorganic.csv'
df_inorganic = pd.read_csv(data_inorganic, index_col=0)

data_organic = abs_path + '/data/mu-gas-organic.csv'
df_organic = pd.read_csv(data_organic, index_col=0)

if formula in df_inorganic.index:

if isinstance(df_inorganic.loc[formula], pd.DataFrame) and cas is None:
raise ValueError(f'Multiple substances available for {formula}. '
'Include CAS number with input parameters.')

mu = _mu(df_inorganic, formula, temp, cas, full)
return mu

elif formula in df_organic.index:

if isinstance(df_organic.loc[formula], pd.DataFrame) and cas is None:
raise ValueError(f'Multiple substances available for {formula}. '
'Include CAS number with input parameters.')
if cas:
df_inorg = pd.read_csv(data_inorganic, index_col=2)
df_org = pd.read_csv(data_organic, index_col=2)

if cas in df_inorg.index:
data = df_inorg.loc[cas]
formula = data['molecular formula']
elif cas in df_org.index:
data = df_org.loc[cas]
formula = data['molecular formula']
else:
raise KeyError(f'CAS number {cas} not found')
else:
df_inorg = pd.read_csv(data_inorganic, index_col=0)
df_org = pd.read_csv(data_organic, index_col=0)

if formula in df_inorg.index:
data = df_inorg.loc[formula]
if isinstance(data, pd.DataFrame):
raise ValueError(f'Multiple substances available for {formula}. '
'Include CAS number with input parameters.')
cas = data['CAS No.']
elif formula in df_org.index:
data = df_org.loc[formula]
if isinstance(data, pd.DataFrame):
raise ValueError(f'Multiple substances available for {formula}. '
'Include CAS number with input parameters.')
cas = data['CAS No.']
else:
raise KeyError(f'Formula {formula} not found')

tmin = data['temperature, Tmin (K)']
tmax = data['temperature, Tmax (K)']
a = data['A']
b = data['B']
c = data['C']
d = data['D']
mu = a + b * temp + c * (temp**2) + d * (temp**3)

mu = _mu(df_organic, formula, temp, cas, full)
return mu
if temp < tmin or temp > tmax:
raise ValueError('Temperature out of range. Applicable values are '
f'{tmin}-{tmax} K for {formula} gas.')

if disp:
print('Formula ', formula)
print('CAS ', cas)
print('Min Temp. (K) ', tmin)
print('Max Temp. (K) ', tmax)
print('A ', a)
print('B ', b)
print('C ', c)
print('D ', d)
print('μ (microPoise)', mu)

else:
raise ValueError(f'Gas viscosity for {formula} is not available.')
return mu


def mu_graham(mus, xs):
Expand Down
68 changes: 44 additions & 24 deletions tests/test_gas_viscosity.py
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
"""
Tests for the gas_viscosity module. Updated by G.W. on 11/30/2018.
Tests for the gas_viscosity module. Updated by G.W. on 12/31/2022.
mu = Gas viscosity [micropoise]
cas = CAS number [-]
Expand All @@ -9,43 +9,63 @@
"""

import chemics as cm
from pytest import approx
from pytest import approx, raises


# Functions to test
# ----------------------------------------------------------------------------

def test_mu_h2():
mu_h2 = cm.mu_gas('H2', 404)
assert mu_h2 == approx(113.18, rel=1e-2)
def test_mu_ch4():
mu = cm.mu_gas('CH4', 810)
assert mu == approx(234.21, rel=1e-2)


def test_mu_n2():
mu_n2 = cm.mu_gas('N2', 773)
assert mu_n2 == approx(363.82, rel=1e-2)
def test_nh3_err():
with raises(KeyError):
_ = cm.mu_gas('NH3', 900)


def test_mu_n2_full():
mu_n2, *stats = cm.mu_gas('N2', 773, full=True)
cas, tmin, tmax, a, b, c, d = stats
assert mu_n2 == approx(363.82, rel=1e-2)
assert cas == '7727-37-9'
assert tmin == approx(63.15, rel=1e-2)
assert tmax == approx(1970.0, rel=1e-2)
assert a == approx(4.465557, rel=1e-2)
assert b == approx(0.63813778, rel=1e-2)
assert c == approx(-0.0002659562, rel=1e-2)
assert d == approx(5.411268e-08, rel=1e-2)
def test_nh3():
mu = cm.mu_gas('NH3', 900, cas='7664-41-7')
assert mu == approx(319.14, rel=1e-2)


def test_mu_ch4():
mu_ch4 = cm.mu_gas('CH4', 810)
assert mu_ch4 == approx(234.21, rel=1e-2)
def test_err():
with raises(ValueError):
_ = cm.mu_gas('C2Cl2F4', 900)


def test_mu_c2cl2f4():
mu_c2cl2f4 = cm.mu_gas('C2Cl2F4', 900, cas='374-07-2')
assert mu_c2cl2f4 == approx(314.90, rel=1e-2)
mu = cm.mu_gas('C2Cl2F4', 900, cas='374-07-2')
assert mu == approx(314.90, rel=1e-2)


def test_mu_h2():
mu = cm.mu_gas('H2', 404)
assert mu == approx(113.18, rel=1e-2)


def test_mu_n2():
mu = cm.mu_gas('N2', 773)
assert mu == approx(363.82, rel=1e-2)


def test_mu_n2_disp(capsys):
mu = cm.mu_gas('N2', 773, disp=True)
assert mu == approx(363.82, rel=1e-2)

captured = capsys.readouterr()
assert captured.out == (
'Formula N2\n'
'CAS 7727-37-9\n'
'Min Temp. (K) 63.15\n'
'Max Temp. (K) 1970.0\n'
'A 4.46555763078484\n'
'B 0.638137789753159\n'
'C -0.0002659562785407\n'
'D 5.41126875437814e-08\n'
'μ (microPoise) 363.8235847080749\n'
)


def test_mu_graham():
Expand Down

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