Conversions

Helper functions for unit conversions.

chemics.massfrac_to_molefrac(y, mw)[source]

Convert mass fraction to mole fraction. Assumes a total mass of 100 grams.

\[ \begin{align}\begin{aligned}m_i = y_i \times 100\\x_i = \frac{\frac{m_i}{MW_i}}{\sum\frac{m_i}{MW_i}}\end{aligned}\end{align} \]

where \(m\) is mass [g], \(y\) is mass fraction [-], \(x\) is mole fraction [-], and \(MW\) is molecular weight [g/mol] of each component.

Parameters:

y (list, tuple or array) – Mass fraction of each component
mw (list, tuple or array) – Molecular weight of each component in g/mol

Returns:

x (array) – Mole fractions of each component

Example

>>> y = [0.36, 0.16, 0.20, 0.28]
>>> mw = [12.011, 1.008, 15.999, 14.007]
>>> cm.massfrac_to_molefrac(y, mw)
array([0.135..., 0.717..., 0.056..., 0.090...])

chemics.molefrac_to_massfrac(x, mw)[source]

Convert mole fraction to mass fraction. Assumes total moles is 100.

\[ \begin{align}\begin{aligned}n_i &= x_i \times 100\\y_i &= \frac{n_i\, MW_i}{\sum n_i\, MW_i}\end{aligned}\end{align} \]

where \(n\) is moles [mol], \(x\) is mole fraction [-], \(y\) is mass fraction [-], and \(MW\) is molecular weight [g/mol] of each component.

Parameters:

x (list, tuple, or array) – Mole fraction of each component [-]
mw (list, tuple or array) – Molecular weight of each component [g/mol]

Returns:

y (array) – Mass fraction of each component [-]

Example

>>> x = [0.36, 0.16, 0.20, 0.28]
>>> mw = [12.011, 1.008, 15.999, 14.007]
>>> cm.molefrac_to_massfrac(x, mw)
array([0.372..., 0.0138..., 0.275..., 0.337...])

chemics.slm_to_lpm(slm, pgas, tgas)[source]

Convert volumetric gas flow.

Convert volumetric gas flow from standard liters per minute (SLM or SLPM) to liters per minute (LPM) where STP is defined as 273.25 K and 101,325 Pa.

\[1\; LPM = 1\; SLPM \times \frac{T_{gas}}{273.15\,K} \times \frac{14.696\,psi}{P_{gas}}\]

Parameters:

slm (float) – Volumetric gas flow in standard liters per minute [SLM]
pgas (float) – Absolute gas pressure [kPa]
tgas (float) – Gas temperature [K]

Returns:

lpm (float) – Volumetric gas flow in liters per minute [LPM]

Example

>>> cm.slm_to_lpm(580, 150, 773)
1108.74...

References

Wikipedia contributors. (2018, February 8). Standard litre per minute. In Wikipedia online. Retrieved from https://en.wikipedia.org/wiki/Standard_litre_per_minute