thermo/vapor_pressure.py
def Sanjari(T, Tc, Pc, omega):
    r'''Calculates vapor pressure of a fluid at arbitrary temperatures using a
    CSP relationship by [1]_. Requires a chemical's critical temperature,
    pressure, and acentric factor. Although developed for refrigerants,
    this model should have some general predictive ability.

    The vapor pressure of a chemical at `T` is given by:

    .. math::
        P^{sat} = P_c\exp(f^{(0)} + \omega f^{(1)} + \omega^2 f^{(2)})

        f^{(0)} = a_1 + \frac{a_2}{T_r} + a_3\ln T_r + a_4 T_r^{1.9}

        f^{(1)} = a_5 + \frac{a_6}{T_r} + a_7\ln T_r + a_8 T_r^{1.9}

        f^{(2)} = a_9 + \frac{a_{10}}{T_r} + a_{11}\ln T_r + a_{12} T_r^{1.9}

    Parameters
    ----------
    T : float
        Temperature of fluid [K]
    Tc : float
        Critical temperature of fluid [K]
    Pc : float
        Critical pressure of fluid [Pa]
    omega : float
        Acentric factor [-]

    Returns
    -------
    Psat : float
        Vapor pressure, [Pa]

    Notes
    -----
    a[1-12] are as follows:
    6.83377, -5.76051, 0.90654, -1.16906,
    5.32034, -28.1460, -58.0352, 23.57466,
    18.19967, 16.33839, 65.6995, -35.9739.

    For a claimed fluid not included in the regression, R128, the claimed AARD
    was 0.428%. A re-calculation using 200 data points from 125.45 K to
    343.90225 K evenly spaced by 1.09775 K as generated by NIST Webbook April
    2016 produced an AARD of 0.644%. It is likely that the author's regression
    used more precision in its coefficients than was shown here. Nevertheless,
    the function is reproduced as shown in [1]_.

    For Tc=808 K, Pc=1100000 Pa, omega=1.1571, this function actually declines
    after 770 K.

    Examples
    --------
    >>> Sanjari(347.2, 617.1, 36E5, 0.299)
    13651.916109552498

    References
    ----------
    .. [1] Sanjari, Ehsan, Mehrdad Honarmand, Hamidreza Badihi, and Ali
       Ghaheri. "An Accurate Generalized Model for Predict Vapor Pressure of
       Refrigerants." International Journal of Refrigeration 36, no. 4
       (June 2013): 1327-32. doi:10.1016/j.ijrefrig.2013.01.007.
    '''
    Tr = T/Tc
    f0 = 6.83377 + -5.76051/Tr + 0.90654*log(Tr) + -1.16906*Tr**1.9
    f1 = 5.32034 + -28.1460/Tr + -58.0352*log(Tr) + 23.57466*Tr**1.9
    f2 = 18.19967 + 16.33839/Tr + 65.6995*log(Tr) + -35.9739*Tr**1.9
    return Pc*exp(f0 + omega*f1 + omega**2*f2)
def Sanjari(T, Tc, Pc, omega):
    r'''Calculates vapor pressure of a fluid at arbitrary temperatures using a
    CSP relationship by [1]_. Requires a chemical's critical temperature,
    pressure, and acentric factor. Although developed for refrigerants,
    this model should have some general predictive ability.

    The vapor pressure of a chemical at `T` is given by:

    .. math::
        P^{sat} = P_c\exp(f^{(0)} + \omega f^{(1)} + \omega^2 f^{(2)})

        f^{(0)} = a_1 + \frac{a_2}{T_r} + a_3\ln T_r + a_4 T_r^{1.9}

        f^{(1)} = a_5 + \frac{a_6}{T_r} + a_7\ln T_r + a_8 T_r^{1.9}

        f^{(2)} = a_9 + \frac{a_{10}}{T_r} + a_{11}\ln T_r + a_{12} T_r^{1.9}

    Parameters
    ----------
    T : float
        Temperature of fluid [K]
    Tc : float
        Critical temperature of fluid [K]
    Pc : float
        Critical pressure of fluid [Pa]
    omega : float
        Acentric factor [-]

    Returns
    -------
    Psat : float
        Vapor pressure, [Pa]

    Notes
    -----
    a[1-12] are as follows:
    6.83377, -5.76051, 0.90654, -1.16906,
    5.32034, -28.1460, -58.0352, 23.57466,
    18.19967, 16.33839, 65.6995, -35.9739.

    For a claimed fluid not included in the regression, R128, the claimed AARD
    was 0.428%. A re-calculation using 200 data points from 125.45 K to
    343.90225 K evenly spaced by 1.09775 K as generated by NIST Webbook April
    2016 produced an AARD of 0.644%. It is likely that the author's regression
    used more precision in its coefficients than was shown here. Nevertheless,
    the function is reproduced as shown in [1]_.

    For Tc=808 K, Pc=1100000 Pa, omega=1.1571, this function actually declines
    after 770 K.

    Examples
    --------
    >>> Sanjari(347.2, 617.1, 36E5, 0.299)
    13651.916109552498

    References
    ----------
    .. [1] Sanjari, Ehsan, Mehrdad Honarmand, Hamidreza Badihi, and Ali
       Ghaheri. "An Accurate Generalized Model for Predict Vapor Pressure of
       Refrigerants." International Journal of Refrigeration 36, no. 4
       (June 2013): 1327-32. doi:10.1016/j.ijrefrig.2013.01.007.
    '''
    Tr = T/Tc
    f0 = 6.83377 + -5.76051/Tr + 0.90654*log(Tr) + -1.16906*Tr**1.9
    f1 = 5.32034 + -28.1460/Tr + -58.0352*log(Tr) + 23.57466*Tr**1.9
    f2 = 18.19967 + 16.33839/Tr + 65.6995*log(Tr) + -35.9739*Tr**1.9
    return Pc*exp(f0 + omega*f1 + omega**2*f2)
r'''Calculates vapor pressure of a fluid at arbitrary temperatures using a
    CSP relationship by [1]_. Requires a chemical's critical temperature,
    pressure, and acentric factor. Although developed for refrigerants,
    this model should have some general predictive ability.

    The vapor pressure of a chemical at `T` is given by:

    .. math::
        P^{sat} = P_c\exp(f^{(0)} + \omega f^{(1)} + \omega^2 f^{(2)})

        f^{(0)} = a_1 + \frac{a_2}{T_r} + a_3\ln T_r + a_4 T_r^{1.9}

        f^{(1)} = a_5 + \frac{a_6}{T_r} + a_7\ln T_r + a_8 T_r^{1.9}

        f^{(2)} = a_9 + \frac{a_{10}}{T_r} + a_{11}\ln T_r + a_{12} T_r^{1.9}

    Parameters
    ----------
    T : float
        Temperature of fluid [K]
    Tc : float
        Critical temperature of fluid [K]
    Pc : float
        Critical pressure of fluid [Pa]
    omega : float
        Acentric factor [-]

    Returns
    -------
    Psat : float
        Vapor pressure, [Pa]

    Notes
    -----
    a[1-12] are as follows:
    6.83377, -5.76051, 0.90654, -1.16906,
    5.32034, -28.1460, -58.0352, 23.57466,
    18.19967, 16.33839, 65.6995, -35.9739.

    For a claimed fluid not included in the regression, R128, the claimed AARD
    was 0.428%. A re-calculation using 200 data points from 125.45 K to
    343.90225 K evenly spaced by 1.09775 K as generated by NIST Webbook April
    2016 produced an AARD of 0.644%. It is likely that the author's regression
    used more precision in its coefficients than was shown here. Nevertheless,
    the function is reproduced as shown in [1]_.

    For Tc=808 K, Pc=1100000 Pa, omega=1.1571, this function actually declines
    after 770 K.

    Examples
    --------
    >>> Sanjari(347.2, 617.1, 36E5, 0.299)
    13651.916109552498

    References
    ----------
    .. [1] Sanjari, Ehsan, Mehrdad Honarmand, Hamidreza Badihi, and Ali
       Ghaheri. "An Accurate Generalized Model for Predict Vapor Pressure of
       Refrigerants." International Journal of Refrigeration 36, no. 4
       (June 2013): 1327-32. doi:10.1016/j.ijrefrig.2013.01.007.