r'''Calculates heat transfer coefficient for laminar film condensation
    of a pure chemical on a flat plate, as presented in [1]_ according to an
    analysis performed by Nusselt in 1916.

    .. math::
        h=0.943\left[\frac{g\sin(\theta)\rho_{liq}(\rho_l-\rho_v)k_{l}^3
        \Delta H_{vap}}{\mu_l(T_{sat}-T_w)L}\right]^{0.25}

    Parameters
    ----------
    Tsat : float
        Saturation temperature at operating pressure [Pa]
    Tw : float
        Wall temperature, [K]
    rhog : float
        Density of the gas [kg/m^3]
    rhol : float
        Density of the liquid [kg/m^3]
    kl : float
        Thermal conductivity of liquid [W/m/K]
    mul : float
        Viscosity of liquid [Pa*s]
    Hvap : float
        Heat of vaporization of the fluid at P, [J/kg]
    L : float
        Length of the plate [m]
    angle : float, optional
        Angle of inclination of the plate [degrees]

    Returns
    -------
    h : float
        Heat transfer coefficient [W/m^2/K]

    Notes
    -----
    Optionally, the plate may be inclined.
    The constant 0.943 is actually:
    
    .. math::
        2\sqrt{2}/3

    Examples
    --------
    p. 578 in [1]_, matches exactly.

    >>> Nusselt_laminar(Tsat=370, Tw=350, rhog=7.0, rhol=585., kl=0.091,
    ... mul=158.9E-6, Hvap=776900, L=0.1)
    1482.206403453679

    References
    ----------
    .. [1] Hewitt, G. L. Shires T. Reg Bott G. F., George L. Shires, and
       T. R. Bott. Process Heat Transfer. 1E. Boca Raton: CRC Press, 1994.

def Nusselt_laminar(Tsat, Tw, rhog, rhol, kl, mul, Hvap, L, angle=90.):
    r'''Calculates heat transfer coefficient for laminar film condensation
    of a pure chemical on a flat plate, as presented in [1]_ according to an
    analysis performed by Nusselt in 1916.

    .. math::
        h=0.943\left[\frac{g\sin(\theta)\rho_{liq}(\rho_l-\rho_v)k_{l}^3
        \Delta H_{vap}}{\mu_l(T_{sat}-T_w)L}\right]^{0.25}

    Parameters
    ----------
    Tsat : float
        Saturation temperature at operating pressure [Pa]
    Tw : float
        Wall temperature, [K]
    rhog : float
        Density of the gas [kg/m^3]
    rhol : float
        Density of the liquid [kg/m^3]
    kl : float
        Thermal conductivity of liquid [W/m/K]
    mul : float
        Viscosity of liquid [Pa*s]
    Hvap : float
        Heat of vaporization of the fluid at P, [J/kg]
    L : float
        Length of the plate [m]
    angle : float, optional
        Angle of inclination of the plate [degrees]

    Returns
    -------
    h : float
        Heat transfer coefficient [W/m^2/K]

    Notes
    -----
    Optionally, the plate may be inclined.
    The constant 0.943 is actually:
    
    .. math::
        2\sqrt{2}/3

    Examples
    --------
    p. 578 in [1]_, matches exactly.

    >>> Nusselt_laminar(Tsat=370, Tw=350, rhog=7.0, rhol=585., kl=0.091,
    ... mul=158.9E-6, Hvap=776900, L=0.1)
    1482.206403453679

    References
    ----------
    .. [1] Hewitt, G. L. Shires T. Reg Bott G. F., George L. Shires, and
       T. R. Bott. Process Heat Transfer. 1E. Boca Raton: CRC Press, 1994.
    '''
    return 2.*2.**0.5/3.*(kl**3*rhol*(rhol - rhog)*g*sin(angle/180.*pi)
                          *Hvap/(mul*(Tsat - Tw)*L))**0.25