def long_tube_coeff(mass_flux, D, c_p, mu, k):
    """Convection coefficient for flow in a long tube.

    This model for convection was developed from experiments with fully-developed
    flow in long tubes. It is taken from Eq. 11.35 in Hill & Peterson:

    .. math::
        \frac{h}{G c_p} = 0.023 (\frac{G D}{ \mu_b})^{-0.2} (\frac{\mu c_p}{k})_b^{-0.67}

    where :math:`G` is the average mass flux through the tube, and the subscript :math:`b`
    denotes properties evaluated at the bulk fluid temperature.

    References:
        [1] P. Hill and C.Peterson, "Mechanics and Thermodynamics of Propulsion",
            2nd edition, 1992.

    Arguments:
        mass_flux (scalar): Mass flux through the tube
            [units: kilogram meter**-2 second**-1].
        D (scalar): Tube (hydraulic) diameter [units: meter].
        c_p (scalar): Heat capacity at constant pressure of the fluid flowing
            through the tube [units: joule kilogram**-1 kelvin**-1].
        mu (scalar): viscosity of the fluid [units: pascal second].
        k (scalar): Thermal conductivty of the fluid [units: watt meter**-1 kelvin**-1]

    Returns:
        scalar: The convection coefficient :math:`h` [units: watt meter**-2 kelvin**-1].
    """
    Pr = mu * c_p / k
    Re = mass_flux *  D / mu
    h = 0.023 * mass_flux * c_p * Re**-0.2 * Pr**-0.67
    return h