def Lazarek_Black(m, D, mul, kl, Hvap, q=None, Te=None):
    r'''Calculates heat transfer coefficient for film boiling of saturated
    fluid in vertical tubes for either upward or downward flow. Correlation
    is as shown in [1]_, and also reviewed in [2]_ and [3]_.
    
    Either the heat flux or excess temperature is required for the calculation
    of heat transfer coefficient.
    
    Quality independent. Requires no properties of the gas.
    Uses a Reynolds number assuming all the flow is liquid.

    .. math::
        h_{tp} = 30 Re_{lo}^{0.857} Bg^{0.714} \frac{k_l}{D}
        
        Re_{lo} = \frac{G_{tp}D}{\mu_l}
    
    Parameters
    ----------
    m : float
        Mass flow rate [kg/s]
    D : float
        Diameter of the channel [m]
    mul : float
        Viscosity of liquid [Pa*s]
    kl : float
        Thermal conductivity of liquid [W/m/K]
    Hvap : float
        Heat of vaporization of liquid [J/kg]
    q : float, optional
        Heat flux to wall [W/m^2]
    Te : float, optional
        Excess temperature of wall, [K]

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

    Notes
    -----
    [1]_ has been reviewed. 
    
    [2]_ claims it was developed for a range of quality 0-0.6,
    Relo 860-5500, mass flux 125-750 kg/m^2/s, q of 1.4-38 W/cm^2, and with a
    pipe diameter of 3.1 mm. Developed with data for R113 only.

    Examples
    --------
    >>> Lazarek_Black(m=10, D=0.3, mul=1E-3, kl=0.6, Hvap=2E6, Te=100)
    9501.932636079293

    References
    ----------
    .. [1] Lazarek, G. M., and S. H. Black. "Evaporative Heat Transfer, 
       Pressure Drop and Critical Heat Flux in a Small Vertical Tube with 
       R-113." International Journal of Heat and Mass Transfer 25, no. 7 (July 
       1982): 945-60. doi:10.1016/0017-9310(82)90070-9.
    .. [2] Fang, Xiande, Zhanru Zhou, and Dingkun Li. "Review of Correlations 
       of Flow Boiling Heat Transfer Coefficients for Carbon Dioxide."
       International Journal of Refrigeration 36, no. 8 (December 2013): 
       2017-39. doi:10.1016/j.ijrefrig.2013.05.015.
    .. [3] Bertsch, Stefan S., Eckhard A. Groll, and Suresh V. Garimella. 
       "Review and Comparative Analysis of Studies on Saturated Flow Boiling in
       Small Channels." Nanoscale and Microscale Thermophysical Engineering 12,
       no. 3 (September 4, 2008): 187-227. doi:10.1080/15567260802317357.
    '''
    G = m/(pi/4*D**2)
    Relo = G*D/mul
    if q:
        Bg = Boiling(G=G, q=q, Hvap=Hvap)
        return 30*Relo**0.857*Bg**0.714*kl/D
    elif Te:
        # Solved with sympy
        return 27000*30**(71/143)*(1./(G*Hvap))**(357/143)*Relo**(857/286)*Te**(357/143)*kl**(500/143)/D**(500/143)
    else:
        raise Exception('Either q or Te is needed for this correlation')