def A_boiler(rho_cond, r_steam, g, mu_cond, L_tube_boiler, lyambda_cond):
    """
    Calculates the coefficent A of boiler.
    Parameters
    ----------
    lyambda_cond : float
        The thermal conducivity of condensate, [W / (m * degrees celcium)]
    rho_cond : float
        The destiny of condensate, [kg / m**3]
    mu_cond : float
        The viscosity of condensate, [Pa / s]
    r_steam : float
        The vaporazation of vapor, [kg/s]
    L_tube_boiler : float
        The tube length of boiler, [m]    
    Returns
    -------
    A_boiler : float
        The coefficent A of boiler, [dismensionless]
    References
    ----------
    Дытнерский, формула 2.23, стр.53
    """                  
    return 1.21 * lyambda_cond * ((rho_cond**2) * r_steam * g / (mu_cond * L_tube_boiler))**(1/3)