def sigma_thermpollution_boiler(pollution_1_boiler, pollution_2_boiler, sigma_boiler, lyambda_wall_boiler):
    """
    Calculates the sum of thermal pollutions for boiler.
    Parameters
    ----------
    pollution_1_boiler : float
        The thermal pollution of the first coolant, [m**2 * degrees celcium / W]
    pollution_2_boiler : float
        The thermal pollution of the second coolant, [m**2 * degrees celcium / W]
    sigma_boiler : float
        The thickness of pipe wall, [m]
    lyambda_wall_boiler : float
        The thermal conducivity of wall, [W / (m * degrees celcium)]  
    Returns
    -------
    sigma_thermpollution_boiler : float
        The the sum of thermal pollutions, [m**2 * degrees celcium / W]
    References
    ----------
    &&&&&
    """                  
    return (sigma_boiler / lyambda_wall_boiler) + (1 / pollution_1_boiler) + (1 / pollution_2_boiler)