def temperature_to_heat_flux(temperature: float, ambient_temperature: float = 293.15):
    """Function returns hot surface heat flux for a given temperature.

    :param temperature: [K] emitter temperature.
    :param ambient_temperature: [K] ambient/receiver temperature, 20 deg.C by default.
    :return heat_flux: [K] calculated emitter temperature based on black body radiation model.
    """

    epsilon = 1.0  # radiation view factor
    sigma = 5.67e-8  # [W/m2/K4] stefan-boltzmann constant

    heat_flux = epsilon * sigma * (temperature ** 4 - ambient_temperature ** 4)

    return heat_flux