def heat_flux_to_temperature(heat_flux: float, exposed_temperature: float = 293.15):
    """Function returns surface temperature of an emitter for a given heat flux.

    :param heat_flux: [W/m2] heat flux of emitter.
    :param exposed_temperature: [K] ambient/receiver temperature, 20 deg.C by default.
    :return temperature: [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
    # E_dash_dash_dot = epsilon * sigma * (T_1 ** 4 - T_0 ** 4)  # [W/m2]
    return ((heat_flux / sigma / epsilon) + exposed_temperature ** 4) ** 0.25