2.6.4 Radiation Exchange

The fibers participate in radiation exchange by absorbing irradiation energy from the surrounding flow irradiation and by emitting irradiation at the fiber temperature. This effect on the irradiation of the surrounding flow is considered by computing the absorbed and emitted energy of the fibers in each cell as

$$G_{abs} = \sum_{fibers} \frac{\epsilon_f}{4} A_f G$$ (2.6-4)

$$G_{emiss} = \sum_{fibers} \frac{\epsilon_f}{4} \frac{A_f}{\pi} \sigma T_f^4$$ (2.6-5)

where
	$A_f$	=	fiber surface area
	$\sigma$	=	Boltzman constant
	$G$	=	irradiation of the surrounding flow
	$\epsilon_{f}$	=	emissivity of the fiber

The transfer of the fiber radiation energy to the surrounding flow is only considered when the single-band Discrete-Ordinate Model is used in the ANSYS FLUENT flow model. While radiation effects on the fibers are taken into account when the P1 model is used, there is no two-way coupling for this model.