This paper reports a new study where radiation effects are studied in details in an SOFC stack. The 3D model used includes and couples fluid dynamics, electrochemistry, electrical conduction, diffusion, and heat transfer physics. The model was built using in-house experimental voltage-current density data for validation purposes. The objective of this study is to understand the effects of radiation in the flow channels of SOFC stacks. Both gas radiation and surface-to-surface heat exchange are considered. This study indicates that gas radiation is negligible when compared to surface-to-surface heat exchange. It is also found that surface-to-surface heat exchange cannot be neglected and actually provides a more uniform temperature distribution along the SOFC stack. Heat transfer via convection is also significant and should be included when modeling similar situations. Finally, the model indicates that viscous dissipation is a negligible source of heat generation.