This paper presents a thermal model of a solar central receiver that volumetrically absorbs concentrated sunlight directly in a flowing gas stream seeded with submicron carbon particles. A modified six-flux radiation model is developed and used with the energy equation to calculate the three-dimensional radiant flux and temperature distributions in a cavity-type particle receiver. Results indicate that the receiver is capable of withstanding very high incident fluxes and delivering high temperatures. The receiver efficiency as a function of mass flow rate as well as the effect of particle oxidation on the temperature profiles are presented.