A study has been made of the flow of air and particles and the heat transfer inside a solar heated, open cavity containing a falling cloud of 100-1000 micron solid particles. Two-way momentum and thermal coupling between the particles and the air are included in the analysis along with the effects of radiative transport within the particle cloud, among the cavity surfaces, and between the cloud and the surfaces. The flow field is assumed to be two-dimensional with steady mean quantities. The PSI-Cell (particle source in cell) computer code is used to describe the gas-particle interaction. The method of discrete ordinates is used to obtain the radiative transfer within the cloud. The results include the velocity and temperature profiles of the particles and the air.