A numerical simulation of nonisothermal gas flows in the hot-gas filter vessel at the Power Systems Development Facility in Wilsonville, Alabama is presented. The gas velocity and thermal simulations are based on the Reynolds stress transport turbulence model of the FLUENT(TM) commercial CFD computer code. While earlier modeling studies were limited to isothermal conditions, in this study, the energy transport equation was solved in addition to the mass and momentum equations. The gas flow and temperature field inside the filter vessel were also studied. Results reveal that the gas flow shows strong rotating flow regions outside the shroud and in the upper and lower parts of the body of the vessel. It is also shown that the temperature distribution is nonuniform with somewhat higher temperatures in the upper part of the filter. The simulated results qualitatively agree with the experimental field observations of the filter vessel.