Effects of momentum and thermal energy exchange on the Rayleigh-Bénard convection of disperse flows

This paper reports some preliminary results of a computational study of the effect of suspended solid particles in a gas ow driven by natural convection. The study is conducted in the point-particle approximation including two-way coupling. It differs from other models of this type in that the particles do not only exert a force on the gas, but also exchange energy with it. Their ability to do so is measured by the ratio J of the gas heat capacity to the particle heat capacity, both per unit volume. This parameter is shown to exert a powerful in uence on the ow. When J = 0 the particles maintain their initial temperature although they heat up the surrounding uid. In spite of this, if they are not too small, they increase the natural convection as, being swept up by the cold descending currents, they increase their weight and accelerate them. As J is increased above 0 the particle-gas temperature difference decereases and a maximum heat transfer is reached when the gas can absorb all the heat carried by the particles. A simple argument suggests that this condition is reached when J equals 1/2 of the particle volume fraction.