HEAT-TRANSFER PAST PARTICLES ENTRAINED IN AN OSCILLATING FLOW WITH AND WITHOUT A STEADY VELOCITY

In order to investigate the heat transfer past particles entrained in an oscillating flow with and without a steady velocity, the two-dimensional, unsteady conservation equations of mass, momentum and energy for laminar flow in the gas phase are solved numerically in spherical coordinates. The particle momentum equation is also solved simultaneously with the gas phase equations in order to consider the effect of the particle entrainment on the heat transfer past particles. The numerical solution gives the particle velocity variation as well as the gas phase velocity and temperature distribution as a function of time. The local and space-averaged Nusselt number with particle entrainment is compared with that without particle entrainment. In the case of an oscillating flow with a steady velocity, the values of the space-averaged Nusselt number with particle entrainment are lower than those without particle entrainment at frequencies of 50 and 2000 Hz, since the moving particle is entrained in the steady velocity. In the case of an oscillating flow without a steady velocity, the space-averaged Nusselt number with entrainment at a frequency of 50 Hz is slightly lower than that without particle entrainment, with a phase lag. At 2000 Hz, the space-averaged Nusselt number with and without particle entrainment is almost the same, due to very small particle entrainment.