A theoretical investigation of acoustic enhancement of heat and mass transfer-II. Oscillating flow with a steady velocity component

In order to study the effects of high intensity acoustic fields superposed on a steady flow on heat and mass transfer around spherical particles, a two-dimensional, unsteady computer code which employs the two-dimensional, unsteady conservation of mass, momentum and energy equations for laminar flow in spherical coordinates has been developed. Numerical solutions of these equations give the velocity and temperature fields around the particle for acoustically oscillating flow as a function of acoustic Reynolds number, Strouhal number, and the ratio of the acoustic velocity to the steady slip velocity between the particles and the main flow. The present results show about 85% increase in the space- and timeaveraged quasi-steady Nusselt number normalized by its steady value when the ratio of the acoustic velocity to the steady slip velocity is about 5. About 10% decrease in heat transfer is obtained when the ratio of the acoustic velocity to the steady slip velocity is about 1. The space- and time-averaged Nusselt numbers have different values for frequencies of 50, 1000 and 2000 Hz due to the combined effects of the curvature, flow acceleration and flow separation. The maximum difference is about 10%. The results demonstrate a definite enhancement of heat and mass transfer in the presence of high intensity acoustic fields particularly for the case of low steady slip velocity.