2016 Volume 29 Issue 5 Pages 501-508
The acoustic levitation is one of the levitation techniques to control a sample in sound pressure. The acoustic levitation induces the internal and external flow of the levitated droplet. It is considered that these flows affect heat and mass transfer of the levitated droplet. The purpose of this study is to investigate the relationship between convective heat transfer and flow behavior of the levitated droplet. The convective heat transfer between ambient air and the droplet is calculated by an evolution of the surface area and temperature. The convective heat transfer increases as the temperature of water droplet increases. The external flow structure is measured by PIV. The non-heated water droplet has a toroidal vortex below a levitated droplet. As the temperature of water droplet increases, the external flow structure changes from that of non-heated droplet. The larger the diameter and temperature of droplet become, the larger external flow velocity near the surface of the levitated droplet becomes. It is suggested that the increase of external flow velocity enhances the convective heat transfer and the convective heat transfer is more enhanced by the increase of temperature.
