Abstract
The present paper was studied on the experimental and numerical results of heat transfer in the acoustic fields induced by ultrasonic waves. The augmentation ratio of heat transfer coefficient was experimentally measured and compared with the profile of the acoustic pressure obtained by numerical prediction when the ultrasonic waves were applied in the liquid paraffin. For the experiments, paraffin (n-octadecane) that was selected as a medium was filled the melting cavity. Two ultrasonic transducers are installed in a cavity and was applied the resonance frequency of 40 kHz. Although a fixed frequency level of 40kHz was selected, output power levels were varied from 75 W to 340 W in order to investigate the effect of the strength ultrasonic vibrations on heat and mass transfer. A particle image velocimetry (PIV) was used for the visualization of flow fields through the visualization. Also, for the numerical analysis, Structure Vibration Sound (SVS) programmed with a Fortran language and based on a coupled finite element-boundary element method (FE-BEM) was used. The results of the present study reveal that the value of acoustic pressure and augmentation ratio of local heat transfer is larger near two ultrasonic transducers then other points. In addition, even though the profiles of acoustic pressure and heat transfer augmentation are rather irregular, they also have a likeness. That is, the higher acoustic pressure is, the higher enhancement of heat transfer is. Also, when output power level varied from 75 W to 340 W, the stronger ultrasonic intensity is, the higher acoustic pressure and enhancement of heat transfer. Further, it is concluded that a correlation exists between acoustic pressure and heat transfer since they phase are roughly same.
