Heat transfer in a sound-assisted fluidized bed

In previous studies of fine powder fluidization, it was found that stable bubbling can be achieved with application of acoustics having high sound intensity. Therefore, utilizing fine powder fluidization with sound assistance, applied to solid mixing, heat transfer, and mass transfer in a gas-solid fluidized bed, becomes practical. The relationship between bubble behavior and heat transfer in a fine powder fluidized bed is investigated in this study.; Experiments were performed to measure bubble dynamics and heat transfer coefficient around a horizontal tube. Two types of data are presented: average and local heat transfer coefficients and data on bubble frequency, packet residence time and the fraction of the particle packet contact time at the tube surface. The data show that bubble frequency increases with an increase in excess air velocity and sound pressure level, and the packet residence time and the fraction of the packet contact time at the tube surface decrease with increasing excess air velocity and sound pressure level. In addition, heat transfer coefficients increase with increasing excess air velocity and sound pressure level.; From fiber optic probe measurements, it is found that a gas film exists next to the tube surface. Based on the existence of a gas film between the heated surface and emulsion phase, a packet renewal model with gas film thickness is proposed to describe heat transfer in a fine powder fluidized bed. Based on this model, a modified heat transfer coefficient equation was developed. The experimental results show that the proposed model is an appropriate approach to predict heat transfer coefficient in a fine powder fluidized bed.