Bed-to-Wall Heat Transfer in the Turbulent Fluidized Beds
Date Issued
2006
Date
2006
Author(s)
Tao, Cheng-Lung
DOI
zh-TW
Abstract
Gas velocities at which transition occurred from bubbling to turbulent fluidization were determined by measurement of pressure fluctuations at various axial positions in a 0.108m i.d., 5.76m high expanded-top fluidized bed. By the method of statistical analysis, mean amplitude of pressure fluctuations were used to determine the transition velocity from bubbling to turbulent flow regimes. On the other hand, the effects of different flow regimes on bed-wall heat transfer coefficients were also determined.
The results show that pressure fluctuations become violent as the superficial increases and the activity of bubbles intensifies progressively owing to the bubbles by coalescence and greater formation frequency of bubbles. When superficial gas velocity increases to Uc, the pressure fluctuations peak gradually decay at the onset of the turbulent regime.
For the heat transfer, the results showed that when the superficial gas velocity increased beyond Uc, the bed-wall heat transfer coefficient would increase again. Besides, the influence of static height of bed on the bed-wall heat transfer coefficient depends on where the heater position is. As to the relationship between the bed-wall heat transfer coefficient and the particle diameter, the results show that the former decreases with the latter in the turbulent fluidized bed.
Subjects
流體化床
床-壁間熱傳
fluidized
Type
thesis