Experimental study on the influence of the orifice size on hydrodynamic characteristics and bubble size distribution of an external loop airlift reactor |
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Authors: | Xia Lu Xiaotao Zheng Yigang Ding Wei Lin Wei Wang Jiuyang Yu |
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Affiliation: | 1. School of Mechanical and Electronic Engineering, Wuhan Institute of Technology, Wuhan City, P. R. China The College of Post and Telecommunication of Wuhan Institute of Technology, Wuhan City, P. R. China;2. School of Mechanical and Electronic Engineering, Wuhan Institute of Technology, Wuhan City, P. R. China;3. School of Chemical and Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan City, P. R. China |
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Abstract: | The orifice size has a significant influence on hydrodynamic characteristics and bubble size distribution (BSD) in gas-liquid flow. However, the mechanism of the influence of orifice size on BSD and hydrodynamic characteristics in an external loop airlift reactor (EL-ALR) has not been fully revealed. In this work, the effects of the orifice size on hydrodynamic characteristics and BSD in a laboratory scale EL-ALR were investigated using the particle image velocimetry (PIV) technique and digital image analysis (DIA). The results show that the transition superficial gas velocity becomes greater when the orifice size is reduced. The time-averaged bubble velocity profiles along the riser radius are parabolic, and the shape of the time-averaged bubble velocity curve is strongly dependent on the orifice diameter. The larger the orifice diameter, the steeper the parabolas. For sparger with lager orifice diameters, the BSD curve is bimodal even at low superficial gas velocity, and its peaks shift to a larger equivalent bubble diameter. The bubble aspect ratio appears to be related only to the equivalent diameter of the bubbles, regardless of the diameter of the orifice. It has a defined relationship between the bubble aspect ratio and the bubble equivalent diameter, and a new correlation is obtained based on the experimental data. This study will help to gain an understanding of the influence of sparger orifice size on the hydrodynamic characteristics and BSD and provide a basis for numerical simulation. |
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Keywords: | BSD bubble shape digital image analysis gas-liquid flow orifice diameter |
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