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현탁이중기포탑에서 현탁액의 열전달 및 물질전달특성에 관한 연구

Heat and Mass Transfer Characteristics in a Solid-Suspended Bubble Column with A Draft Tube

HWAHAK KONGHAK, December 1989, 27(6), 845-854(10), NONE
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Abstract

우수한 혼합효과를 지닌 순환기포탑내 현탁액이 기포교반에 의하여 순환될 때의 열전달 및 물질전달특성을 규명하기 위하여 평균입경이 100㎛이하인 미세한 고체입자가 첨가된 현탁액에 대하여 실험을 행하였다. 실험결과 열전달속도는 공탑기체속도와 입자크기 및 농도의 증가에 따라 증가하였고 실험범위 전반에 걸쳐서 순수용액의 경우보다 크게 나타났지만 물질전달속도는 공탑기체속도의 증가에 따라서는 증가하였으나 입자크기 및 농도의 증가에 따라서는 감소하였고 전반적으로 순수한 용액의 경우보다 작은 값을 나타내었다. 이를 설명하기 위하여 에너지 수지로부터 산출한 탑내 액상의 단위질량당 에너지소멸속도를 표면 재생이론 및 Kolmogoroff의 난류등방성이론과 조합하여 열전달계수를 산출하고 eddy cell 모델과 에너지소멸속도를 조합한 물질전달계수와 기-액계면 비접촉면적의 곱으로 부피물질전달계수에 관한 이론식을 유도하여 실험값과 이론값을 비교한 결과 실험범위내의 전반적인 경향을 잘 설명할 수 있었다.
Heat and mass transfer characteristics in the circulating slurry suspension by bubble-agitation in a bubble column with a draft tube were studied in a 8.90cm I.D.×150cm high acryl column. Heat transfer coefficients increased with increasing superficial gas velocity, particle size and the concentration of particles and were larger than those without the addition of particles. The volumetric mass transfer coefficients increased with an increase in super-ficial gas velocity but decreased with an increase in particle size and concentration of particles and were smaller than those without the addition of particles. To explain these phenomena, the energy dissipation rate estimated from the energy balance was combined with the surface renewal theory and Kolmogoroff’s isotropic turbulence theory to predict the theoretical heat transfer coefficients. Also the volumetric mass transfer coefficient was derived from the eddy cell model and energy dissipation rate with specific gas-liquid interfacial area. These theoretical equations could predict the tendency of the experimental data of heat and mass transfer very well.

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