직경이 0.152 m이고 높이가 2.5 m인 삼상 역 유동층에서 열전달특성에 대한 연구를 수행하였다. 또한, 내부열원과 유동층간의 열전달계에서 수력학적 특성과 열전달과의 연관성을 고찰하기 위해 압력강하, 층팽창, 상체류량 같은 수력학적 특성을 검토하였다. 기체와 액체의 유속 그리고 층공극률이 열전달 계수에 미치는 영향을 결정하였다. 물과 여과된 압축공기 그리고 밀도가 877.3 kg/m(3), 직경이 4 mm인 저밀도 폴리프로필렌을 각각 액체, 기체 및 고체상으로 사용하였다. 액체최소유동화속도와 각 상의 체류량은 압력강하 분포자료로부터 정압강하법에 의해 결정하였다. 삼상 역 유동층에서 열전달계수는 기체의 유속이 증가함에 따라 증가하였으나 액체의 유속 및 층공극률의 변화에 따라서는 최대값을 나타내었다. 액체최소유동화속도는 기체의 유속이 증가함에 따라 점차적으로 감소하였다. 내부열원과 유동층간의 열전달 계수는 본 연구의 실험범위에서 실험변수의 함수와 무차원군으로 각각 상관식을 나타낼 수 있었다.

Heat transfer characteristics have been investigated in a three-phase inverse fluidized bed whose diameter and height are 0.152 m and 2.5 m, respectively. Hydrodynamics such as pressure drop, bed expansion and phase holdups have been also examined to analyze the relation between the hydrodynamics and the heat transfer coefficient in the immersed heater-tobed heat transfer system. Effects of gas and liquid velocities and bed porosity on the heat transfer coefficient have been determined. Tap water, filtered compressed air and low density polypropylene whose density and diameter are 877.3 kg/m(3) and 4 mm have been used as a liquid, gas and solid phase, respectively. The minimum liquid fluidization velocity(U(Lmf)) and individual phase holdups have been obtained from the pressure drop profiles by means of static pressure drop method. It has been found that the heat transfer coefficient has increased with increasing gas velocity, but it has exhibited a maximum value with the variation of liquid velocity or bed porosity in three phase inverse fluidized beds. The minimum liquid fluidization velocity had decreased gradually with an increase in the gas velocity. The heat transfer coefficient has been will correlated as a function of operating variables and in terms of dimensionless groups, respectively, within this experimental conditions.

Three-Phase Inverse Fluidized Bed Heat Transfer Minimum Liquid Fluidization Velocity Bed Porosity

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