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HWAHAK KONGHAK,
Vol.34, No.4, 429-434, 1996
Vol.34, No.4, 429-434, 1996
삼상유동층에서 압력변동의 Spectral해석
Spectral Analysis of Pressure Fluctuations in a Three Phase Fluidized Bed
직경 0.152m, 높이 2.5m인 삼상유동층에서 압력변동신호를 power 스텍트럴 밀도함수를 이용하여 해석하였으며, 그 거시적 거동을 검토하였다. 기체유속(0.01-0.07 m/s), 액체유속(0.06-0.18m/s) 그리고 고체 유동입자의 크기(0.001-0.006m) 등을 변수로 선정하였으며 이들 변수들이 압력변동신호의 특성에 미치는 영향을 고찰하였다. 삼상유동층에서 압력변동의 스펙트럴 지수는 기체유속이 증가하면 감소하였고, 유동입자의 크기가 증가하면 증가하였으나 액체유 속의 증가에 따라서는 국소적인 최대값을 나타내었다. 압력변동의 스펙트럴 지수로 나타낸 삼상유동층에서 다상의 접촉거동은 persistent한 것으로 나타났으나 높은 차원의 deterministic chaos 특성을 나타내었다. 삼상유동층에서 압력변동자료 X(t)의 스펙트럴 지수는 등방난류 이론에 의한 무차원 유동입자의 크기와 무차원 유체유 속의 상관식으로 다음과 같이 나타낼 수 있었다.
α=4.445(dp/Dr)0.0668 (UL/UL+UG)0.7100
α=4.445(dp/Dr)0.0668 (UL/UL+UG)0.7100
Pressure fluctuation signals from three phase fluidized beds(0.152m ID X 2.5m in height) have been analyzed by means of the power spectral density function. Effects of gas flow rate(0.01-0.07m/s), liquid flow rate(0.06-0.18m/s) and particle size(0.001-0.006m) on the characteristics of pressure fluctuations have been investigated. The spectral exponent obtained from the spectral analysis of pressure fluctuations from three phase fluidized beds has dec- reased with an increase in the gas flow rate, but it has increased with particle size, however, it has attained its local maximum with the variation of liquid flow rate. The flow behavior resulting from multiphase contact in three phase fluidized beds has been appeared to be per- sistent and it can be characterized as a higher order determinstic chaos. The spectral expo- nent has been well correlated in terms of dimensionless particle size and dimensionless fluid velocity based on the isotropic turbulence theory.
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