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가압기포탑에서 기 - 액 흐름의 Chaos 해석 및 물질전달 특성
우광재,조용준,김기인,강용,김상돈 ( Kwang Jae Woo,Yong Jun Cho,Ki In Kim,Yong Kang,Sang Done Kim ) 한국화학공학회 1998 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.36 No.6
Since the gas-liquid flow behavior in the pressurized bubble column is highly irregular, random and stochastic, it has been analyzed by resorting to somewhat noble chaos analysis ; the resultant pressure fluctuations describing the complex flow behavior of gas-liquid in the system have been manipulated to form the multidimensional phase-space portraits from which the strange attractor can be obtained. The chaos behavior of pressure fluctuations has been represented by means of correlation dimension. The volumetric gas-liquid mass transfer coefficient in the pressurized bubble column has been determined by adopting the axial dispersion model, and the relation between the hydrodynamic characteristics and the mass transfer coefficient has been also discussed. As a result of this study, the correlation dimension of pressure fluctuations has increased with increasing gas velocity(0.02-0.25 m/s), but it has decreased with an increase in the pressure(0.1-0.6 ㎫) in the column, representing the dynamic gas-liquid flow behavior in the column. The volumetric gas-liquid mass transfer coefficient has increased with increasing gas velocity and pressure. The gas-liquid mass transfer has been well predicted by means of chaotic behavior of gas-liquid flow in the pressurized bubble column.
강용,우광재,고명한,김상돈 ( Yong Kang,Kwang Jae Woo,Myung Han Ko,Sang Done Kim ) 한국화학공학회 1996 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.34 No.4
Pressure fluctuation signals from three phase fluidized beds(0-152 m ID × 2.5 m 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(0.06-0.18 m/s) and particle size(0.001-0.006 m) 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 decreased 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 persistent and it can be characterized as a higher order deterministic chaos. The spectral exponent has been well correlated in terms of dimensionless particle size and dimensionless fluid velocity based on the isotropic turbulence theory.
강용,우광재,고명한,김상돈 ( Yong Kang,Kwang Jae Woo,Myung Han Ko,Sang Done Kim ) 한국화학공학회 1995 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.33 No.5
Characteristics of unsteady state behavior and fluctuations of fluidized particles have been investigated by adopting the stochastic method in a three-phase fluidized bed of 0.152 m ID and 2.5 m in height. Air, water and glass beads whose density is 2500 ㎏/㎥ and diameter is in the range of 1.0-6.0×10^(-3) m have been used as gas, liquid and solid phase, respectively. The mean fraction, mean residence time and fluctuating frequency of fluidized particles in the test section, and the exiting rate of the particles from the test section have been obtained, The exiting rate of the particles has decreased exponentially with time lag during the relaxation of the bed, and the mean residence time of the particles in the test section has decreased with an increment of the gas velocity. The fluctuating frequency of particles has increased with an increment of the gas velocity and particle size, but it has attained its maximum value with an increment of the liquid velocity and bed porosity. The particle fluctuating frequency has been well correlated in terms of dimensionless particle size and dimensionless fluid velocity based on the isotropic turbulence theory.
강용(Yong Kang),우광재(Kwang Jae Woo),조용준(Yong Jun Cho),송평섭(Pyung Seob Song),고명한(Myung Han Ko),김상돈(Sang Done Kim) 한국화학공학회 1997 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.35 No.5
Laser intensity fluctuation signals from a bubble column(0.152 m ID and 2.5 m in height) have been analyzed by resorting to the deterministic chaos theory, to search for the intrinsic order of gas-liquid flow in the column. Some typical chaotic parameters such as Lyapunov exponent and Kolmogorov entropy and attractor in the phase space portrait from the time series of laser intensity fluctuations have been obtained with the variations of operating variables. The attractor which has been constructed with the optimum choice of time lag has been utilized to predict the chaotic behavior of gas-liquid flow in the bubble column. The values of Lyapunov exponent were small but positive; the Kolmogorov entropy increased gradually with an increase in the gas flow rate, however, it exhibited local minimum with the variation of liquid flow rate. It has been found from the results of this study that the dynamic phenomena of gas-liquid contact and flow in the bubble column could be quantified easily. The gas-liquid flow in the column showed the deterministic chaotic behavior in that the Lyapunov exponent and Kolmogorov entropy were finite and positive.
순환유동층에서 기체-고체 흐름 거동의 Stochastic 해석
강용(Yong Kang),송평섭(Pyung Seob Song),우광재(Kwang Jae Woo),정의영(Yi Yeong Jeong),김상돈(Sang Done Kim) 한국화학공학회 1997 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.35 No.6
Pressure fluctuations in the riser of a circulating fluidized bed have been analyzed by means of stochastic analysis such as fractal analysis and phase space portrait, to analyze the characteristics of gas-solid contact and flow behavior in the riser. Polyethylene whose mean diameter is 0.454 ㎜ and density is 920 ㎏/㎥ has been used as a solid. The diameter and height of the riser are 0.102 m and 3.5 m, respectively. Effects of superficial gas velocity and solid circulation rate on the hydrodynamic characteristics such as solid interstitial velocity, slip velocity between gas and solid, and solid holdup have been determined. Effects of operating variables on the Hurst exponent and phase space portrait have been also examined. The values of the Hurst exponent have been recovered from the Pox diagram obtained by the rescaled range analysis of the data. The phase space portraits have been obtained by means of the rearrangement of the data by the multidimensional phase space portrait method. As a result of this study, the concept of choking velocity is very similar to that of transportation velocity in the riser. The Hurst exponent has exhibited its maximum value and the phase space portrait has focused its tracing within the limited boundary at the transition regime of gas-solid flow.
김효식(Hyo Sik Kim),김진호(Jin-Ho Kim),류재홍(Jae-Hong Ryu),정기진(Ki-Jin Jung),오승천(Seong-Cheon Oh),홍범의(Bum-Eu Hong),강석환(Suk-Hwan Kang),박노국(No-Kuk Park),우광재(Kwang-Jae Woo) 한국에너지기후변화학회 2017 에너지기후변화학회지 Vol.12 No.2
The treatment of volatile organic compounds (VOC) emissions and its application are necessary today. The directly catalytic treatment of them has already proven to be environmentally and economically sound technology for the oxidation of the VOCs. Currently, the reforming of VOCs for hydrogen or syngas production are receiving great attention. However, few commercial examples exist. Therefore there exist a vast number of possibilities for VOC utilization via different catalytic processes, which creates also a good research potential for the future.