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Shripad T Revankar - One of the best experts on this subject based on the ideXlab platform.
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investigation of bubble breakup and Coalescence in a packed bed reactor part 1 a comparative study of bubble breakup and Coalescence models
International Journal of Multiphase Flow, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Abstract In a packed-bed reactor a comparative study of bubble breakup and Coalescence models has been investigated to study bubble size distributions as a function of the axial location. The bubble size distributions are obtained by solving population balance equations that describe gas–liquid interactions. Each combination of bubble breakup and Coalescence models is examined under two inlet flow conditions: (1) predominant bubble breakup flow and (2) predominant bubble Coalescence flow. The resulting bubble size distributions, breakup and Coalescence rates estimated by individual models, are qualitatively compared to each other. The change of bubble size distributions along the axial direction is also described with medians. The medians resulting from CFD analyses are compared against the experimental data. Since the predictions estimated by CFD analyses with the existing bubble breakup and Coalescence models do not agree with the experimental data, a new bubble breakup and Coalescence model that takes account of the geometry effects is required to describe gas–liquid interactions in a packed-bed reactor.
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Investigation of bubble breakup and Coalescence in a packed-bed reactor – Part 1: A comparative study of bubble breakup and Coalescence models
International Journal of Multiphase Flow, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Abstract In a packed-bed reactor a comparative study of bubble breakup and Coalescence models has been investigated to study bubble size distributions as a function of the axial location. The bubble size distributions are obtained by solving population balance equations that describe gas–liquid interactions. Each combination of bubble breakup and Coalescence models is examined under two inlet flow conditions: (1) predominant bubble breakup flow and (2) predominant bubble Coalescence flow. The resulting bubble size distributions, breakup and Coalescence rates estimated by individual models, are qualitatively compared to each other. The change of bubble size distributions along the axial direction is also described with medians. The medians resulting from CFD analyses are compared against the experimental data. Since the predictions estimated by CFD analyses with the existing bubble breakup and Coalescence models do not agree with the experimental data, a new bubble breakup and Coalescence model that takes account of the geometry effects is required to describe gas–liquid interactions in a packed-bed reactor.
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investigation of bubble breakup and Coalescence in a packed bed reactor part 2 development of a new bubble breakup and Coalescence model
International Journal of Multiphase Flow, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Abstract A mechanistic model of bubble breakup and Coalescence has been developed for a packed bed. Bubble breakup and Coalescence models are developed for two Coalescence and three breakup mechanisms by taking account of geometry effects and local flow conditions. The bubble size distribution estimated with the present bubble breakup and Coalescence models are compared with the experimental data. Change of bubble size distributions along the axial direction is studied with the median bubble size. Median bubble size as a function of the axial location is estimated under two inlet flow conditions: (1) bubble breakup dominated flow and (2) bubble Coalescence dominated flow. The predictions of the median bubble size with the present model result in the best among other existing bubble breakup and Coalescence models. However, the prediction of the median bubble size for the bubble Coalescence dominated flow is still significantly larger than the experimental data. Breakup and Coalescence coefficients need to be adjusted in order to predict more accurate bubble size distributions and median bubble size for both flow conditions. For the bubble breakup dominated flow, the breakup and Coalescence coefficients are found to be 0.35 and 0.4, respectively. For the bubble Coalescence dominated flow, the breakup and Coalescence coefficients are found to be 0.35 and 0.01, respectively.
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Investigation of bubble breakup and Coalescence in a packed-bed reactor – Part 2: Development of a new bubble breakup and Coalescence model
International Journal of Multiphase Flow, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Abstract A mechanistic model of bubble breakup and Coalescence has been developed for a packed bed. Bubble breakup and Coalescence models are developed for two Coalescence and three breakup mechanisms by taking account of geometry effects and local flow conditions. The bubble size distribution estimated with the present bubble breakup and Coalescence models are compared with the experimental data. Change of bubble size distributions along the axial direction is studied with the median bubble size. Median bubble size as a function of the axial location is estimated under two inlet flow conditions: (1) bubble breakup dominated flow and (2) bubble Coalescence dominated flow. The predictions of the median bubble size with the present model result in the best among other existing bubble breakup and Coalescence models. However, the prediction of the median bubble size for the bubble Coalescence dominated flow is still significantly larger than the experimental data. Breakup and Coalescence coefficients need to be adjusted in order to predict more accurate bubble size distributions and median bubble size for both flow conditions. For the bubble breakup dominated flow, the breakup and Coalescence coefficients are found to be 0.35 and 0.4, respectively. For the bubble Coalescence dominated flow, the breakup and Coalescence coefficients are found to be 0.35 and 0.01, respectively.
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effect of Coalescence and breakup on bubble size distributions in a two dimensional packed bed
Chemical Engineering Science, 2010Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Bubble size distributions in a two-dimensional packed bed are investigated as a function of axial direction by using image processing techniques with a large number of bubble samples. Two inlet conditions, controlled sized bubbles and uncontrolled sized bubbles, are conducted to study the characteristic behaviors of bubbles. With the uncontrolled sized bubbles, the average bubble size corresponding to the two-dimensional bed is found, and is not affected by decrease or increase of flow rates. With the controlled sized bubbles, dominant bubble breakup and Coalescence flows are separately simulated to investigate bubble breakup and Coalescence rates. Unique behavior of bubble size distributions for dominant bubble breakup and Coalescence has been seen, and changes in bubble size distributions along axial direction are studied with median bubble size. Near the inlet the median changes rapidly due to the dominant bubble mechanism of either Coalescence or breakup, and far away from the inlet the median reaches asymptotic value due to the balance of bubble breakup and Coalescence. For both dominant breakup and Coalescence flows, the asymptotic values are close to the average bubble size. Therefore, the average bubble size, resulting from the balance of bubble Coalescence and breakup at far downstream, is irrespective of inlet flow conditions.
Daeseong Jo - One of the best experts on this subject based on the ideXlab platform.
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investigation of bubble breakup and Coalescence in a packed bed reactor part 1 a comparative study of bubble breakup and Coalescence models
International Journal of Multiphase Flow, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Abstract In a packed-bed reactor a comparative study of bubble breakup and Coalescence models has been investigated to study bubble size distributions as a function of the axial location. The bubble size distributions are obtained by solving population balance equations that describe gas–liquid interactions. Each combination of bubble breakup and Coalescence models is examined under two inlet flow conditions: (1) predominant bubble breakup flow and (2) predominant bubble Coalescence flow. The resulting bubble size distributions, breakup and Coalescence rates estimated by individual models, are qualitatively compared to each other. The change of bubble size distributions along the axial direction is also described with medians. The medians resulting from CFD analyses are compared against the experimental data. Since the predictions estimated by CFD analyses with the existing bubble breakup and Coalescence models do not agree with the experimental data, a new bubble breakup and Coalescence model that takes account of the geometry effects is required to describe gas–liquid interactions in a packed-bed reactor.
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Investigation of bubble breakup and Coalescence in a packed-bed reactor – Part 1: A comparative study of bubble breakup and Coalescence models
International Journal of Multiphase Flow, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Abstract In a packed-bed reactor a comparative study of bubble breakup and Coalescence models has been investigated to study bubble size distributions as a function of the axial location. The bubble size distributions are obtained by solving population balance equations that describe gas–liquid interactions. Each combination of bubble breakup and Coalescence models is examined under two inlet flow conditions: (1) predominant bubble breakup flow and (2) predominant bubble Coalescence flow. The resulting bubble size distributions, breakup and Coalescence rates estimated by individual models, are qualitatively compared to each other. The change of bubble size distributions along the axial direction is also described with medians. The medians resulting from CFD analyses are compared against the experimental data. Since the predictions estimated by CFD analyses with the existing bubble breakup and Coalescence models do not agree with the experimental data, a new bubble breakup and Coalescence model that takes account of the geometry effects is required to describe gas–liquid interactions in a packed-bed reactor.
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investigation of bubble breakup and Coalescence in a packed bed reactor part 2 development of a new bubble breakup and Coalescence model
International Journal of Multiphase Flow, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Abstract A mechanistic model of bubble breakup and Coalescence has been developed for a packed bed. Bubble breakup and Coalescence models are developed for two Coalescence and three breakup mechanisms by taking account of geometry effects and local flow conditions. The bubble size distribution estimated with the present bubble breakup and Coalescence models are compared with the experimental data. Change of bubble size distributions along the axial direction is studied with the median bubble size. Median bubble size as a function of the axial location is estimated under two inlet flow conditions: (1) bubble breakup dominated flow and (2) bubble Coalescence dominated flow. The predictions of the median bubble size with the present model result in the best among other existing bubble breakup and Coalescence models. However, the prediction of the median bubble size for the bubble Coalescence dominated flow is still significantly larger than the experimental data. Breakup and Coalescence coefficients need to be adjusted in order to predict more accurate bubble size distributions and median bubble size for both flow conditions. For the bubble breakup dominated flow, the breakup and Coalescence coefficients are found to be 0.35 and 0.4, respectively. For the bubble Coalescence dominated flow, the breakup and Coalescence coefficients are found to be 0.35 and 0.01, respectively.
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Investigation of bubble breakup and Coalescence in a packed-bed reactor – Part 2: Development of a new bubble breakup and Coalescence model
International Journal of Multiphase Flow, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Abstract A mechanistic model of bubble breakup and Coalescence has been developed for a packed bed. Bubble breakup and Coalescence models are developed for two Coalescence and three breakup mechanisms by taking account of geometry effects and local flow conditions. The bubble size distribution estimated with the present bubble breakup and Coalescence models are compared with the experimental data. Change of bubble size distributions along the axial direction is studied with the median bubble size. Median bubble size as a function of the axial location is estimated under two inlet flow conditions: (1) bubble breakup dominated flow and (2) bubble Coalescence dominated flow. The predictions of the median bubble size with the present model result in the best among other existing bubble breakup and Coalescence models. However, the prediction of the median bubble size for the bubble Coalescence dominated flow is still significantly larger than the experimental data. Breakup and Coalescence coefficients need to be adjusted in order to predict more accurate bubble size distributions and median bubble size for both flow conditions. For the bubble breakup dominated flow, the breakup and Coalescence coefficients are found to be 0.35 and 0.4, respectively. For the bubble Coalescence dominated flow, the breakup and Coalescence coefficients are found to be 0.35 and 0.01, respectively.
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effect of Coalescence and breakup on bubble size distributions in a two dimensional packed bed
Chemical Engineering Science, 2010Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Bubble size distributions in a two-dimensional packed bed are investigated as a function of axial direction by using image processing techniques with a large number of bubble samples. Two inlet conditions, controlled sized bubbles and uncontrolled sized bubbles, are conducted to study the characteristic behaviors of bubbles. With the uncontrolled sized bubbles, the average bubble size corresponding to the two-dimensional bed is found, and is not affected by decrease or increase of flow rates. With the controlled sized bubbles, dominant bubble breakup and Coalescence flows are separately simulated to investigate bubble breakup and Coalescence rates. Unique behavior of bubble size distributions for dominant bubble breakup and Coalescence has been seen, and changes in bubble size distributions along axial direction are studied with median bubble size. Near the inlet the median changes rapidly due to the dominant bubble mechanism of either Coalescence or breakup, and far away from the inlet the median reaches asymptotic value due to the balance of bubble breakup and Coalescence. For both dominant breakup and Coalescence flows, the asymptotic values are close to the average bubble size. Therefore, the average bubble size, resulting from the balance of bubble Coalescence and breakup at far downstream, is irrespective of inlet flow conditions.
Yong Jin - One of the best experts on this subject based on the ideXlab platform.
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Theoretical prediction of flow regime transition in bubble columns by the population balance model
Chemical Engineering Science, 2005Co-Authors: Tiefeng Wang, Jinfu Wang, Yong JinAbstract:Theoretical prediction of flow regime transition in bubble columns was studied based on the bubble size distribution by the population balance model (PBM). Models for bubble Coalescence and breakup due to different mechanisms, including Coalescence due to turbulent eddies, Coalescence due to different bubble rise velocities, Coalescence due to bubble wake entrainment, breakup due to eddy collision and breakup due to large bubble instability, were proposed. Simulation results showed that at relatively low superficial gas velocities, bubble Coalescence and breakup were relatively weak and the bubble size was small and had a narrow distribution; with an increase in the superficial gas velocity, large bubbles began to form due to bubble Coalescence, resulting in a much wider bubble size distribution. The regime transition was predicted to occur when the volume fraction of small bubbles sharply decreased. The predicted transition superficial gas velocity was about 4 cm/s for the air-water system, in accordance with the values obtained from experimental approaches. © 2005 Elsevier Ltd. All rights reserved.
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Population balance model for gas - Liquid flows: Influence of bubble Coalescence and breakup models
Industrial and Engineering Chemistry Research, 2005Co-Authors: Tiefeng Wang, Jinfu Wang, Yong JinAbstract:In dispersed gas-liquid flows, the bubble size distribution plays an important role in the phase structure and the interphase forces, which, in turn, determine the multiphase hydrodynamic behaviors, including the spatial profiles of the gas fraction, gas and liquid velocities, and mixing and mass-transfer behaviors. The population balance model (PBM) is an effective method to simulate the bubble size distribution. The bubble Coalescence and breakup models have a distinct influence on the prediction ability of the PBM. This work compares several typical bubble Coalescence and breakup models. The results show that the bubble size distributions predicted by the PBM are quite different when different bubble Coalescence and breakup models are used. By using proper bubble Coalescence and breakup models, the bubble size distribution and regime transition can be reasonably predicted. The results also show that it is necessary to take into account bubble Coalescence and breakup due to different mechanisms.
Tiefeng Wang - One of the best experts on this subject based on the ideXlab platform.
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Theoretical prediction of flow regime transition in bubble columns by the population balance model
Chemical Engineering Science, 2005Co-Authors: Tiefeng Wang, Jinfu Wang, Yong JinAbstract:Theoretical prediction of flow regime transition in bubble columns was studied based on the bubble size distribution by the population balance model (PBM). Models for bubble Coalescence and breakup due to different mechanisms, including Coalescence due to turbulent eddies, Coalescence due to different bubble rise velocities, Coalescence due to bubble wake entrainment, breakup due to eddy collision and breakup due to large bubble instability, were proposed. Simulation results showed that at relatively low superficial gas velocities, bubble Coalescence and breakup were relatively weak and the bubble size was small and had a narrow distribution; with an increase in the superficial gas velocity, large bubbles began to form due to bubble Coalescence, resulting in a much wider bubble size distribution. The regime transition was predicted to occur when the volume fraction of small bubbles sharply decreased. The predicted transition superficial gas velocity was about 4 cm/s for the air-water system, in accordance with the values obtained from experimental approaches. © 2005 Elsevier Ltd. All rights reserved.
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Population balance model for gas - Liquid flows: Influence of bubble Coalescence and breakup models
Industrial and Engineering Chemistry Research, 2005Co-Authors: Tiefeng Wang, Jinfu Wang, Yong JinAbstract:In dispersed gas-liquid flows, the bubble size distribution plays an important role in the phase structure and the interphase forces, which, in turn, determine the multiphase hydrodynamic behaviors, including the spatial profiles of the gas fraction, gas and liquid velocities, and mixing and mass-transfer behaviors. The population balance model (PBM) is an effective method to simulate the bubble size distribution. The bubble Coalescence and breakup models have a distinct influence on the prediction ability of the PBM. This work compares several typical bubble Coalescence and breakup models. The results show that the bubble size distributions predicted by the PBM are quite different when different bubble Coalescence and breakup models are used. By using proper bubble Coalescence and breakup models, the bubble size distribution and regime transition can be reasonably predicted. The results also show that it is necessary to take into account bubble Coalescence and breakup due to different mechanisms.
Andres Leonardo Marquez - One of the best experts on this subject based on the ideXlab platform.
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partial Coalescence in double w1 o w2 emulsions prepared with skimmed milk polyglycerol polyricinoleate and different fats
European Journal of Lipid Science and Technology, 2017Co-Authors: Maria Paula Perez, Jorge R Wagner, Andres Leonardo MarquezAbstract:Partial Coalescence was studied in double (W1/O/W2) emulsions prepared with skimmed milk, polyglycerol polyricinoleate (PGPR) as lipophilic emulsifier and different fats. Microstructural and rheological analyses were performed. Encapsulation efficiency (as a parameter of inner water retention) and solid fat content were estimated by differential scanning calorimetry. The presence of PGPR in dispersed lipid phase promoted partial Coalescence especially at higher concentration. This promotion of partial Coalescence may have been produced by the increase of collision frequency due to protein displacement by PGPR at the outer interface and/or the increase of capture efficiency due to the modification of fat crystals by PGPR. Partial Coalescence was also favored when inner water droplets were released as a consequence of an osmotic unbalance between inner and outer aqueous phases. Thus, the addition of glucose in dispersed aqueous phase decreased the partial Coalescence degree due to the higher encapsulation efficiency given by the balanced osmotic pressures. With respect to the effect of the employed fat on partial Coalescence, the obtained data indicates that the phenomenon was favored at higher solid fat content in lipid phase. Results led to the conclusion that inner osmolality, encapsulation efficiency and inhibition of partial Coalescence were correlated. Practical applications: The originality of this work resides on boarding the subject of partial Coalescence in W1/O/W2 emulsions. The studied systems are proposed as potential lipid-reduced substitutes of dairy creams, with the employment of alternative non-dairy fats such as low trans vegetable fat. The combined analysis of partial Coalescence and encapsulation efficiency allowed studying their reciprocal effects and evaluating the potentiality of the systems for the encapsulation of hydrophilic compounds. The variations of relative osmotic pressures in inner and outer aqueous phases, lipophilic emulsifier concentration and solid fat content may lead to desirable or undesirable rheological properties depending on the required texture of the food emulsion. The findings of this work could be an important step pointing to control the factors leading to partial Coalescence in W1/O/W2 emulsions for food applications.
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Partial Coalescence in double (W1/O/W2) emulsions prepared with skimmed milk, polyglycerol polyricinoleate and different fats†
European Journal of Lipid Science and Technology, 2017Co-Authors: Maria Paula Perez, Jorge R Wagner, Andres Leonardo MarquezAbstract:Partial Coalescence was studied in double (W1/O/W2) emulsions prepared with skimmed milk, polyglycerol polyricinoleate (PGPR) as lipophilic emulsifier and different fats. Microstructural and rheological analyses were performed. Encapsulation efficiency (as a parameter of inner water retention) and solid fat content were estimated by differential scanning calorimetry. The presence of PGPR in dispersed lipid phase promoted partial Coalescence especially at higher concentration. This promotion of partial Coalescence may have been produced by the increase of collision frequency due to protein displacement by PGPR at the outer interface and/or the increase of capture efficiency due to the modification of fat crystals by PGPR. Partial Coalescence was also favored when inner water droplets were released as a consequence of an osmotic unbalance between inner and outer aqueous phases. Thus, the addition of glucose in dispersed aqueous phase decreased the partial Coalescence degree due to the higher encapsulation efficiency given by the balanced osmotic pressures. With respect to the effect of the employed fat on partial Coalescence, the obtained data indicates that the phenomenon was favored at higher solid fat content in lipid phase. Results led to the conclusion that inner osmolality, encapsulation efficiency and inhibition of partial Coalescence were correlated. Practical applications: The originality of this work resides on boarding the subject of partial Coalescence in W1/O/W2 emulsions. The studied systems are proposed as potential lipid-reduced substitutes of dairy creams, with the employment of alternative non-dairy fats such as low trans vegetable fat. The combined analysis of partial Coalescence and encapsulation efficiency allowed studying their reciprocal effects and evaluating the potentiality of the systems for the encapsulation of hydrophilic compounds. The variations of relative osmotic pressures in inner and outer aqueous phases, lipophilic emulsifier concentration and solid fat content may lead to desirable or undesirable rheological properties depending on the required texture of the food emulsion. The findings of this work could be an important step pointing to control the factors leading to partial Coalescence in W1/O/W2 emulsions for food applications.