The Experts below are selected from a list of 16269 Experts worldwide ranked by ideXlab platform
Naoki Shikazono - One of the best experts on this subject based on the ideXlab platform.
-
Liquid Film Thicknesses of oscillating slug flows in a capillary tube
International Journal of Heat and Mass Transfer, 2018Co-Authors: Young Jik Youn, Youngbae Han, Naoki ShikazonoAbstract:Abstract Liquid Film Thickness is an important parameter for predicting boiling and condensation heat transfer coefficients in a microscale slug flow. In the present study, Liquid Film Thickness of oscillating slug flow in a capillary tube is experimentally investigated under adiabatic condition. Laser focus displacement meter is used to measure the initial Liquid Film Thickness. Circular tube with inner diameter of 1 mm is used for the test tube, and water and ethanol are used as working fluids. Measurement is carried out using a capillary tube with one open end and the other connected to a stepping motor. Driving frequency is ranged from 1 to 10 Hz at equivalent slug stroke of 31.7 mm and 51.2 mm. As the frequency and equivalent slug stroke are increased, the Liquid Film Thickness deviates from that in the steady condition and becomes thinner or thicker under flow acceleration or deceleration, respectively. The empirical correlations for the initial Liquid Film Thickness under acceleration and deceleration conditions proposed in the previous study (Youn et al., 2015, 2016) well predict the Liquid Film Thicknesses of the oscillating flows within 15% accuracy.
-
measurement of Liquid Film Thickness in micro tube annular flow
International Journal of Multiphase Flow, 2015Co-Authors: Hiroshi Kanno, Naoki ShikazonoAbstract:Abstract Heat transfer in micro scale two-phase flow attracts large attention since it can achieve large heat transfer area per unit volume. At large flow rate and high quality, annular flow becomes one of the major flow regimes in micro two-phase flow. Heat is transferred by evaporation or condensation of the Liquid Film, which are the dominant mechanisms of micro scale heat transfer. Therefore, Liquid Film Thickness is one of the most important parameters in modeling the heat transfer phenomena. In the present study, time averaged annular Liquid Film Thickness is measured by laser confocal displacement meter (LCDM), and the gas–Liquid interface profile is observed by a high-speed camera. Glass tubes with inner diameters of D = 0.3, 0.5 and 1.0 mm are used. Degassed water and air are used for working fluids, and the total mass flux is varied from G = 100 to 500 kg/m2 s. Flow patterns are observed and flow pattern map based on Reynolds numbers of gas and Liquid flows is suggested. Pressure drop is measured and compared with the prediction using Lockhart and Martinelli parameter. Pressure drop is well predicted with Lockhart–Martinelli correlation. Dimensionless mean Film Thickness is then plotted against quality, and compared with the annular Film model assuming flat gas–Liquid interface. Flat interface model overestimated the experimental data. It is considered that the shear stress on the gas–Liquid interface in the real annular flow is larger than that estimated in the ideal flat interface model. Prediction using new empirical correlation considering the effect of the non-flat gas–Liquid interface showed good agreement with the experiment data.
-
The effect of initial flow velocity on the Liquid Film Thickness in micro tube accelerated slug flow
International Journal of Multiphase Flow, 2015Co-Authors: Young Jik Youn, Youngbae Han, Kenshiro Muramatsu, Naoki ShikazonoAbstract:Abstract Liquid Film Thickness is an important parameter for predicting boiling and condensation heat transfer in micro tubes. In the present study, the effect of initial flow velocity on the Liquid Film Thickness in accelerated flows under adiabatic condition is experimentally investigated. The laser focus displacement meter is used to measure the initial Liquid Film Thickness. Circular tube with inner diameter of 1 mm was used for the test tube, and water, ethanol and FC-40 are used as working fluids. When the flow is accelerated from small initial velocities under small Bond number condition, initial Liquid Film Thickness is identical to that of steady flow at small capillary numbers, and then deviates from the steady condition and eventually follows that of accelerated flow from zero initial velocity as capillary number is increased. When the flow is accelerated from large initial velocities, initial Liquid Film Thickness deviates from the steady condition earlier and starts to follow that of accelerated flow from zero initial velocity as capillary number is increased. It is found that the initial flow velocity cannot be neglected in accelerated flows especially at large initial flow velocities and at large Bond numbers. Finally, an empirical correlation is proposed for the initial Liquid Film Thickness of accelerated flows that accounts for the initial flow velocities.
-
Numerical study on the effect of initial flow velocity on Liquid Film Thickness of accelerated slug flow in a micro tube
International Journal of Heat and Fluid Flow, 2015Co-Authors: Kenshiro Muramatsu, Young Jik Youn, Youngbae Han, Yosuke Hasegawa, Naoki ShikazonoAbstract:Numerical simulation of air–water slug flows accelerated from steady states with different initial velocities in a micro tube is conducted. It is shown that the Liquid Film formed between the gas bubble and the wall in an accelerated flow is significantly thinner than that in a steady flow at the same instantaneous capillary number. Specifically, the Liquid Film Thickness is kept almost unchanged just after the onset of acceleration, and then gradually increases and eventually converges to that of an accelerated flow from zero initial velocity. Due to the flow acceleration, the Stokes layer is generated from the wall, and the instant velocity profile can be given by superposition of the Stokes layer and the initial parabolic velocity profile of a steady flow. It is found that the velocity profile inside a Liquid slug away from the bubble can be well predicted by the analytical solution of a single-phase flow with acceleration. The change of the velocity profile in an accelerated flow changes the balance between the inertia, surface tension and viscous forces around the meniscus region, and thus the resultant Liquid Film Thickness. By introducing the displacement Thickness, the existing correlation for Liquid Film Thickness in a steady flow (Han and Shikazono, 2009) is extended so that it can be applied to a flow with acceleration from an arbitrary initial velocity. It is demonstrated that the proposed correlation can predict Liquid Film Thickness at Re < 4600 within the range of ±10% accuracy.
-
Liquid Film Thickness in Micro-Scale Two-Phase Flow
Two Phase Flow Phase Change and Numerical Modeling, 2011Co-Authors: Naoki Shikazono, Youngbae HanAbstract:Liquid Film formed between confined vapor bubble and tube wall in micro-scale two phase flow plays an important role in heat exchangers and chemical reactors, since local heat and mass transfer is effectively enhanced at the thin Liquid Film region (Taha and Cui, 2006). However, characteristics of the Liquid Film in micro-scale two phase flows are not fully understood, and thus designing two-phase flow systems still remains as a difficult task. It is reported that the Thickness of the Liquid Film is one of the most important parameters for predicting two phase flow heat transfer in micro tubes, see Thome et al., 2004; Kenning et al., 2006; Qu and Mudawar, 2004; Saitoh et al., 2007. For example, in the three zone evaporation model proposed by Thome et al. (2004), initial Liquid Film Thickness is one of the three unknown parameters which must be given from experimental studies. Many researches have been conducted to investigate the characteristics of Liquid Film both experimentally and theoretically. Taylor (1961) experimentally obtained mean Liquid Film Thickness in a slug flow by measuring the difference between bubble velocity and mean velocity. Highly viscous fluids, i.e. glycerol, syrup-water mixture and lubricating oil, were used so that wide capillary number range could be covered. It was found that the ratio of bubble velocity to mean velocity approaches an asymptotic value of 0.55. This asymptotic value was re-evaluated by Cox (1964), which was reported to be 0.60. Schwartz et al. (1986) investigated the effect of bubble length on the Liquid Film Thickness using the same method as Taylor (1961). It was reported that longer bubbles move faster than shorter ones. Bretherton (1961) proposed an analytical theory for the bubble profile and axial pressure drop across the bubble using lubrication equations. Assuming small capillary number, it is shown that the dimensionless Liquid Film Thickness can be scaled by an exponential function of capillary number, Ca2/3. Liquid Film Thickness can also be measured from the temperature change of the channel wall under the assumption that the whole Liquid Film on the wall evaporates and the heat is wholly consumed by the evaporation of the Liquid Film. Cooper (1969) measured Liquid Film Thickness with this method and investigated the bubble growth in nucleate pool boiling. Moriyama and Inoue (1996) measured Liquid Film Thickness during a bubble expansion in a narrow gap. It was reported that Liquid Film Thickness is affected by the viscous boundary layer in the Liquid slug when acceleration becomes large. Their experimental data was correlated in terms of capillary number, Bond number and dimensionless boundary layer Thickness. Heil (2001) numerically investigated the inertial
Mukhtar Abdulkadir - One of the best experts on this subject based on the ideXlab platform.
-
annular Liquid Film Thickness prediction in a vertical 180 return bend
Experimental Thermal and Fluid Science, 2018Co-Authors: Mukhtar Abdulkadir, J N Samson, D U Okhiria, D Zhao, V HernandezperezAbstract:Annular flow is predominant in gas wells. Liquid may be present in form of entrained droplets as well as in the Liquid Film on pipe wall. The knowledge of the average Liquid Film Thickness is vital for detailed mechanistic modelling of churn–annular flow in engineering applications. So far, the models for Liquid Film Thickness prediction are limited to vertical and horizontal pipes. These models were based on limited ranges of experimental data. In addition, exhaustive iterations are needed when these models are used to estimate Liquid Film Thickness. In this work, a new correlation to predict Liquid Film Thickness in a 180o bend under gas–Liquid annular conditions was successfully proposed. The correlation was based on dimensionless numbers (modified gas and Liquid Weber numbers and gas Froude number) which reflect the underlined physics governing gas–Liquid interaction in the bend. The Weber numbers capture the two important forces (inertial and surface tension forces) which govern the formation of the Liquid Film Thickness within the system while gas Froude number quantifies the interaction of two important forces (centrifugal and gravitational forces) which determines the distribution of the phases across a bend. The proposed Liquid Film Thickness correlation was based on the experimental data obtained from a wide range of operating conditions. The Liquid superficial velocities ranges from 0.02 to 0.2 m/s and gas superficial velocities from 3.5 to 16 m/s at different measurement locations of 45o, 90o and 135o of the bend with a diameter of 127 mm. The Liquid Film Thickness in air–water and helium–water annular flow can be predicted by . The validation of the proposed correlation used to predict Liquid Film Thickness in gas–Liquid annular systems with different pipe diameters were examined against the available data in the literature. Good agreement was found between the predicted values of Liquid Film Thickness with the experimental data at different measuring locations of the bend.
-
annular Liquid Film Thickness prediction in a vertical 180o return bend
Experimental Thermal and Fluid Science, 2018Co-Authors: Mukhtar Abdulkadir, J N Samson, D U Okhiria, D Zhao, V HernandezperezAbstract:Annular flow is predominant in gas wells. Liquid may be present in form of entrained droplets as well as in the Liquid Film on pipe wall. The knowledge of the average Liquid Film Thickness is vital for detailed mechanistic modelling of churn–annular flow in engineering applications. So far, the models for Liquid Film Thickness prediction are limited to vertical and horizontal pipes. These models were based on limited ranges of experimental data. In addition, exhaustive iterations are needed when these models are used to estimate Liquid Film Thickness. In this work, a new correlation to predict Liquid Film Thickness in a 180o bend under gas–Liquid annular conditions was successfully proposed. The correlation was based on dimensionless numbers (modified gas and Liquid Weber numbers and gas Froude number) which reflect the underlined physics governing gas–Liquid interaction in the bend. The Weber numbers capture the two important forces (inertial and surface tension forces) which govern the formation of the Liquid Film Thickness within the system while gas Froude number quantifies the interaction of two important forces (centrifugal and gravitational forces) which determines the distribution of the phases across a bend. The proposed Liquid Film Thickness correlation was based on the experimental data obtained from a wide range of operating conditions. The Liquid superficial velocities ranges from 0.02 to 0.2 m/s and gas superficial velocities from 3.5 to 16 m/s at different measurement locations of 45o, 90o and 135o of the bend with a diameter of 127 mm. The Liquid Film Thickness in air–water and helium–water annular flow can be predicted by . The validation of the proposed correlation used to predict Liquid Film Thickness in gas–Liquid annular systems with different pipe diameters were examined against the available data in the literature. Good agreement was found between the predicted values of Liquid Film Thickness with the experimental data at different measuring locations of the bend.
-
Annular Liquid Film Thickness prediction in a vertical 180° return bend
Experimental Thermal and Fluid Science, 2018Co-Authors: Mukhtar Abdulkadir, J N Samson, D U Okhiria, D Zhao, V. Hernandez-perezAbstract:Annular flow is predominant in gas wells. Liquid may be present in form of entrained droplets as well as in the Liquid Film on pipe wall. The knowledge of the average Liquid Film Thickness is vital for detailed mechanistic modelling of churn–annular flow in engineering applications. So far, the models for Liquid Film Thickness prediction are limited to vertical and horizontal pipes. These models were based on limited ranges of experimental data. In addition, exhaustive iterations are needed when these models are used to estimate Liquid Film Thickness. In this work, a new correlation to predict Liquid Film Thickness in a 180o bend under gas–Liquid annular conditions was successfully proposed. The correlation was based on dimensionless numbers (modified gas and Liquid Weber numbers and gas Froude number) which reflect the underlined physics governing gas–Liquid interaction in the bend. The Weber numbers capture the two important forces (inertial and surface tension forces) which govern the formation of the Liquid Film Thickness within the system while gas Froude number quantifies the interaction of two important forces (centrifugal and gravitational forces) which determines the distribution of the phases across a bend. The proposed Liquid Film Thickness correlation was based on the experimental data obtained from a wide range of operating conditions. The Liquid superficial velocities ranges from 0.02 to 0.2 m/s and gas superficial velocities from 3.5 to 16 m/s at different measurement locations of 45o, 90o and 135o of the bend with a diameter of 127 mm. The Liquid Film Thickness in air–water and helium–water annular flow can be predicted by . The validation of the proposed correlation used to predict Liquid Film Thickness in gas–Liquid annular systems with different pipe diameters were examined against the available data in the literature. Good agreement was found between the predicted values of Liquid Film Thickness with the experimental data at different measuring locations of the bend.
-
Liquid Film Thickness behaviour within a large diameter vertical 180 return bend
Chemical Engineering Science, 2014Co-Authors: Mukhtar Abdulkadir, D Zhao, Abdelwahid Azzi, Ian Lowndes, Barry J. AzzopardiAbstract:Experimental results of Liquid Film Thickness distribution of an air–water mixture flowing through a vertical 180° return bend are reported. Measurements of Liquid Film Thickness were achieved using flush mounted pin and parallel wire probes. The bend has a diameter of 127 mm and a curvature ratio (R/D) of 3. The superficial velocities of air ranged from 3.5 to 16.1 m/s and those for water from 0.02 to 0.2 m/s. At these superficial velocity ranges, the flow pattern investigated in this work focused on churn and annular flows. It was found that at Liquid and gas superficial velocities of 0.02 m/s and 6.2 m/s, respectively, the averaged Liquid Film Thickness peak at 90°. At gas superficial velocity of 16.1 m/s, the relationship between them is linear due to the shear forces overcoming gravity. Additionally, it was found that deposition of entrained droplets keeps the Liquid Film on the outside of the bend. The results of polar plots of average Liquid Film Thickness in the bend showed that the distribution of the Liquid Film is not symmetrical with thicker Films on the inside of the bend due to the action of gravity. Experimental results on average Liquid Film Thickness showed good agreement with the simulation data reported in the literature.
-
Liquid Film Thickness behaviour within a large diameter vertical 180° return bend
Chemical Engineering Science, 2014Co-Authors: Mukhtar Abdulkadir, D Zhao, Abdelwahid Azzi, Ian Lowndes, Barry J. AzzopardiAbstract:Experimental results of Liquid Film Thickness distribution of an air–water mixture flowing through a vertical 180° return bend are reported. Measurements of Liquid Film Thickness were achieved using flush mounted pin and parallel wire probes. The bend has a diameter of 127 mm and a curvature ratio (R/D) of 3. The superficial velocities of air ranged from 3.5 to 16.1 m/s and those for water from 0.02 to 0.2 m/s. At these superficial velocity ranges, the flow pattern investigated in this work focused on churn and annular flows. It was found that at Liquid and gas superficial velocities of 0.02 m/s and 6.2 m/s, respectively, the averaged Liquid Film Thickness peak at 90°. At gas superficial velocity of 16.1 m/s, the relationship between them is linear due to the shear forces overcoming gravity. Additionally, it was found that deposition of entrained droplets keeps the Liquid Film on the outside of the bend. The results of polar plots of average Liquid Film Thickness in the bend showed that the distribution of the Liquid Film is not symmetrical with thicker Films on the inside of the bend due to the action of gravity. Experimental results on average Liquid Film Thickness showed good agreement with the simulation data reported in the literature.
D Zhao - One of the best experts on this subject based on the ideXlab platform.
-
annular Liquid Film Thickness prediction in a vertical 180 return bend
Experimental Thermal and Fluid Science, 2018Co-Authors: Mukhtar Abdulkadir, J N Samson, D U Okhiria, D Zhao, V HernandezperezAbstract:Annular flow is predominant in gas wells. Liquid may be present in form of entrained droplets as well as in the Liquid Film on pipe wall. The knowledge of the average Liquid Film Thickness is vital for detailed mechanistic modelling of churn–annular flow in engineering applications. So far, the models for Liquid Film Thickness prediction are limited to vertical and horizontal pipes. These models were based on limited ranges of experimental data. In addition, exhaustive iterations are needed when these models are used to estimate Liquid Film Thickness. In this work, a new correlation to predict Liquid Film Thickness in a 180o bend under gas–Liquid annular conditions was successfully proposed. The correlation was based on dimensionless numbers (modified gas and Liquid Weber numbers and gas Froude number) which reflect the underlined physics governing gas–Liquid interaction in the bend. The Weber numbers capture the two important forces (inertial and surface tension forces) which govern the formation of the Liquid Film Thickness within the system while gas Froude number quantifies the interaction of two important forces (centrifugal and gravitational forces) which determines the distribution of the phases across a bend. The proposed Liquid Film Thickness correlation was based on the experimental data obtained from a wide range of operating conditions. The Liquid superficial velocities ranges from 0.02 to 0.2 m/s and gas superficial velocities from 3.5 to 16 m/s at different measurement locations of 45o, 90o and 135o of the bend with a diameter of 127 mm. The Liquid Film Thickness in air–water and helium–water annular flow can be predicted by . The validation of the proposed correlation used to predict Liquid Film Thickness in gas–Liquid annular systems with different pipe diameters were examined against the available data in the literature. Good agreement was found between the predicted values of Liquid Film Thickness with the experimental data at different measuring locations of the bend.
-
annular Liquid Film Thickness prediction in a vertical 180o return bend
Experimental Thermal and Fluid Science, 2018Co-Authors: Mukhtar Abdulkadir, J N Samson, D U Okhiria, D Zhao, V HernandezperezAbstract:Annular flow is predominant in gas wells. Liquid may be present in form of entrained droplets as well as in the Liquid Film on pipe wall. The knowledge of the average Liquid Film Thickness is vital for detailed mechanistic modelling of churn–annular flow in engineering applications. So far, the models for Liquid Film Thickness prediction are limited to vertical and horizontal pipes. These models were based on limited ranges of experimental data. In addition, exhaustive iterations are needed when these models are used to estimate Liquid Film Thickness. In this work, a new correlation to predict Liquid Film Thickness in a 180o bend under gas–Liquid annular conditions was successfully proposed. The correlation was based on dimensionless numbers (modified gas and Liquid Weber numbers and gas Froude number) which reflect the underlined physics governing gas–Liquid interaction in the bend. The Weber numbers capture the two important forces (inertial and surface tension forces) which govern the formation of the Liquid Film Thickness within the system while gas Froude number quantifies the interaction of two important forces (centrifugal and gravitational forces) which determines the distribution of the phases across a bend. The proposed Liquid Film Thickness correlation was based on the experimental data obtained from a wide range of operating conditions. The Liquid superficial velocities ranges from 0.02 to 0.2 m/s and gas superficial velocities from 3.5 to 16 m/s at different measurement locations of 45o, 90o and 135o of the bend with a diameter of 127 mm. The Liquid Film Thickness in air–water and helium–water annular flow can be predicted by . The validation of the proposed correlation used to predict Liquid Film Thickness in gas–Liquid annular systems with different pipe diameters were examined against the available data in the literature. Good agreement was found between the predicted values of Liquid Film Thickness with the experimental data at different measuring locations of the bend.
-
Annular Liquid Film Thickness prediction in a vertical 180° return bend
Experimental Thermal and Fluid Science, 2018Co-Authors: Mukhtar Abdulkadir, J N Samson, D U Okhiria, D Zhao, V. Hernandez-perezAbstract:Annular flow is predominant in gas wells. Liquid may be present in form of entrained droplets as well as in the Liquid Film on pipe wall. The knowledge of the average Liquid Film Thickness is vital for detailed mechanistic modelling of churn–annular flow in engineering applications. So far, the models for Liquid Film Thickness prediction are limited to vertical and horizontal pipes. These models were based on limited ranges of experimental data. In addition, exhaustive iterations are needed when these models are used to estimate Liquid Film Thickness. In this work, a new correlation to predict Liquid Film Thickness in a 180o bend under gas–Liquid annular conditions was successfully proposed. The correlation was based on dimensionless numbers (modified gas and Liquid Weber numbers and gas Froude number) which reflect the underlined physics governing gas–Liquid interaction in the bend. The Weber numbers capture the two important forces (inertial and surface tension forces) which govern the formation of the Liquid Film Thickness within the system while gas Froude number quantifies the interaction of two important forces (centrifugal and gravitational forces) which determines the distribution of the phases across a bend. The proposed Liquid Film Thickness correlation was based on the experimental data obtained from a wide range of operating conditions. The Liquid superficial velocities ranges from 0.02 to 0.2 m/s and gas superficial velocities from 3.5 to 16 m/s at different measurement locations of 45o, 90o and 135o of the bend with a diameter of 127 mm. The Liquid Film Thickness in air–water and helium–water annular flow can be predicted by . The validation of the proposed correlation used to predict Liquid Film Thickness in gas–Liquid annular systems with different pipe diameters were examined against the available data in the literature. Good agreement was found between the predicted values of Liquid Film Thickness with the experimental data at different measuring locations of the bend.
-
Liquid Film Thickness behaviour within a large diameter vertical 180 return bend
Chemical Engineering Science, 2014Co-Authors: Mukhtar Abdulkadir, D Zhao, Abdelwahid Azzi, Ian Lowndes, Barry J. AzzopardiAbstract:Experimental results of Liquid Film Thickness distribution of an air–water mixture flowing through a vertical 180° return bend are reported. Measurements of Liquid Film Thickness were achieved using flush mounted pin and parallel wire probes. The bend has a diameter of 127 mm and a curvature ratio (R/D) of 3. The superficial velocities of air ranged from 3.5 to 16.1 m/s and those for water from 0.02 to 0.2 m/s. At these superficial velocity ranges, the flow pattern investigated in this work focused on churn and annular flows. It was found that at Liquid and gas superficial velocities of 0.02 m/s and 6.2 m/s, respectively, the averaged Liquid Film Thickness peak at 90°. At gas superficial velocity of 16.1 m/s, the relationship between them is linear due to the shear forces overcoming gravity. Additionally, it was found that deposition of entrained droplets keeps the Liquid Film on the outside of the bend. The results of polar plots of average Liquid Film Thickness in the bend showed that the distribution of the Liquid Film is not symmetrical with thicker Films on the inside of the bend due to the action of gravity. Experimental results on average Liquid Film Thickness showed good agreement with the simulation data reported in the literature.
-
Liquid Film Thickness behaviour within a large diameter vertical 180° return bend
Chemical Engineering Science, 2014Co-Authors: Mukhtar Abdulkadir, D Zhao, Abdelwahid Azzi, Ian Lowndes, Barry J. AzzopardiAbstract:Experimental results of Liquid Film Thickness distribution of an air–water mixture flowing through a vertical 180° return bend are reported. Measurements of Liquid Film Thickness were achieved using flush mounted pin and parallel wire probes. The bend has a diameter of 127 mm and a curvature ratio (R/D) of 3. The superficial velocities of air ranged from 3.5 to 16.1 m/s and those for water from 0.02 to 0.2 m/s. At these superficial velocity ranges, the flow pattern investigated in this work focused on churn and annular flows. It was found that at Liquid and gas superficial velocities of 0.02 m/s and 6.2 m/s, respectively, the averaged Liquid Film Thickness peak at 90°. At gas superficial velocity of 16.1 m/s, the relationship between them is linear due to the shear forces overcoming gravity. Additionally, it was found that deposition of entrained droplets keeps the Liquid Film on the outside of the bend. The results of polar plots of average Liquid Film Thickness in the bend showed that the distribution of the Liquid Film is not symmetrical with thicker Films on the inside of the bend due to the action of gravity. Experimental results on average Liquid Film Thickness showed good agreement with the simulation data reported in the literature.
Youngbae Han - One of the best experts on this subject based on the ideXlab platform.
-
Measurement of Liquid Film Thickness on moving plate during dip-coating process
Korea-Australia Rheology Journal, 2018Co-Authors: Youngbae HanAbstract:Dip-coating can be used to obtain a relatively uniform Film Thickness on a substrate and is widely used in industry. The Thickness of the Liquid Film is a very important parameter for the desired function. In this study, a laser focus displacement meter is used to measure the Liquid Film Thickness. The Thickness of Liquid Film coated on the withdrawing plate increases initially and then becomes constant as time passes. The Liquid Film of the constant Film Thickness zone is in good agreement with these two existing correlations. For the transition region where the Liquid Film Thickness increases, a comparison of the profiles of dimensionless Liquid Film Thickness shows that as the withdrawal speed increases, the profile of dimensionless Liquid Film Thickness becomes more convex. However, at a capillary number higher than 0.1, the profiles are consistent within a certain range. It is confirmed that the profile of dimensionless Liquid Film Thickness can be classified into a viscous dominant region and a surface tension dominant region, similar to the tendency of Liquid Film Thickness in the constant Film Thickness region.
-
Liquid Film Thicknesses of oscillating slug flows in a capillary tube
International Journal of Heat and Mass Transfer, 2018Co-Authors: Young Jik Youn, Youngbae Han, Naoki ShikazonoAbstract:Abstract Liquid Film Thickness is an important parameter for predicting boiling and condensation heat transfer coefficients in a microscale slug flow. In the present study, Liquid Film Thickness of oscillating slug flow in a capillary tube is experimentally investigated under adiabatic condition. Laser focus displacement meter is used to measure the initial Liquid Film Thickness. Circular tube with inner diameter of 1 mm is used for the test tube, and water and ethanol are used as working fluids. Measurement is carried out using a capillary tube with one open end and the other connected to a stepping motor. Driving frequency is ranged from 1 to 10 Hz at equivalent slug stroke of 31.7 mm and 51.2 mm. As the frequency and equivalent slug stroke are increased, the Liquid Film Thickness deviates from that in the steady condition and becomes thinner or thicker under flow acceleration or deceleration, respectively. The empirical correlations for the initial Liquid Film Thickness under acceleration and deceleration conditions proposed in the previous study (Youn et al., 2015, 2016) well predict the Liquid Film Thicknesses of the oscillating flows within 15% accuracy.
-
The effect of initial flow velocity on the Liquid Film Thickness in micro tube accelerated slug flow
International Journal of Multiphase Flow, 2015Co-Authors: Young Jik Youn, Youngbae Han, Kenshiro Muramatsu, Naoki ShikazonoAbstract:Abstract Liquid Film Thickness is an important parameter for predicting boiling and condensation heat transfer in micro tubes. In the present study, the effect of initial flow velocity on the Liquid Film Thickness in accelerated flows under adiabatic condition is experimentally investigated. The laser focus displacement meter is used to measure the initial Liquid Film Thickness. Circular tube with inner diameter of 1 mm was used for the test tube, and water, ethanol and FC-40 are used as working fluids. When the flow is accelerated from small initial velocities under small Bond number condition, initial Liquid Film Thickness is identical to that of steady flow at small capillary numbers, and then deviates from the steady condition and eventually follows that of accelerated flow from zero initial velocity as capillary number is increased. When the flow is accelerated from large initial velocities, initial Liquid Film Thickness deviates from the steady condition earlier and starts to follow that of accelerated flow from zero initial velocity as capillary number is increased. It is found that the initial flow velocity cannot be neglected in accelerated flows especially at large initial flow velocities and at large Bond numbers. Finally, an empirical correlation is proposed for the initial Liquid Film Thickness of accelerated flows that accounts for the initial flow velocities.
-
Numerical study on the effect of initial flow velocity on Liquid Film Thickness of accelerated slug flow in a micro tube
International Journal of Heat and Fluid Flow, 2015Co-Authors: Kenshiro Muramatsu, Young Jik Youn, Youngbae Han, Yosuke Hasegawa, Naoki ShikazonoAbstract:Numerical simulation of air–water slug flows accelerated from steady states with different initial velocities in a micro tube is conducted. It is shown that the Liquid Film formed between the gas bubble and the wall in an accelerated flow is significantly thinner than that in a steady flow at the same instantaneous capillary number. Specifically, the Liquid Film Thickness is kept almost unchanged just after the onset of acceleration, and then gradually increases and eventually converges to that of an accelerated flow from zero initial velocity. Due to the flow acceleration, the Stokes layer is generated from the wall, and the instant velocity profile can be given by superposition of the Stokes layer and the initial parabolic velocity profile of a steady flow. It is found that the velocity profile inside a Liquid slug away from the bubble can be well predicted by the analytical solution of a single-phase flow with acceleration. The change of the velocity profile in an accelerated flow changes the balance between the inertia, surface tension and viscous forces around the meniscus region, and thus the resultant Liquid Film Thickness. By introducing the displacement Thickness, the existing correlation for Liquid Film Thickness in a steady flow (Han and Shikazono, 2009) is extended so that it can be applied to a flow with acceleration from an arbitrary initial velocity. It is demonstrated that the proposed correlation can predict Liquid Film Thickness at Re < 4600 within the range of ±10% accuracy.
-
Liquid Film Thickness in Micro-Scale Two-Phase Flow
Two Phase Flow Phase Change and Numerical Modeling, 2011Co-Authors: Naoki Shikazono, Youngbae HanAbstract:Liquid Film formed between confined vapor bubble and tube wall in micro-scale two phase flow plays an important role in heat exchangers and chemical reactors, since local heat and mass transfer is effectively enhanced at the thin Liquid Film region (Taha and Cui, 2006). However, characteristics of the Liquid Film in micro-scale two phase flows are not fully understood, and thus designing two-phase flow systems still remains as a difficult task. It is reported that the Thickness of the Liquid Film is one of the most important parameters for predicting two phase flow heat transfer in micro tubes, see Thome et al., 2004; Kenning et al., 2006; Qu and Mudawar, 2004; Saitoh et al., 2007. For example, in the three zone evaporation model proposed by Thome et al. (2004), initial Liquid Film Thickness is one of the three unknown parameters which must be given from experimental studies. Many researches have been conducted to investigate the characteristics of Liquid Film both experimentally and theoretically. Taylor (1961) experimentally obtained mean Liquid Film Thickness in a slug flow by measuring the difference between bubble velocity and mean velocity. Highly viscous fluids, i.e. glycerol, syrup-water mixture and lubricating oil, were used so that wide capillary number range could be covered. It was found that the ratio of bubble velocity to mean velocity approaches an asymptotic value of 0.55. This asymptotic value was re-evaluated by Cox (1964), which was reported to be 0.60. Schwartz et al. (1986) investigated the effect of bubble length on the Liquid Film Thickness using the same method as Taylor (1961). It was reported that longer bubbles move faster than shorter ones. Bretherton (1961) proposed an analytical theory for the bubble profile and axial pressure drop across the bubble using lubrication equations. Assuming small capillary number, it is shown that the dimensionless Liquid Film Thickness can be scaled by an exponential function of capillary number, Ca2/3. Liquid Film Thickness can also be measured from the temperature change of the channel wall under the assumption that the whole Liquid Film on the wall evaporates and the heat is wholly consumed by the evaporation of the Liquid Film. Cooper (1969) measured Liquid Film Thickness with this method and investigated the bubble growth in nucleate pool boiling. Moriyama and Inoue (1996) measured Liquid Film Thickness during a bubble expansion in a narrow gap. It was reported that Liquid Film Thickness is affected by the viscous boundary layer in the Liquid slug when acceleration becomes large. Their experimental data was correlated in terms of capillary number, Bond number and dimensionless boundary layer Thickness. Heil (2001) numerically investigated the inertial
Barry J. Azzopardi - One of the best experts on this subject based on the ideXlab platform.
-
Liquid Film Thickness behaviour within a large diameter vertical 180 return bend
Chemical Engineering Science, 2014Co-Authors: Mukhtar Abdulkadir, D Zhao, Abdelwahid Azzi, Ian Lowndes, Barry J. AzzopardiAbstract:Experimental results of Liquid Film Thickness distribution of an air–water mixture flowing through a vertical 180° return bend are reported. Measurements of Liquid Film Thickness were achieved using flush mounted pin and parallel wire probes. The bend has a diameter of 127 mm and a curvature ratio (R/D) of 3. The superficial velocities of air ranged from 3.5 to 16.1 m/s and those for water from 0.02 to 0.2 m/s. At these superficial velocity ranges, the flow pattern investigated in this work focused on churn and annular flows. It was found that at Liquid and gas superficial velocities of 0.02 m/s and 6.2 m/s, respectively, the averaged Liquid Film Thickness peak at 90°. At gas superficial velocity of 16.1 m/s, the relationship between them is linear due to the shear forces overcoming gravity. Additionally, it was found that deposition of entrained droplets keeps the Liquid Film on the outside of the bend. The results of polar plots of average Liquid Film Thickness in the bend showed that the distribution of the Liquid Film is not symmetrical with thicker Films on the inside of the bend due to the action of gravity. Experimental results on average Liquid Film Thickness showed good agreement with the simulation data reported in the literature.
-
Liquid Film Thickness behaviour within a large diameter vertical 180° return bend
Chemical Engineering Science, 2014Co-Authors: Mukhtar Abdulkadir, D Zhao, Abdelwahid Azzi, Ian Lowndes, Barry J. AzzopardiAbstract:Experimental results of Liquid Film Thickness distribution of an air–water mixture flowing through a vertical 180° return bend are reported. Measurements of Liquid Film Thickness were achieved using flush mounted pin and parallel wire probes. The bend has a diameter of 127 mm and a curvature ratio (R/D) of 3. The superficial velocities of air ranged from 3.5 to 16.1 m/s and those for water from 0.02 to 0.2 m/s. At these superficial velocity ranges, the flow pattern investigated in this work focused on churn and annular flows. It was found that at Liquid and gas superficial velocities of 0.02 m/s and 6.2 m/s, respectively, the averaged Liquid Film Thickness peak at 90°. At gas superficial velocity of 16.1 m/s, the relationship between them is linear due to the shear forces overcoming gravity. Additionally, it was found that deposition of entrained droplets keeps the Liquid Film on the outside of the bend. The results of polar plots of average Liquid Film Thickness in the bend showed that the distribution of the Liquid Film is not symmetrical with thicker Films on the inside of the bend due to the action of gravity. Experimental results on average Liquid Film Thickness showed good agreement with the simulation data reported in the literature.