Peter Hamersma - Academia.edu (original) (raw)
Papers by Peter Hamersma
The assembly of flexible polystyrene-block-poly(ethylene oxide) wormlike micelles from chloroform... more The assembly of flexible polystyrene-block-poly(ethylene oxide) wormlike micelles from chloroform droplets by the ‘emulsification and solvent evaporation ’ method
Flexible wormlike micelles show promising results in their application as drug carriers in the fi... more Flexible wormlike micelles show promising results in their application as drug carriers in the field of targeted drug delivery. A method introduced to produce wormlike micelles is the ‘emulsification and solvent evaporation’ method, but the formation mechanism behind this method is not yet fully understood. The aim of this work is to study whether the lengths of the wormlike micelles formed depends on the size of the droplets in the emulsion. Wormlike micelles were formed by dissolving polystyrene-block-poly(ethylene oxide), or PS-PEO, in chloroform, and mixing this into an emulsion with water containing NaCl through vigorous stirring. Interfacial instabilities between the water and chloroform phase caused by increased concentrations of polymer lead to the formation of wormlike micelles. Effects of varying stirring rates and times on the size of the chloroform droplets in the emulsion as well as the lengths of wormlike micelle sizes were studied by analysis through optical and fluor...
This work studies the flow behavior and related pressure losses of viscoelastic polymer solutions... more This work studies the flow behavior and related pressure losses of viscoelastic polymer solutions in microchannels with two different sequences of contraction/expansion, disposed in a symmetric and an asymmetric arrangement, respectively. These microfluidic devices are proposed as simplified microchannel analogues for the flow of Newtonian and viscoelastic fluids through porous media. The results show that the symmetric configuration mimics the pressure gradient of these polymer solutions through a porous medium at low flow rates (below a critical Deborah number, De cr), while the asymmetric arrangement gives the asymptotic limit at high De values (above De cr) as a consequence of the intrinsic differences in the extensional rate profiles defined by each microgeometry.
While the dynamics of single rising gas bubbles in clear liquids has been studied extensively, th... more While the dynamics of single rising gas bubbles in clear liquids has been studied extensively, the dynamics of bubbles in liquid-solid slurries containing small particles (d s < 100µm) is not yet well understood. We have investigated the rise characteristics of single gas bubbles (< d b >=3mm) in a neutrally buoyant suspension of Polystyrene particles (< d s > = 78±5.79µm) in a glycerol-water mixture. Using a four-point optical probe we have obtained information on the bubble motion and shape in the slurry. The velocity of single bubbles, rising at terminal velocity through the suspension, slightly decreases with increasing solids volume fraction; this was accompanied by a change in the shape of the bubbles from oblate ellipsoidal to nearly spherical. The viscosity and the surface tension of the liquid in the presence of suspended particles were also measured. Our results show that the viscosity was almost doubled with a 20% increase in the solids volume fraction. We found that the rise velocity of a bubble in the slurry is close to that in a pseudo-single phase liquid with the same viscosity and surface tension.
Microfluidics and Nanofluidics, 2011
In this study, two microfluidic devices are proposed as simplified 1-D microfluidic analogues of ... more In this study, two microfluidic devices are proposed as simplified 1-D microfluidic analogues of a porous medium. The objectives are twofold: firstly to assess the usefulness of the microchannels to mimic the porous medium in a controlled and simplified manner, and secondly to obtain a better insight about the flow characteristics of viscoelastic fluids flowing through a packed bed. For these purposes, flow visualizations and pressure drop measurements are conducted with Newtonian and viscoelastic fluids. The 1-D microfluidic analogues of porous medium consisted of microchannels with a sequence of contractions/expansions disposed in symmetric and asymmetric arrangements. The real porous medium is in reality, a complex combination of the two arrangements of particles simulated with the microchannels, which can be considered as limiting ideal configurations. The results show that both configurations are able to mimic well the pressure drop variation with flow rate for Newtonian fluids. However, due to the intrinsic differences in the deformation rate profiles associated with each microgeometry, the symmetric configuration is more suitable for studying the flow of viscoelastic fluids at low De values, while the asymmetric configuration provides better results at high De values. In this way, both microgeometries seem to be complementary and could be interesting tools to obtain a better insight about the flow of viscoelastic fluids through a porous medium. Such model systems could be very interesting to use in polymer-flood processes for enhanced oil recovery, for instance, as a tool for selecting the most suitable viscoelastic fluid to be used in a specific formation. The selection of the fluid properties of a detergent for cleaning oil contaminated soil, sand, and in general, any porous material, is another possible application.
Chemical Engineering Science, 1992
Several aspects of solidliquid contacting in a pulsed packed column (PPC) containing structured ... more Several aspects of solidliquid contacting in a pulsed packed column (PPC) containing structured packing are modelled and investigated experimentally. The axial dispersion model for singlephase flow in a PPC, developed by Mak (1991), is extended with one additional ...
AIChE Journal, 1999
A model developed calculates the mass intake fraction of gas and liquid phase during gas–liquid f... more A model developed calculates the mass intake fraction of gas and liquid phase during gas–liquid flow with small liquid holdup values (ϵL ≤ 0.1) through regular T junctions with small branch inclinations. It was derived from the steady-state macroscopic mechanical energy balance (extended Bernoulli equation) applied to the “inlet-to-run” streamline and “inlet-to-branch” streamline of both gas and liquid phases. The model results are compared with experimental data of the system air/water–glycerol (0, 33, and 60 wt. %) flowing through a regular (D1 = D2 = D3 = 0.051 m) T junction with branch inclinations ranging from 0° to 0.5°. It was found that the gas–liquid flow split behavior is affected strongly by the liquid viscosity and by branch inclinations of 0.1° and higher. The results predicted with the model agree well with experimental results obtained in a regular T junction with a horizontal inlet run and an inclined side arm.
AIChE Journal, 2003
ABSTRACT
AIChE Journal, 1991
In gas/liquid/solid slurries, adhesion of small particles to gas bubbles is often encountered, fo... more In gas/liquid/solid slurries, adhesion of small particles to gas bubbles is often encountered, for example, during flotation of finely divided minerals and in slurry reactors where particle-to-bubble adhesion may result in an enhanced gas absorption rate (Wimmers, 1987; Lindner, 1988). The adhesion of smallparticles to gas bubbles in water isstudied with a modified bubblepick-up method. The extent of theparticleto-bubble adhesion is reuealed in the angle amaD by which the gas-bubble surface is covered by adhering particles under static conditions. It is shown that amu depends on the modified Eotvos number, the ratio of the particle and bubble radii, and the effective contact angle 0,. It is also found that 0, is affected by the curvature of the three-phase contact ring and by the type of the gas.
Chemical Engineering Science, 1991
Axial dispersion in single-phase flow through a pulsed packed column (length 4 m; Raschig-ring pa... more Axial dispersion in single-phase flow through a pulsed packed column (length 4 m; Raschig-ring packing) has been investigated using an imperfect pulse method. It has been shown that under certain conditions axial dispersion can be reduced by means of pulsation. A three-parameter model based on the Taylor-Aris dispersion equation for tube flow has been developed. This model, which has been verified experimentally, describes the relation between the axial dispersion coefficient and the interstitial and pulsation velocities.
The Canadian Journal of Chemical Engineering, 2010
We investigate uniform gas injection using a needle sparger as a structuring methodology to reduc... more We investigate uniform gas injection using a needle sparger as a structuring methodology to reduce backmixing in slurry bubble columns. Using optical probes, we determined the gas fraction and the bubble behaviour in 2D and 3D slurry bubble columns with a uniform gas injection. Experimental results for air-water-glass beads (d s = 108 m, U sg = 0-0.10 m/s) indicate that a strong reduction in the vortical structures has been achieved and the homogeneous flow regime can be extended beyond 30% gas fraction. Increasing the solids concentration decreases the gas fraction and widens the bubble velocity distribution. Furthermore, we show by modelling that the reduced backmixing leads to a major improvement of the conversion in case of Fischer-Tropsch synthesis. L'injection uniforme de gaz estétudiée utilisant une aiguille d'aération en tant que méthodologie structurante pour réduire le mélange de retour dans les colonnesà bulles en suspension. Utilisant les sondes optiques, nous avons déterminé la fraction de gaz et le comportement des bulles dans des colonnesà bulles 2D et 3D avec une injection uniforme de gaz. Les résultats expérimentaux pour des billes air-eau-verre (d s = 108 m, U sg = 0-0.10 m/s) indiquent qu'une réduction importante des structures turbulentes aété réalisée et le régime d'écoulement homogène peutêtré etendu au delà de la fraction de gaz de 30%. L'augmentation de la concentration des solides diminue la fraction de gaz etélargit la distribution de vitesse des bulles. En outre, nous démontrons par la modélisation que la réduction du mélange au retour entraîne une amélioration significative de la conversion dans le cas de synthèse Fischer-Tropsch.
Chemical Engineering Journal, 2012
This paper investigates the intensification of Fischer-Tropsch Synthesis in two types of threepha... more This paper investigates the intensification of Fischer-Tropsch Synthesis in two types of threephase catalytic reactors: slurry bubble columns and multi-tubular fixed beds. A simple mathematical model is used to analyse the effect of structuring on the C 5+ productivity of these two types of reactors. The results of the model show that decreasing the backmixing with a factor 4 and increasing the gas residence time in a slurry bubble column considerably enhances the production of C 5+. On the other hand in a fixed bed reactor a similar improvement is obtained when the heat transfer coefficient is improved with a factor 2.5 and the diffusion length in catalyst particles is decreased with a factor 2. Both reactors show a potential improvement in productivity per reactor volume; 20% in the slurry bubble column and 40% in the fixed bed reactor.
AIChE Journal, 1992
A model is presented for a quantitative prediction of the transfer rates of momentum, heat and ma... more A model is presented for a quantitative prediction of the transfer rates of momentum, heat and mass in turbulent pipe flow. In this so-called extended random surface renewal (ERSR) model, the tube wall is assumed to be covered by a mosaic of fluid elements of random age and laminar flow with unsteady profiles of axial velocity, temperature or concentration. Both the age distribution and the mean age of the fluid elements at the tube wall, predicted by the ERSR model, quantitatively agree with experimental results obtained from velocity signals measured with a laser-Doppler anemometer at 5. l o 5 Re I 43. I0 '. The time-averaged radial profiles of the axial velocity, the temperature and the concentration in the wall region, and the heat-and mass-transfer coefficients derived with the ERSR model agree with empirical results presented in literature. Furthermore, the ERSR model provides a basis for explaining the Chilton-Colburn analogy. To calculate the time-averaged radial profiles of the axial velocity, the temperature and the concentration in the wall region. TO derive equations for a quantitative prediction of heatand mass-transfer coefficients. To provide a basis for explaining the analogy between momentum, heat, and mass transfer in turbulent pipe flow.
International Journal of Multiphase Flow
Experimental data and correlations available in the literature for the liquid holdup L and the pr... more Experimental data and correlations available in the literature for the liquid holdup L and the pressure gradient ΔP TP /L for gas-liquid pipe flow, generally, do not cover the domain 0 < L < 0.06. Reliable pressure-drop correlations for this holdup range are important for calculating flow rates of ...
Chemical Engineering Science, 1992
Abe&m&-A model is presented for a quantitative prediction of the transfer coefficients of momentu... more Abe&m&-A model is presented for a quantitative prediction of the transfer coefficients of momentum, heat and mass, and the radial profiles of the axial velocity, the temperature, and the concentration in the nearwall 5uid of a turbulent pipe flow. In this model, the tube wall is assumed to be covered by a mosaic of fluid elements of random age and laminar flow with unsteady profiles of velocity, temperat-, or concentration. This model, which is an extension of the RSR model developed by Fortuin and Klijn, is the extended random surface renewal model, and is refmed to as the ERSR model. The distribution and the mean value of the ages of the fluid elements at the tube wall govern the local time-averaged transfer coefficients and radial profiles in the wall region. The mean age of the fluid elements is derived from the friction factor and the Reynolds number using the ERSR model. Both the distribution and the mean ages of the fluid elements at the tube wall agree quantitatively with the experimental results obtained from velocity signals measured with a laser-Doppler anemometer in turbulent pipe flow at thirteen Reynolds numbers between 5 x 10' and 43 x 103. The equations derived from the ERSR model for the local time-averaged heat and muss transfer coefficients in turbulent pipe flow, and the radial profiles of the axial velocity, the temperature and the concentration in the wall region, agree with correlations or experimental data presented in literature. The analogy between momentum, heat and mass transfer in turbulent pipe flow is elucidated by introducing a dimensionless number for momentum transfer. This so-called Fanning number for momentum transfer (Fo = k,d/v), is comparable with the Nusselt number for heat transfer and the Sherwood number for mass transfer. Furthermore, the ERSR model provides a basis for both explaining the Chilton-Colbum analogy and the relationship between transfer rates and measured mean ages of fluid elements at the wall in turbulent pipe flow. 1. INTRODUCl'ION 1.1. scope .
Chemical Engineering Science, 1993
The effect of small gas-adsorbing particles on the quasi steady-state absorption rate of a gas in... more The effect of small gas-adsorbing particles on the quasi steady-state absorption rate of a gas into a degassed slurry is investigated in an agitated slurry reactor in which no chemical reaction occurs. This investigation shows that, in a slurry reactor, gas-adsorbing particles can adhere to gas bubbles so that during steady-state operation a fraction r of the gas-liquid interface ls covered by adhering particles, resulting in an enhancement of the gas-absorption rate with respect to the particle-free situation. A model is derived to calculate the enhancement of the physical gas-absorption rate as a function of the fraction of bubble-surface coverage r at different particle concentrations in the slurry. This Enhanced Gas-Absorption mode1 is experimentally verified by flotation experiments and by hydrogen absorption into aqueous solutions containing different concentrations of small catalyst particles.
Chemical Engineering Science, 1987
During the transport of natural gas through pipelines small amounts of liquid are present as a re... more During the transport of natural gas through pipelines small amounts of liquid are present as a result of condensate formation. These small amounts of liquid corresponding to a volume how rate fraction CL < 2 x 10-j may result in a liquid holdup cL < 0.04 and a relatively large increase in the pressure drop. In the present paper a model is introduced which describes the liquid holdup and the axial pressure gradient in co-current gas/liquid flow in horizontal tubes with a small liquid holdup (Ed < 0.04), mainly covering the stratified-wavy and annular flow regimes. A good agreement was found between the measured values of the liquid holdup and pressure drop of gas/liquid pipe Row and those obtained from the correlations introduced in this paper. Further, the experimental results were also compared with values calculated with correlations obtained from literature.
The assembly of flexible polystyrene-block-poly(ethylene oxide) wormlike micelles from chloroform... more The assembly of flexible polystyrene-block-poly(ethylene oxide) wormlike micelles from chloroform droplets by the ‘emulsification and solvent evaporation ’ method
Flexible wormlike micelles show promising results in their application as drug carriers in the fi... more Flexible wormlike micelles show promising results in their application as drug carriers in the field of targeted drug delivery. A method introduced to produce wormlike micelles is the ‘emulsification and solvent evaporation’ method, but the formation mechanism behind this method is not yet fully understood. The aim of this work is to study whether the lengths of the wormlike micelles formed depends on the size of the droplets in the emulsion. Wormlike micelles were formed by dissolving polystyrene-block-poly(ethylene oxide), or PS-PEO, in chloroform, and mixing this into an emulsion with water containing NaCl through vigorous stirring. Interfacial instabilities between the water and chloroform phase caused by increased concentrations of polymer lead to the formation of wormlike micelles. Effects of varying stirring rates and times on the size of the chloroform droplets in the emulsion as well as the lengths of wormlike micelle sizes were studied by analysis through optical and fluor...
This work studies the flow behavior and related pressure losses of viscoelastic polymer solutions... more This work studies the flow behavior and related pressure losses of viscoelastic polymer solutions in microchannels with two different sequences of contraction/expansion, disposed in a symmetric and an asymmetric arrangement, respectively. These microfluidic devices are proposed as simplified microchannel analogues for the flow of Newtonian and viscoelastic fluids through porous media. The results show that the symmetric configuration mimics the pressure gradient of these polymer solutions through a porous medium at low flow rates (below a critical Deborah number, De cr), while the asymmetric arrangement gives the asymptotic limit at high De values (above De cr) as a consequence of the intrinsic differences in the extensional rate profiles defined by each microgeometry.
While the dynamics of single rising gas bubbles in clear liquids has been studied extensively, th... more While the dynamics of single rising gas bubbles in clear liquids has been studied extensively, the dynamics of bubbles in liquid-solid slurries containing small particles (d s < 100µm) is not yet well understood. We have investigated the rise characteristics of single gas bubbles (< d b >=3mm) in a neutrally buoyant suspension of Polystyrene particles (< d s > = 78±5.79µm) in a glycerol-water mixture. Using a four-point optical probe we have obtained information on the bubble motion and shape in the slurry. The velocity of single bubbles, rising at terminal velocity through the suspension, slightly decreases with increasing solids volume fraction; this was accompanied by a change in the shape of the bubbles from oblate ellipsoidal to nearly spherical. The viscosity and the surface tension of the liquid in the presence of suspended particles were also measured. Our results show that the viscosity was almost doubled with a 20% increase in the solids volume fraction. We found that the rise velocity of a bubble in the slurry is close to that in a pseudo-single phase liquid with the same viscosity and surface tension.
Microfluidics and Nanofluidics, 2011
In this study, two microfluidic devices are proposed as simplified 1-D microfluidic analogues of ... more In this study, two microfluidic devices are proposed as simplified 1-D microfluidic analogues of a porous medium. The objectives are twofold: firstly to assess the usefulness of the microchannels to mimic the porous medium in a controlled and simplified manner, and secondly to obtain a better insight about the flow characteristics of viscoelastic fluids flowing through a packed bed. For these purposes, flow visualizations and pressure drop measurements are conducted with Newtonian and viscoelastic fluids. The 1-D microfluidic analogues of porous medium consisted of microchannels with a sequence of contractions/expansions disposed in symmetric and asymmetric arrangements. The real porous medium is in reality, a complex combination of the two arrangements of particles simulated with the microchannels, which can be considered as limiting ideal configurations. The results show that both configurations are able to mimic well the pressure drop variation with flow rate for Newtonian fluids. However, due to the intrinsic differences in the deformation rate profiles associated with each microgeometry, the symmetric configuration is more suitable for studying the flow of viscoelastic fluids at low De values, while the asymmetric configuration provides better results at high De values. In this way, both microgeometries seem to be complementary and could be interesting tools to obtain a better insight about the flow of viscoelastic fluids through a porous medium. Such model systems could be very interesting to use in polymer-flood processes for enhanced oil recovery, for instance, as a tool for selecting the most suitable viscoelastic fluid to be used in a specific formation. The selection of the fluid properties of a detergent for cleaning oil contaminated soil, sand, and in general, any porous material, is another possible application.
Chemical Engineering Science, 1992
Several aspects of solidliquid contacting in a pulsed packed column (PPC) containing structured ... more Several aspects of solidliquid contacting in a pulsed packed column (PPC) containing structured packing are modelled and investigated experimentally. The axial dispersion model for singlephase flow in a PPC, developed by Mak (1991), is extended with one additional ...
AIChE Journal, 1999
A model developed calculates the mass intake fraction of gas and liquid phase during gas–liquid f... more A model developed calculates the mass intake fraction of gas and liquid phase during gas–liquid flow with small liquid holdup values (ϵL ≤ 0.1) through regular T junctions with small branch inclinations. It was derived from the steady-state macroscopic mechanical energy balance (extended Bernoulli equation) applied to the “inlet-to-run” streamline and “inlet-to-branch” streamline of both gas and liquid phases. The model results are compared with experimental data of the system air/water–glycerol (0, 33, and 60 wt. %) flowing through a regular (D1 = D2 = D3 = 0.051 m) T junction with branch inclinations ranging from 0° to 0.5°. It was found that the gas–liquid flow split behavior is affected strongly by the liquid viscosity and by branch inclinations of 0.1° and higher. The results predicted with the model agree well with experimental results obtained in a regular T junction with a horizontal inlet run and an inclined side arm.
AIChE Journal, 2003
ABSTRACT
AIChE Journal, 1991
In gas/liquid/solid slurries, adhesion of small particles to gas bubbles is often encountered, fo... more In gas/liquid/solid slurries, adhesion of small particles to gas bubbles is often encountered, for example, during flotation of finely divided minerals and in slurry reactors where particle-to-bubble adhesion may result in an enhanced gas absorption rate (Wimmers, 1987; Lindner, 1988). The adhesion of smallparticles to gas bubbles in water isstudied with a modified bubblepick-up method. The extent of theparticleto-bubble adhesion is reuealed in the angle amaD by which the gas-bubble surface is covered by adhering particles under static conditions. It is shown that amu depends on the modified Eotvos number, the ratio of the particle and bubble radii, and the effective contact angle 0,. It is also found that 0, is affected by the curvature of the three-phase contact ring and by the type of the gas.
Chemical Engineering Science, 1991
Axial dispersion in single-phase flow through a pulsed packed column (length 4 m; Raschig-ring pa... more Axial dispersion in single-phase flow through a pulsed packed column (length 4 m; Raschig-ring packing) has been investigated using an imperfect pulse method. It has been shown that under certain conditions axial dispersion can be reduced by means of pulsation. A three-parameter model based on the Taylor-Aris dispersion equation for tube flow has been developed. This model, which has been verified experimentally, describes the relation between the axial dispersion coefficient and the interstitial and pulsation velocities.
The Canadian Journal of Chemical Engineering, 2010
We investigate uniform gas injection using a needle sparger as a structuring methodology to reduc... more We investigate uniform gas injection using a needle sparger as a structuring methodology to reduce backmixing in slurry bubble columns. Using optical probes, we determined the gas fraction and the bubble behaviour in 2D and 3D slurry bubble columns with a uniform gas injection. Experimental results for air-water-glass beads (d s = 108 m, U sg = 0-0.10 m/s) indicate that a strong reduction in the vortical structures has been achieved and the homogeneous flow regime can be extended beyond 30% gas fraction. Increasing the solids concentration decreases the gas fraction and widens the bubble velocity distribution. Furthermore, we show by modelling that the reduced backmixing leads to a major improvement of the conversion in case of Fischer-Tropsch synthesis. L'injection uniforme de gaz estétudiée utilisant une aiguille d'aération en tant que méthodologie structurante pour réduire le mélange de retour dans les colonnesà bulles en suspension. Utilisant les sondes optiques, nous avons déterminé la fraction de gaz et le comportement des bulles dans des colonnesà bulles 2D et 3D avec une injection uniforme de gaz. Les résultats expérimentaux pour des billes air-eau-verre (d s = 108 m, U sg = 0-0.10 m/s) indiquent qu'une réduction importante des structures turbulentes aété réalisée et le régime d'écoulement homogène peutêtré etendu au delà de la fraction de gaz de 30%. L'augmentation de la concentration des solides diminue la fraction de gaz etélargit la distribution de vitesse des bulles. En outre, nous démontrons par la modélisation que la réduction du mélange au retour entraîne une amélioration significative de la conversion dans le cas de synthèse Fischer-Tropsch.
Chemical Engineering Journal, 2012
This paper investigates the intensification of Fischer-Tropsch Synthesis in two types of threepha... more This paper investigates the intensification of Fischer-Tropsch Synthesis in two types of threephase catalytic reactors: slurry bubble columns and multi-tubular fixed beds. A simple mathematical model is used to analyse the effect of structuring on the C 5+ productivity of these two types of reactors. The results of the model show that decreasing the backmixing with a factor 4 and increasing the gas residence time in a slurry bubble column considerably enhances the production of C 5+. On the other hand in a fixed bed reactor a similar improvement is obtained when the heat transfer coefficient is improved with a factor 2.5 and the diffusion length in catalyst particles is decreased with a factor 2. Both reactors show a potential improvement in productivity per reactor volume; 20% in the slurry bubble column and 40% in the fixed bed reactor.
AIChE Journal, 1992
A model is presented for a quantitative prediction of the transfer rates of momentum, heat and ma... more A model is presented for a quantitative prediction of the transfer rates of momentum, heat and mass in turbulent pipe flow. In this so-called extended random surface renewal (ERSR) model, the tube wall is assumed to be covered by a mosaic of fluid elements of random age and laminar flow with unsteady profiles of axial velocity, temperature or concentration. Both the age distribution and the mean age of the fluid elements at the tube wall, predicted by the ERSR model, quantitatively agree with experimental results obtained from velocity signals measured with a laser-Doppler anemometer at 5. l o 5 Re I 43. I0 '. The time-averaged radial profiles of the axial velocity, the temperature and the concentration in the wall region, and the heat-and mass-transfer coefficients derived with the ERSR model agree with empirical results presented in literature. Furthermore, the ERSR model provides a basis for explaining the Chilton-Colburn analogy. To calculate the time-averaged radial profiles of the axial velocity, the temperature and the concentration in the wall region. TO derive equations for a quantitative prediction of heatand mass-transfer coefficients. To provide a basis for explaining the analogy between momentum, heat, and mass transfer in turbulent pipe flow.
International Journal of Multiphase Flow
Experimental data and correlations available in the literature for the liquid holdup L and the pr... more Experimental data and correlations available in the literature for the liquid holdup L and the pressure gradient ΔP TP /L for gas-liquid pipe flow, generally, do not cover the domain 0 < L < 0.06. Reliable pressure-drop correlations for this holdup range are important for calculating flow rates of ...
Chemical Engineering Science, 1992
Abe&m&-A model is presented for a quantitative prediction of the transfer coefficients of momentu... more Abe&m&-A model is presented for a quantitative prediction of the transfer coefficients of momentum, heat and mass, and the radial profiles of the axial velocity, the temperature, and the concentration in the nearwall 5uid of a turbulent pipe flow. In this model, the tube wall is assumed to be covered by a mosaic of fluid elements of random age and laminar flow with unsteady profiles of velocity, temperat-, or concentration. This model, which is an extension of the RSR model developed by Fortuin and Klijn, is the extended random surface renewal model, and is refmed to as the ERSR model. The distribution and the mean value of the ages of the fluid elements at the tube wall govern the local time-averaged transfer coefficients and radial profiles in the wall region. The mean age of the fluid elements is derived from the friction factor and the Reynolds number using the ERSR model. Both the distribution and the mean ages of the fluid elements at the tube wall agree quantitatively with the experimental results obtained from velocity signals measured with a laser-Doppler anemometer in turbulent pipe flow at thirteen Reynolds numbers between 5 x 10' and 43 x 103. The equations derived from the ERSR model for the local time-averaged heat and muss transfer coefficients in turbulent pipe flow, and the radial profiles of the axial velocity, the temperature and the concentration in the wall region, agree with correlations or experimental data presented in literature. The analogy between momentum, heat and mass transfer in turbulent pipe flow is elucidated by introducing a dimensionless number for momentum transfer. This so-called Fanning number for momentum transfer (Fo = k,d/v), is comparable with the Nusselt number for heat transfer and the Sherwood number for mass transfer. Furthermore, the ERSR model provides a basis for both explaining the Chilton-Colbum analogy and the relationship between transfer rates and measured mean ages of fluid elements at the wall in turbulent pipe flow. 1. INTRODUCl'ION 1.1. scope .
Chemical Engineering Science, 1993
The effect of small gas-adsorbing particles on the quasi steady-state absorption rate of a gas in... more The effect of small gas-adsorbing particles on the quasi steady-state absorption rate of a gas into a degassed slurry is investigated in an agitated slurry reactor in which no chemical reaction occurs. This investigation shows that, in a slurry reactor, gas-adsorbing particles can adhere to gas bubbles so that during steady-state operation a fraction r of the gas-liquid interface ls covered by adhering particles, resulting in an enhancement of the gas-absorption rate with respect to the particle-free situation. A model is derived to calculate the enhancement of the physical gas-absorption rate as a function of the fraction of bubble-surface coverage r at different particle concentrations in the slurry. This Enhanced Gas-Absorption mode1 is experimentally verified by flotation experiments and by hydrogen absorption into aqueous solutions containing different concentrations of small catalyst particles.
Chemical Engineering Science, 1987
During the transport of natural gas through pipelines small amounts of liquid are present as a re... more During the transport of natural gas through pipelines small amounts of liquid are present as a result of condensate formation. These small amounts of liquid corresponding to a volume how rate fraction CL < 2 x 10-j may result in a liquid holdup cL < 0.04 and a relatively large increase in the pressure drop. In the present paper a model is introduced which describes the liquid holdup and the axial pressure gradient in co-current gas/liquid flow in horizontal tubes with a small liquid holdup (Ed < 0.04), mainly covering the stratified-wavy and annular flow regimes. A good agreement was found between the measured values of the liquid holdup and pressure drop of gas/liquid pipe Row and those obtained from the correlations introduced in this paper. Further, the experimental results were also compared with values calculated with correlations obtained from literature.