Abbas J . Sultan | Missouri University of Science and Technology (original) (raw)

Papers by Abbas J . Sultan

Bioresource Technology Reports, 2021

Abstract Eggshell waste which is a serious issue that faces the authorities of food industries wa... more Abstract Eggshell waste which is a serious issue that faces the authorities of food industries was used to adsorb methyl green stain from aqueous solutions. The impact of pH solution of several parameters on the removal efficiency was investigated. The results show that the maximum percent of removal was 69.38 ± 3% and it was directly proportional with pH, agitation speed, adsorbent dose, and contact time. While the relation with temperature and initial concentration was inverse. The isotherm, kinetic and thermodynamic studies were also done under the system optimum conditions. The results show that the pseudo-second order kinetic model and Langmuir isotherm model are the best models that describe the adsorption system, while the thermodynamic investigation illustrates that the removal process was endothermic, spontaneous, and less entropic. This work provides detailed information about an innovative method to utilize eggshell waste as an inexpensive adsorbent to remove methyl green stain from aqueous solutions.

Molecular Catalysis, 2021

Abstract Acetone adsorption and catalytic interactions with a MgO nanoparticle surface was studie... more Abstract Acetone adsorption and catalytic interactions with a MgO nanoparticle surface was studied using in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) at room temperature. Acetone showed adsorption bands at 2965, 1717, 1597, 1422, 1415, 1367, 1238, 1229, and 1204 cm−1. The MgO was found to be a good catalyst for the activation of the aldol condensation reaction of acetone to form di-acetonealcohol (DAA). The OH group role on the MgO surface was found to be a suppression agent to the further dehydration of DAA to mesityl oxide. This is probably because the OH group blocks the active sites on the MgO surfaces that adsorbed the water formed from the dehydration of DAA. This conclusion was confirmed by identifying the basic site concentrations on MgO surface using DRIFTS and TPD studies of CO2 adsorption/desorption on MgO nanoparticles surface. The high-strength basic sites which are required to dehydrate DDA to mesityl oxide was found to represent only 17.5 % of the total basic site concentration, while the low-strength basic sites resulted from hydroxyl surface group represent 22.5 %. On the other hand, the acetone interaction with the MgO surfaces produced several components such as formaldehyde, acetate, ethoxide, as well as other carbonate species such as bicarbonate, bidentate carbonate, and monodentate carbonate. The results of the present investigation supply important essential insights into catalytic reactions resulted from acetone adsorption on MgO nanoparticle surfaces.

International Communications in Heat and Mass Transfer

In this work, CFD is used to simulate the gas-liquid dispersion coupled to the kinetics of the ir... more In this work, CFD is used to simulate the gas-liquid dispersion coupled to the kinetics of the iron(II) removal from drinking water by aeration process in a split-rectangular airlift reactor.

International Journal of Multiphase Flow, 2018

An advanced gamma-ray computed tomography (CT) technique was used for the first time to visualize... more An advanced gamma-ray computed tomography (CT) technique was used for the first time to visualize and quantify the impacts of the presence of heat-exchanging tubes and their configurations on the gas-liquid distributions and their profiles in a 6-inch (0.1524 m O.D.) Plexiglas® bubble column in an air-water reactor. Two superficial gas velocities (i.e., 0.2 and 0.45 m/s) were employed to simulate the churn turbulent flow regime. To investigate the impact of vertical internals configurations, three arrangements (i.e., hexagonal, circular without a central internal, and circular with a central internal) were employed in addition to the column with no internals. Using the same sized vertical internals and the same oc-cluded cross-sectional area (CSA), it was found that the configuration of the vertical internals significantly impacted the gas holdup distribution over the CSA of the column. All studied superficial gas velocities resulted in symmetrical gas holdup distributions over the CSA of the bubble columns without vertical internals; however, the columns equipped densely with vertical internals did not have symmetrical gas holdup distributions. The presence of an extra central tube in the circular configuration played a key role in the gas-liquid distribution over the CSA of the bubble column. The hexagonal configuration had the advantage of providing the best spread of the gas phase over the entire CSA of the column. Gas holdup values at the wall region of the bubble column increased with the addition of vertical tubes in all investigated configurations. However, a remarkable increase in the gas holdup values was obtained with the hexagonal configuration. The experimental data (i.e., gas holdup distributions and their diametrical profiles) can help to evaluate and validate three-dimensional (3-D) computational fluid dynamics (CFD) simulations to better predict the hydrodynamic parameters involved in these types of reactors. Published by Elsevier Ltd.

Chemical Engineering Science, 2018

The effects of the presence of the vertical internals of different sizes at a wide range of super... more The effects of the presence of the vertical internals of different sizes at a wide range of superficial gas velocity on the overall, local gas holdup distributions and their profiles have been studied and quantified in a 6-in. (0.14 m) Plexiglas
bubble column with air-water system using a non-invasive advanced gamma-ray computed tomography (CT) technique. In this study, two sizes of Plexiglas
vertical internals, having the same occupying area (25%) of the column’s cross-sectional area (CSA) that represents those used in Fischer-Tropsch synthesis, have been used within a range of superficial gas velocities that cover bubbly and churn turbulent flow regimes (0.05–0.45 m/s). The reconstructed CT scan images revealed that the bubble columns equipped with or without internals displayed a uniform cross-sectional gas holdup distribution (symmetric) for all studied superficial gas velocities. However, the bubble column equipped with 1-in. vertical internals exhibited more uniform gas holdup distribution than the column with 0.5-in. internals. Also, the visualization of the gas-liquid distributions for bubble columns with and without internals reveal that the well-known phenomenon of the core-annular liquid circulation pattern that observed in the bubble column without internals still exists in bubble column packed densely with vertical internals. Moreover, a remarkable increase in the gas holdup values at the wall region was achieved in the churn turbulent flow regime based on the insertion of the vertical internals inside the column as compared with using a bubble column without obstacles. Furthermore, the values of the gas holdup in the core region of the bubble column with vertical internals are similar to those of the bubble column without vertical internals when they are operated at high superficial gas velocity (churn turbulent flow regime), based on the free cross-sectional area (CSA) for the flow. In general, the magnitude of the gas holdup increased significantly with increasing superficial gas velocity for the bubble columns with and without internals. However, the gas holdup profile was shaped like a wavy line in the bubble column with vertical internals, whereas it exhibited a parabolic gas holdup profile in the bubble column without obstacles.

Chemical Engineering Science, 2017

h i g h l i g h t s Radioactive Particle Tracking (RPT) technique has been developed and applied ... more h i g h l i g h t s Radioactive Particle Tracking (RPT) technique has been developed and applied in this study. Quantification of 3D liquid velocity and turbulent parameters in bubble column with internals. The presence of the internals causes an increase in axial centerline liquid velocity. A remarkable decrease in turbulence parameters for the bubble column with internals. The data and knowledge are worthy as a benchmark data for validation CFD simulation. a b s t r a c t In this study, the effects of the dense vertical internals on the liquid velocity field and turbulence parameters (Reynolds stresses, turbulent kinetic energy, and turbulent eddy diffusivities) are experimentally investigated for the first time by using advanced Radioactive Particle Tracking (RPT) technique. The experimental work was carried out in a Plexiglas bubble column with 5.5 in. (0.14 m) and a height of 72 in. (1.83 m) for the air-water system. In this work, thirty vertical Plexiglass internals of 0.5 in. (0.0127 m) outer diameter were used which covered $25% (typical for Fischer-Tropsch processes) of the total cross-sectional area of the column where they arranged as the triangular pitch of 0.84 in. (0.0214 m). The superficial gas velocities based on both total cross-sectional area and free cross-sectional area available for the flow were utilized (0.08, 0.2, and 0.45 m/s), which covered the transition and churn-turbulent flow regime to meet the industrial applications of FT synthesis. The experimental data show that the presence of the internals at a given superficial gas velocity causes an increase in the axial centerline liquid velocity and a sharp decrease in turbulence parameters while the increase in superficial gas velocity in the presence of internals causes an increase in axial centerline liquid velocity and turbulent parameters. The obtained data are reliable as a benchmark data for validation computational fluid dynamics (CFD) simulation, and models.

Canadian Journal of Chemical Engineering, 2018

This study identifies and addresses some major pitfalls that are involved in the visualization an... more This study identifies and addresses some major pitfalls that are involved in the visualization and quantification of the gas-liquid distributions and their profiles in a bubble column with internals using the gamma-ray computed tomography (CT) technique. Some of these pitfalls encountered in the scanning of bubble columns with internals are using an improper reference scan, and applying the same experimental scanning procedure and mathematical relationships for estimating the gas holdup in the column without internals to the column with internals. The experimental results revealed that the selection of the inappropriate reference scan for CT experiments would significantly affect the reconstructed linear attenuation coefficient values and consequently the gas holdup results. Additionally, the reconstructed linear attenuation values showed good agreement with theoretical values when considering air as reference scans. However, disagreement is observed when using the empty column with internals as a reference scan. Moreover, it was found that using the proper reference scan eliminated the errors not only for the reconstructed linear attenuation coefficients but also for the gas holdup values near the wall region. Furthermore, the CT technique was capable of capturing the small thickness (5 mm) of the wall for phantom and bubble columns as well as the internals when the air was used as the reference scan. Finally, a new methodology has been implemented to exclude the internals from the cross-sectional images, and the azimuthally averaged gas holdup profiles to provide accurate and reliable results for comparison and validation purposes for the bubble column with internals.

Eng.& Tech. Journal, 2012

Artificial neural network (ANN), in comparison with empirical correlations, has recently received... more Artificial neural network (ANN), in comparison with empirical correlations, has recently received more attention. The present paper includes predictive modeling of heat transfer coefficient for binary mixtures in pool boiling for hydrocarbon compounds, using Back propagation techniques through Multilayer Perceptron, one of the types of the artificial neural networks. To train and learn the system, predictive neural network was found, which is capable of understanding and predicting the preset output which is heat transfer coefficient. The principle operation of such neural networks is based on the experimental data collected from some researchers [1-4]. A new ANN model is proposed using five inputs (mole fraction, temperature difference, heat flux, density and viscosity) to predict the heat transfer coefficient. The prediction using ANN shows 0.0026 AARE (Absolute Average Relative Error) with most widely known correlations namely those of Calus, Fujita and Thome which have given 0.086, 0.066 and 0.038 respectively.

Chemical Engineering Science, 2018

In this study, an advanced radioactive particle tracking (RPT) technique was used to investigate ... more In this study, an advanced radioactive particle tracking (RPT) technique was used to investigate for the first time the details of the cells’ movements (trajectory) and multiphase flow hydrodynamics during microalgae culturing in a cylindrical split airlift photobioreactor. The cells’ trajectory, liquid velocity field, distributions of shear stresses, and the turbulent kinetic energy field were studied under superficial gas velocity of 1 and 3 cm/s. The structures of the flow in the whole reactor, the riser, the downcomer, as well as the structure above and below the split plate were characterized. The effects of the cells’ concentration and different aeration rate at different axial levels on the studied parameters were discussed. It has been found that the cells’ fluctuations reduced and its movement frequency between the light (wall) and dark zone decreased during the culturing particularly when the cells concentrations becomes large after 30 days of culturing. Distinguishing behaviors were observed for all the parameters, with a higher magnitude at the superficial gas velocity 3 cm/sec than at 1 cm/sec. This effect positively enhanced the liquid circulation and the movement between the reactor sides, the riser, and the downcomer. This circulation and good mixing phenomena had a large positive impact on the culture's continuity. The obtained results are reliable as benchmark data to validate computational fluid dynamics (CFD) simulation and other models that can be later used to be integrated with dynamic growth and light intensity models for optimized.

Experimental Thermal and Fluid Science, 2018

The impact of dense vertical internal tubes and their configurations on the gas holdup distributi... more The impact of dense vertical internal tubes and their configurations on the gas holdup distributions and their diametrical profiles in pilot-scale bubble column is visualized and quantified for the first time ever using an advanced gamma-ray computed tomography (CT) technique. Two arrangements of vertical internals (circular and hexagonal configurations) occupying the same cross-sectional area (CSA) of the column (about 25% of the total cross-sectional area to represent the heat exchanging tubes that are used in the Fischer-Tropsch synthesis), were examined in addition to the measurement in the bubble column without vertical internals. Moreover, the gas holdup distribution results of the 18-inch (0.46 m in outer diameter, O.D.) bubble column are compared with an available data of 6-inch (0.15 m in O.D.) bubble columns with and without vertical internals. CT scans have been conducted for 18-inch bubble columns with and without vertical internals for the air-water system under a wide range of superficial gas velocity (0.05–0.45 m/s). The experimental results indicate that an improvement in the gas holdup distribution over the column's cross-sectional area is obtained when the vertical internal tubes (arranged in either a circular or a hexagonal configuration) were used. However, better cross-sectional gas holdup distribution was achieved in the bubble column with vertical internals arranged in a hexagonal configuration as compared to the bubble column without and with vertical internals arranged in a circular arrangement. Additionally, the averages of the cross-sectional gas holdup and their profiles for bubble column with and without vertical internals are close to each other when the bubble column with vertical internals is operating at a high superficial gas velocity, which is calculated based on the free cross-sectional area for the flow. Furthermore, the gas holdup distributions are further improved when the larger bubble column with vertical internals was used as compared to the 6-inch bubble columns with and without vertical internals.

Fuel, 2019

The effects of the presence of vertical internal tubes and their diameters on the local gas holdu... more The effects of the presence of vertical internal tubes and their diameters on the local gas holdup and bubble dynamics, including the specific interfacial area, bubble chord length, and bubble velocity were investigated in a 6 in. bubble column for the air-water system by using a four-point optical fiber probe technique. Two different diameters, 0.5-inch, and 1-inch, of vertical internals equally covering 25% of the column's cross-sectional area (CSA) were used to represent the heat-exchanging tubes utilized in the Fischer Tropsch (FT) process. For both sizes, the vertical internals were uniformly distributed over column CSA. The experiments were performed using the air-water system, in a 6-inch bubble column at superficial gas velocities of 20, 30, and 45 cm/s. The experimental results indicated that the presence of vertical internals and their diameters have a significant effect on the hydrodynamic properties of the bubble column reactor at high superficial gas velocities. The local gas holdup significantly increased in the core region and decreased at the wall regions when the 0.5-inch vertical internals were used. Contrarily, the 1-inch vertical internals enhanced the gas holdup near to the wall regions. Additionally, the bubble chord length and the bubble rise velocity were found to be larger in the presence of vertical internals, especially at high superficial gas velocities. The specific interfacial area with the 0.5-inch internal was much lower than bubble column without vertical internals, but while using 1-inch internals, it was enhanced in the wall regions.

International Journal of Multiphase Flow, 2019

The effect of the vertical heat-exchanging tube bundle configurations on local gas holdup and bub... more The effect of the vertical heat-exchanging tube bundle configurations on local gas holdup and bubble dynamics, including specific gas-liquid interfacial area, bubble chord length, bubble rise velocity, and bubble passage frequency have been studied using the 4-point optical fiber probe technique. Two different tube bundle configurations were investigated, circular tube bundle and hexagonal tube bundle. 30 internal tubes, each with a diameter of 0.5 inches (0.013 m), were used in each configuration occupying 25% of the column cross-section area to represent the heat exchanging tubes utilized in the Fischer–Tropsch process. The experimental work was performed in a 0.14 m inner diameter Plexiglas bubble column using an air-water system. The applied superficial gas velocities were based on the free cross-sectional area of the column available for fluid flow and were in the range of 0.02 to 0.45 m/s covering bubbly, transition, and churn turbulent flow regimes. Although the size and the number of the tubes in both configurations were similar, their effects on the hydrodynamics were found to be different. When compared to bubble column without internals, the circular tube bundle showed a significant increase in the local gas holdup in the core region and a decrease in the wall regions. Simultaneously, a substantial increase in the bubble chord length and bubble velocity was seen. Another important observation was the decrease in the interfacial area while using circular tube bundle. A distinct asymmetrical effect on the radial profiles of gas holdup and the specific interfacial area was observed when the hexagonal configuration was used. The gas holdup and interfacial area significantly increased on one side of the column and decreased on the other side. The bubble chord length and bubble rise velocity decreased, exhibiting a narrower distribution with smaller values, in comparison to the bubble column without internals.

Chemical Engineering Journal, 2016

The effect of heat exchanging internals that represent Fischer-Tropsch (FT) synthesis in bubble c... more The effect of heat exchanging internals that represent Fischer-Tropsch (FT) synthesis in bubble column has been investigated for the first time using gamma ray Computed Tomography (CT) in a 5.5″ (0.14 m) inner diameter Plexiglas bubble column operated at atmospheric condition with air water system. Thirty vertical Plexiglas rods of 0.5″ outer diameter were used which covered ~25% of the total cross-sectional area and were arranged in a triangular pitch of 0.84″ (2.14 cm). The superficial gas velocities applied were based on both total cross-sectional area as well as free cross-sectional area available for the flow and were in the range of 5-45 cm/s covering the bubbly through churn-turbulent flow regimes. New knowledge and findings have been obtained which have not been reported in previous studies. In churn turbulent flow regime, the overall gas holdup and the profiles of gas holdup obtained in bubble columns without internals can be extrapolated to those with internals in the central region of the column if the superficial gas velocity is based on the free cross-sectional area (CSA) available for the flow of the phases provide that symmetric time averaged gas holdup cross-sectional distributions are achieved. The results show that a significant increment in overall and local gas holdup are obtained upon inserted of the internals when the velocity measured based on the total cross sectional area of the column. The gas holdup distribution over the cross-sectional area (CSA) of the column in the presence of internals has a symmetrical shape at low gas velocities and asymmetry at higher ones for the honeycomb configuration and its installation used in this study. At a high superficial gas velocity that is based on free CSA for the flow, the influence of dense internal becomes insignificant at the central region of the column. However, the profiles of the gas holdup in the column with internals become less steeper compared to those that are like parabolic shape at high gas velocity in the column without internals due to higher gas holdup was obtained in the region near the wall with internals.

IEEE, 2017

The calibration maps relating counts with the position of the radioactive particle is essential t... more The calibration maps relating counts with the position of the radioactive particle is essential to reconstruct the instantaneous positions of the particle and consequently measurements in a 3D manner of the local velocity field and turbulent parameters in the split photobioreactor for the microalgae system by using advanced radioactive particle tracking (RPT) technique. The calibration experiments should perform at the same operating conditions of an actual test. No studies in literature account for the effect of the growth of microalgae on the physical properties of the culturing medium by employing the calibration curves operations. This work used a Plexiglas split column of 5.0 inch (12.7cm) diameter and 59 inches (150 cm) high with a Plexiglas plate that divides the column into two equal areas. As a result, there is no significant change in counts of gamma ray (calibration system) through deference growth steps, then the experiments show that the one calibration experiment and one isotope tracer particle are enough to perform RPT operations even if the medium of the culturing becomes highly dense at this microorganism system. This knowledge and findings will help to reduce the cost and the efforts of the RPT experiments including air-water-microalgae cell systems during the culturing process.

Al-Khwarizmi Engineering Journal, 2010

The present research focuses on the study of the effect of mass transfer resistance on the rate o... more The present research focuses on the study of the effect of mass transfer resistance on the rate of heat transfer in pool boiling. The nucleate pool boiling heat transfer coefficients for binary mixtures (ethanol-n-butanol, acetone-n-butanol, acetone-ethanol, hexane-benzene, hexane-heptane, and methanol-water) were measured at different concentrations of the more volatile components. The systems chosen covered a wide range of mixture behaviors. The experimental set up for the present investigation includes electric heating element submerged in the test liquid mounted vertically. Thermocouple and a digital indictor measured the temperature of the heater surface. The actual heat transfer rate being obtained by multiplying the voltmeter and ammeter readings. A water cooled coil condenses the vapor produced by the heat input and the liquid formed returns to the cylinder for re-evaporation. The boiling results show that the nucleate pool boiling heat transfer coefficients of binary mixtures were always lower than the pure components nucleate pool boiling heat transfer coefficients. This confirmed that the mass transfer resistance to the movement of the more volatile component was responsible for decrease in heat transfer and that the maximum deterioration that was observed at a point was the absolute concentration differences between vapor and liquid phases at their maximum. All the data points were tested with the most widely known correlations namely those of Calus-Leonidopoulos, Fujita and Thome. It was found that Thome's correlation is the more representative form, for it gave the least mean and standard deviations.

Bioresource Technology Reports, 2021

Abstract Eggshell waste which is a serious issue that faces the authorities of food industries wa... more Abstract Eggshell waste which is a serious issue that faces the authorities of food industries was used to adsorb methyl green stain from aqueous solutions. The impact of pH solution of several parameters on the removal efficiency was investigated. The results show that the maximum percent of removal was 69.38 ± 3% and it was directly proportional with pH, agitation speed, adsorbent dose, and contact time. While the relation with temperature and initial concentration was inverse. The isotherm, kinetic and thermodynamic studies were also done under the system optimum conditions. The results show that the pseudo-second order kinetic model and Langmuir isotherm model are the best models that describe the adsorption system, while the thermodynamic investigation illustrates that the removal process was endothermic, spontaneous, and less entropic. This work provides detailed information about an innovative method to utilize eggshell waste as an inexpensive adsorbent to remove methyl green stain from aqueous solutions.

Molecular Catalysis, 2021

Abstract Acetone adsorption and catalytic interactions with a MgO nanoparticle surface was studie... more Abstract Acetone adsorption and catalytic interactions with a MgO nanoparticle surface was studied using in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) at room temperature. Acetone showed adsorption bands at 2965, 1717, 1597, 1422, 1415, 1367, 1238, 1229, and 1204 cm−1. The MgO was found to be a good catalyst for the activation of the aldol condensation reaction of acetone to form di-acetonealcohol (DAA). The OH group role on the MgO surface was found to be a suppression agent to the further dehydration of DAA to mesityl oxide. This is probably because the OH group blocks the active sites on the MgO surfaces that adsorbed the water formed from the dehydration of DAA. This conclusion was confirmed by identifying the basic site concentrations on MgO surface using DRIFTS and TPD studies of CO2 adsorption/desorption on MgO nanoparticles surface. The high-strength basic sites which are required to dehydrate DDA to mesityl oxide was found to represent only 17.5 % of the total basic site concentration, while the low-strength basic sites resulted from hydroxyl surface group represent 22.5 %. On the other hand, the acetone interaction with the MgO surfaces produced several components such as formaldehyde, acetate, ethoxide, as well as other carbonate species such as bicarbonate, bidentate carbonate, and monodentate carbonate. The results of the present investigation supply important essential insights into catalytic reactions resulted from acetone adsorption on MgO nanoparticle surfaces.

International Communications in Heat and Mass Transfer

In this work, CFD is used to simulate the gas-liquid dispersion coupled to the kinetics of the ir... more In this work, CFD is used to simulate the gas-liquid dispersion coupled to the kinetics of the iron(II) removal from drinking water by aeration process in a split-rectangular airlift reactor.

International Journal of Multiphase Flow, 2018

An advanced gamma-ray computed tomography (CT) technique was used for the first time to visualize... more An advanced gamma-ray computed tomography (CT) technique was used for the first time to visualize and quantify the impacts of the presence of heat-exchanging tubes and their configurations on the gas-liquid distributions and their profiles in a 6-inch (0.1524 m O.D.) Plexiglas® bubble column in an air-water reactor. Two superficial gas velocities (i.e., 0.2 and 0.45 m/s) were employed to simulate the churn turbulent flow regime. To investigate the impact of vertical internals configurations, three arrangements (i.e., hexagonal, circular without a central internal, and circular with a central internal) were employed in addition to the column with no internals. Using the same sized vertical internals and the same oc-cluded cross-sectional area (CSA), it was found that the configuration of the vertical internals significantly impacted the gas holdup distribution over the CSA of the column. All studied superficial gas velocities resulted in symmetrical gas holdup distributions over the CSA of the bubble columns without vertical internals; however, the columns equipped densely with vertical internals did not have symmetrical gas holdup distributions. The presence of an extra central tube in the circular configuration played a key role in the gas-liquid distribution over the CSA of the bubble column. The hexagonal configuration had the advantage of providing the best spread of the gas phase over the entire CSA of the column. Gas holdup values at the wall region of the bubble column increased with the addition of vertical tubes in all investigated configurations. However, a remarkable increase in the gas holdup values was obtained with the hexagonal configuration. The experimental data (i.e., gas holdup distributions and their diametrical profiles) can help to evaluate and validate three-dimensional (3-D) computational fluid dynamics (CFD) simulations to better predict the hydrodynamic parameters involved in these types of reactors. Published by Elsevier Ltd.

Chemical Engineering Science, 2018

The effects of the presence of the vertical internals of different sizes at a wide range of super... more The effects of the presence of the vertical internals of different sizes at a wide range of superficial gas velocity on the overall, local gas holdup distributions and their profiles have been studied and quantified in a 6-in. (0.14 m) Plexiglas
bubble column with air-water system using a non-invasive advanced gamma-ray computed tomography (CT) technique. In this study, two sizes of Plexiglas
vertical internals, having the same occupying area (25%) of the column’s cross-sectional area (CSA) that represents those used in Fischer-Tropsch synthesis, have been used within a range of superficial gas velocities that cover bubbly and churn turbulent flow regimes (0.05–0.45 m/s). The reconstructed CT scan images revealed that the bubble columns equipped with or without internals displayed a uniform cross-sectional gas holdup distribution (symmetric) for all studied superficial gas velocities. However, the bubble column equipped with 1-in. vertical internals exhibited more uniform gas holdup distribution than the column with 0.5-in. internals. Also, the visualization of the gas-liquid distributions for bubble columns with and without internals reveal that the well-known phenomenon of the core-annular liquid circulation pattern that observed in the bubble column without internals still exists in bubble column packed densely with vertical internals. Moreover, a remarkable increase in the gas holdup values at the wall region was achieved in the churn turbulent flow regime based on the insertion of the vertical internals inside the column as compared with using a bubble column without obstacles. Furthermore, the values of the gas holdup in the core region of the bubble column with vertical internals are similar to those of the bubble column without vertical internals when they are operated at high superficial gas velocity (churn turbulent flow regime), based on the free cross-sectional area (CSA) for the flow. In general, the magnitude of the gas holdup increased significantly with increasing superficial gas velocity for the bubble columns with and without internals. However, the gas holdup profile was shaped like a wavy line in the bubble column with vertical internals, whereas it exhibited a parabolic gas holdup profile in the bubble column without obstacles.

Chemical Engineering Science, 2017

h i g h l i g h t s Radioactive Particle Tracking (RPT) technique has been developed and applied ... more h i g h l i g h t s Radioactive Particle Tracking (RPT) technique has been developed and applied in this study. Quantification of 3D liquid velocity and turbulent parameters in bubble column with internals. The presence of the internals causes an increase in axial centerline liquid velocity. A remarkable decrease in turbulence parameters for the bubble column with internals. The data and knowledge are worthy as a benchmark data for validation CFD simulation. a b s t r a c t In this study, the effects of the dense vertical internals on the liquid velocity field and turbulence parameters (Reynolds stresses, turbulent kinetic energy, and turbulent eddy diffusivities) are experimentally investigated for the first time by using advanced Radioactive Particle Tracking (RPT) technique. The experimental work was carried out in a Plexiglas bubble column with 5.5 in. (0.14 m) and a height of 72 in. (1.83 m) for the air-water system. In this work, thirty vertical Plexiglass internals of 0.5 in. (0.0127 m) outer diameter were used which covered $25% (typical for Fischer-Tropsch processes) of the total cross-sectional area of the column where they arranged as the triangular pitch of 0.84 in. (0.0214 m). The superficial gas velocities based on both total cross-sectional area and free cross-sectional area available for the flow were utilized (0.08, 0.2, and 0.45 m/s), which covered the transition and churn-turbulent flow regime to meet the industrial applications of FT synthesis. The experimental data show that the presence of the internals at a given superficial gas velocity causes an increase in the axial centerline liquid velocity and a sharp decrease in turbulence parameters while the increase in superficial gas velocity in the presence of internals causes an increase in axial centerline liquid velocity and turbulent parameters. The obtained data are reliable as a benchmark data for validation computational fluid dynamics (CFD) simulation, and models.

Canadian Journal of Chemical Engineering, 2018

This study identifies and addresses some major pitfalls that are involved in the visualization an... more This study identifies and addresses some major pitfalls that are involved in the visualization and quantification of the gas-liquid distributions and their profiles in a bubble column with internals using the gamma-ray computed tomography (CT) technique. Some of these pitfalls encountered in the scanning of bubble columns with internals are using an improper reference scan, and applying the same experimental scanning procedure and mathematical relationships for estimating the gas holdup in the column without internals to the column with internals. The experimental results revealed that the selection of the inappropriate reference scan for CT experiments would significantly affect the reconstructed linear attenuation coefficient values and consequently the gas holdup results. Additionally, the reconstructed linear attenuation values showed good agreement with theoretical values when considering air as reference scans. However, disagreement is observed when using the empty column with internals as a reference scan. Moreover, it was found that using the proper reference scan eliminated the errors not only for the reconstructed linear attenuation coefficients but also for the gas holdup values near the wall region. Furthermore, the CT technique was capable of capturing the small thickness (5 mm) of the wall for phantom and bubble columns as well as the internals when the air was used as the reference scan. Finally, a new methodology has been implemented to exclude the internals from the cross-sectional images, and the azimuthally averaged gas holdup profiles to provide accurate and reliable results for comparison and validation purposes for the bubble column with internals.

Eng.& Tech. Journal, 2012

Artificial neural network (ANN), in comparison with empirical correlations, has recently received... more Artificial neural network (ANN), in comparison with empirical correlations, has recently received more attention. The present paper includes predictive modeling of heat transfer coefficient for binary mixtures in pool boiling for hydrocarbon compounds, using Back propagation techniques through Multilayer Perceptron, one of the types of the artificial neural networks. To train and learn the system, predictive neural network was found, which is capable of understanding and predicting the preset output which is heat transfer coefficient. The principle operation of such neural networks is based on the experimental data collected from some researchers [1-4]. A new ANN model is proposed using five inputs (mole fraction, temperature difference, heat flux, density and viscosity) to predict the heat transfer coefficient. The prediction using ANN shows 0.0026 AARE (Absolute Average Relative Error) with most widely known correlations namely those of Calus, Fujita and Thome which have given 0.086, 0.066 and 0.038 respectively.

Chemical Engineering Science, 2018

In this study, an advanced radioactive particle tracking (RPT) technique was used to investigate ... more In this study, an advanced radioactive particle tracking (RPT) technique was used to investigate for the first time the details of the cells’ movements (trajectory) and multiphase flow hydrodynamics during microalgae culturing in a cylindrical split airlift photobioreactor. The cells’ trajectory, liquid velocity field, distributions of shear stresses, and the turbulent kinetic energy field were studied under superficial gas velocity of 1 and 3 cm/s. The structures of the flow in the whole reactor, the riser, the downcomer, as well as the structure above and below the split plate were characterized. The effects of the cells’ concentration and different aeration rate at different axial levels on the studied parameters were discussed. It has been found that the cells’ fluctuations reduced and its movement frequency between the light (wall) and dark zone decreased during the culturing particularly when the cells concentrations becomes large after 30 days of culturing. Distinguishing behaviors were observed for all the parameters, with a higher magnitude at the superficial gas velocity 3 cm/sec than at 1 cm/sec. This effect positively enhanced the liquid circulation and the movement between the reactor sides, the riser, and the downcomer. This circulation and good mixing phenomena had a large positive impact on the culture's continuity. The obtained results are reliable as benchmark data to validate computational fluid dynamics (CFD) simulation and other models that can be later used to be integrated with dynamic growth and light intensity models for optimized.

Experimental Thermal and Fluid Science, 2018

The impact of dense vertical internal tubes and their configurations on the gas holdup distributi... more The impact of dense vertical internal tubes and their configurations on the gas holdup distributions and their diametrical profiles in pilot-scale bubble column is visualized and quantified for the first time ever using an advanced gamma-ray computed tomography (CT) technique. Two arrangements of vertical internals (circular and hexagonal configurations) occupying the same cross-sectional area (CSA) of the column (about 25% of the total cross-sectional area to represent the heat exchanging tubes that are used in the Fischer-Tropsch synthesis), were examined in addition to the measurement in the bubble column without vertical internals. Moreover, the gas holdup distribution results of the 18-inch (0.46 m in outer diameter, O.D.) bubble column are compared with an available data of 6-inch (0.15 m in O.D.) bubble columns with and without vertical internals. CT scans have been conducted for 18-inch bubble columns with and without vertical internals for the air-water system under a wide range of superficial gas velocity (0.05–0.45 m/s). The experimental results indicate that an improvement in the gas holdup distribution over the column's cross-sectional area is obtained when the vertical internal tubes (arranged in either a circular or a hexagonal configuration) were used. However, better cross-sectional gas holdup distribution was achieved in the bubble column with vertical internals arranged in a hexagonal configuration as compared to the bubble column without and with vertical internals arranged in a circular arrangement. Additionally, the averages of the cross-sectional gas holdup and their profiles for bubble column with and without vertical internals are close to each other when the bubble column with vertical internals is operating at a high superficial gas velocity, which is calculated based on the free cross-sectional area for the flow. Furthermore, the gas holdup distributions are further improved when the larger bubble column with vertical internals was used as compared to the 6-inch bubble columns with and without vertical internals.

Fuel, 2019

The effects of the presence of vertical internal tubes and their diameters on the local gas holdu... more The effects of the presence of vertical internal tubes and their diameters on the local gas holdup and bubble dynamics, including the specific interfacial area, bubble chord length, and bubble velocity were investigated in a 6 in. bubble column for the air-water system by using a four-point optical fiber probe technique. Two different diameters, 0.5-inch, and 1-inch, of vertical internals equally covering 25% of the column's cross-sectional area (CSA) were used to represent the heat-exchanging tubes utilized in the Fischer Tropsch (FT) process. For both sizes, the vertical internals were uniformly distributed over column CSA. The experiments were performed using the air-water system, in a 6-inch bubble column at superficial gas velocities of 20, 30, and 45 cm/s. The experimental results indicated that the presence of vertical internals and their diameters have a significant effect on the hydrodynamic properties of the bubble column reactor at high superficial gas velocities. The local gas holdup significantly increased in the core region and decreased at the wall regions when the 0.5-inch vertical internals were used. Contrarily, the 1-inch vertical internals enhanced the gas holdup near to the wall regions. Additionally, the bubble chord length and the bubble rise velocity were found to be larger in the presence of vertical internals, especially at high superficial gas velocities. The specific interfacial area with the 0.5-inch internal was much lower than bubble column without vertical internals, but while using 1-inch internals, it was enhanced in the wall regions.

International Journal of Multiphase Flow, 2019

The effect of the vertical heat-exchanging tube bundle configurations on local gas holdup and bub... more The effect of the vertical heat-exchanging tube bundle configurations on local gas holdup and bubble dynamics, including specific gas-liquid interfacial area, bubble chord length, bubble rise velocity, and bubble passage frequency have been studied using the 4-point optical fiber probe technique. Two different tube bundle configurations were investigated, circular tube bundle and hexagonal tube bundle. 30 internal tubes, each with a diameter of 0.5 inches (0.013 m), were used in each configuration occupying 25% of the column cross-section area to represent the heat exchanging tubes utilized in the Fischer–Tropsch process. The experimental work was performed in a 0.14 m inner diameter Plexiglas bubble column using an air-water system. The applied superficial gas velocities were based on the free cross-sectional area of the column available for fluid flow and were in the range of 0.02 to 0.45 m/s covering bubbly, transition, and churn turbulent flow regimes. Although the size and the number of the tubes in both configurations were similar, their effects on the hydrodynamics were found to be different. When compared to bubble column without internals, the circular tube bundle showed a significant increase in the local gas holdup in the core region and a decrease in the wall regions. Simultaneously, a substantial increase in the bubble chord length and bubble velocity was seen. Another important observation was the decrease in the interfacial area while using circular tube bundle. A distinct asymmetrical effect on the radial profiles of gas holdup and the specific interfacial area was observed when the hexagonal configuration was used. The gas holdup and interfacial area significantly increased on one side of the column and decreased on the other side. The bubble chord length and bubble rise velocity decreased, exhibiting a narrower distribution with smaller values, in comparison to the bubble column without internals.

Chemical Engineering Journal, 2016

The effect of heat exchanging internals that represent Fischer-Tropsch (FT) synthesis in bubble c... more The effect of heat exchanging internals that represent Fischer-Tropsch (FT) synthesis in bubble column has been investigated for the first time using gamma ray Computed Tomography (CT) in a 5.5″ (0.14 m) inner diameter Plexiglas bubble column operated at atmospheric condition with air water system. Thirty vertical Plexiglas rods of 0.5″ outer diameter were used which covered ~25% of the total cross-sectional area and were arranged in a triangular pitch of 0.84″ (2.14 cm). The superficial gas velocities applied were based on both total cross-sectional area as well as free cross-sectional area available for the flow and were in the range of 5-45 cm/s covering the bubbly through churn-turbulent flow regimes. New knowledge and findings have been obtained which have not been reported in previous studies. In churn turbulent flow regime, the overall gas holdup and the profiles of gas holdup obtained in bubble columns without internals can be extrapolated to those with internals in the central region of the column if the superficial gas velocity is based on the free cross-sectional area (CSA) available for the flow of the phases provide that symmetric time averaged gas holdup cross-sectional distributions are achieved. The results show that a significant increment in overall and local gas holdup are obtained upon inserted of the internals when the velocity measured based on the total cross sectional area of the column. The gas holdup distribution over the cross-sectional area (CSA) of the column in the presence of internals has a symmetrical shape at low gas velocities and asymmetry at higher ones for the honeycomb configuration and its installation used in this study. At a high superficial gas velocity that is based on free CSA for the flow, the influence of dense internal becomes insignificant at the central region of the column. However, the profiles of the gas holdup in the column with internals become less steeper compared to those that are like parabolic shape at high gas velocity in the column without internals due to higher gas holdup was obtained in the region near the wall with internals.

IEEE, 2017

The calibration maps relating counts with the position of the radioactive particle is essential t... more The calibration maps relating counts with the position of the radioactive particle is essential to reconstruct the instantaneous positions of the particle and consequently measurements in a 3D manner of the local velocity field and turbulent parameters in the split photobioreactor for the microalgae system by using advanced radioactive particle tracking (RPT) technique. The calibration experiments should perform at the same operating conditions of an actual test. No studies in literature account for the effect of the growth of microalgae on the physical properties of the culturing medium by employing the calibration curves operations. This work used a Plexiglas split column of 5.0 inch (12.7cm) diameter and 59 inches (150 cm) high with a Plexiglas plate that divides the column into two equal areas. As a result, there is no significant change in counts of gamma ray (calibration system) through deference growth steps, then the experiments show that the one calibration experiment and one isotope tracer particle are enough to perform RPT operations even if the medium of the culturing becomes highly dense at this microorganism system. This knowledge and findings will help to reduce the cost and the efforts of the RPT experiments including air-water-microalgae cell systems during the culturing process.

Al-Khwarizmi Engineering Journal, 2010

The present research focuses on the study of the effect of mass transfer resistance on the rate o... more The present research focuses on the study of the effect of mass transfer resistance on the rate of heat transfer in pool boiling. The nucleate pool boiling heat transfer coefficients for binary mixtures (ethanol-n-butanol, acetone-n-butanol, acetone-ethanol, hexane-benzene, hexane-heptane, and methanol-water) were measured at different concentrations of the more volatile components. The systems chosen covered a wide range of mixture behaviors. The experimental set up for the present investigation includes electric heating element submerged in the test liquid mounted vertically. Thermocouple and a digital indictor measured the temperature of the heater surface. The actual heat transfer rate being obtained by multiplying the voltmeter and ammeter readings. A water cooled coil condenses the vapor produced by the heat input and the liquid formed returns to the cylinder for re-evaporation. The boiling results show that the nucleate pool boiling heat transfer coefficients of binary mixtures were always lower than the pure components nucleate pool boiling heat transfer coefficients. This confirmed that the mass transfer resistance to the movement of the more volatile component was responsible for decrease in heat transfer and that the maximum deterioration that was observed at a point was the absolute concentration differences between vapor and liquid phases at their maximum. All the data points were tested with the most widely known correlations namely those of Calus-Leonidopoulos, Fujita and Thome. It was found that Thome's correlation is the more representative form, for it gave the least mean and standard deviations.