Gas holdup and interfacial mass transfer in gas-liquid tower contactors with ejector-type gas distributors

1985 ◽  
Vol 50 (11) ◽  
pp. 2535-2544 ◽  
Author(s):  
Jindřich Zahradník ◽  
Jan Kratochvíl ◽  
Milan Rylek
Keyword(s):  
Gas Holdup ◽  
Energy Utilization ◽  
Dissipated Energy ◽  
Favourable Effect ◽  
Experimental Conditions ◽  
Gas Distributor ◽  
Interfacial Mass Transfer ◽  
Tube Type ◽  
Gas Suction ◽  
Nozzle Type

The effect of decisive construction parameters of ejectors on gas holdup and on the rate of interfacial mass transport (characterized by kLa values) was studied in a gas-liquid tower reactor (I.D. 0.3 m) with an ejector (Venturi-tube type) gas distributor. The selected ejector characteristics included diffuser length and angle of diffuser walls inclination as well as nozzle type and geometry. Experimental data confirmed validity of our previously published conclusions on the relation between the rate of energy dissipation in the place of dispersion formation (i.e. in the ejector) and gas holdup and kLa values. The efficiency of dissipated energy utilization was however significantly influenced by the diffuser geometry. According to our experimental evidence the increase of ejector energy effectiveness with increasing diffuser length can be ascribed solely to its favourable effect on the gas suction rate while the mechanism of phases mixing (dispersion formation) in ejector was apparently independent of diffuser geometry within the whole range of experimental conditions.

Hydrodynamic characteristics of gas-liquid beds in contactors with ejector-type gas distributors

1982 ◽  
Vol 47 (7) ◽  
pp. 1939-1949 ◽  
Author(s):  
Jindřich Zahradník ◽  
František Kaštánek ◽  
Jan Kratochvíl ◽  
Milan Rylek
Keyword(s):  
Energy Dissipation ◽  
Energy Dissipation Rate ◽  
Gas Holdup ◽  
Nozzle Geometry ◽  
Hydrodynamic Characteristics ◽  
Gas Distributor ◽  
Liquid Dispersion ◽  
Interfacial Mass Transfer ◽  
Ejector Nozzle ◽  
Nozzle Type

The effect of ejector-nozzle geometry on gas holdup and on the rate of interfacial mass transfer characterized by values of kLa was studied in a tower reactor with ejector-type gas distributor. It has been established that both gas holdup and kLa values are, in contactors of this type, unambiguously determined by the rate of energy dissipation in the place of gas-liquid dispersion formation i.e. in the ejector. No effect of nozzle type and geometry was observed on the character of dependences of gas holdup and kLa on the energy dissipation rate and consequently on the values of coefficients of empirical exponential-type relations used for experimental data correlation.

Gas holdup in an external-loop air-lift fermentor with a contaminated gas distributor

1985 ◽  
Vol 27 (7) ◽  
pp. 1092-1094 ◽  
Author(s):  
W. J. McManamey ◽  
D. A. J. Wase ◽  
S. Raymahasay
Keyword(s):  
Gas Holdup ◽  
External Loop ◽  
Gas Distributor ◽  
Air Lift

Design of Venturi-tube gas distributors for bubble-type reactors

1984 ◽  
Vol 49 (9) ◽  
pp. 1939-1948 ◽  
Author(s):  
Milan Rylek ◽  
Jindřich Zahradník
Keyword(s):  
Experimental Data ◽  
Gas Holdup ◽  
Venturi Tube ◽  
Design Parameters ◽  
Dispersion Characteristics ◽  
Liquid Circulation ◽  
Bed Porosity ◽  
Gas Distributor ◽  
Liquid Dispersion

The effect of individual parts of a Venturi-tube gas distributor on quality of the gas-liquid dispersion formed was studied in a bubble-type reactor with forced liquid circulation. Gas holdup (bubble-bed porosity) was used as the dispersion characteristics, type and geometry of nozzles, suction chamber arrangement, and dimensions of the mixing tube and diffuser were chosen as variable design parameters. Experimental data of gas holdup presented in dependence on the rate of energy dissipation in the place of dispersion formation characterized then the dispersion efficiency of the Venturi tube at given conditions. Recommendations for design of Venturi-tube gas distributors are presented based upon the results of the study.

scholarly journals Building Energy Utilization with LED Lighting and Occupant Sensing System

2019 ◽  
Vol 9 (2) ◽  
pp. 4132-4136
Keyword(s):  
Building Energy ◽  
Energy Utilization ◽  
Motion Sensors ◽  
Lighting System ◽  
Experimental Conditions ◽  
Led Lighting ◽  
Smart Lighting ◽  
Energy Management Systems ◽  
Building Energy Management ◽  
New Energy

Building Energy management systems (BEMSs) are needed to monitor and regulate energy consumption in buildings, thus, contribute in reducing the environmental challenges facing our planet. A new energy saving method based on BEMS is proposed in this paper. The proposed method is a smart LED lighting system based on an Arduino microcontroller, a simple motion sensor, and a camera. A complete design and implementation of the smart lighting system is presented in the paper. In addition, the proposed smart system is validated in the paper under various experimental conditions. The results show that simple installation of commercially available motion sensors and cameras can contribute significantly to reduce the electricity bill and CO2 emission.

scholarly journals Catalytic Electrochemical Water Splitting Using Boron Doped Diamond (BDD) Electrodes as a Promising Energy Resource and Storage Solution

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5265
Author(s):  
Yousef Al-Abdallat ◽  
Inshad Jumah ◽  
Rami Jumah ◽  
Hanadi Ghanem ◽  
Ahmad Telfah
Keyword(s):  
Water Splitting ◽  
Energy Resource ◽  
Electrical Current ◽  
Dissipated Energy ◽  
Boron Doped Diamond ◽  
Zno Nps ◽  
Experimental Conditions ◽  
Cuo Nps ◽  
Boron Doped ◽  
Electrochemical Water Splitting

The present study developed a new system of electrochemical water splitting using a boron doped diamond (BDD) electrode in the electrochemical reactor. The new method assessed the electrical current, acidity (pH), electrical conductivity, absorbance, dissipation, and splitting energies in addition to the water splitting efficiency of the overall process. Employing CuO NPs and ZnO NPs as catalysts induced a significant impact in reducing the dissipated energy and in increasing the efficiency of splitting water. Specifically, CuO NPs showed a significant enhancement in reducing the dissipated energy and in keeping the electrical current of the reaction stable. Meanwhile, the system catalyzed with ZnO NPs induced a similar impact as that for CuO NPs at a lower rate only. The energy dissipation rates in the system were found to be 48% and 65% by using CuO and ZnO NPs, respectively. However, the dissipation rate for the normalized system without catalysis (water buffer at pH = 6.5) is known to be 100%. The energy efficiency of the system was found to be 25% without catalysis, while it was found to be 82% for the system catalyzed with ZnO NPs compared to that for CuO NPs (normalized to 100%). The energy dissipated in the case of the non-catalyzed system was found to be the highest. Overall, water splitting catalyzed with CuO NPs exhibits the best performance under the applied experimental conditions by using the BDD/Niobium (Nb) electrodes.

CFD-PBM simulation of hydrodynamics of microbubble column with shear-thinning fluid

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Xi Zhang ◽  
Ping Zhu ◽  
Shuaichao Li ◽  
Wenyuan Fan ◽  
Jingyan Lian
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Radial Direction ◽  
Liquid Velocity ◽  
Bubble Column ◽  
Gas Holdup ◽  
Gas Velocity ◽  
Gas Distributor ◽  
Superficial Gas Velocity ◽  
The Right

Abstract A numerical simulation was performed to study the hydrodynamics of micro-bubble swarm in bubble column with polyacrylamide (PAM) aqueous solution by using computational fluid dynamics coupled with population balance models (CFD-PBM). By considering rheological characteristics of fluid, this approach was able to accurately predict the features of bubble swarm, and validated by comparing with the experimental results. The gas holdup, turbulent kinetic energy and liquid velocity of bubble column have been elucidated by considering the influences of superficial gas velocity and gas distributor size respectively. The results show that with the rise of the superficial gas velocity, the gas holdup and its peak width increase significantly. Especially, the curve peak corresponding to high gas velocity tends to drift obviously toward the right side. Except for the occurrence of a smooth holdup peak at the column center under the condition of the moderate distributor size, the gas holdups for the small and large distributor sizes become flat in the radial direction respectively. The distribution of turbulent kinetic energy presents an increasingly asymmetrical feature in the radial direction and also its variation amplitude enhances obviously with the rise of gas velocity. The increase in gas distributor size can enhance markedly turbulent kinetic energy as well as its overall influenced width. At the low and moderate superficial gas velocity, the curves of the liquid velocity in radial direction present the Gaussian distributions, whereas the perfect distribution always is broken in the symmetry for high gas velocity. Both liquid velocities around the bubble column center and the ones near both column walls go up consistently with the gas distributor size, especially near the walls at the large distributor size condition.

Energy Evolution and Water Immersion-Induced Weakening Mechanism in the Sandstone Roof of Coal Mines

2021 ◽  
Author(s):  
Wenjie Liu ◽  
Ke Yang ◽  
Shuai Zhang ◽  
Zhainan Zhang ◽  
Rijie Xu
Keyword(s):  
Energy Storage ◽  
Water Content ◽  
Elastic Energy ◽  
Coal Mines ◽  
Energy Utilization ◽  
Dissipated Energy ◽  
Plastic Energy ◽  
Storage Limit ◽  
Energy Share ◽  
Number Of Cycles

Abstract The instability of underground spaces in abandoned coal mines with water-immersed rocks is one of the main hazards hindering the geothermal energy utilization and ecological restoration of post-mining areas. This study conducted graded cyclic loading-unloading tests of five groups of sandstone samples with different water contents. The evolution laws of input, elastic, dissipated, damping, and plastic energies were explored in detail, taking into account the damping effect. The normalized plastic energy was used to characterize the damage evolution of sandstone samples, which failure modes were analyzed from both macroscopic and microscopic perspectives. The X-ray diffraction technique and scanning electron microscopy were used to reveal the softening mechanism of sandstone's strength and elastic energy storage limit. The results showed that the graded cyclic loading's input, elastic, and dissipated energies increased gradually. The elastic energy share first increased and then stabilized, while dissipated energy share variation had the opposite trend. In each cycle, the input energy was primarily stored in the form of elastic energy, while the dissipated energy was mainly used to overcome the damping of sandstone. When the normalized number of cycles approached unity, the plastic energy share sharply increased, while that of the dampening energy featured an abrupt drop. Such change indicated an inevitable instability failure of the water-bearing sandstone. As the water content increased, the pore water exhibited more substantial lubrication, water-wedging, and dissolution effects on mineral particles. As a result, the latter obtained a round form, and the elastic energy storage limit of the sandstone decreased. When the water content was increased, the damage factor of sandstone after the same number of cycles increased at a relatively higher rate, and there was a transition of failure mode from brittle to ductile.

scholarly journals Effects of the Microbubble Generation Mode on Hydrodynamic Parameters in Gas–Liquid Bubble Columns

Processes ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 663
Author(s):  
Shanglei Ning ◽  
Haibo Jin ◽  
Guangxiang He ◽  
Lei Ma ◽  
Xiaoyan Guo ◽  
...  
Keyword(s):  
Bubble Column ◽  
Length Distribution ◽  
Water System ◽  
Gas Holdup ◽  
Chord Length ◽  
Operating Conditions ◽  
Hydrodynamic Parameters ◽  
Gas Distributor ◽  
Liquid Bubble ◽  
Superficial Gas Velocity

The hydrodynamics parameters of microbubbles in a bubble column were studied in an air–water system with a range of superficial gas velocity from 0.013 to 0.100 m/s using a differential pressure transmitter, double probe optical fiber probe, and electrical resistance tomography (ERT) technique. Two kinds of microbubble generators (foam gun, sintered plate) were used to generate microbubbles in the bubble column with a diameter of 90 mm, and to compare the effects of different foaming methods on the hydrodynamics parameters in the bubble column. The hydrodynamic behavior of the homogeneous regime and the transition regime was also studied. The results show that, by changing the microbubble-generating device, the hydrodynamic parameters in the column are changed, and both microbubble-generating devices can obtain a higher gas holdup and a narrower chord length distribution. When the foam gun is used as the gas distributor, a higher gas holdup and a narrower average bubble chord length can be obtained than when the sintered plate is used as the gas distributor. In addition, under different operating conditions, the relative frequency distribution of the chord length at different radial positions is mainly concentrated in the interval of 0–5 mm, and it is the highest in the center of the column.

scholarly journals Mixing Characteristics of External Loop Airlift Bioreactor using Electrical Resistance Tomography

2021 ◽  
Author(s):  
Mian Hamood-Ur-Rehman
Keyword(s):  
Electrical Resistance ◽  
Liquid Velocity ◽  
Mixing Time ◽  
Perforated Plate ◽  
Packed Bed ◽  
Gas Holdup ◽  
External Loop ◽  
Gas Distributor ◽  
Airlift Bioreactors ◽  
Superficial Liquid Velocity

In the present work, a novel packed bed external loop pneumatically agitated airlift bioreactor with an internal gas distributor (perforated plate) between two rolls of packing in the riser was designed and built. This novel approach combines advantages of packed bed and external loop airlift bioreactors. The main objective of this research work was to characterize the hydrodynamic performance of this novel reactor through a non-intrusive flow visualization technique called electrical resistance tomography (ERT). The tomography images, which were generated using a linear back projection algorithm, were employed to explore the effects of different design parameters and operating conditions. These include the effect of the two packing in the riser and the internal gas distributor (perforated plate) installed between the two packing. Other parameters investigated include the effect of sparger configuration, gas flow rate, and liquid height in the bioreactor on the different hydrodynamic parameters such as gas holdup, mixing time, and liquid circulation velocity. Results showed that the gas holdup and mixing time increased in the presence of the gas distributor, while the riser superficial liquid velocity was decreased. Furthermore, gas holdup and mixing time increased, superficial liquid velocity decreased when decreasing liquid height in the reactor, and when using packing or gas distributor between two packings in the riser. These results can be used to improve mixing characteristics in external loop airlift bioreactors for wider range of applications.

scholarly journals Mixing Characteristics of External Loop Airlift Bioreactor using Electrical Resistance Tomography

2021 ◽  
Author(s):  
Mian Hamood-Ur-Rehman
Keyword(s):  
Electrical Resistance ◽  
Liquid Velocity ◽  
Mixing Time ◽  
Perforated Plate ◽  
Packed Bed ◽  
Gas Holdup ◽  
External Loop ◽  
Gas Distributor ◽  
Airlift Bioreactors ◽  
Superficial Liquid Velocity

In the present work, a novel packed bed external loop pneumatically agitated airlift bioreactor with an internal gas distributor (perforated plate) between two rolls of packing in the riser was designed and built. This novel approach combines advantages of packed bed and external loop airlift bioreactors. The main objective of this research work was to characterize the hydrodynamic performance of this novel reactor through a non-intrusive flow visualization technique called electrical resistance tomography (ERT). The tomography images, which were generated using a linear back projection algorithm, were employed to explore the effects of different design parameters and operating conditions. These include the effect of the two packing in the riser and the internal gas distributor (perforated plate) installed between the two packing. Other parameters investigated include the effect of sparger configuration, gas flow rate, and liquid height in the bioreactor on the different hydrodynamic parameters such as gas holdup, mixing time, and liquid circulation velocity. Results showed that the gas holdup and mixing time increased in the presence of the gas distributor, while the riser superficial liquid velocity was decreased. Furthermore, gas holdup and mixing time increased, superficial liquid velocity decreased when decreasing liquid height in the reactor, and when using packing or gas distributor between two packings in the riser. These results can be used to improve mixing characteristics in external loop airlift bioreactors for wider range of applications.

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