Dual Media Research Articles

Design of Dual Media Water Filtration System in Debesmscat Mabigo Water Reserve

Design of Dual Media Water Filtration System in Debesmscat Mabigo Water Reserve

Fractal study of interporosity flow function and shape factor in rough fractured dual porous media

In this paper, the fractal theory is used to consider the roughness of the matrix pore surface based on the previous research, the relative roughness model of the matrix pore surface is established, and the fractal model of anisotropic interporosity flow function and shape factor considering the relative roughness, tortuosity, and starting pressure of matrix pore is derived. The influence of relative roughness on the interporosity flow function and shape factor is also analyzed. It is found that the relative roughness is inversely proportional to the interporosity flow function but proportional to the shape factor. In addition, the rationality of the model is verified by comparing with the existing research.

Study on seepage model of Multiple Horizontal wells with complex fracture networks in tight Reservoir Based on boundary element method

Horizontal well and volume fracturing technology are the key technologies to develop unconventional reservoirs. Tight reservoir is belonging to multi-scale seepage mediaafter fracturing, and theflow of fluid in it is extremely complicated. In this paper, based on the boundary element method (BEM), the seepage model of horizontal wells with complex fracture networks in irregular boundary reservoir is established for the first time. The model takes into account the influence of irregular reservoir boundary, dual media, complex fracture network and interference of multiple wells on horizontal well seepage. Using this model, the sensitivity analysis of wellbore storage coefficient, skin factor, fracture permeability and interporosity transfer coefficient is carried out. The model expands the application scope of BEM in the field of seepage simulation of unconventional oil and gas reservoirs and provides theoretical guidance for the development of tight oil reservoirs.

Study on the Difference in CO2 and Air Injection in the Fracture/Matrix Dual Medium of Continental Shale Reservoirs.

To clarify the impact of different displacement media on the enhanced oil recovery of continental shale and realize the efficient and reasonable development of shale reservoirs, this paper takes the continental shale of the Lucaogou Formation in the Jimusar Sag in the Junggar Basin (China, Xinjiang) as the research object and uses real cores to build the fracture/matrix dual-medium model. Computerized tomography (CT) scanning is used to visually compare and analyze the influence of fracture/matrix dual-medium and single-matrix medium seepage systems on oil production characteristics and clarify the difference between air and CO2 in enhancing the oil recovery of continental shale reservoirs. Through a comprehensive analysis of the production parameters, the whole oil displacement process can be divided into three stages: the oil-rich and gas-poor stage, oil and gas coproduction stage, and gas-rich and oil-poor stage. Shale oil production follows the rule of fractures first and matrix second. However, for CO2 injection, after the crude oil in the fractures is recovered, the oil in the matrix migrates to the fractures under the action of CO2 dissolution and extraction. Overall, the oil displacement effect of CO2 is better than that of air, resulting in a 5.42% higher final recovery factor. Additionally, fractures can increase the permeability of the reservoir, which can greatly enhance oil recovery in the early oil displacement process. However, as the amount of injected gas increases, its impact gradually decreases, and ultimately, it is consistent with the recovery of nonfractured shale, which can achieve nearly the same development effect.

Simulation of NMR response of microfractures based on digital rock technology

The NMR response of microfractures in sandstone reservoirs is important for evaluating and predicting their performance. However, current methods have limitations, including a lack of high-resolution pore structure information and the inability to accurately model the complex geometry of microfractures. In this study, we aimed to overcome these limitations by using digital rock technology to simulate and analyze the NMR response of microfractures in a systematic way. The high-resolution pore structure information of sandstone samples is obtained and segmented by machine learning algorithm, and the 3D digital rock of sandstone with dual media of fracture and pore is reconstructed by using discrete fracture network model. Then, the NMR T2 spectrum of various saturation under various fracture parameters are simulated by using random walk method based on the constructed digital rock. The results show that the aperture, length, dip angle, density and water saturation of microfractures have different effects on the NMR response. An increase in the aperture, length, density, and water saturation increases the T2 relaxation time of the saturated water. At the same time, the closer the fracture dip angle is to 45°, the greater the response to NMR is. The density of microfractures has little effect on NMR response, mainly reflected in the backward shift of the front end of T2 spectrum. When the pore contains oil, the T2 spectrum mainly reflects the relaxation characteristics of the fluid itself, not the pore structure of the core. By using digital rock technology, we were able to accurately model the complex geometry of microfractures and incorporate high-resolution pore structure information, leading to a more comprehensive understanding of the NMR response of these reservoirs.

INITIAL COLLECTION EFFICIENCY FOR GLASS FILTER MEDIA

This study investigated the ability of using crushed glass solid wastes in water filtration by using a pilot plant, constructed in Al-Wathba water treatment plant in Baghdad. Different depths and different grain sizes of crushed glass were used as mono and dual media with sand and porcelaniate in the filtration process. The mathematical model by Tufenkji and Elimelech was used to evaluate the initial collection efficiency η of these filters. The results indicated that the collection efficiency varied inversely with the filtration rate. For the mono media filters the theoretical ηth values were more than the practical values ηprac calculated fromthe experimental work. In the glass filter ηprac was obtained by multiplying ηth by a factor 0.945 where this factor was 0.714 for the sand filter. All the dual filters showed that ηth was less than ηprac. Whereas the dual filter 35cm porcelanite and 35cm glass showed the highest collection efficiency. To obtain ηprac in the dual filter glass and sand, ηth is multiplied by 1.374, as for the dual filters porcelanite and glass the factor was 1.168 and 1.204.

Identifying Suitable Three-Dimensional Bio-Printed Scaffold Architectures to Incubate in a Perfusion Bioreactor: Simulation and Experimental Approaches

Abstract Traditional cell culturing methods are limited in their ability to supply growth medium to cells within scaffolds. To address this, we developed a custom perfusion bioreactor that allows for dynamic medium supply to encapsulated or seeded cells. Our custom-designed bioreactor improves the in vivo stimuli and conditions, which may enhance cell viability and proliferation performance. Some of the efforts include using dual medium tanks to replace the medium without stopping perfusion and a newly designed perfusion chamber that can accommodate an array of cassettes allowing for a wide assortment of scaffold shapes and sizes. In this paper, we explored the response of fluid flow to certain types of scaffold pore geometries and porosities using simulation and experimental approaches. Various pore geometries were considered, such as uniform triangular, square, diamond, circular, and honeycomb having uniform and variable sizes. Finally, bone tissue architecture was mimicked and simulated to identify the impact of fluid flow. Based on the results, optimum pore geometry for scaffolds were determined. We explored real-time fluid flow response on scaffolds fabricated with 8% Alginate, 4% Alginate-4% Carboxymethyl Cellulose (CMC), and 2% Alginate-6% CMC incubated, allowing a constant fluid flow for various periods such as 1, 2, 4, and 8 h. The change of fabricated scaffolds was determined in terms of swelling rate, i.e., change of filament width and material diffusion, i.e., comparison of dry material weight before and after incubation. This comparative study can assist in application-based materials selection suitable for incubating in a perfusion bioreactor.

Modulation of carbon dots hybrids lasers for high security flexible multi-level anti-counterfeiting

Anti-counterfeiting materials development has been raised for a long time to improve the level of security against counterfeiting. Increasing counterfeiting difficulties as well as reducing difficulties of materials preparation are two major concerns in the development of anti-counterfeiting materials. Herein, carbon dots (CDs) and triethyl 1,3,5-benzenetricarboxylate (Et3BTC), both of which show two random lasing peaks located around 325 nm and 450 nm at 265 nm excitation are chosen as two lasing mediums to form hybrids. Moreover, lasing intensity ratio of the two lasing bands from the hybrids can be tuned by changing the working temperature, excitation area, and even bending angle of substrate. As a result, a strategy of dual random lasing medium modulation based high security flexible multi-level anti-counterfeiting technique is developed. Thus, it is suitable for anti-counterfeiting of high-value items due to its high security and excellent waterproofness. This work will provide a perspective to boost the development of high security anti-counterfeiting techniques.

Endothermic relaxation behavior of gangue in longwall gob: Bidirectional heat transfer model and its simulation validation

The collapse of overlying strata in a goaf during coal mining forms many gangue blocks that vary in size and shape. Because the heat released by the coal–oxygen reaction diffuses around the wind flow, endothermic relaxation occurs when the heated gas contacts the gangue. However, only a few studies have addressed this issue. In this study, we first propose a method to investigate the thermal relaxation behavior by expanding the mathematical space of the problem and then establish a bidirectional heat transfer model of a single-gangue-ball in spherical coordinates combined with the energy conservation law, which is solved numerically using the finite difference method. Finally, the reason for the fluctuation of the solid temperature distribution in the gob is determined by extracting the calculation results and comparing them with the gangue temperature curve under transient heat conduction, and the effects of some key factors on the thermal relaxation efficiency of the gangue are quantitatively investigated. The results show that (i) along the high-temperature path of the goaf, the gangue temperature exhibits the same trend as the ambient temperature, and its external and internal temperature difference decreases gradually with an increase in burial depth; (ii) compared with the change in temperature rise under transient heat conduction, the relaxation phenomenon can result in a calculation error of up to 1.3 °C; (iii) the heat transfer efficiency is related to the gangue characteristics and its surface heat transfer resistance, and the accuracy of spontaneous combustion prediction can be guaranteed by increasing the initial temperature, reducing the heat transfer radius, or decreasing the air flow rate. In this study, the thermal relaxation behavior of the gangue in a gas–solid dual medium in a longwall gob is investigated, and a foundation is laid for the establishment of a four-dimensional temperature field model for the gangue in the future.

Influence mechanism of brine-gas two-phase flow on sealing property of anisotropic caprock for hydrogen and carbon energy underground storage

As the simplest saturated hydrocarbon, methane is an important hydrogen and carbon energy. The stability and sealing of caprock are keys to ensure the safe storage of energy in the process of hydrogen and carbon energy underground storage. A fully coupled two-phase flow model is established to analyze the migration mechanism of methane in caprock. This model considers the characteristics of dual porosity medium composed of caprock fractures and matrix, including the seepage of methane and brine. In the model, the replacement process of methane and brine exists in the fracture network, and the dynamic adsorption desorption process of methane exists in the matrix. Under the action of tectonic stress, obvious differences are observed in the fracture and permeability in different directions. All these characteristics are considered in the fully coupled two-phase flow model. The restraining and strengthening effects of caprock in the process of methane leakage are analyzed. The results show that the gas induces the adsorption expansion of the caprock matrix and reduces the fracture opening and permeability of the caprock. With the gradual invasion of gas into the caprock, the sealing characteristics of caprock show the evolution of self-inhibition first and then self-enhancement. With the increase in dip angle, gas tends to invade vertically rather than horizontally. Realizing gas–brine replacement is easier with the existence of large fractures. This study provides an effective numerical analysis method, which can be used to evaluate the sealing efficiency in the caprock in underground methane storage.

Causes of Ponding in Foundation Gallery of Fenhe Reservoir II Gravity Dam

The multi field coupling mechanism of seepage, stress and temperature coupling of concrete gravity dam is analyzed, and its coupling control equation is deduced. Based on the analysis of the temperature effect of cracked concrete dam, a three field coupling model of seepage, stress and temperature based on pore crack dual medium suitable for the characteristics of RCC gravity dam is established, and its implementation strategy in COMSOL Multiphysics is studied. The three-dimensional finite element model of the overflow dam of Fenhe Reservoir II is established, and the annual working behavior of the overflow dam section is simulated in COMSOL Multiphysics. The variation law of dam seepage characteristics under the coupling action of seepage, stress and temperature is obtained. It is considered that the ponding in the gallery mainly comes from the crack leakage, and the temperature and headwater elevation are the main factors affecting the crack leakage of the dam.

Exploring the feasibility of dual media filtration at Morton Jaffray Water Works (Harare, Zimbabwe)

Lake Chivero, Harare’s main potable raw water source, is eutrophic. This has complicated water treatment at Morton Jaffray Water Treatment Works (MJWTW) leading to frequent filter backwashing and reduced plant output. This study investigated the use of dual media filters (DMF) as an alternative to single media filters (SMF) currently employed using pilot filters. Key operational parameters (headloss and flow rate) and water quality parameters [electrical conductivity (EC), pH, total dissolved solids (TDS), turbidity and temperature] were monitored hourly. The change in EC, pH, TDS, and turbidity across the SMF and DMF was 6.3% and 6.3%; 0.5%. and 0.2%; 5.5% and 4.5%; 68% and 69%, respectively thus showing no significant difference. However, headloss development for the SMF was significantly higher reaching 247.3 m compared to 134.6 m for the DMF. Use of DMF could increase the filter run and production at MJWTW.

A new numerical well test method of multi-scale discrete fractured tight sandstone gas reservoirs and its application in the Kelasu Gas Field of the Tarim Basin

The cretaceous gas reservoir in Kelasu Gas Field of the Tarim Basin is a rare ultra-deep and ultra-high pressure fractured tight sandstone gas reservoir where multi-scale discrete fractures of matrix, fracture and fault are developed, so its development cannot be conducted just based on static and dynamic reservoir description. In order to solve this problem, this paper establishes a numerical well test model of vertical wells based on matrix, fractures and faults (large fractures and small faults) by combining the random generation of natural fracture networks with the unstructured discrete fracture modeling method to break through the traditional continuous medium well test model. In addition, the model is solved by using the finite element method with mixed element, and the typical well test type curves under different random fracture networks are obtained. And the following research results are obtained. First, based on the observed data, the fracture network distribution modes of fractured tight sandstone gas reservoirs are classified into three categories. The influence of random generation of fracture networks on typical well test type curves is discussed. The results of discrete fracture well test model are compared with those of the traditional continuous medium well test model, and the applicable conditions of the traditional continuous medium well test model is determined. Second, there are great differences between the results of discrete fracture model and those of dual porosity medium model. 1 The dual porosity medium model is a special case of the discrete fracture model, in which the fractures are evenly distributed within infinitely small spacing. Third, the characteristics of well test type curves under three fracture network distribution modes are discussed. The well test type curves that cannot be interpreted by the conventional dual/triple porosity continuous medium model are successfully interpreted by using the established well test interpretation model of random discrete fracture. The curve matching effect is ideal and the interpreted parameters are reasonable. In conclusion, the new model and the new method reveal the development mechanism of step-by-step production and coordinated gas supply between media of different scales, explain the development characteristics of large inter-well productivity difference and abnormal rapid inter-well pressure response, and provide a reference for the development of similar gas reservoirs.

Forecasting and Optimizing Dual Media Filter Performance via Machine Learning

Four different machine learning algorithms, including Decision Tree (DT), Random Forest (RF), Multivariable Linear Regression (MLR), Support Vector Regressions (SVR), and Gaussian Process Regressions (GPR), were applied to predict the performance of a multi-media filter operating as a function of raw water quality and plant operating variables. The models were trained using data collected over a seven year period covering water quality and operating variables, including true colour, turbidity, plant flow, and chemical dose for chlorine, KMnO4, FeCl3, and Cationic Polymer (PolyDADMAC). The machine learning algorithms have shown that the best prediction is at a 1-day time lag between input variables and unit filter run volume (UFRV). Furthermore, the RF algorithm with grid search using the input metrics mentioned above with a 1-day time lag has provided the highest reliability in predicting UFRV with a RMSE and R2 of 31.58 and 0.98, respectively. Similarly, RF with grid search has shown the shortest training time, prediction accuracy, and forecasting events using a ROC-AUC curve analysis (AUC over 0.8) in extreme wet weather events. Therefore, Random Forest with grid search and a 1-day time lag is an effective and robust machine learning algorithm that can predict the filter performance to aid water treatment operators in their decision makings by providing real-time warning of the potential turbidity breakthrough from the filters.

Arsenic removal and stabilization behavior of schwertmannite@BC (Sch@BC) in contaminated dual media (water/soil): Via sulfate exchange and chemical complexation

Arsenic (As) is extremely harmful to the ecological environment and human health owing to its high toxicity. The composite that biochar (BC) modified by Schwertmannite (Sch), marked as Sch@BC, were prepared to remediate As-contaminated water and soil with a high efficiency. The characterization results showed that the Sch particles were successfully loaded on the BC, providing more active sites for As(V) adsorption. Compared with the pristine BC, the adsorption capacity of Sch@BC-1 was significantly improved (50.00 mg/g), of which the adsorption capacity kept stable over a wide pH range (pH = 2–8). The adsorption process conformed to pseudo-second-order kinetics and Langmuir isotherm model, which indicated that chemical adsorption was the dominant mechanism and the adsorption rate was controlled by intraparticle diffusion. Sch@BC could adsorb As(V) through electrostatic interaction and ion exchange, forming a FeAsO4 complex and removing As(V). The 5-week soil incubation experiment showed that 3% Sch@BC showed the optimal stabilization effect, while the proportion of stable crystalline Fe/Mn-bound fractionation (F4) increased. Moreover, the results of microbial community diversity showed that Sch@BC interacted with As-resistant dominant microorganisms such as Proteobacteria in soil, promoted their growth and reproduction, and improved the stability of As in soil. In summary, Sch@BC is an excellent agent with broad application prospects for remediating As-contaminated water and soil.

Numerical simulation and experimental study on improving gas drainage by hydraulic fracturing

ABSTRACT To address the difficult problem of coal seam gas control that has arisen as a result of the recent development of deep coal mining, hydraulic fracturing technology is applied to the coal seam, the dual porous medium theory is used, and a multi-scale flow model of coal gas is constructed under certain assumptions. The dynamic evolution law of coal porosity and permeability is studied according to the gas multi-scale diffusion equation, gas-bearing coal seepage equation, and other theories. To study the variation law of important parameters such as coal seam pressure and drainage influence range in the process of coal and gas drainage, numerical simulation software is used, and industrial tests are supplemented to verify energy efficiency. The study found that using hydraulic fracturing technology to enhance the permeability of coal seams can significantly improve the average gas extraction concentration, and the maximum increase in the extraction net flow after fracturing is about 60% compared with that no fracturing, and can effectively suppress the attenuation of the extraction flow due to the extension of the extraction time, effectively improving the gas extraction effect of the test borehole. Simultaneously, if other auxiliary measures are implemented, the permeability enhancement effect may be more stable.

Tunable Hydrophobic Octadienyl-Ether Nanocelluloses by In Situ Ultrasonication for Reinforced Polymers and Water-Resistant Paper

One-pot syntheses and in situ ultrasonication have been optimized to generate tunable and highly hydrophobic 2,7-octadienyl-ether (ODE) cellulose nanofibrils (CNFs). Using only butadiene sulfone to serve as dual reaction medium and precursor to 1,3-butadiene (1,3-BD) for telomerization with cellulose hydroxyls, the OH-to-ODE conversion significantly improved from ca. 0.7 to 1.2, 1.8, 3.1, and 4.1 mmol of ODE/g-cellulose at 103–110 °C for 1–2 h. Ultrasonication was highly effective and versatile in the direct disintegration of ODE-cellulose (ODE-cell) in nonpolar organic solvents and plant oils into ODE-CNFs as well as pretreating cellulose for improved functionalization. Mixing 2 wt % in situ ultrasonicated 1.2 mmol of ODE/g-cell improved the modulus of polybutadiene six times and the strength of poly(styrene-b-isoprene-b-styrene) three times, whereas in situ ultrasonication of 1.8 mmol/g-cell directly with linseed oil at merely 0.07 wt % created holistic biobased hydrophobic cellulose paper to resist water penetration while also significantly improving the tensile strength. This optimized telomerization and streamlined in situ ultrasonication approach has presented a sustainable synthesis and processing strategy to generate highly hydrocarbon-compatible nanocelluloses previously unattainable.

Simulation of battery simultaneous cooling based on the dual fluid medium system

The battery thermal management system (BTMS) based on refrigerant cooling can cope with high battery heat production even in the case of high ambient temperature, but the economy is poor. A novel BTMS called dual flow medium system (DFMS) had been proposed in previous studies to improve the economy of refrigerant-based BTMS, including refrigerant and coolant in parallel for battery cooling. Based on a validated simulation system, this study presents and analyzes a new operation mode of the DFMS called simultaneous cooling, in which the refrigerant and coolant cool the battery simultaneously. First, the transient cooling process was studied under different ambient temperatures, compressor speeds, and coolant flow rates. The results show that simultaneous cooling can reduce the average battery temperature by 2.66 °C more than using only refrigerant for battery cooling, and the maximum temperature difference between batteries can reach 0.33 °C. Then different coolant flow control methods are proposed and compared under the premise of constant temperature mode. The results show that compared with only refrigerant cooling, the optimal coolant flow control method can reduce the maximum temperature difference between the batteries by 31.94 % but with an extra 2.24 % power consumption.

Study on Gas Migration Mechanism and Multi-Borehole Spacing Optimization in Coal under Negative Pressure Extraction

In order to study the gas migration in gas-bearing coal, and reasonably arrange gas drainage boreholes to improve the efficiency of gas drainage, a gas-solid coupling model is established based on the pore-fracture dual medium porous model. The solid deformation of coal body, gas seepage and diffusion, and gas adsorption and desorption are considered in this model. The COMSOL software is used to simulate the gas change in the coal matrix and coal fracture under single borehole extraction. We analyze the effective extraction range and study the migration mechanism of gas between coal fracture and borehole, coal matrix and coal fracture, and coal matrix. The effective extraction area of multi-borehole negative pressure gas extraction varies with extraction time and borehole spacing. At 140 d, the effective extraction radius is r = 1.3 m, and the spacing of boreholes is 233 r=1.5 m, 2 r=2.6 m,4 m,5 m,and 6 m, respectively. The influence of the equilateral triangle shape of three boreholes on the gas extraction effect is studied. The simulation results show that when three boreholes are extracted for 140 days under different borehole spacing, different gas extraction effects will be affected by a superposition effect. Considering the change in gas pressure, the effect of gas extraction in the effective extraction area, and the safety and cost performance of gas extraction, it is concluded that the optimal hole spacing is 5 m around 140 d. This study aims to provide reference for underground gas drilling layout and reasonable hole spacing.

FRACTAL ANALYSIS FOR THERMAL CONDUCTIVITY OF DUAL POROUS MEDIA EMBEDDED WITH ASYMMETRIC TREE-LIKE BIFURCATION NETWORKS

Heat transport in tree-like bifurcation networks has been widely studied in various fields. In this work, we investigate heat conduction in the dual porous media embedded with asymmetric tree-like bifurcation networks. In addition, considering the effects of nonuniform tube shape, we assume that the bifurcated tube shows sinusoidal fluctuations. Based on the fractal distribution of pore size and bifurcation structure, we established a dimensionless effective thermal conductivity (ETC) model of the dual porous media. The dimensionless ETC ([Formula: see text] obtained is related to the porosity ([Formula: see text], the fluid–solid thermal conductivity ratio ([Formula: see text], the pore area fractal dimension [Formula: see text] and the structural parameters of the bifurcation network (bifurcation level [Formula: see text], length ratio [Formula: see text], radius ratio [Formula: see text], fluctuation amplitude factor [Formula: see text], bifurcation angle [Formula: see text]. To verify the validity of this model, a comparison of the present dimensionless ETC model with available experimental data was carried out and the results were in good agreement. We have discussed the effects of each parameter on the dimensionless thermal conductivity in detail and constructed parametric planes to evaluate the structural parameters more directly. The model has positive implications for revealing the heat transport mechanism in asymmetric tree-like bifurcation dual porous media.