Drop Distribution Research Articles

A MINI REVIEW ON THE EFFECTS OF SURFACE ROUGHNESS IN MICROFIUIDICS CHANNELS

The effects of surface roughness at low Reynolds numbers are more pronounced and critical in microchannels due to the relative size of roughness to channel dimensions. Surface roughness in microfluidic channels originates from the machining process during fabrication. This review examines how surface roughness, resulting from various manufacturing processes, influences the performance of microfluidic devices. Different patterns of surface roughness generated through techniques such as photolithography, etching, precision machining, and 3D printing are highlighted. These techniques yield distinct surface characteristics that affect critical microchannel properties, including fluid flow, pressure drop, and stress distribution. In addition to that, specific fabrication methods can minimize surface roughness, enhancing the performance of microchannels for applications in diagnostics, lab-on-a-chip systems, and small-scale heat exchangers are addressed. The review provides insights into selecting optimal fabrication techniques to achieve desired performance characteristics in microfluidic devices.

COMPARING THE HYDRODYNAMIC CHARACTERISTICS OF A STANDARD AND A 3D-PRINTED PACKING IN A ROTATING PACKED BED

As rotating packed beds (RPBs) gain prominence in intensified mass transfer operations, efficient packing design is critical for optimizing performance. Traditional packing structures often face limitations in terms of pressure drop, wetting efficiency, and fluid distribution. 3D-printed packings offer new possibilities by allowing complex geometries tailored to specific fluid dynamics. This study presents a detailed comparison of the performance of standard wire mesh packings and an anisotropic 3D-printed packing, focusing on pressure drop variations under varying operational conditions. Compared to the standard packing, the hydrodynamic performance of the 3D printed packing showed a lower pressure drop of about 0.7kPa at the combination of maximum operating conditions investigated of 300Nm3/h, 1000 rpm, and 0.72m3/h in the gas flow, rotation speed, and liquid glow rate respectively. The wet pressure drop per unit packing length of the 3D packing compared favourably with the standard wire mesh packing. The 3D-printed RPB packings proved to be a promising way that has the potential to enhance the separation performance of RPBs.

Optimizing Well Trajectories for Enhanced Oil Production in Naturally Fractured Reservoirs: Integrating Particle Swarm Optimization with an Innovative Semi-Analytical Model Framework

Summary Well trajectory optimization is a crucial component in the drilling engineering of naturally fractured reservoirs. The complex heterogeneity and anisotropy of such reservoirs significantly affect the pressure drop distribution within the well and, consequently, the oil well’s output, impacting the economic benefits of the well. Therefore, optimizing the well segment trajectory is key to efficient reservoir development. However, traditional well trajectory optimization methods primarily focus on geological structures and drilling engineering costs, often overlooking future production benefits of the oil well. This paper proposes a new method that first establishes a semi-analytical production prediction model capable of describing complex well trajectories. Although the semi-analytical model has unique advantages in well trajectory description, it typically treats the reservoir as a homogeneous entity, which complicates handling complex reservoir characteristics. To overcome this limitation, we combined optimization algorithms and neural networks to construct a framework for addressing reservoir heterogeneity (Semianalytical Model Framework for Unconventional Wells in Heterogeneous Reservoirs, USAMF-HR), enhancing the semi-analytical model’s ability to describe reservoir heterogeneity. Building on this framework, we applied the particle swarm optimization (PSO) algorithm and introduced constraints on the rationalization of initial well trajectories, as well as limits on particle movement speed and displacement, with the maximization of net present value (NPV) as the objective function, to optimize well trajectory coordinates. Through specific case analysis, the reasonableness and practicality of this method have been verified. The results show that this method can quickly and effectively plan the optimal well trajectory, significantly increasing productivity while reducing costs.

Synergistic effects of mediated by different 1,2-epoxybutane addition numbers butoxylated alkyl block alcohol ethers and SDS in mixed systems

In this study, nonionic surfactant butoxylated alkyl block ether (AE9Bn) and anionic surfactant sodium dodecyl sulphate (SDS) with different BO additions were mixed at different molar ratios to make a hybrid system. The interaction parameters and aggregation behaviors of the blended systems were investigated by observing the average direct particle drop distribution and microscopic aggregates in combination with the results of static surface tension tests of the blended systems. The diffusion process of the mixed systems was investigated using dynamic surface tension tests. The dynamic contact angle and foam properties of the solutions of the mixed systems were also studied. Finally, based on the experimental results, it was concluded that the mixed system of AE9Bn (n=2,5) and SDS formed a synergistic effect that significantly led to a decrease in CMC, with an increase in the number of BO additions leading to a more significant decrease in CMC. The mixed system is a non-ideal mixed system, which is consistent with the kinetic mechanism of mixing and diffusion. The hybrid system has good aggregation pattern and wetting diffusion behavior and has low foam stability due to slow maturation of Ostwald.

CFD-DEM simulation study on the bed dynamics of a binary mixture with super-quadric particles in a fluidized bed

In biomass thermal conversion processes such as pyrolysis and gasification, biomass often takes on a cylindrical shape. However, most previous studies have modeled biomass as spherical, leaving the fluidization and mixing behaviors of non-spherical biomass particles with approximately spherical bed materials insufficiently explored. To bridge this gap, a super-quadratic particle model coupled with CFD-DEM was used to explore the fluidization characteristics and mixing dynamics of non-spherical binary mixtures. The numerical model successfully validated the pressure drop and spatial distribution within the binary mixture. The results indicate that particle mixing is primarily driven by the rise and movement of bubbles. The large aspect ratio of the cylindrical particles, combined with the narrow thickness of the 2D rectangular fluidized bed, leads to a significant interlocking effect during fluidization. This interlocking hinders both fluidization and mixing, resulting in poor overall performance for non-spherical particles. At a low superficial velocity (Ug), only the cylindrical particles in the lower part are fluidized as a result of the rising central bubble. The two particle types achieve effective mixing as the Ug rises to a high value. The mixing index increases from 0.78 to 0.94 as the Ug increases from 1.8 to 2.1 m/s. However, the stacking pattern of cylindrical particles creates a dead zone at the bed bottom, occupied solely by spherical particles, which limits local bed mixing and fluidization. As the Ug increases from 1.8 to 2.1 m/s and the dimensionless inventory height increases from 0.6 to 1.0, the axial dispersion coefficient of the cylinders increases from 1.17×10−3 to 4.35×10−3 m2/s and from 1.91×10−3 to 9.22×10−3 m2/s, respectively. This study provides new insights into the behavior of non-spherical particles, offering potential avenues for optimizing chemical engineering processes.

A novel tetra hybrid bio-nanofluid model with stenosed artery

Abstract For treating and diagnosing cardiovascular diseases, the field of biomedical engineering is significant because it develops new ways and techniques. Stenosis is the narrowing of an artery, and it leads reduction in the flow rate of blood. This study investigates the blood flow mechanism in an artery using a mathematical model of Carreau nanofluid with four distinct nanoparticles. Tetra nanofluid model produces significant advancement in the simulation of blood flow through the stenosed arteries. The model is capable of predicting the pressure drop and velocity distribution for diagnosing and treating stenosis. The spectral relaxation approach is used to present the model's efficiency and effectiveness, which makes it a suitable method for solving the governing equations of this study. The findings of this study have important implications for the development of new treatments and diagnostic techniques for stenosis and other cardiovascular diseases.

Performance evaluation of different new channel box photovoltaic thermal systems

Current research has highlighted three major gaps in the literature: (a) a rarity of studies on photovoltaic thermal systems with channel boxes, (b) a lack of data on pressure drop and surface temperature distribution in these systems, and (c) absence of analysis regarding the impact of materials (metals and polymers) used in photovoltaic thermal systems on performance, cost, payback time and weight. The novelty of this paper lies in addressing these gaps by studying a new channel-box photovoltaic thermal system, varying the number of channels and the height of the collectors that distribute water to these channels, in order to identify the most efficient design in terms of electrical, and thermal efficiency as well as pressure drop. In addition, the impact of different heat exchanger materials (metals and polymers) on the performance, cost, payback time, and weight of photovoltaic thermal systems was investigated. 3D numerical simulations were carried out using COMSOL Multiphysics software, based on the finite element method, and validated by outdoor experimental research. The results show that the photovoltaic thermal system 8 design performs best, with a total efficiency of 89.42%. In addition, the aluminum photovoltaic thermal system stands out as the most cost-effective option, with a payback time of 0.823 y (300 d) and annual savings of $459.262, while being 38% lighter than the copper system. Based on this study, it is recommended that the photovoltaic thermal system 8 be implemented because of its exceptional performance and ease of implementation.

Linking the spatiotemporal distribution of static stress drops to source faults in a fluid-driven earthquake swarm, northeastern Noto Peninsula, central Japan

We investigated stress drops during an earthquake swarm in northeastern Noto Peninsula, central Japan, which is characterized by ongoing seismic activity in four clusters. We focused on the spatiotemporal distribution of the static stress drop and its relationship with the source faults of the earthquake swarm. Employing the empirical Green’s function method, we estimated static stress drops for 90 earthquakes of MJMA 3.0–5.4. We obtained logarithmic mean stress drops of 13 MPa and 19 MPa from P-wave and S-wave analyses, respectively, which were typical values for crustal earthquakes. We comprehensively analyzed the spatiotemporal distribution of static stress drops in the northern cluster due to the abundance of available data and clarity of fault structures there. We observed larger static stress drops for earthquakes along shallow portions of the source faults, as defined by the hypocentral distribution during a given period. Conversely, we observed smaller static stress drops for earthquakes at medial parts along the faults. These results suggest higher fault strength at shallower parts along the faults and reduced fault strength at medial parts. We attribute the high fault strength at shallow parts to low pore fluid pressure after only limited fluid diffusion near the fault terminus. In contrast, we attribute the reduction in fault strength at medial parts to high pore fluid pressure within the fault following penetration by migrating fluids.Graphical

CFD modeling of gas–solid flow in a two‐stage jetting fluidized bed with an overflow standpipe

AbstractThe two‐fluid model–kinetic theory of granular flow (TFM–KTGF) model and the sub‐grid‐scale (SGS) model are used to conduct a three‐dimensional numerical simulation study on the hydrodynamic characteristics of a two‐stage fluidized bed with an integrated overflow pipe. Using various drag models, the gas–solid flows, bed expansions, pressure drop distributions, and equilibrium conditions in the two‐stage bed are compared, and the conditions for the formation of a stable overflow in the two‐stage bed are thoroughly investigated. In addition, during the simulation of the secondary distribution in the bed, the porous media model simulates the momentum loss caused by the redistribution plate to avoid the direct simulation of the redistribution plate, which requires extensive grid division work and calculation costs. This work can provide technical direction for the industrialization of one‐step coal to multistage fluidized bed natural gas technology.

Fracture Properties of Nitrogen–Slick Water Composite Fracturing in Coal Reservoir

Nitrogen–slick water composite fracturing is a novel, recently developed fracturing technology. Due to its impact on increasing permeability, this technology outperforms hydraulic fracturing. This study adopted the horizontal well XJ-1L, Xinjing coal mine, Qinshui Basin, China, as a study area to statistically analyze the fracture properties, stress drop, and b-value distribution characteristics of 1217 effective micro-seismic events generated during nitrogen–water composite fracturing. The results show that: (1) gradually reducing the proportion of gas in fracturing fluid reduced the proportion of tensile fractures at a ratio of between 15.6% and 0.8%, whereas the proportion of strike-slip fractures gradually increased by between 1.6% and 15.2%; (2) the stress drop and b-values in the nitrogen fracturing (NF) stage, representative of stress disturbance, exceeded those in the hydraulic fracturing (HF) stage, consistent with greater numbers of tensile fractures formed in the NF stage; (3) the greater number of tensile fractures and their increasing permeability could be explained based on the influences of gas compressibility and pore pressure on coal fractures. This study provides a theoretical and practical basis for optimizing the exploitation of low-permeability coal reservoirs.

Quantitative Analysis of the Synergy of Doping and Nanostructuring of Oxide Photocatalysts.

In this paper, the effect of doping and nanostructuring on the electrostatic potential across the electrochemical interface between a transition metal oxide and a water electrolyte is investigated by means of the Poisson-Boltzmann model. For spherical nanoparticles and nanorods, compact expressions for the limiting potentials at which the space charge layer includes the whole semiconductor are reported. We provide a quantitative analysis of the distribution of the potential drop between the solid and the liquid and show that the relative importance changes with doping. It is usually assumed that high doping improves charge dynamics in the semiconductor but reduces the width of the space charge layer. However, nanostructuring counterbalances the latter negative effect; we show quantitatively that in highly doped nanoparticles the space charge layer can occupy a similar volume fraction as in low-doped microparticles. Moreover, as shown by some recent experiments, under conditions of high doping the electric fields in the Helmholtz layer can be as high as 100 mV/Å, comparable to electric fields inducing freezing in water. This work provides a systematic quantitative framework for understanding the effects of doping and nanostructuring on electrochemical interfaces, and suggests that it is necessary to better characterize the interface at the atomistic level.

Study on the uniform flow in adsorption device with perforated plate distributor

The adsorption device is widely used in the purification of impurity-containing wastewater, which is of great significance. However, the problem of non-uniform distribution of liquid in the packed bed has a large impact on the adsorption process. In the current study, CFD is used to simulate the fluid flow state during the adsorption process based on the physical modelling of the adsorption device, where the packed bed is modelled as a porous medium. By studying the effect of hole distribution, perforation rate, thickness and installation position of the perforated plate on flow uniformity and bed pressure drop, the influencing factors affecting the uniform distribution of fluid and pressure drop are discussed. Results show that changing the hole array did not have a significant effect on the fluid uniformity. When the perforation rate of the distributor is 15–29.4 %, the pressure drop is smaller and the flow distribution uniformity is better. The non-uniformity of flow field decreases first and then increases continuously with the increasing of the thickness. When the thickness of the perforated plate is between 10 and 30 mm, the overall performance is the best. Increasing the distance between the perforated plate and the inlet can reduce the impact strength of high-speed fluid on the perforated plate and improve the flow uniformity and increasing the inlet flow rate of the fluid can improve the uniformity of the flow field within a certain range, but it will increase the fluid flow loss.

Mass transfer of gas–liquid two‐phase flow in asymmetric parallel microchannels with liquid feed splitting

AbstractDue to size limitations, the gas–liquid absorption capacity of a single microchannel is limited, making it difficult to achieve large‐scale CO2 capture. Therefore, the parallel microchannels combining the advantages of high efficiency and large throughput stand out. However, when the operating condition is high gas–liquid flow rate ratio, the liquid phase between bubbles almost disappears after multiple distributions, which affects the amount of gas–liquid absorption. In this study, the numbering‐up of the asymmetric parallel microchannels in the gas–liquid absorption process was investigated by splitting the liquid feed stream in two. The flow patterns under different operating conditions were obtained. The flow and distribution of gas–liquid two‐phase flow were investigated, and the reason of the distribution deterioration caused by appearance of long slug bubbles was explained by the pressure drop distribution. The total liquid mass transfer coefficient and bubble residence time were derived and obtained, and the mass transfer was further discussed.

Different earthquake nucleation conditions revealed by stress drop and b-value mapping in the northern Chilean subduction zone

Stress drop is an earthquake property indicative for the characteristic relation of slip to fault dimension. It is furthermore affected by fault strength, fault topography, the presence of fluids, rupture size, slip, and velocity. In this article, the stress drop image of an entire subduction zone, namely for the seismically highly active northernmost part of Chile, is combined with mapped b-values and their corresponding magnitude distribution in order to better constrain the conditions under which earthquakes of different provenances may nucleate. The underlying recent earthquake catalog contains over 180,000 events, covering 15 years of seismicity, from which more than 50,000 stress drop estimates were computed. Their spatial average segments the subduction zone into different parts, i.e., average stress drop between seismotectonic areas is different, although this difference is small compared to the natural scatter of stress drop values. By considering stress drop variations, b-value map, magnitude distribution, and thermal models, candidate earthquake nucleation mechanisms are identified which can explain the observed distributions. This is done for two exemplary regions: (1) The plate interface, where principally lower stress drop events are found, while at the same time a high spatial heterogeneity of stress drop values is observed. This indicates relatively smooth or lubricated rupture surfaces, and locally it suggests the existence of alternating regions controlled by strong asperities, weaker material, or creep. (2) The highly active intermediate depth (ID) seismicity region, where the variation of stress drop and b-value point to a gradual change of nucleation mechanism from dehydration embrittlement at the top of the ID cloud, over dehydration driven stress transfer in its central part, to thermal runaway shear mechanisms at its bottom. In both cases, the combination of stress drop and b-value distribution helps to better understand the origin and the differences of the observed seismicity.

Flow dynamics through cellular material based on a structure with triply periodic minimal surface

Triply Periodic Minimal Surface (TPMS)-based cellular structures are widely adopted due to their high surface-to-volume area, superior mechanical characteristics, and adaptive properties. This paper is dedicated to deriving a new semi-empirical equation for pressure drop in TPMS-based structures (specifically Schwarz-P, Schoen I-WP, Neovius). Both numerical and experimental tests were conducted to analyze the impact of TPMS parameters on pressure drop and velocity distribution. It was determined that flow through the Schwarz-P structure exhibits a tubular flow pattern, flow through the Neovius structure demonstrates active flow mixing, and flow through the Schoen I-WP structure does not have stagnant (dead) zones. A novel semi-empirical equation was formulated to calculate pressure drop as a function of flow parameters and TPMS-based structure parameters. This equation incorporates both viscous resistance (Δp=f(v)) and kinetic energy loss (Δp=f(v2)), enabling its application for predicting pressure drop across a wide range of practically interesting operational parameters.

MAINTAINING GAS RECOVERY IN LOW-PERMEABILITY FORMATIONS

The purpose of this work was to ensure efficient gas production in low-permeability and heterogeneous formations by numerically modeling the distribution of reservoir pressure drop around production and injection wells. To investigate this goal, we used a simulation based on the combined finite-element-difference method for nonstationary Leibenson piezoelectric conductivity problems. The method is based on the combination of elements of the already known finite difference and finite element methods for the nonstationary piezoelectric conductivity problem. The study found that there are many factors that affect the process of maintaining gas production in poorly permeable areas of a gas-bearing formation. Among them, first of all, after increasing the permeability of the corresponding section of the reservoir where production is created. Another important factor for maintaining gas recovery is the ability to naturally or artificially maintain gas phase infiltration within the affected reservoir area. This aspect is especially important for ensuring stable gas recovery over a long period of operation. During the intensive and long-term operation of the working area of the gas-bearing formation, additional injection wells were installed in the complex of production wells to avoid its depletion. It is important to note that provided a high level of gas phase penetration at the beginning of field operation, other factors of the production process, such as additional production wells and infiltration within the working area, have a lesser impact on the overall pressure distribution in this area. Thus, the study shows that with the passage of time and prolonged operation of the working section of the reservoir, the influence of its penetration decreases, but the importance of injected substances in the injection wells and gas phase infiltration within this section of the reservoir increases.

Numerical and experimental investigation of heat transfer enhancement in double tube heat exchanger using nail rod inserts

The Double-tube heat exchanger (DTHX) is widely favored across various industries due to its compact size, low maintenance requirements, and ability to operate effectively in high-pressure applications. This study explores methods to enhance heat transfer within a DTHX using both experimental and numerical approaches, specifically by integrating a nail rod insert (NRI). A steel nails rod insert, 1000 mm in length, is introduced into the DTHX, which is subjected to turbulent flows characterized by Reynolds numbers ranging from 3200 to 5700. Three different pitches of NRI (100 mm, 50 mm, and 25 mm) are investigated. The results indicate a significant increase in the Nusselt (Nu) number upon the insertion of nail rods, with further improvements achievable by reducing the pitch length. Particularly noteworthy is the Nu number enhancement ratio for the 25 mm pitch NRI, which is 1.81–1.9 times higher than that for the plain tube. However, it is observed that pressure drop increases in all configurations with NRI due to heightened turbulence and obstruction by the NRI. Among the various pitch lengths, the 25 mm pitch exhibits the highest pressure drop values. Moreover, exergy efficiency is found to improve across all cases with NRI, corresponding to increased heat transfer, with the 25 mm pitch length showing a remarkable 128% improvement. Numerical analysis reveals that the novel insert enhances flow turbulence through the generation of secondary flows, thereby enhancing heat transfer within the DTHX. This study provides a comprehensive analysis, including temperature, velocity, and pressure drop distributions derived from numerical simulations.

Design and dynamic characteristics of automatic vertical drilling tool

Higher performance is needed in deeper and longer horizontal wellbore drilling. In vertical drilling conditions, wellbore trajectory often be led to deviation due to objective conditions. Based on the engineering issues, this paper presents a new automatic vertical drilling tool, including the innovative design and working mechanism research. This tool working mechanism are carried out, such as the mechanics model of eccentric tube and the relationships between eccentric torque and deflection angle. The eccentric tube torque increases with the wellbore deviation angle. When wellbore deviation angle is constant, the eccentric tube torque reaches maximum value when its deflection angle is 90°. The internal flow parameters are studied by fluid field simulation, such as drilling fluid flow rate, pressure drop, and pressure distribution inside this tool during downhole drilling process. The larger the diameter of switch hole, the higher is the pressure drop around, which leads to the force on push block increasing. The drilling fluid pressure increases with higher input flow rate inside this tool. The comparison of results, the data of simulation and theoretical model calculations, verified the reliability and accuracy of research. This study has provided innovative ideas and reference for drilling tool design and wellbore trajectory control methods.

Numerical investigation of mixing performance for a helical tangential porous tube-in-tube microchannel reactor

The tube-in-tube microchannel reactor (TMCR) is widely applied in chemical engineering and material industries. Two or more fluids are mixed in the annular channel of TMCR. This work aims to introduce a helical tangential porous tube-in-tube microchannel reactor (HTP-TMCR). The performance of HTP-TMCR is analyzed using computational fluid dynamics (CFD) method, focusing on three aspects: mixing index, pressure drop, and velocity distribution. Additionally, this study investigates the impacts of four geometric parameters, including left and right helical directions, pitch, pore size, and length of the non-porous zone, on the mixing performance of HTP-TMCR. The simulation results reveal that the mixing index initially decreases as the flow rate increases, reaching its lowest point (approximately 75%) at Q=2 L/h. Subsequently, there is a sharp rise to a second inflection point at Q=10 L/h, followed by a gradual progression stabilizing around 95%. Specifically, the left helical configuration demonstrates superior performance compared to the right one. Optimal mixing is achieved at low flow rates when the pitch is 4 mm and the pore size is 0.4 mm. Designing the length of the non-porous zone to be 5 mm is recommended. Furthermore, the characteristic of pressure drop for HTP-TMCR indicates its potential for commercial applications.

Numerical and experimental study on designs and performances of multi-serpentine flow field with bend-area block for proton exchange membrane fuel cell

The geometric modification of the flow field is an effective measure to improve the performance of proton exchange membrane fuel cell (PEMFC) and the mass transfer ability of reactants. In this paper, serpentine channels with geometric parameters containing various blocks to generate gas forced convection at the U-bends are established and numerically studied. Setting blocks at different angles at U-bends has different effects at the corners, offering a more flexible and variable region of active gas diffusion in the vertical direction. The area of high vertical velocity is increased by the Angle-Height combination design with low pressure drop and uniform temperature distribution. It is demonstrated that a vertical velocity of 0.4 m s−1 can be achieved around the block in the 135° series with half-height corner blocks, proving the existence of the mass transfer enhancement. Subsequently, experimental testing is conducted to verify the feasibility of the optimized flow field. The experimental results support the trend of block height influencing cell performance, with a maximum power density increase of 3.4 %. Modifying the U-bend corner structure has proven to be an effective technique for improving the overall performance of PEMFC, which can serve an important guidance for future flow field design.