Increasing Flow Rate Research Articles

Short-Term Flow Velocity Stress on the Behavioral, Physiological, and Biochemical Responses of the Large Yellow Croaker (Larimichthys crocea)

Flow velocity is a key environmental factor that affects the behavioral strategies and physiological homeostasis of fish. To study the effects of flow velocity on the behavioral changes and blood physiology of the yellow croaker, the behavioral patterns of yellow croakers in response to flow velocity stress were obtained by analyzing changes in tail wagging frequency and amplitude. Differences in blood glucose, lactate, and cortisol were compared to determine their appropriate flow rate ranges. The juvenile stage of the large yellow croaker is crucial, as environmental changes can affect the physiology of fish. Therefore, juvenile yellow croakers were selected as the experimental subjects for this study. Twenty-four healthy and uniformly sized large yellow croakers with body weights of (90.26 ± 9.91) g and body lengths of (19.91 ± 0.69) cm were randomly assigned to one control group and three experimental groups, with five fish in each group. The experimental group was set with three flow rates, namely 1 bl/s (20 cm/s), 2 bl/s (40 cm/s), and 3 bl/s (60 cm/s), with a flow rate stress duration of 1 h. The results showed that: (1) Under different flow velocities, the fish exhibited different tail wagging patterns. At low flow velocities, their tail fins exhibited a “C”-shaped swing, while at high flow velocities, their bodies exhibited an “S”-shaped swing. (2) Oscillation frequency and amplitude both increased with increasing flow velocity. At a flow velocity of 2 bl/s, the oscillation frequency significantly increased. When the flow velocity reached 3 bl/s, the oscillation amplitude significantly increased (p < 0.05). (3) Blood physiology showed significant changes with increased flow rate, and blood glucose content continuously decreased with increased flow rate, significantly decreasing at a flow rate of 2 bl/s (p < 0.05). Lactic acid and cortisol both increased with increasing flow rate, and significantly increased at a flow rate of 3 bl/s (p < 0.05). In summary, under high-flow velocity stress, significant changes occurred in the behavior and physiology of large yellow croakers, which were consistent with physiological changes in the blood. A flow rate higher than 2 bl/s can lead to intense swimming behavior, decreased blood sugar concentration, and increased lactate accumulation and stress levels. Therefore, the short-term tolerance of yellow croakers is 2 bl/s, and a flow rate of 1 bl/s is more suitable.

Study of municipal solid waste treatment using plasma gasification by application of Aspen Plus

Abstract Plasma gasification is a viable and efficient technique for handling solid waste, including hazardous waste, while also holding the potential for energy recovery. The objective of this study is to analyze the treatment of municipal solid waste (MSW) using plasma gasification by application of Aspen Plus software. An earlier proposed model was used to analyze the effect of employing different types of gasifying agents as plasma gas, on the composition of syngas produced. The lower heating value, cold gasification efficiency and carbon conversion efficiency were calculated and compared in each case. A sensitivity analysis study was also carried out to observe the effect of variation in plasma gas flow rate and feed flow rate on the composition of syngas generated. The capital, operational and maintenance costs of the process were determined using existing correlations. For a feed rate of 20,000 kg per hour of MSW, the highest yield of syngas (CO (33.48 %), and H2 (34.30 %) with the highest LHV (7.9 MJ/N-m3)) were produced when air was employed as plasma gas. The cold gas efficiency and the carbon conversion efficiency were at their peak when air was used as the gasifying agent. The sensitivity analysis revealed that as the flow rate of plasma gas increases syngas production decreases while the increase in MSW flow rate results in an increase in syngas production. Additionally, the cost analysis revealed that for a plasma gasification plant that can handle 500 tons of MSW per day, the estimated capital and annual operational and maintenance costs are $125,496,721 and $9,833,892 respectively.

Hydrogen and Solid Carbon Production via Methane Pyrolysis in a Rotating Gliding Arc Plasma Reactor.

Plasma-induced methane pyrolysis is a promising hydrogen production method. However, few studies have focused the decomposition of pure methane as a discharge gas. Herein, a rotating gliding arc reactor was used for the conversion of methane (discharge gas and feedstock) into hydrogen and solid carbon. Methane conversion, gaseous product selectivity, and energy usage efficiency(specific energy requirement for hydrogen production(SER)) were investigated as functions of operating parameters, e.g., specific energy input(SEI), residence time, and reactor design. SEI was positively(almost linearly)correlated with methane conversion and hydrogen yield and negatively correlated with SER. Conversion and efficiency of energy usage increased when reactor designs providing higher thermal densities were used. With the increasing flow rate of methane at constant SEI, the reaction volume and, hence, the residence time of the gas inside the reaction zone increased, which resulted in methane conversion and hydrogen selectivity enhancement. The solid carbon featured four distinct domains, namely graphitic carbon, turbostratic carbon, few-layer graphene, and amorphous carbon, which indicated a nonuniform temperature distribution in the reaction zone. But it seems that graphitic carbon dominates amorhphous one. This study highlights the potential of rotating gliding arc plasma systems for efficient methane conversion into hydrogen and valuable solid carbon products.

Targeting Full-Hydrogen Operation on Industrial-Scale Gas Turbines: Impact of Unconventional Fuels on Turbine Module Performance and Aeromechanics

Abstract With the trend to full decarbonization, a full hydrogen economy development is a key industrial objective. Gas turbines, currently one of the cleanest fossil fuel-based power generation solutions, provide reliable and on-demand power. The introduction of hydrogen into the fuel mix of existing gas turbines represents a solution with great potential to provide low-carbon or even carbon-free energy. High-hydrogen content fuels, however, challenge the efficient operation of the gas turbine expander, as crucial aspects such as increased flow rate, different gas properties and temperature operating range may affect performance and structural integrity. To evaluate the impact of this conversion, a numerical investigation of five cases with increasing percentages of hydrogen in the fuel was carried out for an industrial four stages gas turbine module. The variation of turbine inlet temperature distribution from combustion chamber was considered, to assess the impact of the unconventional fuel on the well-known aeromechanical behavior of the last stage blades. Variations in capacity, efficiency, power and potential limits due to aeroelasticity were evaluated, identifying the most relevant differences with respect to the full methane case. All these analyses confirm the possibility to employ high-hydrogen fuel operation in a current gas turbine without the need of a further redesign, while maintaining acceptable performance levels.

Impact of hydrothermal aging on microstructure transformation in Poly(L‐lactide) nonwovens under tension in condition close to a living organism

AbstractThe analysis of mechanical properties and structure of bioresorbable polymer nonwoven materials is an important area of research in the medical industry, the properties and structure of which directly affect the processes of cellular activity. In this work, the processes of reorganization of the fibrous microstructure of poly(l‐lactide) nonwoven materials under uniaxial tension in a water environment were investigated. The study which included volumetric ultrasound imaging, mechanical testing, differential scanning calorimetry, X‐ray diffraction, and melting rate measurements was the first attempt to identify correlations between the mechanical behavior of fibrous meshes and changes in the supramolecular structure of the polymer during 3 months of hydrothermal aging T = 37°C. An increase in crystallinity by 4%, a shift of glass transition temperature by 4°C, and a 2 times increase in melt flow rate under hydrolysis were indicated degradation of the amorphous phase. Local degradation of the amorphous phase of fibers led to the formation of surface cracks, an increase in the number of microcracks during hydrothermal aging resulted in a decrease in the mobility of fibers in the volume of the nonwoven material and a decrease in the elasticity of the entire nonwoven material, which was revealed using the volume ultrasound imaging and optical microphotographs.

Advanced Control Scheme Optimization for Stand-Alone Photovoltaic Water Pumping Systems

This study introduces a novel method for controlling an autonomous photovoltaic pumping system by integrating a Maximum Power Point Tracking (MPPT) control scheme with variable structure Sliding Mode Control (SMC) alongside Perturb and Observe (P&O) algorithms. The stability of the proposed SMC method is rigorously analyzed using Lyapunov’s theory. Through simulation-based comparisons, the efficacy of the SMC controller is demonstrated against traditional P&O methods. Additionally, the SMC-based system is experimentally implemented in real time using dSPACE DSP1104, showcasing its robustness in the presence of internal and external disturbances. Robustness tests reveal that the SMC controller effectively tracks Maximum Power Points (MMPs) despite significant variations in load and solar irradiation, maintaining optimal performance even under challenging conditions. The results indicate that the SMC system can achieve up to a 70% increase in water flow rates compared with systems without MPPT controllers. Furthermore, SMC demonstrated high sensitivity to sudden changes in environmental conditions, ensuring efficient power extraction from the photovoltaic panels. This study highlights the advantages of integrating SMC into Photovoltaic Water Pumping Systems (PV-WPSs), providing enhanced control capabilities and optimizing system performance. The findings contribute to the development of sustainable water supply solutions, particularly in remote areas with limited access to the electrical grid.

Efficiency Improvement on Indium Tin Oxide Films for Dye-Sensitized Solar Cell Using Oxygen Plasma by Bias-Magnetron RF Sputtering Process

Dye-sensitized solar cells (DSSCs) are among the most widely studied thin-film solar cells because of their cost-effectiveness, low toxicity, and simple fabrication method. However, there is still much scope for replacing current DSSC materials due to their high cost, low volume, and lack of long-term stability. Accordingly, indium tin oxide (ITO)-nanorod films were fabricated by electron (E)-beam evaporation using the glancing angle deposition method in this study. Then, the ITO-nanorod was treated with oxygen plasma via a bias-magnetron radio-frequency (RF) sputtering process to improve the efficiency of DSSCs under a varying gas flow rate of 20, 40, 60, 80, and 100 sccm. The field emission scanning electron microscopy (FE-SEM) investigation of the ITO film structure revealed that the obtained nanorod structures have slightly different diameters. At the same time, an increase in the oxygen flow rate resulted in a rougher film surface structure. In this, the lower sheet resistance was received because of rougher morphology. When comparing the DSSCs efficiency (η) test results, we found that at a gas flow rate of 100 sccm, the highest efficiency value showed 9.5%. On the other hand, the ITO-nanorod without plasma treatment exhibited the lowest η. Hence, plasma technology can be practically applied to improve the η of DSSC devices. This study will be a prototype of a highly advanced solar cell manufacturing method for the solar cell industry.

A new method to improve the thermal performance of high-level water collecting cooling tower based on the migration of vortices

This study proposes a novel annular inlet hat structure designed to address internal vortex flow within high-level water collecting cooling towers (HCTs). To investigate the effect mechanism of inlet hat, a three-dimensional numerical model for an HCT equipped with inlet hat was developed, allowing for a comprehensive analysis of the flow and temperature fields, as well as several performance parameters. The results manifest that the inlet hat strengthens the tower thermal performance by migrating the longitudinal vortices from the interior to the exterior and reducing the number of longitudinal vortices induced by crosswinds. The strengthening effect of inlet hat shows minimal variation when its width exceeds 8 m. Under the studied water flow rates, an 8-m inlet hat results in increases in air mass flow rate, water temperature drop, Merkel number, and evaporation rate by a maximum of 4.3 %, 4.2 %, 6.4 %, and 1.5 %, respectively. In terms of crosswinds, the inlet hat operates with optimal efficiency at a direction of 0° and a velocity of 13 m/s, achieving maximum increases in air mass flow rate, water temperature drop, and Merkel number of 23.3 %, 25.4 %, and 33.6 %, respectively. These findings demonstrate the feasibility and practical value of the proposed inlet hat.

Flow characterization and structural alterations in Ahmed glaucoma FP7 tubes after in-vitro aging in silicone oil.

Patients with intraocular silicone oil (SO) display higher odds of surgical failure after Ahmed glaucoma valve (AGV) implantation compared to patients without SO. However, the structural impact of SO exposure on silicone-made AGV tubes and the resulting changes in flow rate remain unexplored. This in-vitro study evaluated changes in tube dimensions and flow rates of AGV FP7 tubes after SO exposure to inform clinicians how such changes may impact AGV functionality. AGV FP7 tube segments underwent accelerated aging to approximate 90 days of exposure to the following media: Balanced Salt Solution (BSS), 1000 centistokes (cs) SO, and 5000cs SO. Tube dimensions were measured before and after aging. A constant gravity flow test setup was created to measure flow rates through tubes before and after aging. The students' T-test was used to compare the mean change between groups post-aging. Post-exposure, 1000cs and 5000cs SO tube segments increased in length by 5.94% and 5.55%, respectively, compared to 0.38% of BSS tubes (P < 0.05 for both). The inner lumen area expanded for tube segments in 1000cs and 5000cs SO by 11.75% and 2.70%, respectively, but contracted for tubes in BSS by -2.70% (P < 0.01 and P = 0.068 for 1000cs and 5000cs SO, respectively). Post aging, the flow rates increased on average by 61.0% and 98.6% for 1000cs and 5000cs SO, respectively, whereas flow rates for BSS tube segments slightly decreased by -4.92%. The difference was statistically significant for BSS vs. SO groups (P < 0.01 for both). Prolonged exposure to SO structurally altered the AGV FP7 tube segments by expanding their cross-sectional area, potentially leading to increased flow rates. These results may inform clinicians about potential in-vivo interactions in patients with the simultaneous presence of glaucoma drainage devices and intraocular SO.

Study on the characteristics of cavitation and COD removal of an addendum rotational hydrodynamic cavitation reactors

AbstractThis paper presented an addendum rotational hydrodynamic cavitation reactors (ARHCR) that enabled circumferential shear cavitation, axial cavitation, and the Venturi effect, thus increasing cavitation efficiency. The experiments on hydroxyl (·OH) release and chemical oxygen demand (COD) removal demonstrate the feasibility of cavitation performance characterization and COD removal rate. The findings indicate that the COD removal rate can reach a maximum value of 28% or 30% with an increase in flow rate or rotating speed, respectively. Specifically, the maximum values were achieved at a rotation speed of 2,500 rpm or a flow rate of 1.0 m3·h−1. Based on the mechanism of the addendum cavitation, the wedge angles, and the crucial structural parameters, were examined for optimizing cavitation performance. The results revealed that the cavitation number and cavitation bubble were significantly influenced by wedge angles, as well as the efficiency of cavitation energy. The mechanical shear of fluid was enhanced by wedge angles, resulting in constant compression and release of fluid with increased kinetic energy. This led to stronger effects on bulge blocks, and the formation of vortexes that rebounded constantly, resulting in lower pressure areas and expanded regions of cavitation. Among the wedge angles tested, the wedge angle of 15° exhibited the highest cavitation bubbles with a maximum value of 46%. This was 31% higher than the grooves‐type cavitator reported. Furthermore, the cavitation performance was extremely improved with a wedge angle of 15°, as corresponding with the maximum efficiency of cavitation energy. These explorations provide references for the removal of COD in industrial and agricultural wastewater, as well as the development of novel reactors for wastewater treatment.

Effects of Tube Diameter and Gas Flow Rate on the Discharge Dynamics Characteristics and Reactive Species of Nanosecond Pulsed Discharge Plasma in Contact With Water

ABSTRACTThe use of millimeter quartz tubes to generate non‐thermal plasma in contact with liquid is widely applied in medicine, such as the effective disinfection of catheter tubes and tooth cavities. Here, the effects of tube diameter and gas flow rate on discharge dynamics and reactive species characteristics of nanosecond pulse needle‐water discharge are studied using an ICCD camera and optical emission spectra. The discharge diffusion is increased significantly by an appropriate combination of tube diameter and gas flow rate. Besides, the discharge intensity, emission spectra intensities of reactive species, gas temperature, and electron density increase with the increase of quartz tube diameter and gas flow rate, which contributes to enhance the production of OH and H2O2 species in aqueous samples.

Thermochemical heat storage and material behavior of calcium hydroxide fine powder in a fluidized bed reactor

The Ca(OH)2/CaO reaction has attracted much attention in thermochemical heat storage. However, commercial Ca(OH)2 is usually offered as a fine powder that tends to agglomerate in the fluidized bed and affects heat storage performance. The experimental study on these issues is incomplete. In this paper, a fluidized bed thermochemical heat storage test system is built to study the heat storage and release process of Ca(OH)2 fine powder. The experimental results indicate that the water vapor is the primary factor in agglomeration. The increase in heat storage temperature, fluidization velocity, and inlet water flow rate can all reduce reaction time. However, the effect of heat storage temperature on agglomeration is negligible. While a high fluidization velocity can alleviate the agglomeration, a high inlet water flow rate intensifies the agglomeration. The heat storage density decreases by about 12 % after 5 cycles owing to the material loss, while the agglomeration is trending upward. The specific surface area and specific pore volume decrease by 46.59 %, and 13.89 % respectively, which slows down the heat storage process. This work can serve as a reference for alleviating the agglomeration, as well as the operation and adjustment of the fluidized bed.

Influence of staggered vane shunt plate on performance characteristics of reactor coolant pump

In order to explore the influence of the axial position of the shunt plate of staggered guide vane on reactor coolant pump(RCP), a mixed-flow RCP was taken as the model for numerical simulation. Based on the entropy production theory, the energy loss in the flow component under different flow conditions was analyzed, and the vortex core distribution in volute and the pressure pulsation at the hydrodynamic interface were studied. The results show the staggered guide vane reduces the head and efficiency slightly, the optimal scheme decreases by 0.9% and 0.6%. Placement of the shunt plate significantly influences entropy production within the guide vane and volute, especially when positioned near the front and back plates. When shunt plate is set centrally, the energy loss due to staggered guide vane is relatively smaller and closer to the original structure. The entropy production rate of guide vane inlet and shunt plate leading edge is higher, but with the increase of flow rate, the shunt plate leading edge is no longer the main location of energy dissipation. Middle placement of staggered guide vanes effectively reduces the outflow vortex band by Omega vortex analysis, and the amplitude of pressure pulsation at the interface decreases obviously.

Toxicity Risk from Hip implant CoCrMo Particles: The Impact of Dynamic Flow Rate on Neuronal cells in Microfluidic systems

In patients with total hip replacements (THRs), wear products in the form of nanoparticles and ions are released, especially around implant failure. In this study, we use N2a cells, a neuroblastoma cell line, to evaluate the effects of different flow rates on neuronal toxicity amidst exposure to CoCrMo particles. We hypothesized that increasing flow rates would increase N2a cell viability and decrease N2a cell-degradation products (DPs) toxicity. We conducted four 24-hour experiments, each with four flow rate conditions, 0, 50, 100, and 200 uL/min, based on the physiological shear stress of the vessels in the human body, to evaluate cell viability, cell morphology, and cell-DPs interaction. Steps included microfluidic channel preparation, N2a cell culturing, CoCrMo particle acquisition, microfluidic system assembly, and dynamic flow neurotoxicity evaluation, which included video microscopy, AlamarBlue, live/dead imaging, DAPI, and ROS assay. The results suggest that fewer neurotoxic reactions and greater viability at higher flow rates supported our hypothesis, although the full range of viable flow rates is yet to be studied. While cell-particle interaction is complex and dynamic, flow rate did modulate toxicity, viability, morphology, and growth environment. The microfluidic system should continue to be developed to study toxicology aspects of implants by simulating in vivo conditions more accurately.

COF-5/Pebax mixed-matrix membranes with enhanced CO2 removal ability for ECCO2R system

Extracorporeal CO2 removal (ECCO2R) is a type of extracorporeal life support (ECLS) technology. It aims to remove carbon dioxide (CO2) from small flow of the blood and correct hypercapnia and related acidosis. The ECCO2R system removes CO2 retained in the patient’s body through the gas-blood exchange membranes, which in use, blood flows on the outside of the membrane, and the inside of the membrane is for gas flow. Existing ECCO2R system generally improves the emission rate of CO2 by the increase of the gas flow rate. However, there is a problem that O2 is simultaneously taken out, which will reduce the blood O2 concentration. Therefore, the gas-blood exchange membranes should not only increase the CO2 removal rate by the improvement of CO2/O2 selectivity, but also retain more O2 in the blood and then maintain the oxygen saturation of the blood. In present work, a method was proposed to fabricate COF-5/Pebax mixed matrix membranes (MMMs) on the PMP surface for enhancing CO2/O2 selectivity, which was increased from 0.96 to 5.57. The CO2 removal ability of COF-5/Pebax MMM was tested by blood circulation, and it was found that the CO2 removal effect was increased 10.9% than that of the pristine membranes. The O2 concentration was maintained at a higher level, about 1.69 times that of the pristine membranes. In contrast to the pristine PMP membrane, blood compatibility of COF-5/Pebax MMMs was improved because protein adhesion decreased by 44.75%. The results of cytotoxicity test and rabbit pyrogen test exhibited that the prepared COF-5/Pebax MMM presented great biosafety. Overall, the proposed COF-5/Pebax MMM has good performance in ECCO2R system and attractive potential for medical application.

A study of nano-micro-bubble process for CO2 absorption in water for biogas upgrading application

The work proposed a novel micro-bubble system using swirling jet flow method for improving the physical absorption of CO2 in water. The effects of operating conditions; e.g. gas flow rate (from 500 to 2000 mL/min), inlet pressure (2 and 3.5 bar) and inlet CO2 concentration (from 5 to 60% v/v in CO2/N2 gas mixture) on the physical absorption of CO2 were studied. It was found that the CO2 absorption system reached to steady state after 30 minutes with the outlet CO2 concentrations of 2.9% and 8.8% at 40% and 60% of inlet CO2 concentrations, respectively. These outlet CO2 concentrations demonstrated the standard of bio-methane for replacing natural gas in vehicle use, from which less than 10% CO2 is required. Moreover, the increase of gas flow rate resulted in increase of outlet CO2 concentration. The rising of inlet pressure from 2 to 3.5 bars let to reduction of the outlet CO2 concentration together with enhancing the dissolved CO2 concentration in water from 49.1 to 51.7 mg/L at gas flow rate of 2000 mL/min and 60% of inlet CO2 concentration. The highest efficiency of CO2 removal was 98.41% under gas flow rate at 500 mL/min with 60% of inlet CO2 concentration. Under the optimized conditions, this system was tested with real biogas as raw material containing mainly 57.7% of CH4 and 40.3% of CO2 which achieved to remove the 95.1% of CO2 removal and no significant loss of CH4. This highlight demonstrated the potential application of this technology for biogas upgrading or purification further.

Optimizing Bionic Blades for Multi-blade Centrifugal Fans: Asymmetric Thickness Inspired by Carangiform Fish

Multi-blade centrifugal fans find wide application across various fields, with their internal airflow exhibiting complex turbulent behavior in three dimensions. Historically, blade optimization relied on constant thickness airfoils, limiting the effectiveness of optimization efforts. However, marine organisms have developed airfoil structures with highly efficient drag reduction, offering a novel approach to optimizing multi-blade centrifugal fans. This study proposes an airfoil optimization design method utilizing variable-thickness airfoils to maintain consistent pressure surface leading-edge parameters. By integrating the Non-dominated Sorting Genetic Algorithm II with biomimetic optimization design, performance improvements are achieved. The study constructs an asymmetric bionic blade using a Bezier curve to fit the mean camber line of the blade. Experimental testing validates the optimized fan's performance, demonstrating the effectiveness of the proposed design approach in reducing the unsteady interaction between the impeller and the volute tongue. This reduction significantly diminishes sound pressure fluctuations on the blade surface. Notably, at the maximum volume flow rate, the optimized fan featuring the asymmetric bionic blade exhibits a remarkable enhancement, with a 10.5% increase in volume flow rate and a notable 1.7 dB reduction in noise compared to the original fan configuration.

Enhancing flow uniformity and reducing turbulent kinetic energy in refrigerator freezers through magnetic resonance velocimetry-based structural modifications

High energy efficiency and low operational noise are increasingly demanded in premium household appliances. Magnetic resonance velocimetry (MRV) has recently emerged as a versatile flow visualization technology, particularly suited for the efficient design of such appliances. This study conducted a comprehensive analysis of a 3/5 scale freezer model, incorporating the cooling system, compartment, and cabinets, all fabricated using stereolithography three-dimensional (3D) printing. By focusing on flow characteristics, 3D mean velocity and turbulent kinetic energy (TKE) fields were measured, identifying regions of non-uniform flow and elevated TKE. To address these issues, structural modifications were introduced in an improved model. These modifications included refining the central structure of the fan chamber, altering inlet geometries, and adding a fillet at the inlet edge. The results were significant: a more uniform flow distribution was achieved, with a 15 percentage-point increase in the effective flow rate through the evaporator's finned area, a reduction in secondary flow energy in the fan chamber, and a substantial decrease in TKE. Consequently, the improved model demonstrated enhanced energy efficiency and quieter operation. These findings highlight the potential of MRV as an effective tool for analyzing complex flow systems in appliance design.

Numerical simulation of hydrate particle behavior in vertical pipeline gas-liquid flow

During the extraction of deep terrestrial and deep-sea natural gas reservoirs, changes in temperature and pressure in the production well can lead to the formation of natural gas hydrates in the wellbore, blocking the flow channel and posing significant challenges to gas well production and management. To address this, we have established a mathematical model to describe the flow characteristics of hydrate multiphase flow systems in vertical pipelines. We employ Computational Fluid Dynamics simulations coupled with a Population Balance Model to predict the formation and breakage of hydrate particles, taking into account mechanisms such as particle collision, aggregation, and breakage. We have analyzed the impact of gas flow rate, slurry flow rate, and hydrate volume fraction on hydrate particle size in the pipeline. The results indicate that hydrate particles tend to aggregate at the bottom of the pipeline. The larger the hydrate slurry flow rate, the faster the hydrate particle size increases. As the gas phase flow rate increases, the increase in particle size slows down. High gas phase flow rates help form turbulence to suppress particle aggregation, velocity fluctuations contribute to particle aggregation growth, and stable velocities facilitate particle decomposition. The increase in hydrate volume fraction significantly increases the diameter of hydrates in the center of the pipeline. The research results can provide suggestions for wellbore blockage caused by hydrate particle aggregation on the wall and a decline in gas well production during actual natural gas well production.

Heat mitigation in basal compacted clay liners in municipal solid waste landfills.

In municipal solid waste (MSW) landfills, biodegradation of the organic MSW fraction results in elevated waste and basal liner temperatures which have the potential to cause the clay component of the basal liner to experience severe moisture loss over time and eventually undergo desiccation cracking. Cracking of the basal liner's clay component would result in an uncontrolled release of contaminants into the surrounding environment and ultimately give rise to a variety of major environmental concerns. Accordingly, this study examined the variation of temperature-moisture profiles along the depth of a compacted clay liner (CCL) exposed to different constant elevated waste temperatures (CETs) in the absence and presence of two heat reduction techniques, respectively. Rockwool insulation layers with varying thicknesses and galvanized steel cooling pipes with varying flowrates were introduced separately as the two heat reduction techniques. Introduction of both techniques led to a significant attenuation of the temperature rise and desiccation experienced by the CCL in the face of different CETs. An increase in rockwool thickness increments led to a progressive reduction of CCL temperature, while an increase in flow rate under turbulent condition did not have a significant influence on the temperature and desiccation reduction of the CCL. Nevertheless, the present study certainly highlights the potential of the two proposed heat reduction techniques to minimize desiccation and consequently increase the service life of CCLs exposed to different elevated temperatures in MSW landfills.