Flow Rate Conditions Research Articles

Study on Electrical Characteristics Analysis and Electrical Circuit Model Design of Vanadium Redox Flow Battery Systems Based on Current and Flow Rate Conditions

Study on Electrical Characteristics Analysis and Electrical Circuit Model Design of Vanadium Redox Flow Battery Systems Based on Current and Flow Rate Conditions

Transport of Nanoplastics in Saturated Zeolite: Effects of Flow Rate and Hydro-Chemical Conditions

Transport of Nanoplastics in Saturated Zeolite: Effects of Flow Rate and Hydro-Chemical Conditions

Anatase‐reinforced PtZn@Silicalite‐1 structured catalysts boosting propane dehydrogenation

AbstractStructured catalysts exhibit the advantages of high diffusion efficiency and low heat transfer resistance, which have attracted increasing attention to non‐adiabatic gas–solid process. However, the metal‐supported coating catalysts face the problems of weaker bond strength and severe sintering, especially under the conditions of large flow rate and high temperature. Herein, metal@Silicalite‐1 structured catalysts with high adhesion and thermal stability were successfully prepared by hydroxylating the substrate with anatase. Rich surface Ti‐OH significantly strengthened the adhesion stability of the zeolite coating. In propane dehydrogenation reaction, the optimized PtZn@S‐1‐15Ti showed a high specific activity of 49.6 molC3H6·molPt−1·s−1 with propylene selectivity above 99% at 600°C. The introduction of anatase accelerated the aggregation of silicon sources and induced nucleation with growth content of zeolite increased by 3.6 times. It breaks the inherent contradiction between high loading amount and strong binding ability of coated catalysts, which broadens the avenues for industrial applications.

PIV experimental study on dynamic and static interference flow field of multi-operating centrifugal pump under the influence of impeller wake

In order to study the influence law of the impeller wake on dynamic and static interference flow field of the centrifugal pump, this paper obtains the dynamic and static interference flow field of the centrifugal pump under different flow conditions (15 m3/h, 50 m3/h, 70 m3/h) based on PIV technology, and analyzes the influence mechanism of the impeller wake change on dynamic and static interference flow field. The results show that rotating stall occurs in the centrifugal pump under low flow condition, but it has little effect on the head loss in the centrifugal pump. In the dynamic and static interference flow field, under the condition of the low flow rate, the impeller wake collides with the baffle tongue, resulting in serious velocity fluctuation, and then there will be the secondary collision with the volute wall, which will eventually cause the wake to dissipate, and the change process of the wake shows the periodic characteristic. In the design condition and the large flow condition, the spacer tongue will have the cutting effect on the wake, and the high-speed accumulation phenomenon will occur in the volute flow path near the spacer tongue. In the side flow path of the volute, under the condition of the low flow, the impeller wake is mainly located at the exit of the impeller, and the end of the impeller wake is easy to fall off and gradually break up under the impact of the main stream. Under the design condition, the flow stability is good, and the wake vortex is close to the trailing edge of the blade, and there is no obvious shedding phenomenon. Under the condition of the large flow rate, the velocity fluctuates sharply, and many large-scale vortex structures appear on the cross section of the flow channel due to the cutting of the wake near the diaphragm tongue. In the impeller passage, the movement and distribution of the wake are significantly affected by changes in flow conditions. The research results provide a basis for optimizing volute channel.

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 μL/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.

Performance of a sedimentation tank for standing column wells coupled with geothermal heat pump systems

Ground heat exchangers used with heat pumps have the potential to lower energy consumption and reduce greenhouse gas emissions of buildings. In particular, standing column wells that directly use groundwater have a significant potential in dense urban areas. However, recirculation of groundwater in the well may induce a sediment load that tends to reduce the flow rate of the injection wells, leading to efficiency loss. To avoid this problem, the use of a sedimentation tank placed before the injection well is investigated numerically in this work. To assess the feasibility of this solution, a fully coupled numerical model has been developed based on typical operating conditions and on laboratory analyses performed on sediments. The multiphysics model developed integrates the fluid dynamics and settling processes inside the tank. The capacity of the tank to collect sediments has been investigated for different flow rates and tank geometries. Results obtained show that a commercially-available sedimentation tank can reduce the sediment load in the groundwater returned to the injection well for different flow rate conditions. Indeed, with tank efficiencies ranging from 46.8% to 85% and a capacity to recover 100% of the largest particles, use of intermediate sedimentation tank has a real potential for reducing clogging phenomena. Results also show that for the typical conditions used in the study, usage of inlet baffles enhance tank efficiency and reduce the inlet kinetic energy of the flow, allowing use of tanks having a lower footprint.

Performance evaluation of nanofiltration membranes for SWRO brine valorisation: Insights from a pilot plant under real conditions

The success of a desalination brine valorisation process heavily depends on the effectiveness of the pre-treatment stage, which purifies the brine by reducing the concentration of ions that could form insoluble compounds and hinder system performance. This study focused on testing an innovative nanofiltration (NF) pilot plant operating with 144 m3/d of actual brine from an upstream seawater reverse osmosis (SWRO) pilot plant located in the Canary Islands (North Atlantic Ocean). The NF membranes tested (NE8040-40) played a critical role, demonstrating exceptional rejection rates for divalent ions, therefore also increasing their concentration in the divalent-rich stream, setting the stage for future valorisation of the related by-products. Simultaneously, these NF membranes allowed the achievement of a high-purity monovalent-rich stream with Na+ and Cl– concentrations reaching approximately 98 %, potentially enabling the generation of valuable commercial products in subsequent stages. The NF system was thoroughly assessed under different conditions of flow, pressure, and recovery rates, incorporating extensive process monitoring with comprehensive sensor data.

Multi-objective optimization of comprehensive performance in airfoil channel PCHEs using Bézier curves

The airfoil fin (AFF) Printed circuit heat exchanger (PCHE) has attracted significant attention for its excellent comprehensive performance. This study proposes an optimized design for AFF PCHE to enhance the comprehensive performance by integrating Bézier curves, computational fluid dynamics (CFD), and multi-objective genetic algorithm (MOGA). A set of 12 Bézier curve-based variables is utilized to define and control the airfoil geometry, with optimization targets set on two comprehensive evaluation criteria: the first enhanced ratio (η1) and the third enhanced ratio (η3). The MOGA-generated Pareto front reveals the evolution of AFF structures in relation to η1 and η3. Results show that as the leading and trailing edges of the AFFs become sharper and the thickness decreases, the η1 of the PCHE channel gradually increases, while η3 decreases. Conversely, as the thickness of the AFFs increases and the trailing edge shape transitions from blunt to elliptical and finally to round, η3 significantly increases while η1 decreases. Furthermore, when changes focus mainly on the leading edge of the AFFs, η3 improves without markedly affecting η1. Compared to the traditional airfoil channel, the η1 of the Fin-b channel increases by 3.1%-10.8%, demonstrating its greater suitability under identical flow rate conditions. Similarly, the η3 of the Fin-g channel is 1.4%-11.6% higher than that of the traditional airfoil channel, highlighting its superior performance under identical pumping power conditions. The present work provides a valuable reference for optimizing the design of AFF PCHEs under identical flow rate and pumping power conditions.

Improvement and effectiveness analysis of dynamic/static imbibition experiments.

In low-permeability fractured reservoirs, there is a generalized fluid displacement between the replacement fluid in the fracture and the matrix crude oil. This imbibition behavior plays a crucial role in the development of this type of reservoir. The experimental devices for studying static imbibition behavior are generally susceptible to air pollution on the surface of the test core and a long testing period; the experimental devices for studying dynamic imbibition behavior are generally unable to eliminate the driving action. A dual-purpose experimental setup and an experimental method for dynamic or static imbibition that can avoid the above defects were designed. A method of fracture fluid flow rate calculation and motor speed conversion is proposed, and the method is used to assist in setting the parameters of dynamic imbibition experiments. The device was applied to compare the experimental effects with the static imbibition bottle and the dynamic replacement imbibition, respectively, and the effect of fracture width on the dynamic imbibition of repellent oil was investigated. The results show that: the static imbibition recovery rate of the dynamic/static imbibition experimental device is 1.55 percentage points higher than that of the imbibition bottle; the dynamic imbibition recovery rate is 3-6 percentage points lower than that of the driving dynamic imbibition method, and it can reflect the influence of a single flow rate condition on the imbibition; imbibition in low-permeability fractured reservoirs is more likely to take place in the fracture in the interval of 50-100 μm in the width.

Topology optimization of regenerative cooling structures under high Reynolds number flow with variable thermo-physical properties

In the design of thermal protection system for hypersonic vehicles, the efficient convective heat transfer within regenerative cooling channels plays a critical role in maintaining their thermal performance. This study focuses on the topology optimization (TO) of the cooling channels that operate at high Reynolds number and have variable thermo-physical properties. A novel approach is introduced to enhance the density-based method by incorporating an effective artificial force correction and tabulating the temperature-dependent thermal properties. Several topology-optimized cooling layouts were generated to minimize the maximum temperature within the design domain while considering different power dissipation constraints. This confirms the validity of the proposed lumped correction term in momentum equation accounting both viscous and convective body forces. Regarding the thermal performance of the optimized layouts, the staggered arrangement of cellular ribs in the TO channel was found to induce multiple flow separations and promote turbulent mixing, thereby improving heat transfer efficiency and mitigating the thermal acceleration effect. Conjugate heat transfer calculations revealed that the optimal topology-optimized channel achieved a 24.3% improvement in overall thermal performance while being 15.3% lighter than the straight channel design. Furthermore, the optimal topology optimized layout consistently outperformed the straight channel design by 6.6% to 24.3% in terms of the overall thermal performance across a wide range of heat flux distribution and mass flow rate conditions. This investigation highlights the effectiveness of topology optimization in designing regenerative cooling structures featuring high Reynolds number hydrocarbon thermal fluid flow.

Identification and monitoring of wall-attached vortices in open pump intake based on continuous wavelet transform

Abstract Wall-attached vortices in pump intake commonly appear and has a negative impact on the safety and efficiency of the pumping stations. The monitoring of these vortices are crucial for safe operation of the pump intake. In this paper, SAS model were performed on a pump intake with an axial-flow pump installed in the suction pipe. Two submergences (500mm and 600mm, namely 3.33DL and 4DL ) and three flow rates (0.8Qd , 1.0Qd , 1.2Qd ) were studied. The continuous wavelet transform (CWT) was applied to the pressure signals near the vortices, showed the similarity of time-frequency characteristics at different points under the same flow rate and water level condition.. It was found that the generation and development were slower for larger submergence. At low flow rate 0.8Qd, the flow angle shows larger deviation from 90°, which causes the higher CWT power. By analyzing the powers of dominant frequencies at all the monitor points, it is recommended to set the monitor points within a rectangle that is 0.77DL and 0.97 DL from the back wall and side wall respectively. The conclusions are suitable for similar intakes under similar conditions with 1.2Qd of the pump. Also, they can be good guidance for more generalized open pump intakes.

Analysis of submersible axial flow pump fitted with variable IGV at design and off-design conditions

Abstract Submersible axial flow pump is capable of generating large flow rate at high efficiency and is widely used in agriculture, irrigation, water supply and drainage in factories, urban areas, etc. Pumps are always designed to operate at the designed conditions of flowrate and head, but in certain practical applications, their off- design operation seems to be more important, like if there is waterflooding due to heavy rainfall or in case of variable flowrate, variable head operations or long-distance water supply. These situations arise for limited operation (time) and hence it is not economical to change the existing pumping system. The present work deals with the analysis of submersible axial flow pump at design as well as off-design conditions. This off-design operation was controlled by the variable inlet guide vane (VIGV) with the task of making it energy efficient for all conditions. The scope of this work was to investigate the performance of selected pump at designed rotational speed, at designed flowrate (Q/Qd =1) as well as Q/Qd =0.8 and Q/Qd =1.2, using Computational Fluid Dynamics (CFD) and at various VIGV angles in the range of ±25°. The fluid flow analysis was performed using commercial CFD tool ANSYS CFX v17.0. From the numerical study, it was concluded that the performance of the considered AFP significantly increased due to the presence of VIGV at positive rotation angles. The best performance was observed for IGV angle of +25° for all flowrates. As compared to the reference case of 0° IGV rotation, the performance of the AFP increased by 28.42% in terms of head ratio and 0.235% in terms of hydraulic efficiency, for +25° IGV angle, at the designed flowrate. Also, an increment of 69.05% in terms of head ratio and 14.49% in terms of hydraulic efficiency was observed at overload condition of Q/Qd =1.2.

Study on the inlet backflow characteristics and particle deposition of screw mixed-flow deep-sea mining pump under small flow conditions

Abstract When a screw mixed-flow deep-sea mining pump operates under small flow conditions, significant backflow occurs at the impeller inlet and in the inlet pipe, which seriously affects the pump performance. To investigate this backflow characteristic, this paper presents a numerical study of the internal flow field of the mining pump based on the CFD-DEM coupling method. The flow state at the impeller inlet, the velocity distribution law in the inlet pipe, and the particle motion state under the flow rate condition of 0.52Qd are obtained. The results show that, when the pump operates under small flow conditions, the leakage from the tip gap of the impeller head causes a screw high-speed backflow with the same rotation direction as the impeller on the wall of the inlet pipe. The backflow intensity attenuates as it propagates towards the pump inlet. The backflow mixes with the main flow in the middle of the pipe and reaches a balanced state, which causes the particles to deposit here. The deposition process can be divided into a formation stage and a stable stage. When the particles in the middle of the pipe reach the stable stage, their shape and position become stable. The velocity pulsation of the monitoring points near the wall is periodic, and its pulsation frequency is the same as the impeller rotation frequency.

Design of novel bracket structure for falling film devolatilizer and numerical simulation of its film-forming property

The falling film devolatilizer is a new type of devolatilization equipment, which has the advantages of high film-forming efficiency and no mechanical transmission. In this study, a devolatilizer with an open falling film substrate was designed, and the film-forming performance and surface renewal performance of high viscosity fluids under the falling film structure were numerically simulated. The results indicate that the opening of the falling film substrate makes the liquid film thinner, which is beneficial for the stretching of the liquid film. The advantages of the falling film under low viscosity and high flow rate conditions are more significant. Simultaneously, four bracket structures were designed. Compared with the rectangular bracket, the renewal frequency of fan-shaped brackets can be increased by more than 20%, and the flow rate can be increased by about 10%. The improvement of the two can directly improve the falling film devolatilization performance, so as to improve the polymer polymerization degree and improve the product performance. Therefore, exploring the falling film support frame with high devolatilization performance provides a certain engineering practical significance for the design of devolatilization equipment.

Hybrid artificial neural networks-based approaches predicting the heat transfer and flow characteristics of manifold microchannels

Aiming at meeting the requirement of high heat flux electronics cooling, the geometric complexity of manifold microchannels as an energy-saving technique has been increasing rapidly. It is well worth exploring optimal prediction models for the heat transfer and flow characteristics of manifold microchannels to reduce computing resources and time costs in the optimization process. In this paper, hybrid prediction approaches based on artificial neural networks are proposed for manifold microchannels. Four optimization algorithms, namely, genetic algorithm, particle swarm optimization algorithm, artificial hummingbird algorithm, and zebra optimization algorithm were adopted to enhance the prediction performance. Initially, all prediction models were trained and tested by a numerical database including six input parameters, and the thermal resistance and pumping power were taken as the target outputs. Compared to the original method, hybrid prediction models show higher accuracy and reliability on the numerical data with regression coefficients beyond 0.987. The prediction model optimized by the artificial hummingbird algorithm shows the best performance with the mean average error for thermal resistance and pumping power decreased by 88.7% and 81.4% respectively. Additionally, the runtime of all prediction models is compared and the model optimized by the zebra optimization algorithm takes the longest time, but is still two orders of magnitude shorter than that of the traditional simulation method. Finally, the generalizability of all prediction models is further validated by a database amassed from six experimental studies on manifold microchannels. The results showed that three hybrid models can provide accurate outputs with regression coefficients beyond 0.84 which differs from the poor prediction of the original method. The model optimized by the zebra optimization algorithm shows superior prediction performance for six individual studies, two fluids, three fin shapes, and wide flow rate conditions. The trained hybrid prediction models in this study perform higher accuracy and can be cost-effective and reliable prediction tools for the rapid optimization process of various manifold microchannel applications.

Study on gas–liquid sulfonation reaction under annular flow pattern in micro-reactor: Mechanism, model and process optimization

Micro-sulfonation is a new sulfonation method with great development potential. The gas–liquid micro-sulfonation are safe, efficient and low-cost, however, limited by the research progress and application scope of micro-reactors, the development of gas–liquid micro-sulfonation technique is far from enough. The gas–liquid sulfonation reaction process under annular flow pattern in micro-reactor is experimentally studied in this paper. The maximum MESA (fatty acid methyl ester sulfonic acid) yield under the experimental conditions in this study achieves 89.771 %, which is obviously higher than that (64.1 % for gas–liquid sulfonation and 76.82 % for liquid–liquid sulfonation) in conventional reactors and should be higher if the micro-reactor structure or operating conditions being further optimized. Based on the analyses of experimental results, the effect mechanisms of mass transfer and reaction on the gas–liquid micro-sulfonation efficiency are explored, and the sulfonation efficiency models and pressure drop model of four micro-reactors are established by dimensional analysis method. On account of both the mass transfer characteristics of gas–liquid two-phase flow and the high-viscosity of sulfonation products, enhancing the local disturbance of liquid phase can significantly improve the reaction efficiency. Finally, the operating conditions of two-phase flow rates and reaction time are optimized to ensure the high sulfonation product yield meanwhile reduce the fluid pressure drop or energy consumption of sulfonation process using the improved NSGA-II algorithm.

Emphasizing on the envelope spectra of hydraulic turbomachinery vibration response towards cavitation diagnosis

Cavitation attracts the interest of engineers who target the better understanding of its complex physics and the development of efficient detection tools. This research explores the effectiveness of vibration-based indicators in the prompt and effective diagnosis of cavitation initiating in the rotating flow fields of turbomachinery. The indicators are derived from the envelope spectra estimated with the use of Hilbert Transform, Spectral Kurtosis and Cyclic Spectral Correlation algorithms and data acquired from two semi-open impellers. By utilizing a transparent casing, the onset of cavitation can be observed, enabling the establishment of reliable criteria for evaluating the new indicators. Also, their applicability is assessed across a wide range of flow-rate and suction pressure conditions and in two different geometries. The results demonstrate the consistent ability of the indicators to exploit the high frequency carrier information related with the resonances excited from bubble implosions, to promptly and efficiently detect the phenomenon.

Study on the Destruction Law and Main Controlling Factors of Corrosion Product Film in H2S-CO2 Coexistence System

Abstract The failure law and main controlling factors of corrosion product film in this corrosion environment were studied according to the characteristics of H2S-CO2 coexistence in a gas field pipeline, so as to provide guidance for corrosion prevention and control of gas field pipeline. Sediment effects of sand particles in the pipeline on corrosion, the influence of flow rate, dissolved oxygen and sediment on corrosion products were analyzed by conducting corrosion experiments at 0.5m/s, 1m/s and 2m/s, corrosion experiments without oxygen and aerobic conditions. The destruction law of corrosion product film in pipeline and the main controlling factors of corrosion product film in single well pipeline and gathering and transportation line were determined. The results show that high flow rate will cause local damage of corrosion product film and promote pitting corrosion, dissolved oxygen will destroy the integrity of corrosion product film, and sediment is one of the factors causing local corrosion and perforation of pipeline inner wall. The corrosion product film structure of the gas field pipeline will be destroyed and pitting corrosion under the condition of high flow rate, oxygen and sand deposition. Meanwhile, the main control factor affecting the corrosion product film destruction of the gas field single well pipeline is dissolved oxygen, and the main control factor affecting the corrosion product film destruction of the gas field gathering and transportation main line is sediment.

Migration of dissolution front in a fracture network − Implications for weathering of fractured bedrock systems and boulder formation

Fracture networks contribute to the differential weathering of fractured bedrock at multiple scales. The influence of competing fracture networks is discussed in light of hydrogeochemical conditions to predict the dissolution pattern resulting from spheroidal weathering. The investigation of the dimensionless Péclet (Pe) and Damköhler (Da) numbers on a simple case of a dual-scale fracture network and its application to three fracture network weathering reveals the influence of fluid flow and reaction rate conditions on the dissolution patterns.The conceptual model was numerically validated and compared with observations on lateritic nickel deposits in New Caledonia. A fracture network will contribute to boulder development if the associated fluid flow regime reaches a Pe threshold of around 10. On the other hand, predominant diffusion will inhibit the fracture set in favour of a higher permeability fracture network. The Da drives, for its part, the width of the dissolution halo. Owing to the dependency of the fluid flow regime on the fracture network characteristics, scaling laws were established to estimate the size of the boulders at different scales by predicting the fracture contribution as a function of their Pe.

Investigation of mechanisms on leading edge vortex generation and suppression in vaned diffuser of a centrifugal compressor

This study numerically investigates the mechanisms for generating and suppressing the leading edge vortex (LEV) in a vaned diffuser of a centrifugal compressor, aiming to enhance the compressor's stable operating range. Detailed analyses focus on the mechanisms of the rotating stall and the initiation process of the LEV. Notably, the end wall contouring method is applied to vaned diffuser to suppress the LEV and improve diffuser stability. The suppression mechanisms of the LEV are examined to deepen the understanding of stability enhancement mechanisms. Results demonstrate that, under stall conditions, the vaned diffuser experiences two-cell rotating stalls moving opposite to the impeller rotation direction, each rotating at approximately 12% of impeller rotation speed. The formation of diffuser stall is attributed to a longitudinal vortex developing from the LEV and causing the passage blockage. The increasing spanwise distortion of leading edge (LE) incidence angles and circumferential distortion of static pressures at the diffuser inlet promote the evolution of the longitudinal vortex from LEV. The end wall contouring of vaned diffuser effectively enhances the compressor's stable operating range by 15.10% and 8.90% toward lower flow rate conditions for machine Mach numbers 1.3 and 1.2, respectively. At near-stall points, the end wall contoured diffuser reduces spanwise distortion of LE incidence angles and circumferential distortion of static pressures at the diffuser inlet, mitigates the LE flow separation and corner separation, suppresses the generation and development of the LEV, delays the onset of rotating stall in vaned diffuser, and thereby improves the stable operating range of centrifugal compressor stage.