Flow Channel Width Research Articles

Investigation of roll forming process and quality control factors for metal bipolar plates

Metal bipolar plates (BPPs) are crucial components of proton exchange membrane fuel cells (PEMFCs), with the quality of their formation affects the power generation efficiency and lifespan of the fuel cells. The predominant manufacturing method, stamping, often results in localized excessive stretching of metal BPPs, thereby limiting the depth of the flow channels. Roll forming, dominated by bending deformation, is a forming process that ensures uniform thinning and greater depth of BPPs. The multi-directional flow channel roll forming model for BPPs is constructed in this paper for the first time, the characteristics of the roll forming process is investigated. Effects of process parameters on the forming results are discussed. The investigation indicates that during the roll forming process, the channel ports and corners are critical areas where defects are most likely to occur. The average filling ratio of the longitudinal flow channels is 5.6% higher than that of the transverse flow channels. The plastic strain in the longitudinal flow channels is about 36% higher than in the transverse ones, which making the form is more difficult to form, but the thickness is more uniform. Increasing the diameter of the rollers can enhance the filling ratio and flatness, but it will exacerbate thinning at the corners of the flow channels. When the ratio of the flow channel width to the rib width is close to 1, the filling ratio of the BPP is higher, with less thinning, resulting in a better forming result. As the depth of the flow channel increases, resulting in a thinner BPP, when depth-to-width ratio exceeding 0.6 is more likely to lead to failure. Increasing the speed of roll forming can lead to a greater thinning of the BPP and may even cause it to crack. The thinner the sheet metal is, the higher the filling ratio of the BPP and the more uniform its thickness. Those results can provide technical references for the structural design and forming process optimization of BPPs.

Design and performance estimation of a novel solar multiplate mirror concentration PVT system based on nanofluid spectral filter

This paper presents the design and performance evaluation of a novel solar multiplate mirror concentration photovoltaic and thermal (MPVT) system using ethylene glycol/indium tin oxide liquid spectral filter (LSF). The LSF is prepared, and the test results show that its average spectral transmissivity and average spectral absorptivity are 69.2 % and 30.8 %. Optical characteristics and operation performance of the MPVT system are evaluated, and parametric interaction analysis is also carried out to reveal the relationships of optical and structural parameters of the MPVT system. The results indicate that the MPVT system is technically feasible and has acceptable adaptability on solar tracking error. The decrease in LSF flow channel width and increase in LSF flow channel installation height can increase the concentration ratio. The electric power and photoelectric efficiency of the photovoltaic module are 818.2 W and 29.07 %. The thermal and exergy efficiencies of the MPVT system are 23.88 % and 32.81 %. By increasing the inlet LSF flow velocity and ambient temperature or decreasing the inlet LSF temperature properly, the thermal performance of the MPVT system can be improved. But the effects of the three parameters on the exergy efficiency of the MPVT system are all relatively small.

Cathode fine-scale flow channel optimization enhancing the performance of proton exchange membrane fuel cells

High performance and long durability have been the continuous pursuit of proton exchange membrane fuel cells (PEMFCs). Performance and durability are related to the PEMFC distributional uniformity of internal state, which are deeply influenced by the flow channel structures and operating conditions. Therefore, this study proposes a fine-scale flow channel (FSFC) with gradually decreasing flow channel widths (wch) based on parallel flow field. Following, fixing wch at 0.3 mm, the effects of different rib width (wrib), cathode humidity (RHc), stoichiometric ratio (ξc) and coolant mass flow rate (mcool) are studied. Simulation results indicate that FSFC can significantly enhance the various properties of fuel cells, especially the performance and uniformity. Reducing the wrib can enhance the performance and reduce the pressure drop. The appropriate RH and ξc can improve the performance and uniformity while avoiding flooding and purging effects. Similarly, mcool should be kept in the appropriate range to avoid unnecessary pump power loss. This study aims to develop the flow fields in a more fined direction, offering solutions that strike a balance between durability and power density for PEMFC optimization.

Wetted Ramps Selectively Block Upstream Passage of Adult Sea Lampreys

Dams fragment stream habitats and fishways around dams typically serve few species that are strong swimmers or jumpers. We tested a prototype wetted ramp designed to allow upstream passage of small-bodied fishes while blocking upstream movement of invasive sea lampreys in the Laurentian Great Lakes. We tested short, smooth ramps with 5–10 mm water depth in various combinations of ramp angle, water flow, and swim channel width with the aim to selectively block adult migrating sea lampreys (Petromyzon marinus) while passing sub-adult white suckers (Catostomus commersonii) and creek chubs (Semotilus atromaculatus). Sea lampreys easily passed a 0.75 ramp at a 5° angle, but very few individuals passed a similar ramp at a 10° angle, and none passed a longer ramp at a 5° angle. Limiting the amplitude of tailbeats in a narrow channel did not hamper lampreys or the other species. Greater water flow, and thereby greater immersion depth on the ramp, fostered passage for all species. Smaller-bodied individuals of creek chubs and white suckers performed best on the ramp. We showed that wetted ramps could be incorporated into fishways at low-head dams to aid the passage of smaller-bodied fishes while also blocking the spawning migration of adult sea lampreys.

A High-Throughput Circular Tumor Cell Sorting Chip with Trapezoidal Cross Section.

Circulating tumor cells are typically found in the peripheral blood of patients, offering a crucial pathway for the early diagnosis and prediction of cancer. Traditional methods for early cancer diagnosis are inefficient and inaccurate, making it difficult to isolate tumor cells from a large number of cells. In this paper, a new spiral microfluidic chip with asymmetric cross-section is proposed for rapid, high-throughput, label-free enrichment of CTCs in peripheral blood. A mold of the desired flow channel structure was prepared and inverted to make a trapezoidal cross-section using a micro-nanotechnology process of 3D printing. After a systematic study of how flow rate, channel width, and particle concentration affect the performance of the device, we utilized the device to simulate cell sorting of 6 μm, 15 μm, and 25 μm PS (Polystyrene) particles, and the separation efficiency and separation purity of 25 μm PS particles reached 98.3% and 96.4%. On this basis, we realize the enrichment of a large number of CTCs in diluted whole blood (5 mL). The results show that the separation efficiency of A549 was 88.9% and the separation purity was 96.4% at a high throughput of 1400 μL/min. In conclusion, we believe that the developed method is relevant for efficient recovery from whole blood and beneficial for future automated clinical analysis.

Influence of vapor core design on thermal and hydraulic performance of mesh-type ultra-thin vapor chamber

The mesh-type ultra-thin vapor chamber(UTVC), with an internal mesh porous structure, is a cost-effective and efficient heat transfer element for compact spaces. The design of the vapor core plays an important part in enhancing the heat transfer performance of the mesh-type UTVC within the confined space requirements. The present study proposes to design cavities in the supporting coarse mesh inside the vapor core to form a multi-scale combination of vapor channels with the mesh channels. Utilizing a numerical model that considers microporous evaporation as well as the Marangoni effect, the effects of different flow channel designs and designed channel widths on the performance of the UTVC were analyzed. The study determined the flow and heat transfer characteristics of the working medium within the mesh-type UTVC, and found that the most significant performance enhancement was achieved when the designed flow channel passed through part of the UTVC evaporation and condensation sections, reducing the thermal resistance by 17.45%. Whereas the design flow channel width has less influence on the performance of mesh-type UTVC, it satisfies the changing trend of vapor flow pressure drop and thermal resistance decreasing firstly and subsequently increasing with the expansion of the designed channel width.

Flow front mobility of rock avalanches as a function of flow volume, grain size, channel width, basal friction and flow scale

The ability to predict the mobility of rock avalanches is necessary when designing strategies to mitigate the risks they pose. A popular mobility indicator of the flow front is the Heim’s apparent friction coefficient μH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mu }_{H}$$\\end{document}. In the field, μH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mu }_{H}$$\\end{document} shows a decrease in value as flow volume V increases. But this correlation has been a mystery as to whether it is due to a causal relationship between V and mobility since: (1) field data of μH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mu }_{H}$$\\end{document} do not collapse onto a single curve because typically widely scattered and (2) laboratory experiments have shown an opposite volume effect on the center of mass mobility of miniature flows. My numerical simulations confirm for the first time the existence of a functional relationship of scaling parameters where μH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mu }_{H}$$\\end{document} decreases as V increases in unsteady and nonuniform 3D flows. Data scatter is caused by μH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mu }_{H}$$\\end{document} that is affected by numerous other variables besides V. The interplay of these variables produces different granular regimes with opposite volume effects. In particular, μH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mu }_{H}$$\\end{document} decreases as V increases in the regime characterized by a relatively rough subsurface. The relationship holds for large-scale flows that, like rock avalanches, consist of a very large number of fine clasts traveling in wide channels. In these dense flows, flow front mobility increases as flow volume increases, as channel width increases, as grain size decreases, as basal friction decreases and as flow scale increases. Larger-scale flows are more mobile because they have larger Froude number values.

Parametric Analysis on Formability of SS304 Metal Bipolar Plate with Wave Flow Field Structure

The main production method of metal bipolar plate is stamping, and the size parameters of the flow field structure can not only change the performance of the fuel cell, but also affect the stamping quality of the metal bipolar plate. In the case of ensuring the performance of the fuel cell, it is necessary to study the stamping of the metal bipolar plate with different flow field structures. In the past, there were few studies on the wave flow field stamping forming. This paper analyzed the wave flow field, formulated several sets of bipolar plate structural dimension parameters, and evaluated the stamping forming quality of the reaction zone of SS304 metal bipolar plate through finite element simulation. By reducing the rib height ΔH=0.075mm in the corner part, the maximum thinning rate can be reduced from 34.833% to 24.689% and the thickness can reach 0.0753mm when the flow channel width S=1.0mm, the rib width W=1.5mm and the forming depth H=0.5mm. It provides some guidance for optimizing the structural dimension parameters of metal bipolar plates.

A Forked Microvascular Phantom for Ultrasound Localization Microscopy Investigations.

In the development of ultrasound localization microscopy (ULM) methods, appropriate test beds are needed to facilitate algorithmic performance calibration. Here, we present the design of a new ULM-compatible microvascular phantom with a forked, V-shaped wall-less flow channel pair ( 250 μ m channel width) that is bifurcated at a separation rate of 50 μ m/mm. The lumen core was fabricated using additive manufacturing, and it was molded within a polyvinyl alcohol (PVA) tissue-mimicking slab using the lost-core casting method. Measured using optical microscopy, the lumen core's flow channel width was found to be 252 ± 15 μ m with a regression-derived flow channel separation gradient of 50.89 μ m/mm. The new phantom's applicability in ULM performance analysis was demonstrated by feeding microbubble (MB) contrast flow (1.67 to 167 μ L/s flow rates) through the phantom's inlet and generating ULM images with a previously reported method. Results showed that, with longer acquisition times (10 s or longer), ULM image quality was expectedly improved, and the variance of ULM-derived flow channel measurements was reduced. Also, at axial depths near the lumen's bifurcation point, the current ULM algorithm showed difficulty in properly discerning between the two flow channels because of the narrow channel-to-channel separation distance. Overall, the new phantom serves well as a calibration tool to test the performance of ULM methods in resolving small vasculature.

Operando Neutron Imaging of Water Distribution inside Running Anion-Exchange Membrane Fuel Cell

IntroductionAnion-exchange membrane fuel cell (AEMFC) has a potential use of non-precious metal catalysts under an alkaline environment. Furthermore, anion-exchange membranes (AEMs) are expected to be used for water electrolysis. However, the performance of AEMFC is still lower than that of proton-exchange membrane fuel cell (PEMFC). During the power generation, the PEMFC only produces H2O at the cathode, whereas the AEMFC consumes H2O at the cathode and produces twice as much as H2O at the anode. The main factors for the increase in polarization of AEMFC are limitation of H2 diffusion due to liquid water flooding at the anode and lack of H2O as a reactant at the cathode. Therefore, elucidating the water distribution in the AEMFC is essentially important. In this study, we imaged liquid water in an AEMFC during power generation. The data were compared with those of a PEMFC.ExperimentalThe water distribution in the AEMFC was imaged by neutron beams in the directions, perpendicular and parallel to the membrane-electrode assembly (MEA) surface during power generation. Imaging was conducted at the beamline BL-22 of the MLF, J-PARC(2). The cell size was 100×70 mm2, and the active area was 20×20 mm2. Single serpentine flow channels were used for the gas flow channels. The depth and the width of the gas flow channels were both 1 mm. The end plates were made of aluminum to avoid neutron scattering. The thickness of the end plate was10 mm. Both the H2 and O2 gas flow rate was 100 ml/min. Pt/CB was used as a catalyst. For the electrolyte membrane and the binder, QPAF-4(1) was used. The temperature of the cell was 60°C and the humidity was 100% RH.Results and DiscussionFig. 1 shows the water distribution inside the AEMFC parallel to the MEA. In Fig. 1(a), the left side is the anode and the right side is the cathode. In the image, three vertical blue lines are seen. The two outer lines are of a Kapton tape made of silicone. The middle line is of the water on the anode side of the AEMFC. There are blue squares on both side the anode and cathode; the bule squares on the anode side are very clear, whereas those on the cathode side are vague. These blue squares are gas flow channels. The relative thickness of water is represented by the color bar shown on the right in Fig. 1. In the dark area, water hardly existed. As the water increased, the color changed to red. Fig. 1(b) is an enlarged image of the gas flow path and the MEA. In the middle of the image, an MEA (0.55 mm thick) existed with GDLs (anode side 330 µm thick, cathode side 210 µm thick) sandwiching the CCM using a QPAF-4 membrane (30 µm thick). At the cathode, water was hardly imaged, but a small amount of water was observed in the gas flow channels near the outlet, mostly on the wall of flow channel in purple. In the GDL at the cathode, a small amount of water was observed on the CCM. At the anode, water was observed both in the gas flow channel and under the ribs. A larger amount of water was observed in the gas flow channel especially near the outlet, whereas near the inlet, a smaller amount of water was observed in the gas flow channel and under the ribs. In the gas flow channel, a large amount of liquid water was seen on the wall surface of the gas channel of the anode. Therefore, In the gas channel of the AEMFC, the gas path existed on the GDL side. Fig. 2 shows the water distribution inside the AEMFC perpendicular to the MEA. The thickness of liquid water in the gas channel and the entire MEA area at different current densities are calculated. In AEMFC, at low current density, liquid water existed near the outlet of the gas channels. As the current density increases, liquid water was also generated near the ribs and near the inlet of the gas flow channels. In PEMFC (not shown), at low current density, almost no liquid water existed in the gas channel and MEA. As the current density increased, liquid water is generated only near the gas channel outlet. The water distribution trends of PEMFC and AEMFC were significantly different. References Ono et al. J. Mater. Chem. A, 5 (47), 24804-24812 (2017)Shinohara et al., Rev. Sci. Instrum. 91, 043302 (2020). Figure 1

Investigation of the Effect of Graphite Bipolar Plate Flow Channel Inhomogeneities and Faults on HT-PEM Fuel Cell Stack Performance

Bipolar plates are a key component of fuel cell stacks. Bipolar plates have multiple functions. They connect the single cells of the stack electrically and must be therefore electrically conductive. They separate oxidant and fuel gases and distribute them on each side over the membrane-electrode-assembly (MEA). Bipolar plates separate coolant liquid too. Fuel cell stack is cooled by coolant liquid which is flowing through the cooling flow channels in the middle of bipolar plates.Especially the bipolar plates for HT-PEM must endure a low pH environment, continuous electrical potential, and higher temperatures up to 200°C. The focus here is on investigations of anode and cathode side flow channels of graphite bipolar plates. Inhomogeneities and faults of flow channels are examined and their effects on fuel cell stack performance are analyzed. The analyses are based on optical scan data of flow channel geometry and measurement data of a HT-PEM fuel cell full stack consisting of 120 cells operated on a testbed under different variations. Inlet pressure and stoichiometry of both anode and cathode were varied, anode was fed with pure hydrogen and with different reformate gas compositions consisting of hydrogen, nitrogen, carbon dioxide and carbon monoxide. For each variation point, polarization curves between 0 A/cm2 – 0,55 A/cm2 in step of 0,05 A/cm2 were recorded.With an on testbed installed cell voltage monitoring (CVM) system voltages of every cell were measured and logged. Enormous amount of optical scan data consisting of width and depth information of flow channels was merged to certain statistical data for anode and cathode bipolar plates. Correlations between statistical data and cell voltages are still being investigated. It is planned to repeat the measurements with another 120 cells HT-PEM fuel cell full stack and compare the results.

Numerical study of thermal-hydraulic and structural parameters effects on CHF in subcooled forced convection flow during external reactor vessel cooling

Advanced nuclear reactors employ External Reactor Vessel Cooling (ERVC) as a crucial measure to safeguard the structural integrity of the Reactor Pressure Vessel's (RPV) lower head and to confine molten material within it during severe accidents. The ERVC technique effectively mitigates severe accidents by efficiently dissipating decay heat from the molten pool located within the lower head, utilizing coolant flow boiling. The key determinant of the upper limit of ERVC cooling capability is primarily contingent on the Critical Heat Flux (CHF). In this study, flow boiling in downward heating curved flow channel under forced convection is numerically investigated using the Eulerian-Eulerian two-fluid model and realizable k-ε turbulence model. Compared with the experiment, the maximum deviation of numerically predicted CHF is less than 5%, indicating that the numerical method is reliable. A thorough analysis is conducted on the impact of variable structure and thermal-hydraulic operating conditions on CHF. The results indicate that as the coolant mass flow rate, system pressure, and inlet subcooling increase, the CHF exhibits a corresponding increase. The CHF increases by 56.6% when the mass flow rate increases from 400 to 1000 kg/(m2·s). The CHF at the pressure of 0.3 MPa is 16% higher than that of 0.1 MPa. The CHF increases from 1.14 to 1.84 MW/m2 as the inlet subcooling escalates from 10 to 20 K, with a 60% growth rate, while the CHF increases to 2.03 MW/m2 when the inlet subcooling increases from 20 to 50 K, with a 10.33% increase. The maximum difference in CHF for the three flow channel widths (120, 150, and 170 mm) is only 1.7%, indicating that the influence of flow channel widths is insignificant. This study can provide theoretical guidance for the design and optimization of ERVC in advanced nuclear reactors.

Integrated Taguchi and response surface methods in geometric and parameter optimization of PEM fuel cells

AbstractProton exchange membrane (PEM) fuel cell has emerged as a promising alternative to fossil fuels as it is employed to generate electricity for portable applications with low carbon emissions. However, the high cost of the technology hinders its widespread commercialization. Optimizing PEM fuel cell model parameters is crucial in performance improvement and production cost reduction. This study presents an optimization approach for a PEM fuel cell operating and design parameters by integrating Taguchi and Response Surface Methodology. A 3D‐CFD model of a PEM fuel cell is developed and used as a base model for the optimization study. Thirteen input parameters with notable effects on the fuel cell's performance are selected for this study. By the Taguchi method, these parameters decreased from thirteen to five. A response surface methodology (RSM) Box‐Behnken experimental design is employed to study the interactions of the parameters on the power density. The optimum working parameters that result in optimum power density of 0.8476 W cm−2 include an operating pressure (2.5 bar), temperature (80°C), flow channel width (1.30 mm), membrane thickness (0.036 mm), and catalyst layer thickness of 0.01 mm. This study provides a quick and efficient way of optimizing PEM fuel cell model for maximum power density.

Enhancing Air-Breathing Direct Methanol Fuel-Cell Performance by Optimizing Anode Flow-Channel Widths and Open Ratios of Cathode Current Collectors

Enhancing Air-Breathing Direct Methanol Fuel-Cell Performance by Optimizing Anode Flow-Channel Widths and Open Ratios of Cathode Current Collectors

Smartphone as a fluorescence detector for high-performance liquid chromatography

BackgroundFluorescence detection is employed in high-performance liquid chromatography (HPLC) due to its high specificity and sensitivity. However, it is often limited by expensive components and bulkiness. Recently, advances in technology and electronics have led to the development of smartphones that can serve as portable recording, analysis, and monitoring tools. Smartphone-based detection provides advantages of cost effectiveness, rapid signal/data processing, and the display of results on a handhold monitor. The combination of smartphone-based detection with HPLC can offer unique features that are beneficial in overcoming limitations of commercial fluorescence detectors. (90) ResultsA miniaturized and low-cost HPLC fluorescence detector based on a smartphone is introduced for the detection of six fluorescent molecules. The smartphone is able to capture emitted fluorescence in video format while MATLAB code is used for data processing to provide chromatograms based on different detection channels. A custom designed double-channel flow cell was utilized to enable simultaneous detection of fluorescent compounds with different excitation wavelengths. The detector consists of a lab-made flow cell, monochromatic LEDs as the light source, 3D printed housing and connector box, fiber optic cables, and a smartphone. The effects of flow cell geometry, channel width and light slit diameter, as well as a comparison of different flow cell manufacturing techniques, are studied and discussed. The validated system was successfully applied to samples from diverse water sources, yielding spiking recoveries within the range of 91.7% and 109.7%. (141) SignificanceThis study introduces the first smartphone-based fluorescence detector for HPLC with cost-effective and customizable flow cells, allowing for the simultaneous detection of fluorescent compounds with different excitation wavelengths and offering a potential solution for the analysis of co-eluting compounds. Beyond its user-friendly interface and low-cost, smartphone detection in HPLC provides tremendous opportunities in further miniaturizing chromatographic instrumentation while offering high sensitivity and can be expanded to other mechanisms of detection. (70)

The Study of Structural Optimization on Hydraulic Performance and Anti-Clogging Performance of Labyrinth Drip Irrigation Emitters

The core component of a properly functioning drip irrigation system is the drip irrigation emitter. Irrigation water containing impurities and sand particles can easily lead to clogging of the drip irrigation emitter, reducing the efficiency of the drip irrigation system. In this paper, orthogonal tests were used to optimize the flow channel structure, combined with the computational fluid dynamics–discrete element method (CFD-DEM) to analyze the flow index and sand particle motion characteristics. Clear water tests and short-cycle anticlogging tests were used to validate the results of the numerical simulation, and the relationship between the hydraulic performance and anti-clogging performance was revealed via linear regression. The results showed that the structural parameters of drip irrigation emitters were important factors affecting the flow index and sand movement characteristics. The order from largest to smallest was the turning angle, amount of interdental reference, flow channel depth, flow channel width, and width of the top base. The sand passage rate and the percentage decrease in velocity can be used as important indicators of anti-clogging performance, and there was a negative correlation between the two indicators. The flow channel with a 65° turning angle had the lowest flow index, and the sand passage rate can reach up to 91.48%; the reason was that the main flow region velocity was higher, the vortex region and the sand energy loss were small, which was not easy to clog. The equation for the relationship between flow index and sand passage rate was a negative correlation for drip irrigation emitters between a 65° and 75° turning angle. The drip irrigation emitter with a 65° turning angle had better hydraulic performance and anti-clogging performance.

О структуре гидравлических потерь при работе многоступенчатых лопастных насосов

The paper proposes methodology for assessing hydraulic resistance of the vane pump stages. The methodology makes it possible to reveal the hydraulic losses structure during liquid pumping and assess contribution of each type of these losses to the overall balance of the pumping stage energy consumption. Dependence of hydraulic losses on the width of the inter-vane flow channels is shown. Theoretical method was developed to predict the effect achieved by altering the vane design and production technology. Prospects of research, design, development and industrial production of the new type of multistage vane pumps with the oval-type stages are substantiated.

A high-performance solar chimney in building integrated with photocatalytic technology for atmospheric methane removal

The techniques for the removal of methane from the atmosphere are highly challenging due to its stable chemical properties, dispersed sources, and low concentrations. This paper proposes a practical small-scale solar chimney (SC) in buildings with photocatalytic reactors (PCRs) for atmospheric methane removal. Two comprehensive numerical models on photocatalytic reaction and indoor ventilation are developed. The numerical simulation considers the performance of methane removal and indoor air ventilation of the proposed system, as well as its specific crucial parameters such as the type of PCRs, solar radiation, and flow channel width. The obtained results show that the SC with honeycomb photocatalytic reactor (HPCR) is more able to remove atmospheric methane than SC with plate photocatalytic reactor (PPCR) under the premise of meeting the ventilation standards. In addition, there is a maximum methane purification rate of 57.27 μg/s under the condition that the air gap width is 0.3 m, the length of the HPCR is 1.5 m, and the porosity is 0.85. It is then proved that the SC in buildings with PCRs can allow small-scale, zero-energy consumption, continuable, and decentralized low-concentration atmospheric methane removal while improving the indoor ventilation.

The optimal electrode pore size and channel width in electrochemical flow cells

Microfluidic fuel cells, electrolyzers, and redox flow batteries utilize laminar flow channels to provide reactants, remove products and avoid their crossover. These devices often also employ porous flow-through electrodes as they offer a high surface area for the reaction and excellent mass transfer. The geometrical features of these electrodes and flow channels strongly influence energy efficiency. We derive explicit analytical relations for the optimal flow channel width and porous electrode volumetric surface area from the perspective of energy efficiency. These expressions are verified using a two-dimensional tertiary current distribution and porous electrode flow model in COMSOL and are shown to be able to predict optimal parameters in commonly used flow-through and interdigitated flow fields. The obtained analytical models can dramatically shorten modelling time and expedite the industrial design process. The optimal channel width and pore sizes we obtain, in the order of 100 microns and 1 micron respectively, are much smaller than those often used. This shows that there is a significant room for improvement of energy efficiency in flow cells that can sustain the resulting pressure drop.

Modeling the pressure drop in vanadium redox flow batteries-interdigitated configuration

Simulations are performed to study the effect of performance parameters on the pressure drop of a vanadium redox flow battery. The effect of flow rate, viscosity, porosity, electrode thickness, effect of channel height, effect of channel width and effect of number of channels on the pressure drop in a vanadium redox flow battery are studied. The channel height, channel width and number of channels are found to have a substantial effect on the pressure drop across the battery. The effect of flow rate, viscosity, porosity, electrode thickness, channel height and channel width are found to be much more pronounced in Serpentine configuration than the Interdigitated configuration. Model results are compared with experimental data and found to compare well.