Hydraulic Resistance Research Articles

Parameter Study of a Loss Reducing Passive Flow Control Method in a Square-to-square Sudden Expansion

The energy consumption of mechanical ventilation in buildings needs to be reduced. An efficient way to achieve this goal is to reduce the hydraulic resistance of the ventilation duct system elements, for example, that of sudden expansions. Ventilation ducts and pipe fittings are frequently of rectangular cross-section. The present paper investigates a passive flow control method in order to reduce the loss coefficient of a square-to-square sudden expansion, where the loss-reducing appendages are short guide vanes, termed as miniflaps, placed at the step edge of the sudden expansion. The turbulent flow is examined numerically using the generalized k-ω model of the Ansys Fluent software for different area ratios of the sudden expansion, miniflap lengths, and miniflap angle setups. The Reynolds number is kept constant at 1.08·105. Based on the results of the numerical simulations, the loss coefficient of the sudden expansion can be reduced by ~20–25% for an optimum miniflap angle between 9° and 12°. Increasing the length of the miniflaps leads to a greater reduction of the loss coefficient up to a miniflap length of 0.3 dh1, where dh1 is the upstream hydraulic diameter of the duct.

АНАЛІЗ СКЛАДОВИХ ЕКСЕРГЕТИЧНОГО ККД КАМЕРНОЇ КОНВЕКТИВНОЇ СУШАРКИ

A methodology for calculating individual components of the exergy balance and the exergy coefficient of useful action for non-stationary heat and mass transfer processes, in particular drying processes, is proposed. It is shown that the analysis of the drying process by exergetic characteristics is more effective than by thermal characteristics, as it makes it possible to estimate both internal and external losses, as well as the potential of energy flows. Calculations of exergetic and thermal efficiency of the chamber convective dryer were performed on the basis of the proposed methodology. It was established that when the temperature of the incoming heat carrier changes from 5 to 35°С, the exergetic efficiency of the drying unit changes within 4...16%, while the thermal efficiency determined using heat balance equations is about 50%. It is shown that with an increase in the temperature of the surrounding environment, the exergetic efficiency of chamber drying units decreases significantly, and the thermal efficiency changes within 5%, while it increases with an increase in the temperature of the heat carrier at the input, and decreases with an increase in the temperature of the heat carrier at the outlet in such the very limits. Exergy losses in drying plants are due to losses caused by flows of substances that carry exergy out of the system, losses as a result of heat exchange at a finite temperature difference, or mass exchange at a finite concentration difference, as a result of mechanical friction and hydraulic resistance, chemical reactions in non-equilibrium conditions, reduction of the magnetic or electric field under the action of electric resistance, etc. To increase the exergy efficiency of chamber drying units, it is necessary to reduce the exergy losses in the heaters, therefore it is preferable not to use steam heaters, it is worth giving preference to electric heaters or pyrolysis boilers of indirect air heating. It is also necessary to reduce heat loss during mixing of spent and fresh heat carrier, to reduce the temperature of the incoming heat carrier.

Ultrafiltration with in-line coagulation (FeCl3) to enhance arsenic removal and improve drinking water quality: From bench to pilot-scale

There is a growing interest in advanced technologies to guarantee drinking water safety in scenarios of increasingly polluted water sources. Based on that, this paper discusses the use of ultrafiltration membranes aided by in-line coagulation with FeCl3 (0.086 – 0.172 mg/L) to improve the resilience of drinking water treatment plants. The process was considered after the settling units and was first studied on a bench scale, later validated in a pilot plant that operated continuously for approximately 31 days. In experiments without an in-line dose of FeCl3, the average flux values corresponded to 189.9 ± 11.8 L/m2h, compared with 193.4 ± 5.3 L/m2h for experiments when the coagulant was considered. The flux decay was lower in experiments with an in-line dose of FeCl3 (J/J0 > 0.95) and analysis of particle sizes revealed that the average diameter increased from 24.1 to 29.2 µm after the coagulant was added. Consequences related to a greater particle size were a fouling layer more porous permeable, and with a lower hydraulic resistance. The additional coagulant dosage also acts on the residual natural organic matter, monitored by excitation-emission matrices. Furthermore, the results show that the concentrate recirculation to the beginning of the water treatment plant did not affect its overall performance. In fact, concentrate recycling would increase the recovery rate of ultrafiltration membranes and reduce losses during water treatment. Similar observations were obtained in pilot-scale operations, that validated the in-line dose on a more representative system that is closer to the full-scale treatment process.

Hydraulic resistance analyses of selected elements of the prototype Stirling engine

The paper presents the results of simulation tests of hydraulic resistance and temperature distribution of the prototype Stirling alpha engine supplied with waste heat. The following elements were analyzed: heater, regenerator and cooler. The engine uses compressed air as a working gas. Analyses were carried out for three working pressure values and different engine speeds. The work was carried out in order to optimize the configuration of the engine due to the minimization of hydraulic resistance, while maintaining the required thermal capacity of the device. Preliminary tests carried out on the real object allowed to determine boundary and initial conditions for simulation purposes. The simulation assumes that there is no heat exchange between the regenerator and the environment. The solid model used in simulation tests includes the following elements: supply channel, heater, regenerator, cooler, discharge channel. Due to the symmetrical structure of the analyzed elements, simulation tests were carried out using 1/6 of the volume of the system.

Experimental hydraulic parameters of drainage grate inlets with a horizontal outflow in the broad-crested weir mode.

The accurate assessment of discharge coefficients for different types of water inlets is crucial for minimizing modelling errors in drainage systems thus reducing the risk of flooding in adjacent areas. This study experimentally investigated the hydraulic characteristics of gully grate inlets with water seal and horizontal outflow, with nominal outlet pipe diameters of 100 and 150 mm, using a laboratory setup that meets the requirements of a special European regulation. Transition depths from the weir to the orifice mode were determined, and it was found that the perforated grates significantly increased the hydraulic resistance compared to the bar grates, resulting in a corresponding decrease in the discharge capacity of gully inlets. Power-law relationships between the weir discharge coefficient and gauge head were obtained for both bar and perforated grate inlets, as well as between the discharge coefficient and Froude number at the perimeter of grate inlets. These findings provide important insights for optimizing the design and performance of water inlets, particularly in the weir mode, which is critical for the proper functioning of drainage systems.

Subchannel Analysis of LFR Wire-Wrapped Fuel Bundle with RELAP5-3D

A computational campaign was carried out at the Department of Astronautical, Electrical and Energy Engineering of Sapienza University of Rome aiming at the assessment of RELAP5-3D© capabilities for subchannel analysis. More specifically, the investigation involved a lead-bismuth-eutectic–cooled wire-spaced fuel pin bundle and compared simulation outcomes with experimental data coming from the NAtural CIrculation Experiment-Upgraded (NACIE-UP) facility, hosted at ENEA Brasimone Research Center. Thermal-hydraulic nodalization of the facility was developed with detailed subchannel modeling of the fuel pin simulator (FPS). Three different methodologies for the subchannel simulation were investigated, increasing step by step the complexity of the thermal-hydraulic model. In the simplest approach, the subchannels were modeled one by one. In addition, mass transfer between them was considered thanks to multiple cross junction components, realizing the hydraulic connection between adjacent subchannels. In this case, mass transfer depends on the pressure gradient and hydraulic resistance only, ignoring the turbulent mixing promoted by the wire-wrapped subassembly. Simulation results were not satisfactory, and an improvement was introduced in the second approach. In this case, several control variables calculate at each time step the energy transfer between adjacent control volumes associated with the turbulent mixing induced by the wires. This energy is transferred using ad hoc heat structures (HSs), where the boundary conditions are calculated by the control variables. The present model highlighted good capabilities in the prediction of the radial temperature distribution within the FPS, considerably reducing disagreement with experimental data. Finally, the influence of radial conduction within the fluid domain was assessed, introducing further HSs. Although this most complex model provided the best estimation of the experimental acquisition, the improvements given by radial conduction were not so relevant to justify the correspondent increase of the computational cost.

Sizes and shapes of perivascular spaces surrounding murine pial arteries

BackgroundFlow of cerebrospinal fluid (CSF) through brain perivascular spaces (PVSs) is essential for the clearance of interstitial metabolic waste products whose accumulation and aggregation is a key mechanism of pathogenesis in many diseases. The PVS geometry has important implications for CSF flow as it affects CSF and solute transport rates. Thus, the size and shape of the perivascular spaces are essential parameters for models of CSF transport in the brain and require accurate quantification.MethodsWe segmented two-photon images of pial (surface) PVSs and the adjacent arteries and characterized their sizes and shapes of cross sections from 14 PVS segments in 9 mice. Based on the analysis, we propose an idealized model that approximates the cross-sectional size and shape of pial PVSs, closely matching their area ratios and hydraulic resistances.ResultsThe ratio of PVS-to-vessel area varies widely across the cross sections analyzed. The hydraulic resistance per unit length of the PVS scales with the PVS cross-sectional area, and we found a power-law fit that predicts resistance as a function of the area. Three idealized geometric models were compared to PVSs imaged in vivo, and their accuracy in reproducing hydraulic resistances and PVS-to-vessel area ratios were evaluated. The area ratio was obtained across different cross sections, and we found that the distribution peaks for the original PVS and its closest idealized fit (polynomial fit) were 1.12 and 1.21, respectively. The peak of the hydraulic resistance distribution is 1.73times 10^{15} Pa s/m^{5} and 1.44times 10^{15} Pa s/m^{5} for the segmentation and its closest idealized fit, respectively.ConclusionsPVS hydraulic resistance can be reasonably predicted as a function of the PVS area. The proposed polynomial-based fit most closely captures the shape of the PVS with respect to area ratio and hydraulic resistance. Idealized PVS shapes are convenient for modeling, which can be used to better understand how anatomical variations affect clearance and drug transport.

Consolidation analysis of composite ground improved by granular piles with a high replacement ratio considering overlapping smear zones

A mathematical model for composite ground improved with granular piles with a high replacement ratio is presented, accounting for the overlapping smear zones, horizontal and vertical permeability coefficients of piles, and time- and depth- dependent surcharge stress in the foundation. Subsequently, solutions for excess pore-water pressure, settlement, and consolidation degree of composite ground are derived analytically using the finite sine Fourier transform. The correctness of the solutions is assessed by comparing with the degenerated cases and numerical results obtained by the finite difference method. Parametric studies are conducted to explore the influence of parameters, such as the loading time, radial permeability coefficient of piles, and overlapping smear zones on the consolidation rate of the foundation and the dissipation process of excess pore-water pressure. Results show that the overlapping smear zones and smaller radial hydraulic resistance of piles can slow down the consolidation rate of composite ground. Furthermore, the optimal layout spacing of piles under different conditions is discussed through numerical analyses. Based on a comprehensive consideration of accelerating the consolidation rate and reducing the total foundation settlement, this investigation provides some reference values of the optimal pile spacing for use in design.

Hydrodynamics and electrical insulation of PbLi flow with SiC flow channel inserts in a strong magnetic field

Experimental and numerical research in a strong magnetic field is described in this article testing silicon carbide (SiC) flow channel inserts (FCI) in lead-lithium (PbLi) liquid metal flow. The study aims to further develop the High-Temperature Dual-Coolant Lead-Lithium nuclear fusion blanket concept by testing new variations of SiC inserts operating in the relevant electromagnetic conditions. These inserts act as electrical insulators in magnetohydrodynamic lead-lithium flow and can also play the role of the thermal insulator in the potentially real fusion environment. The liquid metal pressure and integral flowrate measurements were performed on up to 5T DC magnetic field created by a superconducting magnet at high temperatures up to 700 °C, which is close to the real fusion environment. Comparisons of several cases with and without inserts are provided, demonstrating their impact on hydraulic resistance. Additionally, electrical potential distribution is recorded on the lead-lithium channel walls, which can be used to evaluate the character of liquid metal velocity distribution in the lead-lithium channel.

Numerical analysis of slurry penetration and filter cake formation in front of tunnel face

The bentonite slurry penetration in front of the tunnel face significantly influences the face stability during slurry shield tunneling. In this study, the mechanism of slurry-soil interaction is clarified through the soil microstructural evolution. A transient model coupling the slurry transport and deposition theory is proposed to estimate the slurry penetration and filter cake formation. The time-dependent parameters are considered, including the flow parameters (flow path and pressure gradient) and the hydraulic resistance of soils (soil permeability, porosity, and shear resistance). The proposed model is compared with the infiltration column tests and shows a good agreement.Moreover, a parametric study is conducted to investigate the influence of the soil and slurry properties on the slurry-soil interaction. The results indicate the soil-bentonite relative size is the main factor influencing the formed filter cake type. The filter cake of type Ⅲ (external filter cake and penetration zone) could be formed when the bentonite particle size is between the range of 0.01d10–0.5d10. This type of filter cake has good tightness and could help to improve the face stability when tunneling by slurry shield machine.

Inhibiting Polyamide Intrusion of Thin Film Composite Membranes: Strategies and Environmental Implications.

Thin film composite polyamide (TFC) nanofiltration (NF) membranes represent extensive applications at the water-energy-environment nexus, which motivates unremitting efforts to explore membranes with higher performance. Intrusion of polyamide into substrate pores greatly restricts the overall membrane permeance because of the excessive hydraulic resistance, while the effective inhibition of intrusion remains technically challenging. Herein, we propose a synergetic regulation strategy of pore size and surface chemical composition of the substrate to optimize selective layer structure, achieving the inhibition of polyamide intrusion effective for the membrane separation performance enhancement. Although reducing the pore size of the substrate prevented polyamide intrusion at the intrapore, the membrane permeance was adversely affected due to the exacerbated "funnel effect". Optimizing the polyamide structure via surface chemical modification of the substrate, where reactive amino sites were in situ introduced by the ammonolysis of polyethersulfone substrate, allowed for maximum membrane permeance without reducing the substrate pore size. The optimal membrane exhibited excellent water permeance, ion selectivity, and emerging contaminants removal capability. The accurate optimization of selective layer is anticipated to provide a new avenue for the state-of-the-art membrane fabrication, which opens opportunities for promoting more efficient membrane-based water treatment applications.

Protein valorisation from acid whey – Screening of various micro- and ultrafiltration membranes concerning the filtration performance

Cross-flow filtration allows a product-preserving and energy-saving unit operation for the production of whey protein concentrates (WPC) from acid whey. In micro- and ultrafiltration applications, size-exclusion is the governing separation mechanism. Flux and retention characteristics of 12 organic membranes of pore sizes between 5 and 450 nm were compared. Screening on a laboratory filtration plant revealed large differences regarding hydraulic resistance of the membrane and resistance of the deposit layer that forms on the membrane surface during filtration. As a result, notable variations in the permeate flux were observed between membranes. In contrast, the differences in protein retention were less pronounced. The protein transmission for all ultrafiltration membranes was below 5% whereas microfiltration membranes showed a deposit layer-dependent transmission behaviour. Compared with the conventional WPC35 production, the overall filtration efficiency with regard to the process duration for a comparable membrane area was 3-fold enhanced by a more appropriate membrane selection.

Characterization and associated pressure-dependent behavior of deposits formed during sterile filtration of mRNA-Lipid nanoparticles

The recent success of mRNA vaccines has generated increased interest in the use of Lipid Nanoparticles (LNPs) for delivery of nucleic acids. The objective of this study was to characterize the deposit formed on the surface of membranes during sterile filtration of mRNA-LNPs using a combination of scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM), atomic force microscopy (AFM), and hydraulic resistance measurements. The microscopic characterizations showed an amorphous deposit fouling the surface of the filter and blocking the membrane pores. The resistance of the deposit showed an unusual biphasic behavior, increasing at low pressure (consistent with a compressible filtration medium) but decreasing at high pressure, in a reversible manner. The surprising reduction in resistance at high pressure has not previously been identified in the filtration literature. The pressure corresponding to the maximum resistance (Pcritical) was found to be proportional to the inverse of the membrane pore size, as described by the Young-Laplace relationship. The hydraulic resistance measurements and microscopic characterization are consistent with a mechanism whereby an amorphous fouling deposit intrudes through membrane pores at high transmembrane pressures. These results provide important insights into the physical properties of the fouling deposit that governs the sterile filtration of LNPs.

Numerical simulation of non-isothermal supercritical water flow in ground pipeline and wellbore: An interactive sensitivity analysis and injection parameters optimization

Supercritical water injection is promising in enhanced heavy oil recovery, in which precise prediction and regulation of bottomhole parameters are the prerequisite for improving the recovery efficiency. However, dramatically changing thermophysical properties make it difficult to calculate the hydraulic and thermal resistances of supercritical water flow in ground pipeline and wellbore. In this work, a comprehensive mathematical model was established to simulate the non-isothermal flow of supercritical water from boiler outlet to bottomhole. Modified correlations of friction coefficients and convective heat transfer coefficients respectively developed for vertical and horizontal flow of supercritical water were coupled in momentum and energy conservation equations to calculate the hydraulic and thermal resistance. The model was validated by oilfield and laboratory data with the relative deviations of pressure and temperature less than 2%. The interactive sensitivity analysis was carried out by response surface method for injection parameters optimization. The results indicated that the heat loss in ground pipeline was comparable to that in wellbore once it reached 10 times longer than wellbore and should be taken into consideration. Increasing mass flux was found to be efficient for reducing the heat loss resulted from the decline of wellbore insulation. But there existed a matching combination of injection pressure and mass flux that making bottomhole temperature the highest. For a typical injection case with a poor insulation wellbore and limited injection temperature, a combination of high mass flux and low injection pressure was recommended for achieving targeted bottomhole temperature due to its high thermal efficiency.

Analytical and numerical investigations of fluid flow and heat transfer in turbulent slip incompressible flow in a cylindrical channel

Based on two analytical approaches (Prandtl model and von Kármán model), turbulent flow in a cylindrical channel with flow slippage on the wall was considered. The results of the analytical solution are supplemented with numerical simulations based on the lattice Boltzmann model (LBM). Validations of the analytical model against numerical computations showed their good agreement. The analytical model enabled obtaining relations for the velocity profile, hydraulic resistance coefficient and Stanton number, which make it possible to evaluate the influence of the slip effect (Kn) and the flow rate (Re) on their variation.

Prediction of test results to determine the hydraulic resistance coefficient of an axially symmetrical check valve

The urgency of the paper is determined by the necessity to predict the results of tests for determining the coefficient of hydraulic resistance of axially symmetrical check valve DN 100-600 with operating pressure up to 20 MPa and operating temperature from plus 50C to plus 3500C according to TS 6981-254-08847871-07. This paper suggests to reduce the volume of tests by excluding the tests for intermediate samples of valves (DN 100, DN125, DN 200, DN 300, DN 500, DN 600) situated in DN between the valve type models (DN 100, DN 175, DN 400) and replaced the tests by calculations in the programme module ANSYS CFX of the calculation complex ANSYS. The results of the tests for determining the coefficient of hydraulic resistance are given. An estimate of hydraulic resistance coefficient values is offered and recommendations for its determination are given. The experimental determination of hydraulic characteristics was carried out in the region of quadratic resistance and in absence of cavitation (the tests were done on water). The region of quadratic resistance comes at Reynolds numbers Re ≥ 2 × 104 for check valve of nominal diameters DN ≤ 250. The region of quadratic resistance ReKB is determined in the process of experimental determination of drag and flow capacity factors for valves of nominal diameters DN ≥ 250. The procedure of determination of ReKB is described in 7.2.3 of GOST 55508-2013. These test results for determination of hydraulic resistance coefficient for valves DN 150, DN 175, DN 400 according to TU 6981-254-08847871-07 can be used when developing acceptance test programs to set the number of tested samples according to the design features and number of versions of check valves (DN 100, DN125, DN 200, DN 300, DN 500, DN 600), replacing the testing by calculation.

Experimental Investigation of Thermal-Hydraulic Performance of Externally Finned Tubes

Currently there are various concepts of heat transfer intensification, on the basis of which methods have been developed to increase the heat transfer coefficient in the channels of heat exchange surfaces, which do not lead to significant additional energy costs for flow movement. The article presents the results of an experimental study on the influence of various types of fins on heat transfer processes and hydraulic resistance. The results obtained show that fins in the form of crosses and triangles are the most efficient in terms of heat transfer. However, they create the greatest hydraulic resistance. The largest value of the Nusselt number is relevant for fins type 5 and 6 due to a more active effect on the core of the flow owing to its shape. Fins 7 and 4 have the minimal influence, since they have the ‘smoothest’ shape. Studies have shown that with Reynolds numbers in the range of 13,000–32,000, fins of type 4 and 7 show the greatest resistance. It is shown that it is possible to switch from pipes without fins to pipes with fins by including the coefficient B in the Nusselt equation having a range of 0.03–0.061. It is shown that under certain conditions, heat transfer when using fins can decrease with increasing Reynolds number.

THERMO-HYDRAULIC CHARACTERISTICS OF ADDITIVELY MANUFACTURED MINI-CHANNELS

The aim of this work is to analyze the heat transfer, hydraulic resistance and thermo-hydraulic performance of a new type of heat exchange channels made by additive technology. The main factors affecting the quality of products and determining the heat transfer and hydraulic resistance of the channels are noted. Well-known ratios for calculating hydraulic resistance and heat transfer are not suitable for such high roughness. Data on the AT resistance coefficient of the channels show that even at low Reynolds numbers there is a contribution of roughness. With increasing roughness, the intensification of resistance and heat exchange increases. The transition occurs at 700 < Re < 2000. Comparison of data on heat transfer augmentation and increase of hydraulic losses, as well as their thermo-hydraulic characteristics has been carried out. The hydraulic resistance coefficient of AT channels is significantly higher than the resistance coefficient of smooth channels. Heat transfer augmentation in wave-shaped channels is 2 times higher than augmentation in straight channels. Channels with pin fins allow to achieve a very high heat transfer augmentation (up to 8). Channels with internal grids provide high intensification, but have the highest hydraulic losses. The dependence of the Reynolds analogy factor on the resistance increase factor showed that the straight channels of all geometric forms fit on one dependence closed to the lower boundary line, and have a low hydraulic resistance. Data on channels with pin fins have a large spread. A number of points are above the upper boundary line, which refers to channels with low surface roughness.

THE FLOW OF LUBRICANT IN A NARROW WEDGE-SHAPED SLOT WITH A MOVABLE WALL IS CONSIDERED

The article presents the results of a study of the lubricant flow in a narrow wedge-shaped slot with a movable wall. A solution to the problem with slip boundary conditions on the channel walls is obtained. The effect of slippage on the change in hydrostatic lift and hydraulic resistance in the slotted channel is shown.
 It was determined in the work that with an increase in the slip intensity (an increase in the value of the Knudsen number), the pressure variation weakens. This is due to the weakening of the interaction of the flow with the wall. As a result, the hydraulic resistance is reduced.
 The dependence of the relative hydrostatic lifting force on the Knudsen number and the opening angle of the channel is obtained. It is determined that with an increase in the Knudsen number, the magnitude of the hydrostatic lifting force decreases, since the influence of the flow on the wall weakens. The influence of slippage weakens with an increase in the opening angle of the channel.

Influence of thickness of metal foam on the conduction and convection heat transfer for a flat plate with metal foam impinged by a single circular air jet

ABSTRACT The effect of the metal foam thickness on the conduction and convection heat transfer for a metal foam flat plate impinged by a circular air jet is investigated. The IR thermography and thin-metal foil technique are used for the measurement of local heat transfer. An open-cell aluminum metal foam is used for the metal foam flat plate. A 3D-printed resin foam and detached metal foam flat plate are used for the appreciation of the conduction and convection heat transfer. The varying parameters are the thickness of the foam, Reynolds number, and the nozzle exit to plate distance. The presence of the metal foam offers a conduction effect. This predominates over the attenuation in the convective heat transfer by foam due to additional hydraulic resistance. The additional hydraulic resistance offered by the porous foam increases with the increase in the foam thickness. The heat transfer of a porous foamed flat plate decreases with the increase in the foam thickness. The local Nusselt number of the resin foam and detached foam flat plate is almost the same. The conduction effect and attenuation in the convection heat transfer of a metal foam flat plate are quantified by attenuation and enhancement factors. The overall augmentation offered by 4, 8, and 12 mm thick metal foam flat plates is 1.71, 1.42, and 1.43 times compared to the smooth flat plate case, respectively. Hence, it is advisable to use a metal foam flat plate with 4-mm-thick metal foam under circular air jet impingement.