Bar Pressure Drop Research Articles

Tungsten based divertor development for Wendelstein 7-X

Wendelstein 7-X, the world’s largest superconducting stellarator in Greifswald (Germany), started plasma experiments with a water-cooled plasma-facing wall in 2022, allowing for long pulse operation. In parallel, a project was launched in 2021 to develop a W based divertor, replacing the current CFC divertor, to demonstrate plasma performance of a stellarator with a reactor relevant plasma facing materials with low tritium retention. The project consists of two tasks: Based on experience from the previous experimental campaigns and improved physics modelling, the geometry of the plasma-facing surface of the divertor and baffles is optimized to prevent overloads and to improve exhaust. In parallel, the manufacturing technology for a W based target module is qualified.This paper gives a status update of project. It focusses on the conceptual design of a W based target module, the manufacturing technology and its qualification, which is conducted in the framework of the EUROfusion funded WPDIV program. A flat tile design in which a target module is made of a single target element is pursued. The technology must allow for moderate curvatures of the plasma-facing surface to follow the magnetic field lines. The target element is designed for steady state heat loads of 10 MW/m2 (as for the CFC divertor). Target modules of a similar size and weight as for the CFC divertor are assumed (approx. < 0.25 m2 and < 60 kg) using the existing water cooling infrastructure providing 5 l/s and roughly maximum 15 bar pressure drop per module.The main technology under qualification is based on a CuCrZr heat sink made either by additive manufacturing using laser powder bed fusion (LPBF) or by uniaxial diffusion welding of pre-machined forged CuCrZr plates. After heat treatment, the plasma-facing side of the heat sink is covered by W or if feasible by the more ductile WNiFe, preferably by coating or alternatively by hot isostatic pressing W based tiles with a soft OFE-Cu interlayer. Last step is a final machining of the plasma-exposed surface and the interfaces to the water supply lines and supports to correct manufacturing deformations.

Separation Properties of Porous MoS2 Membranes Decorated with Small Molecules.

Using first-principles simulations, we surveyed the interactions between porous MoS2 monolayers in the 2H phase and 15 small molecules (H2, O2, H2O, H2S, CO, CO2, SO2, N2, NO, NO2, NH3, HF, HCl, CH4, and CH3OH). Four types of molecules including H2, O2, H2S, and NO2 directly dissociate and saturate the corners of the most common S-rimmed triangular pores, while other molecules only molecularly adsorb. The trisublayered structure of a MoS2 monolayer allows a new in-pore stable adsorption configuration in addition to the most studied above-pore adsorption configuration. Furthermore, the gas penetration pathways through the MoS2 membranes are no longer the conventional single-peak curve with one transition state like in the case of porous graphenes but are the "M"-shaped curve featuring two transition states connected by a stable in-pore adsorption state. The irreversible pore passivation via dissociative adsorption and reversible pore decoration by molecular adsorption will lead to very different separation performances of the MoS2 membranes, largely by changing the effective pore size. For example, the S-rimmed pores in the pore-3Mo2S membrane allow free pass of CH4 and CO2 molecules. If passivated by H atoms, the membrane can be used to separate gas mixtures like H2/CH4 and H2/CO2 with selectivities of 109:1 and 108:1, respectively. The permeance value of H2 is estimated to be about 0.15 mol m-2 s-1 Pa-1 at room temperature and 0.1 bar pressure drop across the membrane. In contrast, the medium strong adsorption of a SO2 molecule in the center of the pore will completely block the passage of CO2 and CH4, whose removal only needs heating. Our work reveals the complex behaviors of porous transition metal dichalcogenides (TMDs) toward guest molecules.

A computational methodology for estimation of aerosol retention in a sand-bed based filtering system for severe accident venting strategies

A computational methodology to estimate the capacity of aerosol particle retention in a filter- ing system based on sand bed is described in this work. This methodology uses a combination of computational fluid dynamics and mechanistic models in the calculation procedure. The methodology is applied to venting actions during a severe accident in a BWR Mark II primary containment. The SALOME and OpenFoam platforms were used to generate the geometric and numerical models of a full scale model of a sand bed filtering system. The Eulerian/Lagrangian approach was used to determine the steady-state of a compressible turbulent flow through a porous media and to compute the aerosol particle transport, respectively. Collection efficiency was calculated by means of a mechanistic model based on the capture efficiency of a single grain. The obtained Eulerian results include velocity, pressure, and temperature fields inside the filtering systems. The Lagrangian tracking of aerosol particles showed that particles crossing the coarser sand tend to accumulate initially on the periphery of the filter. The parametric studies showed that mass-flows of up to 4.7 kgs?1 satisfy the constraint of 1.1 bar pressure drop across the sand depth. Additionally, the efficiency of 99.5 % of retention was determined for 1.0 ?m aerosol particles in the 0.6 mm sand grain zone, for a gas velocity m of ms?1.

Design and off-design analysis of a Tesla Turbine utilizing CO2 as working fluid

The Tesla turbine is a bladeless expander; which principle of operation is based on the conversion of the viscous forces, developed by the flow while expanding through the rotor, in mechanical energy. It is especially suitable for small/micro size distributed energy systems (kW scale), mainly due to its very low cost, which results from the simple structure of the machine. The Tesla turbine works well at relatively moderate expansion ratios. Therefore, it is fit for CO2 power cycles applications that are characterised by small expansion ratio, despite the high pressure involved. In this work, the design and off-design analysis of a Tesla turbine for small/micro power application utilizing CO2 cycles is proposed. The optimized design was targeted for an inlet temperature of 150 °C and an inlet pressure of 220 bar. The final optimized geometry of the expander was defined, achieving a 23.4 W per channel power output with a 63% isentropic efficiency, when working with a 10.1 bar pressure drop at 2000 rpm. Furthermore, the turbine placement on the Baljè diagram was performed in order to understand the direct competitors of this machine. Finally, starting from the design configuration, the maps of efficiency at variable load and flow coefficients and that of reduced mass flowrate at variable pressure ratio were realized. Through the merging of these curves, the off-design maps of the Tesla turbine were obtained, highlighting a very limited sensitivity of the efficiency to variable working conditions, if rotational speed is adequately adjusted.

Design of header and coil steam generators for concentrating solar power applications accounting for low-cycle fatigue requirements

Concentrating solar power plants are experiencing an increasing share in the renewable energy generation market. Among them, parabolic trough plants are the most commercially mature technology. These plants still experience many challenges, one of which is the cyclic daily start-up and shut-down procedures. These pose new challenges to industrially mature components like the steam generator system, as frequent load changes might decrease their lifetime considerably due to cyclic thermo-mechanical stress loads. In this context, the header and coil design is a promising configuration to minimize the stresses.This paper presents a method to design the header and coil heat exchangers of the steam generator, taking into account low-cycle fatigue requirements, by defining minimum allowable heating rates for the evaporator and superheater. Optimal designs were obtained by minimizing the total water pressure drops and purchase equipment costs. A comparison with a sizing routine without accounting for low-cycle fatigue constraints was also conducted.The model was validated against the component data of a 55 MWe power plant, with a maximum deviation on the total area estimation of +2.5%. The results suggest that including the heating rate constraints in the design routine substantially affects the optimal design configuration, with a 41% cost increase for a 1 bar pressure drop. The optimal design for maximizing the lifetime of the components uses tube outer diameters of 38 mm and 50 mm and a low number of tubes per layer (4–10) for the superheater.

Comparison of compressible and incompressible numerical methods in simulation of a cavitating jet through a poppet valve

ABSTRACTThe regime of compressible flow generally refers to the super/subsonic case. However, several remarkable cases with low Mach number could not be appropriately described with the incompressible method. It is a similar case for a cavitating jet inside a poppet valve. In order to comprehensively address the discrepancy between incompressible and compressible methods, both non-cavitating and cavitating cases are performed in experiment and calculation based on OpenFOAM. Experiment reveals a transition in flow pattern in both non-cavitating and cavitating flow. For example, for 0.7 mm openness and 30-degree poppet angle, transition happens at approximately 29 and 27 bar pressure drop for the two cases, respectively. In general, results from the compressible method exhibit better agreement with experiment regarding both flow performance and flow structure. By contrast, the incompressible method could not provide an accurate description for the transition process under the applied flow condition. A series of studies are carried out with emphasis on such discrepancy. Firstly, the deviation in flow performance is addressed based on velocity profile and turbulence level. Secondly, the disparity in flow structure is illustrated and the mechanism for cavitation inception is discussed, which combined provide an interpretation of the deficiency of the incompressible method. Thirdly, different inlet boundary conditions are applied, and the results confirm the independence of deficiency of the incompressible method for inlet fluctuation. Finally, a re-examination is proposed concerning traditional notion of compressible flow as well as the applicability of incompressible numerical method.

Analisis Termal-hidrolik Reaktor Cepat Berpendingin Gas (Gas Cooled Fast Reactor) Menggunakan Metode Runge Kutta

The Research of Gas Cooled Fast Reactor (GCFR) thermal-hydraulics analysis has been done. This reseacrh aim to solve fuel rod heat conduction equation by Runge Kutta method and to get thermal-hydraulics parameters such as coolant axial temperature distribution, pressure drops, convection heat transfer coefficient, and fuel rod radial temperature distribution. Heat transfer of the reactors was assumted steady state (time independent) then obtained coolant inlet tempertaure about 450 o C, outlet temperature about 474,752 o C and convection heat transfer coefficient about 2,5903 W/cm 2 o C. Pressure drop by friction was 0,16968 bar, pressure drop by form was 0,31292 bar, pressure drop by gravity was 0,20580 bar and total pressure drop was 0,68838 bar. While centerline fuel obtained the maximum temperature of fuel rod about 2720,33812 o C and the lowest fuel rod temperature at cladding surface about 488,8205 o C.

Analisis Termal-hidrolik Reaktor Air Bertekanan (Pressurized Water Reactor) Menggunakan Metode LU Faktorisasi

The Research about Pressurized Water Reactors (PWR) thermal-hydraulics analysis has been done. This reseacrh aim to solve fuel rod heat conduction equation by LU Factorization method and to get thermal-hydraulics parameters such as coolant axial temperature distribution, pressure drops, convection heat transfer coefficient, and fuel rod radial temperature distribution. Heat transfer of the reactors was assumted steady state (time independent) then obtained coolant inlet tempertaure about 300 o C, outlet temperature about 326,6 o C and convection heat transfer coefficient about 1,43 W/cm 2 o C. Pressure drop by friction was 0,423 bar, pressure drop by form was 0,51 bar, pressure drop by gravity was 0,25 bar and total pressure drop was 1,183 bar. While centerline fuel obtained the maximum temperature of fuel rod about 1.589,2 o C and the lowest fuel rod temperature at cladding surface about 360,9953 o C

Tuning Water Nanofiltration Performance of Few-Layered, Reduced Graphene Oxide Membranes by Oxygen Plasma

Ultrathin, graphene oxide (GO) membranes have shown great potential for water nanofiltration applications. However, due to the difficulties in controlling the intrinsic oxygen-containing functional groups on GO and the swelling of GO interlayers in aqueous solution, it is highly challenging to tune GO membranes’ nanofiltration performance by adjusting their hydrophilicity and interlayer nanochannel size. In this study, oxygen plasma was reported as an effective technique to tune water nanofiltration performance of few-layered, reduced graphene oxide (rGO) membranes, by improving rGO membranes’ hydrophilicity and/or adjusting effective permeation nanochannel/pore sizes. The 5 nm thick GO membranes were fabricated through a layer-by-layer deposition method and subsequently reduced at 220 °C under vacuum. No detectable water permeance (<1.0 L/(m2·h·bar)) under 5 bar pressure drop suggests the high quality of the rGO membranes possibly with very small hydrophobic nanochannels/pores. Exposure to oxygen plasma ...

Gas-phase polymerization of propylene at low reaction rates: a precise look at catalyst fragmentation

In this work, we reported the development of a mini-reactor experimental setup for synthesizing of polypropylene with heterogeneous Ziegler–Natta catalysts in gas-phase. Use of pro-activated 4th generation of Ziegler–Natta catalyst and preheated monomer feed enabled the polymerization reaction to be carried out at constant temperature. Evaluation of monomer consumption with high precision (0.01 bar pressure drop) allowed the detection of polymerization yield at low reaction rates. In this regard, polymerization yield, particle morphology and catalyst fragmentation were studied, as well. The results of melt microscopy showed that catalyst fragmentation was developed during the reaction, and was not restricted to the initial rupture of catalyst particles. The rate determination showed a peak during the polymerization (not necessarily at the initial stage). The results showed that depending on the reaction condition, this peak could be either a consequence of a major catalyst fragmentation or overheating. Low reaction yield, large fragments of catalyst and agglomeration of particles were considered as evidence of particle overheating and polymer local melting. As we imposed the results of melt microscopy for the polymerization conditions, a layer-by-layer fragmentation of the catalyst was found to be the main fragmentation process, at least at the beginning of the polymerization reaction.

ITER ECH Switch Design and Analysis

The electron cyclotron heating system (ECH) on ITER uses 24 evacuated microwave transmission lines carrying up to 1.4 MW of power each at 170 GHz to provide resonance heating of electrons in the ITER plasma and to enable plasma current drive. A critically important component in this system is the microwave switch that allows the microwaves to be directed from the gyrotrons to either dummy loads or between launchers in the upper and equatorial ports of the ITER tokamak while maintaining the vacuum integrity of the transmission lines. A moveable, water-cooled CuCrZr mirror is used to redirect the microwave transmission between two orthogonal waveguides.In this article we describe the optimized design of the mirror cooling passages produced by computational fluid dynamics analysis using ANSYS CFX with k-ε and k-ω shear stress transport turbulence models, and verify that the design parameters for mass flow rate, inlet temperature and pressure are adequate for good thermomechanical performance. Non-uniform heating of the mirror face from the incident microwaves induces deflections that should be less than 25 microns to meet the integrated transmission line efficiency specification. In the current 1.4 MW switch design, 0.03 kg/s of 36°C water at 10 bar inlet pressure can remove the 2660 W of ohmic heating in the mirror produced by the elliptical polarization power and maintain the surface temperature below 150°C. The water delta-T is 21°C with a 0.5 bar pressure drop in the mirror. The maximum predicted displacement in the center of the mirror face is less than 25 μm.

Comparative study of seeding methods; dip-coating, rubbing and EPD, in SAPO-34 thin film fabrication

Seeding methods; including rubbing, dip-coating and electro-phoretic deposition (EPD) were comparatively implemented for silicoalumino phosphate-34 (SAPO-34) thin film fabrication via secondary growth. The size of surface particles and thicknesses of fabricated layers were characterized by Scanning Electron Microscopy. The so-called properties were analyzed and modified to achieve a fairly defect free surface coverage and thin layers with finest particles. One-step dip-coating method provided well-distributed seeds on the support surface with a very poor coverage. Rubbing and EPD methods preferentially provided defect free and uniform surface coverage, however the grown particles from EPD method were bigger than those from rubbing method. It was revealed that in situ (no seeding) crystallization and one-step dip-coating method failed to produce defect free qualified membranes whereas EPD and rubbing methods caused continuous and defect free SAPO-34 membrane layers. To control synthesis parameters in the secondary growth crystallization, two important parameters were studied; crystallization time at three levels of 12, 24 and 48h and crystallization temperature at three levels of 458, 473, and 488K were simultaneously examined with the aforesaid seeding methods. Significant effects of crystallization temperature and time were observed on the formed layer qualities. The fabricated membrane by rubbing method during 24h crystallization time at 473K temperature was tested under equimolar gas mixture of hydrogen–methane at 293K with pressure drops ranging from 1 to 6bar. At one bar pressure drop, H2 was enriched up to 84.2mol% in the permeate side with the permeance of 6×10−8mol/(m2sPa).

Development of a Liquid Flow Meter for Aerospace Instrumentation

This paper deals with the analysis, design, manu-facturing, testing and evaluation a turbine flow meter to measure liquid propellant flow in launching rockets. Axial turbine flow-meters exhibit superior performance when used with low kinematic viscosity fluids. Under subsonic turbulent flow conditions these instruments show a highly linear behavior with very good repeatability without any additional compensation (neither hardware nor software) and they also exhibit a low pressure drop at maximum liquid flow. A 10 liter/s @ 1 bar pressure drop flow-meter designed to be used with MMH and NTO liquid propellants is exposed. Starting from the turbine's motion equations, the relative incidence of active and parasitic torques is analyzed, both in stationary and transient flow conditions. The dependence of the instrument's proportionality factor (K-factor: pulses per liter) related to the properties of the flowing fluid and turbine dynamics is evaluated in both aforesaid situations. The instrument has been assembled and successfully tested. The paper includes some abridged benchmark results.

Cyclic Filtration-Cleaning of Chlorella vulgaris Using Surface-Modified Hydrophilic Polytetrafluoroethylene Membrane with Polyaluminum Chloride as Coagulant

Membrane filtration can efficiently harvest microalgae from culture broth. The performances of cyclic filtration and cleaning tests on Chlorella vulgaris were evaluated with polyaluminum chloride (PACl) coagulation and with a surface-modified hydrophilic polytetrafluoroethylene (PTFE) membrane under 1 bar pressure drop. Filtration of the original algal suspension without PACl coagulation could lead to severe irreversible fouling on the PTFE membrane. Coagulation using 10 mgl−1 PACl can mitigate pore blocking but cannot enhance filtration flux. With 500 mgl−1 PACl, most fines were incorporated into large flocs to build up cakes of low resistance and protect membrane pores from severe blocking. Flux recovery all exceeded 95% with ≥10 mgl−1 PACl dosage. The PACl-coagulation and surface modified PFTE membrane are feasible to dehydrate Chlorella vulgaris ESP-6 isolate using cyclic filtration-cleaning process. Supplemental materials are available for this article. Go to the publisher's online edition of Drying Technology to view the free supplemental file.

Optimal Generation of 254nm ultraviolet radiation

The science of the application of 254nm UV from mercury doped glow discharge tubes has been a major topic since Johann Ritter discovered UV via its chemical inducing reactions in 1801 and Niels Finsen's 1860 work on UV therapy in treating rickets. In 1857 Siemens AG patented UV254nm creation via filamentary discharge, subsequently widely used for ozone production. By 1932 the Coblentz Congress had defined the three regions of the UV action spectrum. This paper presents the science of a new design for a sterilizer module fabricated from extruded, recycled aluminium. This novel design achieves better than D10 performance using six UV tubes per module driven by three electronic ballasts drawing a total current of only 1.26 amps at 240V single phase. This module delivers more than 45,000 microwatts per square centimetre of 254nm UV which sterilises one litre per second in a module with a dwell time of 1.6 seconds in a design with less than 0.5 bar pressure drop across each module. This system takes the electrical efficiency of 254 UV generation from less than 25% to more than 92% as measured by an NPL-traceable calibration against a current industry standard. Since 254nm UV generating tubes are also the basis of fluorescent lighting this new work on optimising the generation of 254nm UV also has application worldwide to improved efficiency of fluorescent tube electrical lighting, because we have shown that most of the fluorescent lamps operating today (particularly the T8 1 diameter) are running at less than 25% efficiency as opposed to the over 92% which is possible with the methods we describe. The work reported here shows that the Townsend equation for electron transport in glow discharge plasmas is not adequate since it does not address either plasma diameter or plasma drive frequency both of which fundamentally alter the electron energy transfer efficiencies to mercury atoms in the plasma.

Ultra high pressure liquid chromatography: Column permeability and changes of the eluent properties

The behavior of four similar liquid chromatography columns (2.1 mm i.d. × 30, 50, 100, and 150 mm, all packed with fine particles, average d p ≈ 1.7 μ m, of bridged ethylsiloxane/silica hybrid-C 18, named BEH-C 18) was studied in wide ranges of temperature and pressure. The pressure and the temperature dependencies of the viscosity and the density of the eluent (pure acetonitrile) along the columns were also derived, using the column permeabilities and applying the Kozeny–Carman and the heat balance equations. The heat lost through the external surface area of the chromatographic column was directly derived from the wall temperature of the stainless steel tube measured with a precision of ± 0.2 ° C in still air and ± 0.1 ° C in the oven compartment. The variations of the density and viscosity of pure acetonitrile as a function of the temperature and pressure was derived from empirical correlations based on precise experimental data acquired between 298 and 373 K and at pressures up to 1.5 kbar. The measurements were made with the Acquity UPLC chromatograph that can deliver a maximum flow rate of 2 mL/min and apply a maximum column inlet pressure of 1038 bar. The average Kozeny–Carman permeability constant of the columns was 144 ± 3.5 % . The temperature hence the viscosity and the density profiles of the eluent along the column deviate significantly from linear behavior under high-pressure gradients. For a 1000 bar pressure drop, we measured Δ T = 25 – 30 K, ( Δ η / η ) ≃ 100 % , and ( Δ ρ / ρ ) ≃ 10 % . These results show that the radial temperature profiles are never fully developed within 1% for any of the columns, even under still-air conditions. This represents a practical advantage regarding the apparent column efficiency at high flow rates, since the impact of the differential analyte velocity between the column center and the column wall is not maximum. The interpretation of the peak profiles recorded in UPLC is discussed.

Application of diamond to enhance choke valve life in erosive duties

As part of a LINK surface engineering project, a consortium of universities, hard materials suppliers, valve manufacturers and end users have investigated the incorporation of CVD diamond into choke valves to enhance valve life in erosive duties. Diamond was applied to regions of the valve trim and tested under full scale conditions in a high pressure valve loop test facility and compared with standard uncoated tungsten carbide trims. The valve trims were tested with a 60 bar pressure drop and a flow rate of 7.5 l s −1 using water–sand slurry containing 1% (w/w) solids with a mean diameter of 194 μm. The results show that valve seats and plugs with a partial coverage of CVD diamond exhibit 50–60% greater resistance to damage caused by sand particle impingement. Moreover, it is felt that further improvements are attainable with subtle improvement of the design of the trim and coating processes to allow complete coating of critical components with complex design.