Electron Heat Flow Due to Magnetic Field Fluctuations

Radial heat transport induced by magnetic field line fluctuations is obtained from the integral parallel heat flow closure for arbitrary collisionality. The parallel heat flow and its radial component are computed for a single harmonic sinusoidal field line perturbation. In the collisional and collisionless limits, averaging the heat flow over an unperturbed surface yields Rechester-Rosenbluth like formulae with quantitative factors. The single harmonic result is generalized to multiple harmonics given a spectrum of small magnetic perturbations. In the collisionless limit, the heat and particle transport relations are also derived. © 2016 IOP Publishing Ltd

Design of a Combined Redrawing-Ironing Process to Manufacture a CNG Pressure Vessel Liner

The liner of a compressed natural gas pressure vessel is manufactured by D.D.I. (deep drawing and ironing), which is a continuous process that uses deep drawing to reduce the diameter of a billet and ironing to reduce the thickness of the billet. In the second stage of the existing D.D.I. process, drawing and two steps of ironing have been performed separately with different dies, which requires a long processing time, high manufacturing cost, and installation space. To solve the above problems, this study suggests a new second stage using a combined redrawing-ironing die. A theoretical formula to calculate the forming load of the combined redrawing-ironing process was established and verified with finite element analysis results. The forming load, maximum thickness reduction ratio in the second stage, and forming defects in the third stage were analyzed by varying the redrawing-ironing ratio in the second stage. The results show that the number of dyes (3 → 1), punch diameter (394.1 mm → 383 mm), and processing time (39.8 s → 20 s) in the second stage were obtained to save production time and cost

Determination Of Membrane Pore Size Distribution Using The Fractional Rejection Of Nonionic And Charged Macromolecules

The objective of this study was to develop a new measurement technique for the determination of pore size distributions (PSDs) of polymeric and ceramic membranes, including NF, UF, and MF membranes. The proposed method uses the fractional rejection (FR) concept of a solute in membrane pores. Experimental measurements were conducted using a high performance liquid chromatography (HPLC) equipped with size exclusion chromatography (SEC) columns and a refractive index (RI) detector. A specially designed membrane filtration unit was also used. Two different macromolecules, including nonionic polyethylene glycols (PEG) and natural organic matter (NOM) with ionizable functional (carboxylic and phenolic) groups, were used as solutes. Membrane PSDs, determined with PEG and NOM, can be defined as absolute and effective membrane PSDs, respectively. Two different types of membranes (flat-sheet polymeric and tubular ceramic) were used in this work. Experimental procedures include three major steps: (1) measurements of relative molecular mass (RMM) distributions of solutes included in the membrane feed and corresponding permeate, (2) the calculation of solute FR, and (3) PSD determination.The main results and advantages of this method are: (1) the PSD of various membranes with different pore sizes can be measured using a relatively easy method without significant limitations of pore size and membrane type; (2) various factors that affect membrane PSD, including pH, ionic strength, ion binding, and hydrodynamics, can also be evaluated; (3) the effective PSD of membranes with negatively-charged surfaces, and which exhibit significant shifts in PSD towards the lower RMM region can also be determined. Copyright © 2002 Elsevier Science B.V

Optimization of Screw Mixer to Improve Drying Performance of Livestock Manure Dryer Using CFD Analysis

Scarcity of fossil fuels and their emissions of fossil fuel pollutants, such as carbon dioxide, into the atmosphere, and the resulting consequences, have led energy policymakers to look for alternative renewable and clean energy sources. The use of animal wastes is one of the very promising renewable energy alternatives paving the way for a more sustainable energy network. Animal manure produced by livestock farms has a moisture content of about 80%, and such livestock manure is dehydrated to a moisture content of 20–25% and solidified to be used as biomass and fuel for thermal power plants. Previous studies on manure dryers have been concentrated on convection-type dryers, but this type of dryer has the disadvantage of inadequate processing capacity per hour because it cannot agitate manure. In this study, to deal with the drawbacks of conventional livestock manure drying methods, a screw-type dryer was proposed. CFD analysis of the dryer was performed by selecting the viscosity of livestock manure and design parameters of the screw using Ansys Workbench. Through the response surface method, optimal design of the screw shape for the improvement of drying efficiency and smooth discharge of residual manure was carried out

Evidence of perpendicular flow bifurcation at the onset of ELM-crash suppression

The evidence of perpendicular electron flow (v ⊥,e \begin{figure}[htbp] \centerline{\includegraphics[width=0.23in,height=0.18in]{140720171.eps}} \label{fig1} \end{figure} ) bifurcation at the onset of ELM-crash suppression has been measured using electron cyclotron emission imaging (ECEI) system [1] for the first time in KSTAR. The ECEI has shown that (1) resonant magnetic perturbation (RMP) enhances small scale turbulent fluctuations in the edge toward the ELM-crash suppression phase, (2) the induced turbulence regulates growth of the ELM filament via nonlinear interaction between them [2]. Cross spectra and correlation analysis among the ECEI channels revealed that the ELM crashes get suppressed along with a rapid reduction of v ⊥,e \begin{figure}[htbp] \centerline{\includegraphics[width=0.23in,height=0.18in]{140720172.eps}} \label{fig2} \end{figure} close to zero (small but finite value) together with decrease of its shear. The v ⊥,e ∼ 0 km/s \begin{figure}[htbp] \centerline{\includegraphics[width=0.78in,height=0.18in]{140720173.eps}} \label{fig3} \end{figure} is sustained during the ELM-crash suppression even under a large variation of RMP current and external torque and when this condition is violated, ELM crashes are reappeared. [1] G.S. Yun et al., Rev. Sci. Instrum., 81 (2010) 10D930 [2] J. Lee et al., Phys. Rev. Lett., 117 (2016) 0750011

Determination of membrane pore size distribution using the fractional rejection of nonionic and charged macromolecules

The objective of this study was to develop a new measurement technique for the determination of pore size distributions (PSDs) of polymeric and ceramic membranes, including NF, UF, and MF membranes. The proposed method uses the fractional rejection (FR) concept of a solute in membrane pores. Experimental measurements were conducted using a high performance liquid chromatography (HPLC) equipped with size exclusion chromatography (SEC) columns and a refractive index (RI) detector. A specially designed membrane filtration unit was also used. Two different macromolecules, including nonionic polyethylene glycols (PEG) and natural organic matter (NOM) with ionizable functional (carboxylic and phenolic) groups, were used as solutes. Membrane PSDs, determined with PEG and NOM, can be defined as absolute and effective membrane PSDs, respectively. Two different types of membranes (flat-sheet polymeric and tubular ceramic) were used in this work. Experimental procedures include three major steps: (1) measurements of relative molecular mass (RMM) distributions of solutes included in the membrane feed and corresponding permeate, (2) the calculation of solute FR, and (3) PSD determination. The main results and advantages of this method are: (1) the PSD of various membranes with different pore sizes can be measured using a relatively easy method without significant limitations of pore size and membrane type; (2) various factors that affect membrane PSD, including pH, ionic strength, ion binding, and hydrodynamics, can also be evaluated; (3) the effective PSD of membranes with negatively-charged surfaces, and which exhibit significant shifts in PSD towards the lower RMM region can also be determined. (C) 2002 Elsevier Science B.V. All rights reservedclose566

Tailoring tokamak error fields to control plasma instabilities and transport

Abstract A tokamak relies on the axisymmetric magnetic fields to confine fusion plasmas and aims to deliver sustainable and clean energy. However, misalignments arise inevitably in the tokamak construction, leading to small asymmetries in the magnetic field known as error fields (EFs). The EFs have been a major concern in the tokamak approaches because small EFs, even less than 0.1%, can drive a plasma disruption. Meanwhile, the EFs in the tokamak can be favorably used for controlling plasma instabilities, such as edge-localized modes (ELMs). Here we show an optimization that tailors the EFs to maintain an edge 3D response for ELM control with a minimized core 3D response to avoid plasma disruption and unnecessary confinement degradation. We design and demonstrate such an edge-localized 3D response in the KSTAR facility, benefiting from its unique flexibility to change many degrees of freedom in the 3D coil space for the various fusion plasma regimes. This favorable control of the tokamak EF represents a notable advance for designing intrinsically 3D tokamaks to optimize stability and confinement for next-step fusion reactors

Overview of recent progress in 3D field physics in KSTAR

Various 3D field physics challenges of magnetically confined plasmas arise when the driving source comes from either externally applied non-axisymmetric 3D magnetic perturbations or plasma instabilities inside the plasma. Recently, several key outstanding topics of 3D field physics have been extensively studied in the Korean Superconducting Tokamak Advanced Research (KSTAR), such as edge-localized-mode (ELM) control by resonant magnetic perturbation (RMP), error field (EF) control, 3D field effects on rotation and transport, and RMP-induced alteration of divertor heat flux and detachment. KSTAR has a few physically unique features (i.e., high rotation and long-pulse plasmas with a low intrinsic EF) and machine/diagnostic capabilities (i.e., 3-row in-vessel control coil and state-of-the-art 2D/3D imaging diagnostics), which have been taken advantage of until now to address critical 3D field physics issues relevant to ITER and K-DEMO. Among many remarkable achievements are the robust access to and control of n = 1 RMP ELM suppression, along with a development of its physics basis tools, parameter expansion, optimization, and long-pulse control techniques. Nonetheless, a series of unresolved 3D physics themes, as well as limited coverage of 3D field operating regimes, have also been identified as future works for the 3D field research in KSTAR. In this paper, we provide an overview about the recent progress of KSTAR 3D field physics and present future plans of KSTAR 3D research toward a future fusion reactor