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Sample records for supercritical quasi-perpendicular shocks

  1. Two Types of Whistler Instabilities in the Foot of Quasi-perpendicular Supercritical Shocks: a Poynting Flux Analysis

    Science.gov (United States)

    Muschietti, L.; Lembege, B.

    2016-12-01

    Supercritical shocks in collisionless plasmas are characterized by a substantial population of ions reflected off of the steep shock ramp. These ions carry a significant amount of energy and are fundamental to the transformation of directed kinetic energy into thermal energy. For quasi-perpendicular geometries and as seen in the normal incidence frame (NIF), the velocity of the reflected ions is mostly directed at 90o to the magnetic field Bo. Streaming instabilities can develop, which are excited by the relative drifts between incoming ions, reflected ions, and electrons across the shock's foot. Two types of waves from the whistler branch and with frequencies in the lower-hybrid range are shown to be unstable:Oblique waves with wavelengths a fraction of the ion inertia length that propagate toward upstream at angles about 50o to Bo. Quasi-perpendicular waves with wavelengths several times the electron inertia length that propagate toward downstream at angles larger than 80o to Bo. For each type of whistlers we perform electromagnetic pseudo-oblique 1D PIC simulations. These are carried out in the proper frame where the total momentum density vanishes. Field data issued from the simulations are used to construct hodograms and compute the Poynting fluxes. We apply the Lorentz transformation in order to express the results in the NIF, where they can be discussed and compared to measurements from Cluster at Earth's bow shock [Sundkvist D, et al., PRL 108, 2012].

  2. Identification of two types of whistler instabilities excited in the foot of quasi-perpendicular supercritical shocks: a Poynting flux analysis

    Science.gov (United States)

    Muschietti, Laurent; Lembege, Bertrand

    2017-04-01

    Supercritical shocks in collisionless plasmas are characterized by the presence of a noticeable fraction of ions that are reflected off of the shock front and form a foot upstream of the ramp. These ions carry a significant amount of energy; they are the source of microturbulence within the shock front itself and play a key role in transforming the directed bulk energy (upstream) into thermal energy (downstream). For quasi-perpendicular geometries and as seen in the normal incidence frame (NIF), the velocity of the reflected ions is mostly directed at 90° to the magnetic field Bo. Streaming instabilities can develop, which are excited by the relative drifts between the populations of incoming ions, reflected ions, and electrons across Bo in the shock's foot. Two types of waves from the whistler branch and with frequencies in the lower-hybrid range are shown to be unstable: 1) Oblique waves with wavelengths a fraction of the ion inertia length which propagate toward upstream at angles about 50° to Bo. 2) Quasi-perpendicular waves with wavelengths several times the electron inertia length which propagate toward downstream at angles larger than 80° to Bo. For each type of whistler we perform electromagnetic pseudo-oblique 1D PIC simulations. These are carried out in the proper frame where the total momentum density vanishes. Field data issued from the simulations are used to construct hodograms and compute the Poynting fluxes. We apply the Lorentz transformation in order to express the results in the shock frame, specifically the normal incidence frame. The outcome is then discussed and compared to previous simulations [Comisel et al, Ann. Geophys. 29, 2011] and to measurements at Earth's bow shock from Cluster [Sundkvist et al, PRL 108, 2012] and more recently from the MMS mission .

  3. Direct measurement of the cross-shock electric potential at low plasma $\\beta$, quasi-perpendicular bow shocks

    OpenAIRE

    Bale, S. D.; Mozer, F.S.; Krasnoselskikh, V.V.

    2008-01-01

    We use the Cluster EFW experiment to measure the cross-shock electric field at ten low $\\beta$, quasi-perpendicular supercritical bow shock crossings on March 31, 2001. The electric field data are Lorentz-tranformed to a Normal Incidence frame (NIF), in which the incoming solar wind velocity is aligned with the shock normal. In a boundary normal coordinate system, the cross-shock (normal) electric field is integrated to obtain the cross shock potential. Using this technique, we measure the cr...

  4. Electric field scales at quasi-perpendicular shocks

    Directory of Open Access Journals (Sweden)

    S. N. Walker

    2004-07-01

    Full Text Available This paper investigates the short scale structures that are observed in the electric field during crossings of the quasi-perpendicular bow shock using data from the Cluster satellites. These structures exhibit large amplitudes, as high as 70 m Vm-1 and so make a significant contribution to the overall change in potential at the shock front. It is shown that the scale size of these short-lived electric field structures is of the order of a few cpe. The relationships between the scale size and the upstream Mach number and θBn are studied. It is found that the scale size of these structures decreases with increasing plasma β and as θBn→90°. The amplitude of the spikes remains fairly constant with increasing Ma and appears to increase as θBn→90°.

  5. Kinetic structures of quasi-perpendicular shocks in global particle-in-cell simulations

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Ivy Bo, E-mail: bopeng@kth.se; Markidis, Stefano; Laure, Erwin [KTH Royal Institute of Technology, Stockholm (Sweden); Johlander, Andreas; Vaivads, Andris; Khotyaintsev, Yuri [Swedish Institute of Space Physics, Uppsala (Sweden); Henri, Pierre [LPC2E-CNRS, Orléans (France); Lapenta, Giovanni [Centre for mathematical Plasma-Astrophysics, KU Leuven, Leuven (Belgium)

    2015-09-15

    We carried out global Particle-in-Cell simulations of the interaction between the solar wind and a magnetosphere to study the kinetic collisionless physics in super-critical quasi-perpendicular shocks. After an initial simulation transient, a collisionless bow shock forms as a result of the interaction of the solar wind and a planet magnetic dipole. The shock ramp has a thickness of approximately one ion skin depth and is followed by a trailing wave train in the shock downstream. At the downstream edge of the bow shock, whistler waves propagate along the magnetic field lines and the presence of electron cyclotron waves has been identified. A small part of the solar wind ion population is specularly reflected by the shock while a larger part is deflected and heated by the shock. Solar wind ions and electrons are heated in the perpendicular directions. Ions are accelerated in the perpendicular direction in the trailing wave train region. This work is an initial effort to study the electron and ion kinetic effects developed near the bow shock in a realistic magnetic field configuration.

  6. Kinetic Structures of Quasi-Perpendicular Shocks in Global Particle-in-Cell Simulations

    Science.gov (United States)

    Peng, I. B.; Markidis, S.; Laure, E.; Johlander, A.; Vaivads, A.; Khotyaintsev, Y. V.; Pierre, H.; Lapenta, G.

    2015-12-01

    We carried out global Particle-in-Cell simulations of the interaction between the solar wind and a magnetosphere to study the kinetic collisionless physics in super-critical quasi-perpendicular shocks. After an initial simulation transient, a collisionless bow shock forms as a result of the interaction of the solar wind and a planet magnetic dipole. The shock ramp has a thickness of approximately one ion skin depth and is followed by a trailing wave train in the shock downstream. At the downstream edge of the bow shock, whistler waves propagate along the magnetic field lines and the presence of electron cyclotron waves has been identified. A small part of the solar wind ion population is specularly reflected by the shock while a larger part is deflected and heated by the shock. Solar wind ions and electrons are heated in the perpendicular directions. Ions are accelerated in the perpendicular direction in the trailing wave train region. This work is an initial effort to study the electron and ion kinetic effects developed near the bow shock in a realistic magnetic field configuration.

  7. Direct measurement of the cross-shock electric potential at low plasma $\\beta$, quasi-perpendicular bow shocks

    CERN Document Server

    Bale, S D; Krasnoselskikh, V V

    2008-01-01

    We use the Cluster EFW experiment to measure the cross-shock electric field at ten low $\\beta$, quasi-perpendicular supercritical bow shock crossings on March 31, 2001. The electric field data are Lorentz-tranformed to a Normal Incidence frame (NIF), in which the incoming solar wind velocity is aligned with the shock normal. In a boundary normal coordinate system, the cross-shock (normal) electric field is integrated to obtain the cross shock potential. Using this technique, we measure the cross-shock potential at each of the four Cluster satellites and using an electric field profile averaged between the four satellites. Typical values are in the range 500-2500 volts. The cross-shock potential measurements are compared with the ion kinetic energy change across the shock. The cross-shock potential is measured to be from 23 to 236% of the ion energy change, with large variations between the four Cluster spacecraft at the same shock. These results indicate that solar wind flow through the shock is likely to be ...

  8. Dispersion of low frequency plasma waves upstream of the quasi-perpendicular terrestrial bow shock

    Directory of Open Access Journals (Sweden)

    A. P. Dimmock

    2013-08-01

    Full Text Available Low frequency waves in the foot of a supercritical quasi-perpendicular shock front have been observed since the very early in situ observations of the terrestrial bow shock (Guha et al., 1972. The great attention that has been devoted to these type of waves since the first observations is explained by the key role attributed to them in the processes of energy redistribution in the shock front by various theoretical models. In some models, these waves play the role of the intermediator between the ions and electrons. It is assumed that they are generated by plasma instability that exist due to the counter-streaming flows of incident and reflected ions. In the second type of models, these waves result from the evolution of the shock front itself in the quasi-periodic process of steepening and overturning of the magnetic ramp. However, the range of the observed frequencies in the spacecraft frame are not enough to distinguish the origin of the observed waves. It also requires the determination of the wave vectors and the plasma frame frequencies. Multipoint measurements within the wave coherence length are needed for an ambiguous determination of the wave vectors. In the main multi-point missions such as ISEE, AMPTE, Cluster and THEMIS, the spacecraft separation is too large for such a wave vector determination and therefore only very few case studies are published (mainly for AMPTE UKS AMPTE IRM pair. Here we present the observations of upstream low frequency waves by the Cluster spacecraft which took place on 19 February 2002. The spacecraft separation during the crossing of the bow shock was small enough to determine the wave vectors and allowed the identification of the plasma wave dispersion relation for the observed waves. Presented results are compared with whistler wave dispersion and it is shown that contrary to previous studies based on the AMPTE data, the phase velocity in the shock frame is directed downstream. The consequences of this

  9. The properties and causes of rippling in quasi-perpendicular collisionless shock fronts

    Directory of Open Access Journals (Sweden)

    R. E. Lowe

    Full Text Available The overall structure of quasi-perpendicular, high Mach number collisionless shocks is controlled to a large extent by ion reflection at the shock ramp. Departure from a strictly one-dimensional structure is indicated by simulation results showing that the surface of such shocks is rippled, with variations in the density and all field components. We present a detailed analysis of these shock ripples, using results from a two-dimensional hybrid (particle ions, electron fluid simulation. The process that generates the ripples is poorly understood, because the large gradients at the shock ramp make it difficult to identify instabilities. Our analysis reveals new features of the shock ripples, which suggest the presence of a surface wave mode dominating the shock normal magnetic field component of the ripples, as well as whistler waves excited by reflected ions.

    Key words. Space plasma physics (numerical simulation studies; shock waves; waves and instabilities

  10. Effect of upstream rotational field on the formation of magnetic depressions in a quasi-perpendicular shock downstream

    Science.gov (United States)

    Tsubouchi, K.; Matsumoto, H.

    2005-04-01

    One-dimensional hybrid simulations are performed to investigate the interaction between an interplanetary rotational magnetic field (RF) and the terrestrial bow shock (a quasi-perpendicular and supercritical regime). A magnetic depression structure called a transient density event (TDE) that is anticorrelated to the density peak is built up and is enlarged from the RF region after its entry into the magnetosheath. Contrary to the MHD view, in which such a diamagnetic structure is sandwiched by two slow or time-dependent intermediate shocks, the TDE generation mechanism is strongly associated with effects of particle kinetics. Within the TDE, the proton temperature parallel to the ambient magnetic field Tp∥ increases to be isotropic, while the ordinary shock downstream consists of strong anisotropic protons (Tp⊥/Tp∥ > 1). This parallel heating is due to enforced conversion of the perpendicular proton motion into a parallel one by the imposed RF. The resultant intense parallel/antiparallel flows generate the field gradient at the leading and trailing edges, which act as a mirror force and reduce the magnetic intensity. In this kinetic sense, slow or Alfvén modes predicted by MHD theories are inadequate for regarding as edges of such a structure. Similar to the normal mirror mode process, particles are concentrated and trapped within the weak field region, leading to a density buildup. The trapped particles lose their energy and undergo cooling as they are bounced at the diverging mirror points. Accordingly, the TDE structure hardly collapses and endures through the magnetosheath. Compared with the mirror instability, isotropization forced by external field fluctuations works more efficiently to produce such a magnetic depression. Thus the presence of the quasi-perpendicular shock, where large temperature anisotropy is generated, is one of the suitable situations for the TDE when interaction with the rotational field has taken place. This interaction model may

  11. Average observed properties of the Earth's quasi-perpendicular and quasi-parallel bow shock

    CERN Document Server

    Czaykowska, A; Treumann, R A; Baumjohann, W

    2000-01-01

    We present a statistical analysis of 132 dayside (LT 0700-1700) bow shock crossings of the AMPTE/IRM spacecraft. We perform a superposed epoch analysis of plasma and magnetic field parameters as well as of low frequency magnetic power spectra some minutes upstream and downstream of the bow shock by dividing the events into categories depending on the angle between bow shock normal and interplanetary magnetic field and on the plasma-beta, i.e., the ratio of plasma to magnetic pressure. Downstream of the quasi-perpendicular low-beta (beta 1.0) crossings mirror waves are identified. However, there are also cases where the conditions for mirror modes are met downstream of the nearly perpendicular shock, but no mirror waves are observed.

  12. The acceleration of low energy protons by quasi-perpendicular interplanetary shocks

    Energy Technology Data Exchange (ETDEWEB)

    Erdos, G. (Hungarian Academy of Sciences, Budapest (Hungary). Central Research Inst. for Physics); Balogh, A. (Imperial Coll. of Science and Technology, London (UK). Blackett Lab.)

    1990-03-01

    New aspects of the acceleration of low energy (35-1000 keV) protons by quasi-perpendicular interplanetary shocks are presented, using observations and numerical simulations. Time reverse trajectory calculations of particles are used to derive the behaviour of the angular distribution and spectrum through the shock. These calculations show that for simple planar geometries of the magnetic field and for a power-law spectrum of pre-accelerated particles the expected omnidirectional enhancements are smaller than observed. Pitch angle distributions in the vicinity of six interplanetary shocks have been determined from the measurements carried out onboard the ISEE-3 spacecraft. Reflection of particles was clearly identifiable by the loss cone type angular distribution observed upstream of the shock. Downstream of the shock, the shape and the energy dependence of the pitch angle distributions provide support for the scatter-free model in some cases. However, the observed spikes at the shock passage and bidirectional upstream distributions measured at the nearest to perpendicular shocks, together with other features of particle spectra and angular distributions which cannot be readily explained by model calculations suggest that fluctuations in the magnetic field might also seriously affect the acceleration process. (author).

  13. Laser-driven, magnetized quasi-perpendicular collisionless shocks on the Large Plasma Device

    Energy Technology Data Exchange (ETDEWEB)

    Schaeffer, D. B., E-mail: dschaeffer@physics.ucla.edu; Everson, E. T.; Bondarenko, A. S.; Clark, S. E.; Constantin, C. G.; Vincena, S.; Van Compernolle, B.; Tripathi, S. K. P.; Gekelman, W.; Niemann, C. [Department of Physics and Astronomy, University of California - Los Angeles, Los Angeles, California 90095 (United States); Winske, D. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2014-05-15

    The interaction of a laser-driven super-Alfvénic magnetic piston with a large, preformed magnetized ambient plasma has been studied by utilizing a unique experimental platform that couples the Raptor kJ-class laser system [Niemann et al., J. Instrum. 7, P03010 (2012)] to the Large Plasma Device [Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] at the University of California, Los Angeles. This platform provides experimental conditions of relevance to space and astrophysical magnetic collisionless shocks and, in particular, allows a detailed study of the microphysics of shock formation, including piston-ambient ion collisionless coupling. An overview of the platform and its capabilities is given, and recent experimental results on the coupling of energy between piston and ambient ions and the formation of collisionless shocks are presented and compared to theoretical and computational work. In particular, a magnetosonic pulse consistent with a low-Mach number collisionless shock is observed in a quasi-perpendicular geometry in both experiments and simulations.

  14. On the Possibility of Radio Emission from Quasi-parallel and Quasi-perpendicular Propagation of Shocks

    Indian Academy of Sciences (India)

    A. Shanmugaraju; S. Umapathy

    2000-09-01

    A set of 21 solar type II radio bursts observed using Hiraiso radio spectrograph have been analysed to study the direction of propagation of coronal shocks. Α simple analysis is carried out to find the approximate angle between the shock normal and magnetic field by solving the Rankine-Hugoniot MHD relation with assumption of Alfven speed and plasma beta. From this analysis, it is suggested that both quasi-parallel shocks (favourable) and quasi-perpendicular shocks can generate type II bursts depending upon the circumstances of the corona.

  15. Characterization of Saturn's bow shock: Magnetic field observations of quasi-perpendicular shocks

    CERN Document Server

    Sulaiman, A H; Dougherty, M K

    2016-01-01

    Collisionless shocks vary drastically from terrestrial to astrophysical regimes resulting in radically different characteristics. This poses two complexities. Firstly, separating the influences of these parameters on physical mechanisms such as energy dissipation. Secondly, correlating observations of shock waves over a wide range of each parameter, enough to span across different regimes. Investigating the latter has been restricted since the majority of studies on shocks at exotic regimes (such as supernova remnants) have been achieved either remotely or via simulations, but rarely by means of in-situ observations. Here we present the parameter space of MA bow shock crossings from 2004-2014 as observed by the Cassini spacecraft. We find that Saturn's bow shock exhibits characteristics akin to both terrestrial and astrophysical regimes (MA of order 100), which is principally controlled by the upstream magnetic field strength. Moreover, we determined the {\\theta}Bn of each crossing to show that Saturn's (days...

  16. Particle-in-cell simulations of particle energization via shock drift acceleration from low Mach number quasi-perpendicular shocks in solar flares

    CERN Document Server

    Park, Jaehong; Workman, Jared C; Blackman, Eric G

    2012-01-01

    Low Mach number, high beta fast mode shocks can occur in the magnetic reconnection outflows of solar flares. These shocks, which occur above flare loop tops, may provide the electron energization responsible for some of the observed hard X-rays and contemporaneous radio emission. Here we present new 2D particle-in-cell simulations of low Mach number/high beta quasi-perpendicular shocks. The simulations show that electrons above a certain energy threshold experience shock-drift-acceleration. The transition energy between the thermal and non-thermal spectrum and the spectral index from the simulations are consistent with some of the X-ray spectra from RHESSI in the energy regime, $E\\lesssim 40\\sim 100$ keV. Plasma instabilities associated with the shock structure such as the modified-two-stream and the electron whistler/mirror instabilities are examined and compared with the numerical solutions of the kinetic dispersion relations.

  17. Remote sensing of local structure of the quasi-perpendicular Earth's bow shock by using field-aligned beams

    Directory of Open Access Journals (Sweden)

    B. Miao

    2009-03-01

    Full Text Available Field-aligned ion beams (FABs originate at the quasi-perpendicular Earth's bow shock and constitute an important ion population in the foreshock region. The bulk velocity of these FABs depends significantly on the shock normal angle, which is the angle between shock normal and upstream interplanetary magnetic field (IMF. This dependency may therefore be taken as an indicator of the local structure of the shock. Applying the direct reflection model to Cluster measurements, we have developed a method that uses proton FABs in the foreshock region for remote sensing of the local shock structure. The comparison of the model results with the multi-spacecraft observations of FAB events shows very good agreement in terms of wave amplitude and frequency of surface waves at the shock front.

  18. Origin of the Ion Foreshock in a Quasi-perpendicular Curved Collisionless Shock: Particles Trajectory Analysis in 2D PIC Simulations

    Science.gov (United States)

    Savoini, P.; Lembege, B.

    2015-12-01

    The ion foreshock located upstream of the Earth's shock wave is populated with ions having interacted with the shock, and then, reflected back with an high energy gain. Spacecrafts have clearly established the existence of two distinct populations in the quasi-perpendicular shock region (i.e. for 45° ≤ ΘBn ≤ 90°, where ΘBn is the angle between the shock normal and the upstream magnetic field) : (i) field-aligned ion beams or « FAB » characterized by a gyrotropic distribution, and (ii) gyro-phase bunched ions or « GPB » characterized by a NON gyrotropic distribution. One of the important unresolved problem is the exact origin of the particles contributing to these two populations. To our knowledge, it was the first time that full-particle simulations have been performed including self-consistently the shock front curvature and nonstationarity, and the time-of-flight effects. Our analysis evidences that these two backstreaming populations may be reflected by the front itself and can be differentiated both in terms of interaction time and trajectory within the shock front. In particular, simulations evidence that "GPB" population is characterized by a short interaction time (ΔTinter = 1 to 2 τci) while the "FAB" population corresponds to a much larger time range (from 1 τci to 10 τci), where tci is the upstream ion gyroperiod. Present individual ion trajectories evidence that "FAB" population shows a strong perpendicular drift at the shock front (i.e. strong dependence of the pitch angle to the perpendicular velocity) whereas the "GPB" population shows no perpendicular drift (i.e. its pitch angle is mainly driven by the parallel velocity). Such differences explain why the "FAB" population loses their gyro-phase coherency and become gyrotropic which is not the case for the "GPB". This important result was not expected and greatly simplifies the question of their origin.

  19. More than mass proportional heating of heavy ions by supercritical collisionless shocks in the solar corona

    CERN Document Server

    Zimbardo, Gaetano

    2009-01-01

    We propose a new model for explaining the observations of more than mass proportional heating of heavy ions in the polar solar corona. We point out that a large number of small scale intermittent shock waves can be present in the solar corona. The energization mechanism is, essentially, the ion reflection off supercritical quasi-perpendicular collisionless shocks in the corona and the subsequent acceleration by the motional electric field ${\\bf E} = - (1/c) {\\bf V} \\times {\\bf B}$. The acceleration due to ${\\bf E}$ is perpendicular to the magnetic field, in agreement with observations, and is more than mass proportional with respect to protons, because the heavy ion orbit is mostly upstream of the quasi-perpendicular shock foot. The observed temperature ratios between O$^{5+}$ ions and protons in the polar corona, and between $\\alpha$ particles and protons in the solar wind are easily recovered.

  20. Electromagnetic Whistler Precursors at Supercritical Interplanetary Shocks

    Science.gov (United States)

    Wilson, L. B., III

    2012-01-01

    We present observations of electromagnetic precursor waves, identified as whistler mode waves, at supercritical interplanetary shocks using the Wind search coil magnetometer. The precursors propagate obliquely with respect to the local magnetic field, shock normal vector, solar wind velocity, and they are not phase standing structures. All are right-hand polarized with respect to the magnetic field (spacecraft frame), and all but one are right-hand polarized with respect to the shock normal vector in the normal incidence frame. Particle distributions show signatures of specularly reflected gyrating ions, which may be a source of free energy for the observed modes. In one event, we simultaneously observe perpendicular ion heating and parallel electron acceleration, consistent with wave heating/acceleration due to these waves.

  1. Physics of Collisionless Shocks Space Plasma Shock Waves

    CERN Document Server

    Balogh, André

    2013-01-01

    The present book provides a contemporary systematic treatment of shock waves in high-temperature collisionless plasmas as are encountered in near Earth space and in Astrophysics. It consists of two parts. Part I develops the complete theory of shocks in dilute hot plasmas under the assumption of absence of collisions among the charged particles when the interaction is mediated solely by the self-consistent electromagnetic fields. Such shocks are naturally magnetised implying that the magnetic field plays an important role in their evolution and dynamics. This part treats both subcritical shocks, which dissipate flow energy by generating anomalous resistance or viscosity, and supercritical shocks. The main emphasis is, however, on super-critical shocks where the anomalous dissipation is insufficient to retard the upstream flow. These shocks, depending on the direction of the upstream magnetic field, are distinguished as quasi-perpendicular and quasi-parallel shocks which exhibit different behaviours, reflecti...

  2. Unstable whistlers and Bernstein waves within the front of supercritical perpendicular shocks

    Science.gov (United States)

    Muschietti, Laurent; Lembege, Bertrand

    2016-04-01

    In supercritical shocks a significant fraction of ions is reflected at the steep shock ramp and carries a considerable amount of energy. The existence of reflected ions enables streaming instabilities to develop which are excited by the relative drifts between the populations of incoming ions, reflected ions, and electrons. The processes are fundamental to the transformation of directed kinetic energy into thermal energy, a tenet of shock physics. We model the particle distributions as a broad electron population and two ion populations, namely a core and a beam (representing the reflected ions) in order to investigate the kinetic instabilities possible under various wave propagation angles. Recently, assuming the ion beam is directed along the shock normal at 90° to the magnetic field Bo, we analyzed the linear dispersion properties by computing the full electromagnetic dielectric tensor [Muschietti and Lembege, AGU Fall meeting 2015]. Three types of waves were shown to be unstable: (1) Oblique whistlers with wavelengths about the ion inertia length which propagate toward upstream at angles about 50° to the magnetic field. Frequencies are a few times the lower-hybrid. The waves share many similarities to the obliquely propagating whistlers measured in detail by Polar [Hull et al., JGR 117, 2012]. (2) Quasi-perpendicular whistlers with wavelength covering a fraction of the electron inertia length which propagate toward downstream at angles larger than 80° to Bo. Frequencies are close to the lower-hybrid. (3) Bernstein waves with wavelengths close to the electron gyroradius which propagate toward upstream at angles within 5° of perpendicular to the magnetic field. Frequencies are close to the electron cyclotron. The waves have similarities to those reported by Wind and Stereo [Breneman et al., JGR 118, 2013; Wilson et al., JGR 115, 2010]. We will present electromagnetic 1D3V PIC simulations with predetermined propagation angles which illustrate the three types

  3. Atypical Particle Heating at a Supercritical Interplanetary Shock

    Science.gov (United States)

    Wilson, Lynn B., III

    2010-01-01

    We present the first observations at an interplanetary shock of large amplitude (> 100 mV/m pk-pk) solitary waves and large amplitude (approx.30 mV/m pk-pk) waves exhibiting characteristics consistent with electron Bernstein waves. The Bernstein-like waves show enhanced power at integer and half-integer harmonics of the cyclotron frequency with a broadened power spectrum at higher frequencies, consistent with the electron cyclotron drift instability. The Bernstein-like waves are obliquely polarized with respect to the magnetic field but parallel to the shock normal direction. Strong particle heating is observed in both the electrons and ions. The observed heating and waveforms are likely due to instabilities driven by the free energy provided by reflected ions at this supercritical interplanetary shock. These results offer new insights into collisionless shock dissipation and wave-particle interactions in the solar wind.

  4. Quasiperpendicular high Mach number Shocks

    CERN Document Server

    Sulaiman, A H; Dougherty, M K; Burgess, D; Fujimoto, M; Hospodarsky, G B

    2015-01-01

    Shock waves exist throughout the universe and are fundamental to understanding the nature of collisionless plasmas. Reformation is a process, driven by microphysics, which typically occurs at high Mach number supercritical shocks. While ongoing studies have investigated this process extensively both theoretically and via simulations, their observations remain few and far between. In this letter we present a study of very high Mach number shocks in a parameter space that has been poorly explored and we identify reformation using in situ magnetic field observations from the Cassini spacecraft at 10 AU. This has given us an insight into quasi-perpendicular shocks across two orders of magnitude in Alfven Mach number (MA) which could potentially bridge the gap between modest terrestrial shocks and more exotic astrophysical shocks. For the first time, we show evidence for cyclic reformation controlled by specular ion reflection occurring at the predicted timescale of ~0.3 {\\tau}c, where {\\tau}c is the ion gyroperio...

  5. Observations of Electromagnetic Whistler Precursors at Supercritical Interplanetary Shocks

    Science.gov (United States)

    Wilson, L. B., III; Koval, A.; Szabo, Adam; Breneman, A.; Cattell, C. A.; Goetz, K.; Kellogg, P. J.; Kersten, K.; Kasper, J. C.; Maruca, B. A.; Pulupa, M.

    2012-01-01

    We present observations of electromagnetic precursor waves, identified as whistler mode waves, at supercritical interplanetary shocks using the Wind search coil magnetometer. The precursors propagate obliquely with respect to the local magnetic field, shock normal vector, solar wind velocity, and they are not phase standing structures. All are right-hand polarized with respect to the magnetic field (spacecraft frame), and all but one are right-hand polarized with respect to the shock normal vector in the normal incidence frame. They have rest frame frequencies f(sub ci) < f much < f(sub ce) and wave numbers 0.02 approx < k rho (sub ce) approx <. 5.0. Particle distributions show signatures of specularly reflected gyrating ions, which may be a source of free energy for the observed modes. In one event, we simultaneously observe perpendicular ion heating and parallel electron acceleration, consistent with wave heating/acceleration due to these waves. Al though the precursors can have delta B/B(sub o) as large as 2, fluxgate magnetometer measurements show relatively laminar shock transitions in three of the four events.

  6. Interplanetary shocks and foreshocks observed by STEREO during 2007-2010

    Science.gov (United States)

    Blanco-Cano, X.; Kajdič, P.; Aguilar-Rodríguez, E.; Russell, C. T.; Jian, L. K.; Luhmann, J. G.

    2016-02-01

    Interplanetary shocks in the heliosphere modify the solar wind through which they pass. In particular, shocks play an important role in particle acceleration. During the extended solar minimum (2007-2010) STEREO observed 65 forward shocks driven by stream interactions (SI), with magnetosonic Mach numbers Mms ≈ 1.1-4.0 and shock normal angles θBN ~ 20-87°. We analyze the waves associated with these shocks and find that the region upstream can be permeated by whistler waves (f ~ 1 Hz) and/or ultra low frequency (ULF) waves (f ~ 10-2-10-1 Hz). While whistlers appear to be generated at the shock, the origin of ULF waves is most probably associated with local kinetic ion instabilities. We find that when the Mach number (Mms) is low and the shock is quasi-perpendicular (θBN > 45°) whistler waves remain close to the shock. As Mms increases, the shock profile changes and can develop a foot and overshoot associated with ion reflection and gyration. Whistler precursors can be superposed on the foot region, so that some quasi-perpendicular shocks have characteristics of both subcritical and supercritical shocks. When the shock is quasi-parallel (θBN modified probably by reflected and/or leaked ions and by almost circularly polarized waves at lower frequencies that may be locally generated by ion instabilities. In contrast with planetary bow shocks, most of the upstream waves studied here are mainly transverse and no steepening occurs. Some quasi-perpendicular shocks (45° Earth's orbit and have been accelerating ions for a shorter interval of time.

  7. Reforming perpendicular shocks in the presence of pickup protons: initial ion acceleration

    Directory of Open Access Journals (Sweden)

    R. E. Lee

    2005-02-01

    Full Text Available Acceleration processes associated with the heliospheric termination shock may provide a source of anomalous cosmic rays (ACRs. Recent kinetic simulations of supercritical, quasi-perpendicular shocks have yielded time varying shock solutions that cyclically reform on the spatio-temporal scales of the incoming protons. Whether a shock solution is stationary or reforming depends upon the plasma parameters which, for the termination shock, are ill defined but believed to be within the time-dependent regime. Here we present results from high phase space resolution particle-in-cell simulations for a three-component plasma (solar wind protons, electrons and pickup protons appropriate for the termination shock. We find reforming shock solutions which generate suprathermal populations for both proton components, with the pickup ions reaching energies of order twenty times the solar wind inflow energy. This suprathermal "injection" population is required as a seed population for subsequent acceleration at the shock which can in turn generate ACRs.

  8. Contributions to the cross shock electric field at supercritical perpendicular shocks: Impact of the pickup ions

    CERN Document Server

    Yang, Zhongwei; Yang, Huigen; Hu, Hongqiao; Zhang, Beichen; Zhang, Qinhe; Liu, Ruiyuan

    2012-01-01

    A particle-in-cell code is used to examine contributions of the pickup ions (PIs) and the solar wind ions (SWs) to the cross shock electric field at the supercritical, perpendicular shocks. The code treats the pickup ions self-consistently as a third component. Herein, two different runs with relative pickup ion density of 25% and 55% are presented in this paper. Present preliminary results show that: (1) in the low percentage (25%) pickup ion case, the shock front is nonstationary. During the evolution of this perpendicular shock, a nonstationary foot resulting from the reflected solar wind ions is formed in front of the old ramp, and its amplitude becomes larger and larger. At last, the nonstationary foot grows up into a new ramp and exceeds the old one. Such a nonstationary process can be formed periodically. hen the new ramp begins to be formed in front of the old ramp, the Hall term mainly contributed by the solar wind ions becomes more and more important. The electric field Ex is dominated by the Hall t...

  9. Effect of cavity on shock oscillation in transonic flow over RAE2822 supercritical airfoil

    Science.gov (United States)

    Rahman, M. Rizwanur; Labib, Md. Itmam; Hasan, A. B. M. Toufique; Ali, M.; Mitsutake, Y.; Setoguchi, T.

    2016-07-01

    Transonic flow past a supercritical airfoil is strongly influenced by the interaction of shock wave with boundary layer. This interaction induces unsteady self-sustaining shock wave oscillation, flow instability, drag rise and buffet onset which limit the flight envelop. In the present study, a computational analysis has been carried out to investigate the flow past a supercritical RAE2822 airfoil in transonic speeds. To control the shock wave oscillation, a cavity is introduced on the airfoil surface where shock wave oscillates. Different geometric configurations have been investigated for finding optimum cavity geometry and dimension. Unsteady Reynolds averaged Navier-Stokes equations (RANS) are computed at Mach 0.729 with an angle of attack of 5°. Computed results are well validated with the available experimental data in case of baseline airfoil. However, in case of airfoil with control cavity; it has been observed that the introduction of cavity completely suppresses the unsteady shock wave oscillation. Further, significant drag reduction and successive improvement of aerodynamic performance have been observed in airfoil with shock control cavity.

  10. Large-Amplitude Electrostatic Waves Observed at a Supercritical Interplanetary Shock

    Science.gov (United States)

    Wilson, L. B., III; Cattell, C. A.; Kellogg, P. J.; Goetz, K.; Kersten, K.; Kasper, J. C.; Szabo, A.; Wilber, M.

    2010-01-01

    We present the first observations at an interplanetary shock of large-amplitude (> 100 mV/m pk-pk) solitary waves and large-amplitude (approx.30 mV/m pk-pk) waves exhibiting characteristics consistent with electron Bernstein waves. The Bernstein-like waves show enhanced power at integer and half-integer harmonics of the cyclotron frequency with a broadened power spectrum at higher frequencies, consistent with the electron cyclotron drift instability. The Bernstein-like waves are obliquely polarized with respect to the magnetic field but parallel to the shock normal direction. Strong particle heating is observed in both the electrons and ions. The observed heating and waveforms are likely due to instabilities driven by the free energy provided by reflected ions at this supercritical interplanetary shock. These results offer new insights into collisionless shock dissipation and wave-particle interactions in the solar wind.

  11. Wind Observations of Wave Heating and/or Particle Energization at Supercritical Interplanetary Shocks

    Science.gov (United States)

    Wilson, Lynn Bruce, III; Szabo, Adam; Koval, Andriy; Cattell, Cynthia A.; Kellogg, Paul J.; Goetz, Keith; Breneman, Aaron; Kersten, Kris; Kasper, Justin C.; Pulupa, Marc

    2011-01-01

    We present the first observations at supercritical interplanetary shocks of large amplitude (> 100 mV/m pk-pk) solitary waves, approx.30 mV/m pk-pk waves exhibiting characteristics consistent with electron Bernstein waves, and > 20 nT pk-pk electromagnetic lower hybrid-like waves, with simultaneous evidence for wave heating and particle energization. The solitary waves and the Bernstein-like waves were likely due to instabilities driven by the free energy provided by reflected ions [Wilson III et al., 2010]. They were associated with strong particle heating in both the electrons and ions. We also show a case example of parallel electron energization and perpendicular ion heating due to a electromagnetic lower hybrid-like wave. Both studies provide the first experimental evidence of wave heating and/or particle energization at interplanetary shocks. Our experimental results, together with the results of recent Vlasov [Petkaki and Freeman, 2008] and PIC [Matsukyo and Scholer, 2006] simulations using realistic mass ratios provide new evidence to suggest that the importance of wave-particle dissipation at shocks may be greater than previously thought.

  12. ABRUPT DEFLECTED SUPERCRITICAL WATER FLOW-REVISED THEORY OF SHOCK WAVE

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The shock wave angle and depth ratio of the abrupt deflected supercritical water flow due to deflector was investigated experimentally and theoretically. A correction coefficient of the hydro-dynamic pressure ξ was introduced to generalize the momentum equation in the perpendicular direction to the shock front. An extensive series of tests were conducted in a 1 m wide flume with the Froude number ranging from 1.70 to 8.37, the deflection angle ranging from 5° to 40° and the length of deflector ranging from 0.28 m to 1 m. A dimensionless parameter K was defined to depict the ratio of the flow height to flow thickness. Test results show that the value of ξ, the correction coefficient of the non-hydrostatic pressure distribution, decreases with the increase of the value of K. An empirical relationship between the value of ξ and the value of K was proposed. It is indicated that the relative errors of the results calculated by the revised theory is much smaller than that obtained from the Ippen theory. Finally, a simple explicit expression was suggested to calculate the shock wave height ratio in consideration of the effect of the non-hydrostatic pressure distribution.

  13. An oscillation free shock-capturing method for compressible van der Waals supercritical fluid flows

    Science.gov (United States)

    Pantano, C.; Saurel, R.; Schmitt, T.

    2017-04-01

    Numerical solutions of the Euler equations using real gas equations of state (EOS) often exhibit serious inaccuracies. The focus here is the van der Waals EOS and its variants (often used in supercritical fluid computations). The problems are not related to a lack of convexity of the EOS since the EOS are considered in their domain of convexity at any mesh point and at any time. The difficulties appear as soon as a density discontinuity is present with the rest of the fluid in mechanical equilibrium and typically result in spurious pressure and velocity oscillations. This is reminiscent of well-known pressure oscillations occurring with ideal gas mixtures when a mass fraction discontinuity is present, which can be interpreted as a discontinuity in the EOS parameters. We are concerned with pressure oscillations that appear just for a single fluid each time a density discontinuity is present. The combination of density in a nonlinear fashion in the EOS with diffusion by the numerical method results in violation of mechanical equilibrium conditions which are not easy to eliminate, even under grid refinement. A cure to this problem is developed in the present paper for the van der Waals EOS based on previous ideas. A special extra field and its corresponding evolution equation is added to the flow model. This new field separates the evolution of the nonlinear part of the density in the EOS and produce oscillation free solutions. The extra equation being nonconservative the behavior of two established numerical schemes on shocks computation is studied and compared to exact reference solutions that are available in the present context. The analysis shows that shock conditions of the nonconservative equation have important consequence on the results. Last, multidimensional computations of a supercritical gas jet is performed to illustrate the benefits of the present method, compared to conventional flow solvers.

  14. Phenomenology of the earth's bow shock system - A summary description of experimental results

    Science.gov (United States)

    Greenstadt, E. W.

    1976-01-01

    Observational data on the earth's bow shock system are classified and characterized. Foreshock components, midshock components, and aftershock components are discussed separately. Schematic representations of the field and plasma particle parameters are elaborated, with attention given to quasi-perpendicular geometry and quasi-parallel geometry. Magnetic pulsation structure is delineated. Schematic profiles of field, particle, and wave behavior through a representative quasi-perpendicular shock crossing are displayed.

  15. The connection between supernova remnants and the Galactic magnetic field: An analysis of quasi-parallel and quasi-perpendicular cosmic ray acceleration for the axisymmetric sample

    CERN Document Server

    West, J L; Ferrand, G

    2016-01-01

    The mechanism for acceleration of cosmic rays in supernova remnants (SNRs) is an outstanding question in the field. We model a sample of 32 axisymmetric SNRs using the quasi-perpendicular and quasi-parallel cosmic-ray-electron (CRE) acceleration cases. The axisymmetric sample is defined to include SNRs with a double-sided, bilateral morphology, and also those with a one-sided morphology where one limb is much brighter than the other. Using a coordinate transformation technique, we insert a bubble-like model SNR into a model of the Galactic magnetic field. Since radio emission of SNRs is dominated by synchrotron emission and since this emission depends on the magnetic field and CRE distribution, we are able to simulate the SNRs emission and compare this to data. We find that the quasi-perpendicular CRE acceleration case is much more consistent with the data than the quasi-parallel CRE acceleration case, with G327.6+14.6 (SN1006) being a notable exception. We propose that SN1006 may be a case where both quasi-p...

  16. Impact of pickup ions on the shock front nonstationarity and energy dissipation of the heliospheric termination shock: Two-dimensional full particle simulations and comparison with Voyager 2 observations

    CERN Document Server

    Yang, Zhongwei; Richardson, John D; Lu, Quanming; Huang, Can; Wang, Rui

    2015-01-01

    The transition between the supersonic solar wind and the subsonic heliosheath, the termination shock (TS), was observed by Voyager 2 (V2) on 2007 August 31-September 1 at a distance of 84 AU from the Sun. The data reveal multiple crossings of a complex, quasi-perpendicular supercritical shock. These experimental data are the starting point for a more sophisticated analysis that includes computer modeling of a shock in the presence of pickup ions (PUIs). here, we present two-dimensional (2-D) particle-in-cell (PIC) simulations of the TS including PUIs self-consistently. We also report the ion velocity distribution across the TS using the Faraday cup data from V2. A relatively complete plasma and magnetic field data set from V2 gives us the opportunity to do a full comparison between the experimental data and PIC simulation results. Our results show that: (1) The nonstationarity of the shock front is mainly caused by the ripples along the shock front and these ripples from even if the percentage of PUIs is high...

  17. Non-thermal Electrons at the Earth's Bow Shock: A `Gradual' Event

    CERN Document Server

    Oka, M; Fujimoto, M; Matsui, H; Kasaba, Y; Saitô, Y; Kojima, H; Matsumoto, H; Mukai, T

    2008-01-01

    Earth's bow shock is known to produce non-thermal electrons which are generally observed as a `spike' in their flux profile. Here, in this paper, we present an analysis of electron and whistler wave properties for a quasi-perpendicular shock crossing that is supercritical, but subcritical to the so-called whistler critical Mach number, M$^w_{\\rm crit}$, above which whistler waves cannot propagate upstream. We have found that the amplitudes of whistler waves increased exponentially as a function of time prior to the shock encounter, while the suprathermal ($>$ 2 keV) electron flux similarly increased with time, although with differing $e$-folding time scales. Comparison of the electron energy spectrum measured within the ramp with predictions from diffusive shock acceleration theory was poor, but the variation of pitch angle distribution showed scattering of non-thermal electrons in the upstream region. While not finding a specific mechanism to account for the electron diffusion, we suggest that the whistlers ...

  18. Heating heavy ions in the polar corona by collisionless shocks: A one-dimensional simulation

    Science.gov (United States)

    Nisticò, Giuseppe; Zimbardo, Gaetano

    2012-01-01

    Recently a new model for explaining the observations of preferential heating of heavy ions in the polar solar corona was proposed (Zimbardo, 2010, 2011). In that model the ion energization mechanism is the ion reflection off supercritical quasi-perpendicular collisionless shocks in the corona and the subsequent acceleration by the motional electric field E = -V × B/c. The mechanism of heavy ion reflection is based on ion gyration in the magnetic overshoot of the shock. The acceleration due to the motional electric field is perpendicular to the magnetic field, giving rise to large temperature anisotropy with T⊥ ≫ T∥, in agreement with SoHO observations. Such a model is tested here by means of a one dimensional test particle simulation where ions are launched toward electric and magnetic profiles representing the shock transition. We study the dynamics of O5+, as representative of coronal heavy ions for Alfvénic Mach numbers of 2-4, as appropriate to solar corona. It is found that O5+ ions are easily reflected and gain more than mass proportional energy with respect to protons.

  19. An in situ Comparison of Electron Acceleration at Collisionless Shocks under Differing Upstream Magnetic Field Orientations

    Science.gov (United States)

    Masters, A.; Sulaiman, A. H.; Stawarz, Ł.; Reville, B.; Sergis, N.; Fujimoto, M.; Burgess, D.; Coates, A. J.; Dougherty, M. K.

    2017-07-01

    A leading explanation for the origin of Galactic cosmic rays is acceleration at high-Mach number shock waves in the collisionless plasma surrounding young supernova remnants. Evidence for this is provided by multi-wavelength non-thermal emission thought to be associated with ultrarelativistic electrons at these shocks. However, the dependence of the electron acceleration process on the orientation of the upstream magnetic field with respect to the local normal to the shock front (quasi-parallel/quasi-perpendicular) is debated. Cassini spacecraft observations at Saturn’s bow shock have revealed examples of electron acceleration under quasi-perpendicular conditions, and the first in situ evidence of electron acceleration at a quasi-parallel shock. Here we use Cassini data to make the first comparison between energy spectra of locally accelerated electrons under these differing upstream magnetic field regimes. We present data taken during a quasi-perpendicular shock crossing on 2008 March 8 and during a quasi-parallel shock crossing on 2007 February 3, highlighting that both were associated with electron acceleration to at least MeV energies. The magnetic signature of the quasi-perpendicular crossing has a relatively sharp upstream-downstream transition, and energetic electrons were detected close to the transition and immediately downstream. The magnetic transition at the quasi-parallel crossing is less clear, energetic electrons were encountered upstream and downstream, and the electron energy spectrum is harder above ˜100 keV. We discuss whether the acceleration is consistent with diffusive shock acceleration theory in each case, and suggest that the quasi-parallel spectral break is due to an energy-dependent interaction between the electrons and short, large-amplitude magnetic structures.

  20. Supercritical water

    CERN Document Server

    Marcus, Yizhak

    2012-01-01

    Discover the many new and emerging applications of supercritical water as a green solvent Drawing from thousands of original research articles, this book reviews and summarizes what is currently known about the properties and uses of supercritical water. In particular, it focuses on new and emerging applications of supercritical water as a green solvent, including the catalytic conversion of biomass into fuels and the oxidation of hazardous materials. Supercritical Water begins with an introduction that defines supercritical fluids in general. It then defines supercritical wa

  1. Computer modeling of test particle acceleration at oblique shocks

    Science.gov (United States)

    Decker, Robert B.

    1988-01-01

    The present evaluation of the basic techniques and illustrative results of charged particle-modeling numerical codes suitable for particle acceleration at oblique, fast-mode collisionless shocks emphasizes the treatment of ions as test particles, calculating particle dynamics through numerical integration along exact phase-space orbits. Attention is given to the acceleration of particles at planar, infinitessimally thin shocks, as well as to plasma simulations in which low-energy ions are injected and accelerated at quasi-perpendicular shocks with internal structure.

  2. STEREO interplanetary shocks and foreshocks

    Energy Technology Data Exchange (ETDEWEB)

    Blanco-Cano, X. [Instituto de Geofisica, UNAM, CU, Coyoacan 04510 DF (Mexico); Kajdic, P. [IRAP-University of Toulouse, CNRS, Toulouse (France); Aguilar-Rodriguez, E. [Instituto de Geofisica, UNAM, Morelia (Mexico); Russell, C. T. [ESS and IGPP, University of California, Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095 (United States); Jian, L. K. [NASA Goddard Space Flight Center, Greenbelt, MD and University of Maryland, College Park, MD (United States); Luhmann, J. G. [SSL, University of California Berkeley (United States)

    2013-06-13

    We use STEREO data to study shocks driven by stream interactions and the waves associated with them. During the years of the extended solar minimum 2007-2010, stream interaction shocks have Mach numbers between 1.1-3.8 and {theta}{sub Bn}{approx}20-86 Degree-Sign . We find a variety of waves, including whistlers and low frequency fluctuations. Upstream whistler waves may be generated at the shock and upstream ultra low frequency (ULF) waves can be driven locally by ion instabilities. The downstream wave spectra can be formed by both, locally generated perturbations, and shock transmitted waves. We find that many quasiperpendicular shocks can be accompanied by ULF wave and ion foreshocks, which is in contrast to Earth's bow shock. Fluctuations downstream of quasi-parallel shocks tend to have larger amplitudes than waves downstream of quasi-perpendicular shocks. Proton foreshocks of shocks driven by stream interactions have extensions dr {<=}0.05 AU. This is smaller than foreshock extensions for ICME driven shocks. The difference in foreshock extensions is related to the fact that ICME driven shocks are formed closer to the Sun and therefore begin to accelerate particles very early in their existence, while stream interaction shocks form at {approx}1 AU and have been producing suprathermal particles for a shorter time.

  3. Shock

    Science.gov (United States)

    Shock can be caused by any condition that reduces blood flow, including: Heart problems (such as heart attack or heart failure ) Low blood volume (as with heavy bleeding or dehydration ) Changes in blood vessels (as with infection ...

  4. Structure of mass-loading shocks. 2: Comparison of theory and observation at comet Halley

    Science.gov (United States)

    Zank, G. P.; Coates, A. J.; Neubauer, F. M.; Reme, H.; Mazelle, C. X.

    1995-01-01

    The multifluid diffusive model of G. P. Zank et al. (1994), which describes the interaction of the solar wind with a cometary plasma in the outer coma, has been used to model the structure of the Halley bow shock. The theoretical results are compared to in situ observations made by Giotto. We compare the solar wind and cometary ion number densities and pressures upstream and through the quasi-perpendicular and quasi-parallel shocks (observed on the inbound and outbound legs of the encounter, respectively). In general, good agreement is found between theory and observations in terms of shock structure, strength, and location, especially for the quasi-parallel shock. The comparison between tha quasi-perpendicular shock observations and theory is complicated by the apparently nonstationary behavior of the shock, a feature which has been remarked upon by other investigators. The cometary bow shock appears to be an excellent example of an energetic-particle-mediated shock where the energetic particles comprise less than 10% of the total number density.

  5. Magnetic field fluctuations across the Earth’s bow shock

    Directory of Open Access Journals (Sweden)

    A. Czaykowska

    Full Text Available We present a statistical analysis of 132 dayside (LT 0700-1700 bow shock crossings of the AMPTE/IRM spacecraft. We perform a superposed epoch analysis of low frequency, magnetic power spectra some minutes up-stream and downstream of the bow shock. The events are devided into categories depending on the angle θBn between bow shock normal and interplanetary magnetic field, and on plasma-β. In the foreshock upstream of the quasi-parallel bow shock, the power of the magnetic fluctuations is roughly 1 order of magnitude larger (δB ~ 4 nT for frequencies 0.01–0.04 Hz than upstream of the quasi-perpendicular shock. There is no significant difference in the magnetic power spectra upstream and downstream of the quasi-parallel bow shock; only at the shock itself, is the magnetic power enhanced by a factor of 4. This enhancement may be due to either an amplification of convecting upstream waves or to wave generation at the shock interface. On the contrary, downstream of the quasi-perpendicular shock, the magnetic wave activity is considerably higher than upstream. Down-stream of the quasi-perpendicular low-β bow shock, we find a dominance of the left-hand polarized component at frequencies just below the ion-cyclotron frequency, with amplitudes of about 3 nT. These waves are identified as ion-cyclotron waves, which grow in a low-β regime due to the proton temperature anisotropy. We find a strong correlation of this anisotropy with the intensity of the left-hand polarized component. Downstream of some nearly perpendicular (θBn ≈ 90° high-β crossings, mirror waves are identified. However, there are also cases where the conditions for mirror modes are met downstream of the nearly perpendicular shock, but no mirror waves are observed.

    Key words. Interplanetary physics (plasma waves and turbulence – Magnetospheric physics (magnetosheath; plasma waves and

  6. Simulations of ion acceleration at non-relativistic shocks: i) Acceleration efficiency

    CERN Document Server

    Caprioli, Damiano

    2013-01-01

    We use 2D and 3D hybrid (kinetic ions - fluid electrons) simulations to investigate particle acceleration and magnetic field amplification at non-relativistic astrophysical shocks. We show that diffusive shock acceleration operates for quasi-parallel configurations (i.e., when the background magnetic field is almost aligned with the shock normal) and, for large sonic and Alfv\\'enic Mach numbers, produces universal power-law spectra proportional to p^(-4), where p is the particle momentum. The maximum energy of accelerated ions increases with time, and it is only limited by finite box size and run time. Acceleration is mainly efficient for parallel and quasi-parallel strong shocks, where 10-20% of the bulk kinetic energy can be converted to energetic particles, and becomes ineffective for quasi-perpendicular shocks. Also, the generation of magnetic turbulence correlates with efficient ion acceleration, and vanishes for quasi-perpendicular configurations. At very oblique shocks, ions can be accelerated via shoc...

  7. Transport of Solar Wind H+ and He++ Ions across Earth’s Bow Shock

    Science.gov (United States)

    Parks, G. K.; Lee, E.; Fu, S. Y.; Kim, H. E.; Ma, Y. Q.; Yang, Z. W.; Liu, Y.; Lin, N.; Hong, J.; Canu, P.; Dandouras, I.; Rème, H.; Goldstein, M. L.

    2016-07-01

    We have investigated the dependence of mass, energy, and charge of solar wind (SW) transport across Earth’s bow shock. An examination of 111 crossings during quiet SW in both quasi-perpendicular and quasi-parallel shock regions shows that 64 crossings had various degrees of heating and thermalization of SW. We found 22 crossings where the SW speed was flat top distribution is ˜50 Volts. We find that the temperatures of H+ and He++ beams that penetrate the shock can sometimes be nearly the same in the upstream and downstream regions, indicating little or no heating had occurred crossing the bow shock. None of the models predict that the SW can cross the bow shock without heating. Our observations are important constraints for new models of collisionless shocks.

  8. On the proper Mach number and ratio of specific heats for modeling the Venus bow shock

    Science.gov (United States)

    Tatrallyay, M.; Russell, C. T.; Luhmann, J. G.; Barnes, A.; Mihalov, J. D.

    1984-01-01

    Observational data from the Pioneer Venus Orbiter are used to investigate the physical characteristics of the Venus bow shock, and to explore some general issues in the numerical simulation of collisionless shocks. It is found that since equations from gas-dynamic (GD) models of the Venus shock cannot in general replace MHD equations, it is not immediately obvious what the optimum way is to describe the desired MHD situation with a GD code. Test case analysis shows that for quasi-perpendicular shocks it is safest to use the magnetospheric Mach number as an input to the GD code. It is also shown that when comparing GD predicted temperatures with MHD predicted temperatures total energy should be compared since the magnetic energy density provides a significant fraction of the internal energy of the MHD fluid for typical solar wind parameters. Some conclusions are also offered on the properties of the terrestrial shock.

  9. Electron - whistler interaction at the Earth`s bow shock: 1. Whistler instability

    Energy Technology Data Exchange (ETDEWEB)

    Veltri, P.; Zimbardo, G. [Universita della Calabria, Cosenza (Italy)

    1993-08-01

    The authors model the interaction of whistler waves with the quasi-perpendicular bow shock observed on Nov 7, 1977. Using a Monte Carlo technique they are able to construct the resulting electron distribution function. This distribution function is asymmetric, and includes a loss cone which the data supports. This distribution function asymmetry is able to drive instabilites which couple to generate additional whister energy. A significant amount of the whistler energy is observed to originate from the region where the loss cone is observed.

  10. Electromagnetic Structure and Electron Acceleration in Shock–Shock Interaction

    Science.gov (United States)

    Nakanotani, Masaru; Matsukiyo, Shuichi; Hada, Tohru; Mazelle, Christian X.

    2017-09-01

    A shock–shock interaction is investigated by using a one-dimensional full particle-in-cell simulation. The simulation reproduces the collision of two symmetrical high Mach number quasi-perpendicular shocks. The basic structure of the shocks and ion dynamics is similar to that obtained by previous hybrid simulations. The new aspects obtained here are as follows. Electrons are already strongly accelerated before the two shocks collide through multiple reflection. The reflected electrons self-generate waves upstream between the two shocks before they collide. The waves far upstream are generated through the right-hand resonant instability with the anomalous Doppler effect. The waves generated near the shock are due to firehose instability and have much larger amplitudes than those due to the resonant instability. The high-energy electrons are efficiently scattered by the waves so that some of them gain large pitch angles. Those electrons can be easily reflected at the shock of the other side. The accelerated electrons form a power-law energy spectrum. Due to the accelerated electrons, the pressure of upstream electrons increases with time. This appears to cause the deceleration of the approaching shock speed. The accelerated electrons having sufficiently large Larmor radii are further accelerated through the similar mechanism working for ions when the two shocks are colliding.

  11. The interaction of turbulence with parallel and perpendicular shocks

    Science.gov (United States)

    Adhikari, L.; Zank, G. P.; Hunana, P.; Hu, Q.

    2016-11-01

    Interplanetary shocks exist in most astrophysical flows, and modify the properties of the background flow. We apply the Zank et al 2012 six coupled turbulence transport model equations to study the interaction of turbulence with parallel and perpendicular shock waves in the solar wind. We model the 1D structure of a stationary perpendicular or parallel shock wave using a hyperbolic tangent function and the Rankine-Hugoniot conditions. A reduced turbulence transport model (the 4-equation model) is applied to parallel and perpendicular shock waves, and solved using a 4th- order Runge Kutta method. We compare the model results with ACE spacecraft observations. We identify one quasi-parallel and one quasi-perpendicular event in the ACE spacecraft data sets, and compute various turbulent observed values such as the fluctuating magnetic and kinetic energy, the energy in forward and backward propagating modes, the total turbulent energy in the upstream and downstream of the shock. We also calculate the error associated with each turbulent observed value, and fit the observed values by a least square method and use a Fourier series fitting function. We find that the theoretical results are in reasonable agreement with observations. The energy in turbulent fluctuations is enhanced and the correlation length is approximately constant at the shock. Similarly, the normalized cross helicity increases across a perpendicular shock, and decreases across a parallel shock.

  12. Observational evidence on the origin of ions upstream of the earth's bow shock

    Science.gov (United States)

    Thomsen, M. F.; Gosling, J. T.; Schwartz, S. J.

    1983-01-01

    The kinematic formalism described by Schwartz et al. (1983) is used to quantitatively compare the zeroth order predicted energies for four different source hypotheses for ions detected upstream of the earth's bow shock with previously published observations of upstream field-aligned beams and gyrating ion events. Specular reflection of a fraction of the incident solar wind is found to be the most credible explanation of gyrating ion events observed upstream of shocks ranging from quasi-parallel to nearly perpendicular. The recent hypothesis that field-aligned beams are the result of leakage from the magnetosheath of ions which were originally specularly reflected at quasi-perpendicular portions of the shock provides good agreement with observed energies of many field-aligned beams. Only magnetic moment conserving reflection of solar wind ions is capable of accounting for two very energetic beam events.

  13. Shock Geometry and Spectral Breaks in Large SEP Events

    Science.gov (United States)

    Li, G.; Zank, G. P.; Verkhoglyadova, Olga; Mewaldt, R. A.; Cohen, C. M. S.; Mason, G. M.; Desai, M. I.

    2009-09-01

    Solar energetic particle (SEP) events are traditionally classified as "impulsive" or "gradual." It is now widely accepted that in gradual SEP events, particles are accelerated at coronal mass ejection-driven (CME-driven) shocks. In many of these large SEP events, particle spectra exhibit double power law or exponential rollover features, with the break energy or rollover energy ordered as (Q/A)α, with Q being the ion charge in e and A the ion mass in units of proton mass mp . This Q/A dependence of the spectral breaks provides an opportunity to study the underlying acceleration mechanism. In this paper, we examine how the Q/A dependence may depend on shock geometry. Using the nonlinear guiding center theory, we show that α ~ 1/5 for a quasi-perpendicular shock. Such a weak Q/A dependence is in contrast to the quasi-parallel shock case where α can reach 2. This difference in α reflects the difference of the underlying parallel and perpendicular diffusion coefficients κ|| and κbottom. We also examine the Q/A dependence of the break energy for the most general oblique shock case. Our analysis offers a possible way to remotely examine the geometry of a CME-driven shock when it is close to the Sun, where the acceleration of particle to high energies occurs.

  14. The Dynamics of Very High Alfvén Mach Number Shocks in Space Plasmas

    Science.gov (United States)

    Sundberg, Torbjörn; Burgess, David; Scholer, Manfred; Masters, Adam; Sulaiman, Ali H.

    2017-02-01

    Astrophysical shocks, such as planetary bow shocks or supernova remnant shocks, are often in the high or very-high Mach number regime, and the structure of such shocks is crucial for understanding particle acceleration and plasma heating, as well inherently interesting. Recent magnetic field observations at Saturn’s bow shock, for Alfvén Mach numbers greater than about 25, have provided evidence for periodic non-stationarity, although the details of the ion- and electron-scale processes remain unclear due to limited plasma data. High-resolution, multi-spacecraft data are available for the terrestrial bow shock, but here the very high Mach number regime is only attained on extremely rare occasions. Here we present magnetic field and particle data from three such quasi-perpendicular shock crossings observed by the four-spacecraft Cluster mission. Although both ion reflection and the shock profile are modulated at the upstream ion gyroperiod timescale, the dominant wave growth in the foot takes place at sub-proton length scales and is consistent with being driven by the ion Weibel instability. The observed large-scale behavior depends strongly on cross-scale coupling between ion and electron processes, with ion reflection never fully suppressed, and this suggests a model of the shock dynamics that is in conflict with previous models of non-stationarity. Thus, the observations offer insight into the conditions prevalent in many inaccessible astrophysical environments, and provide important constraints for acceleration processes at such shocks.

  15. Supercritical fluid extraction

    Science.gov (United States)

    Wai, Chien M.; Laintz, Kenneth

    1994-01-01

    A method of extracting metalloid and metal species from a solid or liquid material by exposing the material to a supercritical fluid solvent containing a chelating agent. The chelating agent forms chelates that are soluble in the supercritical fluid to allow removal of the species from the material. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is a fluorinated or lipophilic crown ether or fluorinated dithiocarbamate. The method provides an environmentally benign process for removing contaminants from industrial waste without using acids or biologically harmful solvents. The chelate and supercritical fluid can be regenerated, and the contaminant species recovered, to provide an economic, efficient process.

  16. Global Explicit Particle-in-cell Simulations of the Nonstationary Bow Shock and Magnetosphere

    Science.gov (United States)

    Yang, Zhongwei; Huang, Can; Liu, Ying D.; Parks, George K.; Wang, Rui; Lu, Quanming; Hu, Huidong

    2016-07-01

    We carry out two-dimensional global particle-in-cell simulations of the interaction between the solar wind and a dipole field to study the formation of the bow shock and magnetosphere. A self-reforming bow shock ahead of a dipole field is presented by using relatively high temporal-spatial resolutions. We find that (1) the bow shock and the magnetosphere are formed and reach a quasi-stable state after several ion cyclotron periods, and (2) under the B z southward solar wind condition, the bow shock undergoes a self-reformation for low β i and high M A . Simultaneously, a magnetic reconnection in the magnetotail is found. For high β i and low M A , the shock becomes quasi-stationary, and the magnetotail reconnection disappears. In addition, (3) the magnetopause deflects the magnetosheath plasmas. The sheath particles injected at the quasi-perpendicular region of the bow shock can be convected downstream of an oblique shock region. A fraction of these sheath particles can leak out from the magnetosheath at the wings of the bow shock. Hence, the downstream situation is more complicated than that for a planar shock produced in local simulations.

  17. Comparative Study of Electromagnetic Waves at the Bow Shocks of Venus and Earth

    Science.gov (United States)

    Wei, Hanying; Russell, Christopher T.; Strangeway, Robert J.; Schwartz, Steven J.; Zhang, Tielong

    2016-04-01

    Although the solar interactions with Venus and Earth are quite different in many ways, they both have bow shocks formed upstream of the planet where the solar wind decelerates from a super- to sub- magnetosonic flow. In the upstream foreshock region, there is abundant wave activity generated by the shock or by the back-streaming ions and electrons from the shock. In the downstream magnetosheath region, there is also abundant wave activity either locally generated by the heated electrons or ions from the shock or transported from the shock or foreshock regions by the solar wind. The magnetometers of Venus Express and Magnetospheric Multiscale missions both occasionally record 128 Hz data during their shock crossing, which allow us the search for and analyze waves at such high frequencies. We have found short-duration wave bursts around both Venus and Earth bow shocks, with certain similarities. These waves are mostly quasi-perpendicular propagating and have amplitude and occurrence rate decreasing with distance from the bow shock. In this paper we perform statistical and comparative studies on wave properties to understand their generation mechanisms and their effects to the shock or magnetosheath plasmas.

  18. ABRUPT DEFLECTED SUPERCRITICAL WATER FLOW IN SLOPED CHANNELS

    Institute of Scientific and Technical Information of China (English)

    LIU Ya-kun; NI Han-gen

    2008-01-01

    The effect of the bottom slope on abrupt deflected supercritical water flow was experimentally and theoretically studied. Model tests were conducted in a flume of 1.2 m wide and 2.6 m long with sloped bottom at an angle 35.54o, its length of deflector was 0.2 m and the deflection angles were 15o and 30o. An approximate method for calculatjng the shock wave angle and depth ratio of the abrupt deflected supercritical water flow was suggested, and a correction coefficient for the hydrodynamic pressure was introduced to generalize the momentum equation in the direction perpendicular to the shock front. It must be noticed that in the sloped channel the shock wave angle and the depth ratio are no longer constant as those in the horizontal channels, but slowly change along the shock front. The calculated results are in good agreement with measured data.

  19. Electrochemistry in supercritical fluids

    Science.gov (United States)

    Branch, Jack A.; Bartlett, Philip N.

    2015-01-01

    A wide range of supercritical fluids (SCFs) have been studied as solvents for electrochemistry with carbon dioxide and hydrofluorocarbons (HFCs) being the most extensively studied. Recent advances have shown that it is possible to get well-resolved voltammetry in SCFs by suitable choice of the conditions and the electrolyte. In this review, we discuss the voltammetry obtained in these systems, studies of the double-layer capacitance, work on the electrodeposition of metals into high aspect ratio nanopores and the use of metallocenes as redox probes and standards in both supercritical carbon dioxide–acetonitrile and supercritical HFCs. PMID:26574527

  20. Electrochemistry in supercritical fluids.

    Science.gov (United States)

    Branch, Jack A; Bartlett, Philip N

    2015-12-28

    A wide range of supercritical fluids (SCFs) have been studied as solvents for electrochemistry with carbon dioxide and hydrofluorocarbons (HFCs) being the most extensively studied. Recent advances have shown that it is possible to get well-resolved voltammetry in SCFs by suitable choice of the conditions and the electrolyte. In this review, we discuss the voltammetry obtained in these systems, studies of the double-layer capacitance, work on the electrodeposition of metals into high aspect ratio nanopores and the use of metallocenes as redox probes and standards in both supercritical carbon dioxide-acetonitrile and supercritical HFCs.

  1. The role of the interplanetary shock surface fluctuations in shaping energetic storm particle events

    Science.gov (United States)

    Lario, D.; Decker, R. B.

    2006-12-01

    Solar cycle 23 has provided us with a large variety of shocks and associated energetic particle storm (ESP) events. Statistical analysis of shocks and ESP events detected by ACE has shown a tendency for observing more quasi-perpendicular shocks; whereas the most common types of event are those that do not display any >47 keV ion intensity increase [Lario et al., 2005a; Proc. SW11, ESA SP-592, pp. 81-86]. Faster and stronger shocks have greater effects on the particle intensities at their passage by 1 AU, but the shock parameters do not determine unequivocally the characteristics of the ESP events. A few of these events show characteristics similar to those predicted by the theory of diffusive shock acceleration, although detailed analysis reveals significant inconsistencies between observations and theory [Lario et al., 2005b; Proc. 4th IGPP Conf., AIP-781, pp. 180-184]. A common type of event has irregular structure, showing multiple intensity bursts before and/or after the shock passage. We present both the observations of one of these events and the results of a test-particle, full-orbit-integration simulation of ion shock-acceleration in a corrugated shock surface [Decker, 1990; JGR 95, pp. 11993-12003]. Although meso-scale fluctuations of the shock surface or in magnetic field direction, or both, can produce similar features in shock-accelerated particle distributions, we invoke the rippled shock model in this case because the measured pre-shock field is relatively steady. These simulations allow us to reproduce not only the evolution of the ion intensities but also the observed ion anisotropies and energy spectra. Fluctuations of both the solar wind plasma where the shock travels and of the shock surface may determine the main features of those ESP events with irregular variations of intensities and angular distributions. This presentation constitutes a progress report on NASA LWS TR{&}T grant NAG5-13487.

  2. Supercritical Airfoil Coordinates

    Data.gov (United States)

    National Aeronautics and Space Administration — Rectangular Supercritical Wing (Ricketts) - design and measured locations are provided in an Excel file RSW_airfoil_coordinates_ricketts.xls . One sheet is with Non...

  3. Global explicit particle-in-cell simulations of the nonstationary bow shock and magnetosphere

    CERN Document Server

    Yang, Zhongwei; Liu, Ying D; Parks, George K; Wang, Rui; Lu, Quanming; Hu, Huidong

    2016-01-01

    We carry out two-dimensional global particle-in-cell simulations of the interaction between the solar wind and a dipole field to study the formation of the bow shock and magnetosphere. A self-reforming bow shock ahead of a dipole field is presented by using relatively high temporal-spatial resolutions. We find that (1) the bow shock and the magnetosphere are formed and reach a quasi-stable state after several ion cyclotron periods, and (2) under the Bz southward solar wind condition the bow shock undergoes a self-reformation for low \\b{eta}i and high MA. Simultaneously, a magnetic reconnection in the magnetotail is found. For high \\b{eta}i and low MA, the shock becomes quasi-stationary, and the magnetotail reconnection disappears. In addition, (3) the magnetopause deflects the magnetosheath plasmas. The sheath particles injected at the quasi-perpendicular region of the bow shock can be convected to downstream of an oblique shock region. A fraction of these sheath particles can leak out from the magnetosheath ...

  4. Exp6-polar thermodynamics of dense supercritical water

    Energy Technology Data Exchange (ETDEWEB)

    Bastea, S; Fried, L E

    2007-12-13

    We introduce a simple polar fluid model for the thermodynamics of dense supercritical water based on a Buckingham (exp-6) core and point dipole representation of the water molecule. The proposed exp6-polar thermodynamics, based on ideas originally applied to dipolar hard spheres, performs very well when tested against molecular dynamics simulations. Comparisons of the model predictions with experimental data available for supercritical water yield excellent agreement for the shock Hugoniot, isotherms and sound speeds, and are also quite good for the self-diffusion constant and relative dielectric constant. We expect the present approach to be also useful for other small polar molecules and their mixtures.

  5. Search Coil vs. Fluxgate Magnetometer Measurements at Interplanetary Shocks

    Science.gov (United States)

    Wilson, L.B., III

    2012-01-01

    We present magnetic field observations at interplanetary shocks comparing two different sample rates showing significantly different results. Fluxgate magnetometer measurements show relatively laminar supercritical shock transitions at roughly 11 samples/s. Search coil magnetometer measurements at 1875 samples/s, however, show large amplitude (dB/B as large as 2) fluctuations that are not resolved by the fluxgate magnetometer. We show that these fluctuations, identified as whistler mode waves, would produce a significant perturbation to the shock transition region changing the interpretation from laminar to turbulent. Thus, previous observations of supercritical interplanetary shocks classified as laminar may have been under sampled.

  6. The adiabatic energy change of plasma electrons and the frame dependence of the cross-shock potential at collisionless magnetosonic shock waves

    Science.gov (United States)

    Goodrich, C. C.; Scudder, J. D.

    1984-01-01

    The adiabatic energy gain of electrons in the stationary electric and magnetic field structure of collisionless shock waves was examined analytically in reference to conditions of the earth's bow shock. The study was performed to characterize the behavior of electrons interacting with the cross-shock potential. A normal incidence frame (NIF) was adopted in order to calculate the reversible energy change across a time stationary shock, and comparisons were made with predictions made by the de Hoffman-Teller (HT) model (1950). The electron energy gain, about 20-50 eV, is demonstrated to be consistent with a 200-500 eV potential jump in the bow shock quasi-perpendicular geometry. The electrons lose energy working against the solar wind motional electric field. The reversible energy process is close to that modeled by HT, which predicts that the motional electric field vanishes and the electron energy gain from the electric potential is equated to the ion energy loss to the potential.

  7. Drug delivery goes supercritical

    Directory of Open Access Journals (Sweden)

    Patrick J. Ginty

    2005-08-01

    Full Text Available In the field of drug delivery, the ability to control the size, morphology, and release of drug particles is fundamental to good targeting, but is often hampered by harsh processing conditions or inadequate methods; likewise for the processing of polymeric controlled-release systems. However, the use of supercritical fluids such as supercritical CO2 (scCO2 has provided a ‘clean’ and effective alternative to traditional methods of drug and polymer processing. In particular, scCO2 has a number of unique properties that make it possible to process both bioactive molecules and amorphous polymers without using toxic organic solvents or elevated temperatures. Here, we review the positive impact that supercritical fluids have had on the micronization, encapsulation, and impregnation of molecules of interest to both the pharmaceutical and biotechnology industries.

  8. Index to the Shock and Vibration Bulletins

    Science.gov (United States)

    1968-02-01

    facilities Reynold’s number graph, 26-2-172 supercritical in study of flow of incompressi- ble fluids, 26-2-147 vortex discharge at, 26-2-147, 180...used in shipboard shock tests, 29-1-12 Velocity generators, waterjet actuators, for sled tests, 35-6-47 Vermiculite, shock mitigating character...towers and other struc- tures, 34-2-279 at supercritical Reynolds number, 26-2-147,180 Vulnerability of aircraft to blast, 28-1-56 to nuclear

  9. Materials processing using supercritical fluids

    Directory of Open Access Journals (Sweden)

    Orlović Aleksandar M.

    2005-01-01

    Full Text Available One of the most interesting areas of supercritical fluids applications is the processing of novel materials. These new materials are designed to meet specific requirements and to make possible new applications in Pharmaceuticals design, heterogeneous catalysis, micro- and nano-particles with unique structures, special insulating materials, super capacitors and other special technical materials. Two distinct possibilities to apply supercritical fluids in processing of materials: synthesis of materials in supercritical fluid environment and/or further processing of already obtained materials with the help of supercritical fluids. By adjusting synthesis parameters the properties of supercritical fluids can be significantly altered which further results in the materials with different structures. Unique materials can be also obtained by conducting synthesis in quite specific environments like reversed micelles. This paper is mainly devoted to processing of previously synthesized materials which are further processed using supercritical fluids. Several new methods have been developed to produce micro- and nano-particles with the use of supercritical fluids. The following methods: rapid expansion of supercritical solutions (RESS supercritical anti-solvent (SAS, materials synthesis under supercritical conditions and encapsulation and coating using supercritical fluids were recently developed.

  10. Supercritical Synthesis of Biodiesel

    Directory of Open Access Journals (Sweden)

    Michel Vaultier

    2012-07-01

    Full Text Available The synthesis of biodiesel fuel from lipids (vegetable oils and animal fats has gained in importance as a possible source of renewable non-fossil energy in an attempt to reduce our dependence on petroleum-based fuels. The catalytic processes commonly used for the production of biodiesel fuel present a series of limitations and drawbacks, among them the high energy consumption required for complex purification operations and undesirable side reactions. Supercritical fluid (SCF technologies offer an interesting alternative to conventional processes for preparing biodiesel. This review highlights the advances, advantages, drawbacks and new tendencies involved in the use of supercritical fluids (SCFs for biodiesel synthesis.

  11. ION ACCELERATION AT THE QUASI-PARALLEL BOW SHOCK: DECODING THE SIGNATURE OF INJECTION

    Energy Technology Data Exchange (ETDEWEB)

    Sundberg, Torbjörn; Haynes, Christopher T.; Burgess, D. [School of Physics and Astronomy, Queen Mary University of London, London, E1 4NS (United Kingdom); Mazelle, Christian X. [IRAP, Université Paul Sabatier Toulouse III-CNRS, 31028 Toulouse Cedex 4 (France)

    2016-03-20

    Collisionless shocks are efficient particle accelerators. At Earth, ions with energies exceeding 100 keV are seen upstream of the bow shock when the magnetic geometry is quasi-parallel, and large-scale supernova remnant shocks can accelerate ions into cosmic-ray energies. This energization is attributed to diffusive shock acceleration; however, for this process to become active, the ions must first be sufficiently energized. How and where this initial acceleration takes place has been one of the key unresolved issues in shock acceleration theory. Using Cluster spacecraft observations, we study the signatures of ion reflection events in the turbulent transition layer upstream of the terrestrial bow shock, and with the support of a hybrid simulation of the shock, we show that these reflection signatures are characteristic of the first step in the ion injection process. These reflection events develop in particular in the region where the trailing edge of large-amplitude upstream waves intercept the local shock ramp and the upstream magnetic field changes from quasi-perpendicular to quasi-parallel. The dispersed ion velocity signature observed can be attributed to a rapid succession of ion reflections at this wave boundary. After the ions’ initial interaction with the shock, they flow upstream along the quasi-parallel magnetic field. Each subsequent wavefront in the upstream region will sweep the ions back toward the shock, where they gain energy with each transition between the upstream and the shock wave frames. Within three to five gyroperiods, some ions have gained enough parallel velocity to escape upstream, thus completing the injection process.

  12. Non-thermal Electron Acceleration in Low Mach Number Collisionless Shocks. I. Particle Energy Spectra and Acceleration Mechanism

    Science.gov (United States)

    Guo, Xinyi; Sironi, Lorenzo; Narayan, Ramesh

    2014-10-01

    Electron acceleration to non-thermal energies in low Mach number (Ms Diffusive shock acceleration, also known as first-order Fermi acceleration, cannot be directly invoked to explain the acceleration of electrons. Rather, an additional mechanism is required to pre-accelerate the electrons from thermal to supra-thermal energies, so they can then participate in the Fermi process. In this work, we use two- and three-dimensional particle-in-cell plasma simulations to study electron acceleration in low Mach number shocks. We focus on the particle energy spectra and the acceleration mechanism in a reference run with Ms = 3 and a quasi-perpendicular pre-shock magnetic field. We find that about 15% of the electrons can be efficiently accelerated, forming a non-thermal power-law tail in the energy spectrum with a slope of p ~= 2.4. Initially, thermal electrons are energized at the shock front via shock drift acceleration (SDA). The accelerated electrons are then reflected back upstream where their interaction with the incoming flow generates magnetic waves. In turn, the waves scatter the electrons propagating upstream back toward the shock for further energization via SDA. In summary, the self-generated waves allow for repeated cycles of SDA, similarly to a sustained Fermi-like process. This mechanism offers a natural solution to the conflict between the bright radio synchrotron emission observed from the outskirts of galaxy clusters and the low electron acceleration efficiency usually expected in low Mach number shocks.

  13. Magnetosheath Filamentary Structures Formed by Ion Acceleration at the Quasi-Parallel Bow Shock

    Science.gov (United States)

    Omidi, N.; Sibeck, D.; Gutynska, O.; Trattner, K. J.

    2014-01-01

    Results from 2.5-D electromagnetic hybrid simulations show the formation of field-aligned, filamentary plasma structures in the magnetosheath. They begin at the quasi-parallel bow shock and extend far into the magnetosheath. These structures exhibit anticorrelated, spatial oscillations in plasma density and ion temperature. Closer to the bow shock, magnetic field variations associated with density and temperature oscillations may also be present. Magnetosheath filamentary structures (MFS) form primarily in the quasi-parallel sheath; however, they may extend to the quasi-perpendicular magnetosheath. They occur over a wide range of solar wind Alfvénic Mach numbers and interplanetary magnetic field directions. At lower Mach numbers with lower levels of magnetosheath turbulence, MFS remain highly coherent over large distances. At higher Mach numbers, magnetosheath turbulence decreases the level of coherence. Magnetosheath filamentary structures result from localized ion acceleration at the quasi-parallel bow shock and the injection of energetic ions into the magnetosheath. The localized nature of ion acceleration is tied to the generation of fast magnetosonic waves at and upstream of the quasi-parallel shock. The increased pressure in flux tubes containing the shock accelerated ions results in the depletion of the thermal plasma in these flux tubes and the enhancement of density in flux tubes void of energetic ions. This results in the observed anticorrelation between ion temperature and plasma density.

  14. Structural Transition in Supercritical Fluids

    Directory of Open Access Journals (Sweden)

    Boris I. Sedunov

    2011-01-01

    Full Text Available The extension of the saturation curve ( on the PT diagram in the supercritical region for a number of monocomponent supercritical fluids by peak values for different thermophysical properties, such as heat capacities and and compressibility has been studied. These peaks signal about some sort of fluid structural transition in the supercritical region. Different methods give similar but progressively diverging curves st( for this transition. The zone of temperatures and pressures near these curves can be named as the zone of the fluid structural transition. The outstanding properties of supercritical fluids in this zone help to understand the physical sense of the fluid structural transition.

  15. EVIDENCE FOR A SHOCK IN INTERSTELLAR PLASMA: VOYAGER 1

    Energy Technology Data Exchange (ETDEWEB)

    Burlaga, L. F. [NASA Goddard Space Flight Center, Code 673, Greenbelt, MD 20771 (United States); Ness, N. F. [Institute for Astrophysics and Computational Sciences, Catholic University of America, Washington, DC 20064 (United States); Gurnett, D. A.; Kurth, W. S., E-mail: lburlagahsp@verizon.net, E-mail: nfnudel@yahoo.com, E-mail: donald-gurnett@uiowa.edu, E-mail: william-kurth@uiowa.edu [University of Iowa, Iowa City, IA 52242 (United States)

    2013-11-20

    Voyager 1 (V1) observed electron plasma oscillations preceding a jump by a factor of 1.4 in the magnetic field intensity B near the end of 2012. The frequency of the electron plasma oscillations gives an electron density n{sub e}  = 0.05 cm{sup –3}, which implies that V1 was immersed in plasma from the interstellar medium. The last day on which plasma oscillations were observed is day 332, 2012, and the jump in the B was centered on day 335, 2012 after a data gap in the wave data. The close association between the electron plasma oscillations and the jump in B suggests a causal connection, such as that frequently observed between electron plasma oscillations and interplanetary shocks at 1 AU. Based on the observed parameters and the smooth profile of B(t), the jump in B appears to be associated with a weak, subcritical, laminar, low beta, quasi-perpendicular, resistive, collisionless shock. However, the width of the jump is of the order of 10{sup 4} times that expected for such a stationary shock at 1 AU. The large width of the jump in B might be the result of differences between the structure of shocks in the interstellar medium and the plasma near 1 AU. Alternatively, the subcritical resistive shock might have decayed during a few days after producing the plasma waves, leaving a broad profile in B(t) without significantly changing ambient parameters. Another possibility is that the jump in B is a pressure wave.

  16. Quasiperpendicular High Mach Number Shocks

    Science.gov (United States)

    Sulaiman, A. H.; Masters, A.; Dougherty, M. K.; Burgess, D.; Fujimoto, M.; Hospodarsky, G. B.

    2015-09-01

    Shock waves exist throughout the Universe and are fundamental to understanding the nature of collisionless plasmas. Reformation is a process, driven by microphysics, which typically occurs at high Mach number supercritical shocks. While ongoing studies have investigated this process extensively both theoretically and via simulations, their observations remain few and far between. In this Letter we present a study of very high Mach number shocks in a parameter space that has been poorly explored and we identify reformation using in situ magnetic field observations from the Cassini spacecraft at 10 AU. This has given us an insight into quasiperpendicular shocks across 2 orders of magnitude in Alfvén Mach number (MA ) which could potentially bridge the gap between modest terrestrial shocks and more exotic astrophysical shocks. For the first time, we show evidence for cyclic reformation controlled by specular ion reflection occurring at the predicted time scale of ˜0.3 τc , where τc is the ion gyroperiod. In addition, we experimentally reveal the relationship between reformation and MA and focus on the magnetic structure of such shocks to further show that for the same MA , a reforming shock exhibits stronger magnetic field amplification than a shock that is not reforming.

  17. Supercritical solvent coal extraction

    Science.gov (United States)

    Compton, L. E. (Inventor)

    1984-01-01

    Yields of soluble organic extract are increased up to about 50% by the supercritical extraction of particulate coal at a temperature below the polymerization temperature for coal extract fragments (450 C.) and a pressure from 500 psig to 5,000 psig by the conjoint use of a solvent mixture containing a low volatility, high critical temperature coal dissolution catalyst such as phenanthrene and a high volatility, low critical temperature solvent such as toluene.

  18. Dispersive nature of high mach number collisionless plasma shocks: Poynting flux of oblique whistler waves.

    Science.gov (United States)

    Sundkvist, David; Krasnoselskikh, V; Bale, S D; Schwartz, S J; Soucek, J; Mozer, F

    2012-01-13

    Whistler wave trains are observed in the foot region of high Mach number quasiperpendicular shocks. The waves are oblique with respect to the ambient magnetic field as well as the shock normal. The Poynting flux of the waves is directed upstream in the shock normal frame starting from the ramp of the shock. This suggests that the waves are an integral part of the shock structure with the dispersive shock as the source of the waves. These observations lead to the conclusion that the shock ramp structure of supercritical high Mach number shocks is formed as a balance of dispersion and nonlinearity.

  19. Thermodynamic behaviour of supercritical matter.

    Science.gov (United States)

    Bolmatov, Dima; Brazhkin, V V; Trachenko, K

    2013-01-01

    Since their discovery in 1822, supercritical fluids have been of enduring interest and have started to be deployed in many important applications. Theoretical understanding of the supercritical state is lacking and is seen to limit further industrial deployment. Here we study thermodynamic properties of the supercritical state and discover that specific heat shows a crossover between two different regimes, an unexpected result in view of currently perceived homogeneity of supercritical state in terms of physical properties. We subsequently formulate a theory of system thermodynamics above the crossover, and find good agreement between calculated and experimental specific heat with no free-fitting parameters. In this theory, energy and heat capacity are governed by the minimal length of the longitudinal mode in the system only, and do not explicitly depend on system-specific structure and interactions. We derive a power law and analyse supercritical scaling exponents in the system above the Frenkel line.

  20. Particle Acceleration and Nonthermal Emission in Relativistic Astrophysical Shocks

    Science.gov (United States)

    Sironi, Lorenzo

    The common observational feature of Pulsar Wind Nebulae (PWNe), gamma-ray bursts (GRBs), and AGN jets is a broad nonthermal spectrum of synchrotron and inverse Compton radiation. It is usually assumed that the emitting electrons are accelerated to a power-law distribution at relativistic shocks, via the so-called Fermi mechanism. Despite decades of research, the Fermi acceleration process is still not understood from first principles. An assessment of the micro-physics of particle acceleration in relativistic shocks is of paramount importance to unveil the properties of astrophysical nonthermal sources, and it is the subject of this dissertation. In the first part of this thesis, I explore by means of fully-kinetic first-principle particle-in-cell (PIC) simulations the properties of relativistic shocks that propagate in electron-positron and electron-proton plasmas carrying uniform magnetic fields. I find that nonthermal particle acceleration only occurs if the upstream magnetization is weak (sigma0.01) and quasi-perpendicular, yet they need to be efficient particle accelerators, in order to explain the prominent nonthermal signatures of these sources. Motivated by this discrepancy, I then relax the assumption of uniform pre-shock fields, and investigate the acceleration efficiency of perpendicular shocks that propagate in high-sigma flows with alternating magnetic fields. This is the geometry expected at the termination shock of pulsar winds, but it could also be relevant for Poynting-dominated jets in GRBs and AGNs. I show by means of PIC simulations that compression of the flow at the shock will force annihilation of nearby field lines, a process known as shock-driven reconnection. Magnetic reconnection can efficiently transfer the energy of alternating fields to the particles, generating flat power-law tails containing most of the particles. Finally, I directly relate the results of my PIC simulations to observations of nonthermal sources, by presenting a

  1. The dynamic quasiperpendicular shock: Cluster discoveries

    CERN Document Server

    Krasnoselskikh, V; Walker, S N; Schwartz, S; Sundkvist, D; Lobzin, V; Gedalin, M; Bale, S D; Mozer, F; Soucek, J; Hobara, Y; Comisel, H

    2013-01-01

    The physics of collisionless shocks is a very broad topic which has been studied for more than five decades. However, there are a number of important issues which remain unresolved. The energy repartition amongst particle populations in quasiperpendicular shocks is a multi-scale process related to the spatial and temporal structure of the electromagnetic fields within the shock layer. The most important processes take place in the close vicinity of the major magnetic transition or ramp region. The distribution of electromagnetic fields in this region determines the characteristics of ion reflection and thus defines the conditions for ion heating and energy dissipation for supercritical shocks and also the region where an important part of electron heating takes place. All of these processes are crucially dependent upon the characteristic spatial scales of the ramp and foot region provided that the shock is stationary. The earliest studies of collisionless shocks identified nonlinearity, dissipation, and dispe...

  2. Corrosion in supercritical fluids

    Energy Technology Data Exchange (ETDEWEB)

    Propp, W.A.; Carleson, T.E.; Wai, Chen M.; Taylor, P.R.; Daehling, K.W.; Huang, Shaoping; Abdel-Latif, M.

    1996-05-01

    Integrated studies were carried out in the areas of corrosion, thermodynamic modeling, and electrochemistry under pressure and temperature conditions appropriate for potential applications of supercritical fluid (SCF) extractive metallurgy. Carbon dioxide and water were the primary fluids studied. Modifiers were used in some tests; these consisted of 1 wt% water and 10 wt% methanol for carbon dioxide and of sulfuric acid, sodium sulfate, ammonium sulfate, and ammonium nitrate at concentrations ranging from 0.00517 to 0.010 M for the aqueous fluids. The materials studied were Types 304 and 316 (UNS S30400 and S31600) stainless steel, iron, and AISI-SAE 1080 (UNS G10800) carbon steel. The thermodynamic modeling consisted of development of a personal computer-based program for generating Pourbaix diagrams at supercritical conditions in aqueous systems. As part of the model, a general method for extrapolating entropies and related thermodynamic properties from ambient to SCF conditions was developed. The experimental work was used as a tool to evaluate the predictions of the model for these systems. The model predicted a general loss of passivation in iron-based alloys at SCF conditions that was consistent with experimentally measured corrosion rates and open circuit potentials. For carbon-dioxide-based SCFs, measured corrosion rates were low, indicating that carbon steel would be suitable for use with unmodified carbon dioxide, while Type 304 stainless steel would be suitable for use with water or methanol as modifiers.

  3. ENGINEERING BULLETIN: SUPERCRITICAL WATER OXIDATION

    Science.gov (United States)

    This engineering bulletin presents a description and status of supercritical water oxidation technology, a summary of recent performance tests, and the current applicability of this emerging technology. This information is provided to assist remedial project managers, contractors...

  4. Cardiogenic shock

    Science.gov (United States)

    Shock - cardiogenic ... electrical system of the heart (heart block) Cardiogenic shock occurs when the heart is unable to pump ... orthostatic hypotension) Weak (thready) pulse To diagnose cardiogenic shock, a catheter (tube) may be placed in the ...

  5. Supercritical fluid technology

    Energy Technology Data Exchange (ETDEWEB)

    Penninger, J.M.L.; McHugh, M.A.; Radosz, M.; Krukonis, V.J.

    1985-01-01

    This book presents the state-of-the-art in the science and technology of supercritical fluid (scf) processing. Current research as described in the book, focuses on developments in equations of state for binary and multicomponent mixtures (including polymer solutions), solubility measurements at near-critical conditions, measurements of critical properties of binary mixtures and their correlation with equations of state. Progress in thermodynamics, coupled with advances in the design and construction of high pressure equipment, has opened up a wide avenue of commercial application (e.g. decaffeination of coffee beans, extractions of flavours and spices, purification of pharmaceutical products, separations of polymeric materials, deodorization and deacidification of vegetable oils, fractionation of fatty acids, coal liquefaction, wood delignitication, etc.)

  6. Analysis of supercritical vapor explosions using thermal detonation wave theory

    Energy Technology Data Exchange (ETDEWEB)

    Shamoun, B.I.; Corradini, M.L. [Univ. of Wisconsin, Madison, WI (United States)

    1995-09-01

    The interaction of certain materials such as Al{sub 2}O{sub 3} with water results in vapor explosions with very high (supercritical) pressures and propagation velocities. A quasi-steady state analysis of supercritical detonation in one-dimensional multiphase flow was applied to analyze experimental data of the KROTOS (26-30) set of experiments conducted at the Joint Research Center at Ispra, Italy. In this work we have applied a new method of solution which allows for partial fragmentation of the fuel in the shock adiabatic thermodynamic model. This method uses known experiment values of the shock pressure and propagation velocity to estimate the initial mixing conditions of the experiment. The fuel and coolant were both considered compressible in this analysis. In KROTOS 26, 28, 29, and 30 the measured values of the shock pressure by the experiment were found to be higher than 25, 50, 100, and 100 Mpa respectively. Using the above data for the wave velocity and our best estimate for the values of the pressure, the predicted minimum values of the fragmented mass of the fuel were found to be 0.026. 0.04, 0.057, and 0.068 kg respectively. The predicted values of the work output corresponding to the above fragmented masses of the fuel were found to be 40, 84, 126, and 150 kJ respectively, with predicted initial void fractions of 112%, 12.5%, 8%, and 6% respectively.

  7. Venus Express Observations of Electromagnetic Waves at the Bow Shock and Magnetosheath

    Science.gov (United States)

    Wei, H.; Russell, C.; Hart, R. A.; Strangeway, R. J.; Zhang, T.

    2015-12-01

    The interaction between the solar wind and the ionosphere of Venus forms an induced magnetosphere around the planet, which consists of regions near the planet and in its wake where magnetic pressure dominates the other pressure contributions. This induced magnetosphere and the ionosphere of Venus act as a barrier to the solar wind, leading to a bow shock with standoff distance very close the planet. Upstream of the bow shock, there is abundant wave activity generated by the shock or by the back-streaming ions and electrons from the shock. Previous studies found upstream waves with 1 Hz or lower frequencies, but Venus Express occasionally provides 128 Hz data that cover the regions up to the bow shock and allow us the search for and analyze higher frequency waves. Inside the magnetosheath and at the Venus ionopause, there are lightning-associated whistler waves detected from the 128 Hz data, which generally propagate along the magnetic field lines. Besides, there is another type of waves at such high frequencies which propagate quasi-perpendicular to the magnetic field and strongly associated with current sheets near the ionopause. They either occur at the center of a sharp current, or at the edge of a current. These waves may be generated from the free energy of currents at the ionopause and could lead to dissipation of those currents. In this paper, we perform statistical studies on the current-associated waves and examine their effects on current dissipation and on plasma heating. We examine waves at the bow shock in this higher frequency range.

  8. Nanotechnology and supercritical fluids | Hamidreza | Journal of ...

    African Journals Online (AJOL)

    Several techniques have been proposed to produce nanomaterials using ... of the supercritical based techniques applied to the production of nanoparticles materials. Keywords: Supercritical fluids; Nanoparticles; SCF technology; RESS; SAS.

  9. Location Estimation of the Bow Shock and Theta angle (B, n) cuasiperpendicular magnetospheric, using data from 14 different events crossings shock recorded by THEMIS-C.

    Science.gov (United States)

    Amazo-Gomez, Eliana; Alvarado-Gomez, Julian David; Calvo Mozo, Benjamin

    In this Work we calculated the average position of the bow shock, through the eigenvalues ​​and corresponding eigenvectors of the covariance matrix for the magnetic field developed from 10 different crosses shock events recorded by THEMIS A, during the years 2009 and 2010. With data obtained from previous calibration and the propagation direction of the magnetic field of the plasma is able to find the interaction quasi perpendicular angle Theta (B,n) which depends on the direction normal shock and the direction of incidence of field magnetic plasma. The importance of this type of analysis is that the understanding of the phenomenology of the bow shock, which is vital for the characterization of processes such as magnetic reconnection between magnetospheric lines terrestrial and interplanetary field lines carrying a large contribution from the Sun apparently lines will also be important for the description of how to enter the plasma charged particles from impacting the bow shock to the internal field lines to these particles subsequently lead to the Earth's atmosphere, these initially enter through the polar region (Polar Cusp) and then disseminated depending on the conditions of the plasma into the Earth's atmosphere , and parameters such as the position of the bow shock, this variation and interaction angle Theta (B,n) are basic to reach a minimal representation of the phenomenon. In events of great magnitude can have undesirable effects on satellites, power lines, communications and air travel, the latter is the interest on discrimination of some parameters of the phenomenon presented in this work. The study of the Bow shock, bow shock and Magnetospheric has as its starting point a detailed description of Earth's magnetosphere and solar wind phenomena must be understood independently initially and then trying to relate in terms of their interaction and communion in their respective limits, parameters such as the balance between dynamic and magnetic pressure

  10. Dynamic transition in supercritical iron.

    Science.gov (United States)

    Fomin, Yu D; Ryzhov, V N; Tsiok, E N; Brazhkin, V V; Trachenko, K

    2014-11-26

    Recent advance in understanding the supercritical state posits the existence of a new line above the critical point separating two physically distinct states of matter: rigid liquid and non-rigid gas-like fluid. The location of this line, the Frenkel line, remains unknown for important real systems. Here, we map the Frenkel line on the phase diagram of supercritical iron using molecular dynamics simulations. On the basis of our data, we propose a general recipe to locate the Frenkel line for any system, the recipe that importantly does not involve system-specific detailed calculations and relies on the knowledge of the melting line only. We further discuss the relationship between the Frenkel line and the metal-insulator transition in supercritical liquid metals. Our results enable predicting the state of supercritical iron in several conditions of interest. In particular, we predict that liquid iron in the Jupiter core is in the "rigid liquid" state and is highly conducting. We finally analyse the evolution of iron conductivity in the core of smaller planets such as Earth and Venus as well as exoplanets: as planets cool off, the supercritical core undergoes the transition to the rigid-liquid conducting state at the Frenkel line.

  11. Observations and simulations of specularly reflected He++ at Earth's quasiperpendicular bow shock

    Science.gov (United States)

    Broll, J. M.; Fuselier, S. A.; Trattner, K. J.; Anderson, B. J.; Burch, J. L.; Giles, B. L.

    2016-12-01

    Specular reflection of protons at Earth's quasiperpendicular bow shock is an important process for supercritical shock dissipation. Previous studies have found evidence of He++ specular reflection from reduced particle distributions downstream from the shock, but confirmation of the process for heavier ions in the shock foot was not possible due to time resolution constraints. We present He++ distributions, observed by MMS in a quasiperpendicular bow shock crossing, that are consistent with specularly reflected He++. We also investigate the He++ dynamics with test-particle simulations in a simulated shock based on this crossing and we conduct wave analysis to determine what processes lead to separate gyrotropization timescales for the transmitted and reflected populations.

  12. Nonlinear indirect combustion noise for compact supercritical nozzle flows

    Science.gov (United States)

    Huet, M.

    2016-07-01

    In this paper, indirect combustion noise generated by the acceleration of entropy perturbations through a supercritical nozzle is investigated in the nonlinear regime and in the low-frequency limit (quasi-static hypothesis). This work completes the study of Huet and Giauque (Journal of Fluid Mechanics 733 (2013) 268-301) for nonlinear noise generation in nozzle flows without shock and particularly focuses on shocked flow regimes. It is based on the analytical model of Marble and Candel for compact nozzles (Journal of Sound and Vibration 55 (1977) 225-243), initially developed for excitations in the linear regime and rederived here for nonlinear perturbations. Full nonlinear analytical solutions are provided in the absence of shock as well as second-order analytical expressions when a shock is present in the diffuser. An analytical evaluation of the shock displacement inside the nozzle caused by the forcing is proposed and maximum possible forcings to avoid unchoke and 'over-choke' are discussed. The accuracy of the second-order model and the nonlinear contributions to the generated waves are then addressed. This model is found to be very accurate for the generated entropy wave with negligible nonlinear contributions. Nonlinearities are more visible, but still limited, for the downstream acoustic wave for large inlet Mach numbers. Analytical developments are validated thanks to comparisons with numerical simulations.

  13. Supercritical Fluid Reactions for Coal Processing

    Energy Technology Data Exchange (ETDEWEB)

    Charles A. Eckert

    1997-11-01

    Exciting opportunities exist for the application of supercritical fluid (SCF) reactions for the pre-treatment of coal. Utilizing reactants which resemble the organic nitrogen containing components of coal, we developed a method to tailor chemical reactions in supercritical fluid solvents for the specific application of coal denitrogenation. The tautomeric equilibrium of a Schiff base was chosen as one model system and was investigated in supercritical ethane and cosolvent modified supercritical ethane. The Diels-Alder reaction of anthracene and 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) was selected as a second model system, and it was investigated in supercritical carbon dioxide.

  14. Generation of shock fronts in the interaction of the short pulses of intense laser light in supercritical plasma; Generacion de frentes de choque en la interaccion de pulsos cortos de luz laser intensa en plasmas supercriticos

    Energy Technology Data Exchange (ETDEWEB)

    Lopez V, V.E

    2004-07-01

    these being of important consequence in the effective absorption of the energy of a laser in the plasma. In this work we begin with a simulation program of particles that is based on the code ES1 (Electrostatic Program in one dimension) which modified for to implement the initial conditions as well as for diverse diagnostics. This code initializes a system of charged particles to which are applied external electric and magnetic fields. Later on its are analyzed the codes EM1 and EM1BND for periodic systems and enclosed systems. with the presence of electric and magnetic fields, having by this way an electromagnetic program. In the following chapter the energy absorption it is studied for solid densities of plasma with intensities among 10{sup 20} and 10{sup 21} W/cm{sup 2} simulations made by J. Denavit in 1992. One of the results but important it corresponds to the case of an intensity pulse of 10{sup 21} W/cm{sup 2} and a wavelength of 0.8 {mu} m with normal incidence in a sheet of carbon in which the ions acquire speeds {approx} 10{sup 8} m/s. The energy of the electrons is {approx} 20 keV having in this case an absorption of {approx} 1%. This efficiency increases to intensities but high. It is presented this way results of shock fronts under certain parameters. For finish, each one of the subroutines of the Program ES1 was studied (Electrostatic, 1-dimension), which is explained in the chapter 2, where the phase space diagram is used to study the dynamics of the particles. Once explained the structure of the program it will continue to make simulations changing certain parameters, to obtain by this way a diagnostic of the interaction physics. (Author)

  15. Hypovolemic shock

    Science.gov (United States)

    ... thready Tests that may be done include: Blood chemistry, including kidney function tests and those tests looking ... severe shock. Severe hypovolemic shock may lead to death, even with immediate medical attention. Older adults are ...

  16. Removing Solids From Supercritical Water

    Science.gov (United States)

    Hong, Glenn T.

    1992-01-01

    Apparatus removes precipitated inorganic salts and other solids in water-recycling process. Designed for use with oxidation in supercritical water which treats wastes and yields nearly pure water. Heating coils and insulation around vessel keep it hot. Locking bracket seals vessel but allows it to be easily opened for replacement of filled canisters.

  17. Supercritical multicomponent solvent coal extraction

    Science.gov (United States)

    Corcoran, W. H.; Fong, W. S.; Pichaichanarong, P.; Chan, P. C. F.; Lawson, D. D. (Inventor)

    1983-01-01

    The yield of organic extract from the supercritical extraction of coal with larger diameter organic solvents such as toluene is increased by use of a minor amount of from 0.1 to 10% by weight of a second solvent such as methanol having a molecular diameter significantly smaller than the average pore diameter of the coal.

  18. The Supercritical Pile Model for GRBs

    Science.gov (United States)

    Kazanas, Demos

    2006-01-01

    We present the spectral and temporal radiative signatures expected within the Supercritical Pile model of Gamma Ray Bursts (GRB). This model is motivated by the need for a process that provides the dissipation necessary in GRB and presents a well defined scheme for converting the energy stored in the relativistic protons of the Relativistic Blast Waves (RBW) associated with GRB into radiation; at the same time it leads to spectra which exhibit a peak in the burst nuF(sub nu) distribution at an energy E(sub p) approximately equal to 1 MeV in the observer s frame, in agreement with observation and largely independent of the Lorentz factor GAMMA of the associated relativistic outflow. Furthermore, this scheme does not require (but does not preclude) acceleration of particles at the shock other than that provided by the isotropization of the flow bulk kinetic energy on the RBW frame. In the present paper we model in detail the evolution of protons, electrons and photons from a RBW to produce detailed spectra of the prompt GRB phase as a function of time from across a very broad range spanning roughly 4 log10 GAMMA decades in frequency. The model spectra are in general agreement with observations and provide a means for the delineating of the model parameters through direct comparison with trends observed in GRB properties.

  19. Comparison of accelerated ion populations observed upstream of the bow shocks at Venus and Mars

    Directory of Open Access Journals (Sweden)

    M. Yamauchi

    2011-03-01

    Full Text Available Foreshock ions are compared between Venus and Mars at energies of 0.6~20 keV using the same ion instrument, the Ion Mass Analyser, on board both Venus Express and Mars Express. Venus Express often observes accelerated protons (2~6 times the solar wind energy that travel away from the Venus bow shock when the spacecraft location is magnetically connected to the bow shock. The observed ions have a large field-aligned velocity compared to the perpendicular velocity in the solar wind frame, and are similar to the field-aligned beams and intermediate gyrating component of the foreshock ions in the terrestrial upstream region. Mars Express does not observe similar foreshock ions as does Venus Express, indicating that the Martian foreshock does not possess the intermediate gyrating component in the upstream region on the dayside of the planet. Instead, two types of gyrating protons in the solar wind frame are observed very close to the Martian quasi-perpendicular bow shock within a proton gyroradius distance. The first type is observed only within the region which is about 400 km from the bow shock and flows tailward nearly along the bow shock with a similar velocity as the solar wind. The second type is observed up to about 700 km from the bow shock and has a bundled structure in the energy domain. A traversal on 12 July 2005, in which the energy-bunching came from bundling in the magnetic field direction, is further examined. The observed velocities of the latter population are consistent with multiple specular reflections of the solar wind at the bow shock, and the ions after the second reflection have a field-aligned velocity larger than that of the de Hoffman-Teller velocity frame, i.e., their guiding center has moved toward interplanetary space out from the bow shock. To account for the observed peculiarity of the Martian upstream region, finite gyroradius effects of the solar wind protons compared to the radius of the bow shock curvature and

  20. Universal scaling behavior of supercritical matter

    CERN Document Server

    Bolmatov, Dima; Trachenko, K

    2013-01-01

    Properties of supercritical fluids have been of enduring interest since the critical phenomena were discovered by Cagniard de la Tour in 1822, stimulating fundamental theoretical work and development of experimental techniques. Here, we study the thermodynamic properties of the supercritical state, and discover that specific heat shows a crossover between two different dynamic regimes of the low-temperature rigid liquid and high-temperature non-rigid supercritical fluid. We formulate a theory of heat capacity above the crossover, and find good agreement between calculated and experimental data for rare-gas supercritical liquids (Ne, Ar, Kr and Xe) with no free fitting parameters. We derive the relationship between scaling exponents of heat capacity and viscosity in the supercritical region, and show that these exponents exhibit universality. The universality is explained by the universal temperature behavior of the maximal length of the longitudinal phonons that can exist in the supercritical system and that ...

  1. Pulsed discharge plasmas in supercritical carbon dioxide

    OpenAIRE

    Kiyan, Tsuyoshi; Uemura, A.; Tanaka, K.; Zhang, C. H.; Namihira, Takao; Sakugawa, Takashi; Katsuki, Sunao; Akiyama, Hidenori; Roy, B.C.; Sasaki, M.; Goto, M.; キヤン, ツヨシ; ナミヒラ, タカオ; サクガワ, タカシ; カツキ, スナオ

    2005-01-01

    In recent years, several studies about electrical discharge plasma in supercritical carbon dioxide (CO2) have been carried out. One of the unique characteristics of supercritical fluid is a large density fluctuation near the critical point that can result in marked dramatic changes of thermal conductivity. Therefore, the electrical discharge plasma produced in supercritical fluid has unique features and reactions unlike those of normal plasma produced in gas phase. In our experiments, two typ...

  2. Electromagnetic waves and electron anisotropies downstream of supercritical interplanetary shocks

    CERN Document Server

    Wilson, L B; Szabo, A; Breneman, A; Cattell, C A; Goetz, K; Kellogg, P J; Kersten, K; Kasper, J C; Maruca, B A; Pulupa, M

    2012-01-01

    We present waveform observations of electromagnetic lower hybrid and whistler waves with f_ci 1.01. Thus, the whistler mode waves appear to be driven by a heat flux instability and cause perpendicular heating of the halo electrons. The lower hybrid waves show a much weaker correlation between \\partialB and normalized heat flux magnitude and are often observed near magnetic field gradients. A third type of event shows fluctuations consistent with a mixture of both lower hybrid and whistler mode waves. These results suggest that whistler waves may indeed be regulating the electron heat flux and the halo temperature anisotropy, which is important for theories and simulations of electron distribution evolution from the sun to the earth.

  3. Lipidomics by Supercritical Fluid Chromatography

    Directory of Open Access Journals (Sweden)

    Laurent Laboureur

    2015-06-01

    Full Text Available This review enlightens the role of supercritical fluid chromatography (SFC in the field of lipid analysis. SFC has been popular in the late 1980s and 1990s before almost disappearing due to the commercial success of liquid chromatography (LC. It is only 20 years later that a regain of interest appeared when new commercial instruments were introduced. As SFC is fully compatible with the injection of extracts in pure organic solvent, this technique is perfectly suitable for lipid analysis and can be coupled with either highly universal (UV or evaporative light scattering or highly specific (mass spectrometry detection methods. A short history of the use of supercritical fluids as mobile phase for the separation oflipids will be introduced first. Then, the advantages and drawbacks of SFC are discussed for each class of lipids (fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterols, prenols, polyketides defined by the LIPID MAPS consortium.

  4. Lipidomics by Supercritical Fluid Chromatography

    Science.gov (United States)

    Laboureur, Laurent; Ollero, Mario; Touboul, David

    2015-01-01

    This review enlightens the role of supercritical fluid chromatography (SFC) in the field of lipid analysis. SFC has been popular in the late 1980s and 1990s before almost disappearing due to the commercial success of liquid chromatography (LC). It is only 20 years later that a regain of interest appeared when new commercial instruments were introduced. As SFC is fully compatible with the injection of extracts in pure organic solvent, this technique is perfectly suitable for lipid analysis and can be coupled with either highly universal (UV or evaporative light scattering) or highly specific (mass spectrometry) detection methods. A short history of the use of supercritical fluids as mobile phase for the separation oflipids will be introduced first. Then, the advantages and drawbacks of SFC are discussed for each class of lipids (fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterols, prenols, polyketides) defined by the LIPID MAPS consortium. PMID:26090714

  5. Recuperative supercritical carbon dioxide cycle

    Science.gov (United States)

    Sonwane, Chandrashekhar; Sprouse, Kenneth M; Subbaraman, Ganesan; O'Connor, George M; Johnson, Gregory A

    2014-11-18

    A power plant includes a closed loop, supercritical carbon dioxide system (CLS-CO.sub.2 system). The CLS-CO.sub.2 system includes a turbine-generator and a high temperature recuperator (HTR) that is arranged to receive expanded carbon dioxide from the turbine-generator. The HTR includes a plurality of heat exchangers that define respective heat exchange areas. At least two of the heat exchangers have different heat exchange areas.

  6. [Cardiogenic shock].

    Science.gov (United States)

    Houegnifioh, Komlanvi Kafui; Gfeller, Etienne; Garcia, Wenceslao; Ribordy, Vincent

    2014-08-13

    Cardiogenic shock, especially when it complicates a myocardial infarction, is still associated with high mortality rate. Emergency department or first care physicians are often the first providers to assess the cardiogenic shock patient, and plays thereby a key role in achieving a timely diagnosis and treatment. This review will detail the actual physiopathology understanding of the cardiogenic shock, its diagnosis and management focusing on the care within the emergency department.

  7. Supercritical Fluid Chromatography, Pressurized Liquid Extraction and Supercritical Fluid Extraction

    Energy Technology Data Exchange (ETDEWEB)

    Henry, Matthew C.; Yonker, Clement R.

    2006-06-15

    In this review we examine the related fields of supercritical fluid chromatography (SFC) and supercritical fluid extraction (SFE). We reviewed the published literature in the period from November 2003 to November 2005. Well over 300 papers were published in this period. This large body of work indicates continuing active growth of the field, but an exhaustive review is beyond the scope of this work. We have chosen to include a sampling of publications that best represent the continuing trends and new ideas in the field. In keeping with past reviews on this subject1, we have broadened our scope to include fluid systems operating at high temperature and pressure, but below the critical point. Various terms have been applied to this state: sub-critical fluid extraction, pressurized liquid extraction, and accelerated solvent extraction. The term accelerated solvent extraction has been used by instrument manufacturers to refer to this process, but we will use the more descriptive term pressurized liquid extraction (PLE) to refer to these systems. Most of the research in the field is of an “evolutionary” rather than “revolutionary” nature. As in the previous review period, applications papers make up a majority of the published work. Pharmaceutical applications continue to be a strong theme. Most of the pharmaceutical work has centered on preparative, rather than analytical, separations. Chiral separations are an exception, as analytical scale separations of chiral compounds are an area of intense interest. Food and natural products represent the next largest body of work. Major themes are the isolation and characterization of high-value added foodstuffs, fragrances, and flavor compounds from novel natural materials or agricultural by-products. The areas of food, natural products, and pharmaceutical separation science converge in the area of so-called nutraceuticals. These are typically high-value products, either sold alone or as part of a fortified food, that

  8. Supercritical Water Mixture (SCWM) Experiment

    Science.gov (United States)

    Hicks, Michael C.; Hegde, Uday G.

    2012-01-01

    The subject presentation, entitled, Supercritical Water Mixture (SCWM) Experiment, was presented at the International Space Station (ISS) Increment 33/34 Science Symposium. This presentation provides an overview of an international collaboration between NASA and CNES to study the behavior of a dilute aqueous solution of Na2SO4 (5% w) at near-critical conditions. The Supercritical Water Mixture (SCWM) investigation, serves as important precursor work for subsequent Supercritical Water Oxidation (SCWO) experiments. The SCWM investigation will be performed in DECLICs High Temperature Insert (HTI) for the purpose of studying critical fluid phenomena at high temperatures and pressures. The HTI includes a completely sealed and integrated test cell (i.e., Sample Cell Unit SCU) that will contain approximately 0.3 ml of the aqueous test solution. During the sequence of tests, scheduled to be performed in FY13, temperatures and pressures will be elevated to critical conditions (i.e., Tc = 374C and Pc = 22 MPa) in order to observe salt precipitation, precipitate agglomeration and precipitate transport in the presence of a temperature gradient without the influences of gravitational forces. This presentation provides an overview of the motivation for this work, a description of the DECLIC HTI hardware, the proposed test sequences, and a brief discussion of the scientific research objectives.

  9. INTEGRATED SUPERCRITICAL FLUID EXTRACTION AND BIOPROCESSING

    Directory of Open Access Journals (Sweden)

    Owen Catchpole

    2012-01-01

    Full Text Available Supercritical fluids are increasingly being used and promoted at a laboratory and pilot scale to produce high value, natural bioactives from biologically based raw materials. Supercritical CO2 is overwhelmingly the solvent of choice for these operations, but is largely limited to the processing of dry raw materials and the extraction of low polarity, low molecular weight compounds. The use of co-solvents and the use of alternative ‘near-critical’ extraction fluids such as dimethyl ether show potential to mitigate these limitations. Commercialisation of new supercritical extraction processes has arguably been limited because the supercritical extraction process has been developed in isolation of other processing steps necessary to achieve a successful product. This study reviews recent developments in integrated processing that incorporate the use of supercritical fluids for bioseparations and in particular process schemes that produce high value natural bioactives. Integrated processes include prior operation (fermentation, extraction, enzyme pre-treatment, physical fractionation or size reduction followed by supercritical extraction or fractionation and processes in which operations are carried out in situ in supercritical fluids (supercritical chromatography, enzymatic conversion, precipitation and coating of solutes. The use of co-solvents and alternative extraction solvents in these processes is discussed. Prospects for future developments are also discussed.

  10. Reentry Shock

    Institute of Scientific and Technical Information of China (English)

    Dorine; Houston

    1998-01-01

    Dear Xiao Lan, You remember the pain of culture and reentry shock; humor me please; let mereview the facts for the sake of the students you are sending here in greater numbers.Culture shock is the emotional pain that people experience when they visit a newcountry and find customs, experiences, smells, and non-verbal communication stylesto be different from their own country.

  11. Supercritical water oxidation - Microgravity solids separation

    Science.gov (United States)

    Killilea, William R.; Hong, Glenn T.; Swallow, Kathleen C.; Thomason, Terry B.

    1988-01-01

    This paper discusses the application of supercritical water oxidation (SCWO) waste treatment and water recycling technology to the problem of waste disposal in-long term manned space missions. As inorganic constituents present in the waste are not soluble in supercritical water, they must be removed from the organic-free supercritical fluid reactor effluent. Supercritical water reactor/solids separator designs capable of removing precipitated solids from the process' supercritical fluid in zero- and low- gravity environments are developed and evaluated. Preliminary experiments are then conducted to test the concepts. Feed materials for the experiments are urine, feces, and wipes with the addition of reverse osmosis brine, the rejected portion of processed hygiene water. The solid properties and their influence on the design of several oxidation-reactor/solids-separator configurations under study are presented.

  12. Ultra supercritical pressure. Cho rinkaiatsu kara chocho rinkaiatsu e

    Energy Technology Data Exchange (ETDEWEB)

    Matsuo, T. (Mitsubishi Heavy Industries Ltd., Tokyo (Japan))

    1992-10-05

    In Japanese thermoelectric power plants the steam condition was made higher in pressure and temperature with a rise in the requirement to enhance the plant efficiency being spurred by a rapid increasement in the demand of electric power since 1955. It was 1967 when a supercritical power plant of 24.2 MPa steam pressure started its operation. Afterwards, the enhancement of the plant efficiency by upgrading the steam condition was again paid attention against the sharp rise in fuel cost caused by oil shock in two times originating from 1973. In 1989 Japan's first ultra supercritical pressure plant of 31.1 MPa steam pressure, Kawagoe No.1 of Chubu Electric Power Co.,Inc. began its operation and achieved an efficiency of 41.9 %, approximately 5 % higher than hitherto. In Kawagoe No.1 boiler, a 9Cr-1 Mo system material excellent in high temperature strength was put to practical use and applied to main steam tubes and super-heater tube exit headers, also a fine grained 18Cr-11Ni-Nb-Ta steel excellent in high temperature strength as well as steam oxidizing property was developed and adopted to super-heater tubes. Thus, the reduction of thermal stress and the improvement of responsiveness were attained by thinning the thickness of tube with these materials. 3 refs., 2 figs.

  13. Role of Magnetosonic Solitons in Perpendicular Collisionless Shock Reformation

    Science.gov (United States)

    Gueroult, Renaud; Ohsawa, Yukiharu; Fisch, Nathaniel J.

    2017-03-01

    The nature of the magnetic structure arising from ion specular reflection in shock compression studies is examined by means of 1D particle-in-cell simulations. Propagation speed, field profiles, and supporting currents for this magnetic structure are shown to be consistent with a magnetosonic soliton. Coincidentally, this structure and its evolution are typical of foot structures observed in perpendicular shock reformation. To reconcile these two observations, we propose, for the first time, that shock reformation can be explained as the result of the formation, growth, and subsequent transition to a supercritical shock of a magnetosonic soliton. This argument is further supported by the remarkable agreement found between the period of the soliton evolution cycle and classical reformation results. This new result suggests that the unique properties of solitons can be used to shed new light on the long-standing issue of shock nonstationarity and its role on particle acceleration.

  14. Degradation Characteristics of Wood Using Supercritical Alcohols

    Directory of Open Access Journals (Sweden)

    Jeeban Poudel

    2012-11-01

    Full Text Available In this work, the characteristics of wood degradation using supercritical alcohols have been studied. Supercritical ethanol and supercritical methanol were used as solvents. The kinetics of wood degradation were analyzed using the nonisothermal weight loss technique with heating rates of 3.1, 9.8, and 14.5 °C/min for ethanol and 5.2, 11.3, and 16.3 °C/min for methanol. Three different kinetic analysis methods were implemented to obtain the apparent activation energy and the overall reaction order for wood degradation using supercritical alcohols. These were used to compare with previous data for supercritical methanol. From this work, the activation energies of wood degradation in supercritical ethanol were obtained as 78.0–86.0, 40.1–48.1, and 114 kJ/mol for the different kinetic analysis methods used in this work. The activation energies of wood degradation in supercritical ethanol were obtained as 78.0–86.0, 40.1–48.1, and 114 kJ/mol. This paper also includes the analysis of the liquid products obtained from this work. The characteristic analysis of liquid products on increasing reaction temperature and time has been performed by GC-MS. The liquid products were categorized according to carbon numbers and aromatic/aliphatic components. It was found that higher conversion in supercritical ethanol occurs at a lower temperature than that of supercritical methanol. The product analysis shows that the majority of products fall in the 2 to 15 carbon number range.

  15. Are gauge shocks really shocks?

    CERN Document Server

    Alcubierre, M

    2005-01-01

    The existence of gauge pathologies associated with the Bona-Masso family of generalized harmonic slicing conditions is proven for the case of simple 1+1 relativity. It is shown that these gauge pathologies are true shocks in the sense that the characteristic lines associated with the propagation of the gauge cross, which implies that the name ``gauge shock'' usually given to such pathologies is indeed correct. These gauge shocks are associated with places where the spatial hypersurfaces that determine the foliation of spacetime become non-smooth.

  16. Using supercritical fluids to refine hydrocarbons

    Science.gov (United States)

    Yarbro, Stephen Lee

    2015-06-09

    A system and method for reactively refining hydrocarbons, such as heavy oils with API gravities of less than 20 degrees and bitumen-like hydrocarbons with viscosities greater than 1000 cp at standard temperature and pressure, using a selected fluid at supercritical conditions. A reaction portion of the system and method delivers lightweight, volatile hydrocarbons to an associated contacting unit which operates in mixed subcritical/supercritical or supercritical modes. Using thermal diffusion, multiphase contact, or a momentum generating pressure gradient, the contacting unit separates the reaction products into portions that are viable for use or sale without further conventional refining and hydro-processing techniques.

  17. Forest-fire model as a supercritical dynamic model in financial systems.

    Science.gov (United States)

    Lee, Deokjae; Kim, Jae-Young; Lee, Jeho; Kahng, B

    2015-02-01

    Recently large-scale cascading failures in complex systems have garnered substantial attention. Such extreme events have been treated as an integral part of self-organized criticality (SOC). Recent empirical work has suggested that some extreme events systematically deviate from the SOC paradigm, requiring a different theoretical framework. We shed additional theoretical light on this possibility by studying financial crisis. We build our model of financial crisis on the well-known forest fire model in scale-free networks. Our analysis shows a nontrivial scaling feature indicating supercritical behavior, which is independent of system size. Extreme events in the supercritical state result from bursting of a fat bubble, seeds of which are sown by a protracted period of a benign financial environment with few shocks. Our findings suggest that policymakers can control the magnitude of financial meltdowns by keeping the economy operating within reasonable duration of a benign environment.

  18. Oxy-combustor operable with supercritical fluid

    Energy Technology Data Exchange (ETDEWEB)

    Brun, Klaus; McClung, Aaron M.; Owston, Rebecca A.

    2017-04-04

    An oxy-combustor is provided which comprises a combustion vessel including at least one solid fuel slurry inlet port, at least one oxygen inlet port and at least one supercritical fluid inlet port, wherein the combustion vessel is operable at an operating pressure of at least 1,100 psi; an interior of the combustion vessel comprises a combustion chamber and a supercritical fluid infusion chamber surrounding at least a part of the combustion chamber, the supercritical fluid infusion chamber and the combustion chamber are separated by a porous liner surrounding the combustion chamber, and the supercritical infusion chamber is located between the porous liner and an outer casing of the combustion vessel.

  19. Determination of solvation kinetics in supercritical fluids

    Energy Technology Data Exchange (ETDEWEB)

    Bright, F.V.

    1993-01-01

    Objective was to study solvation processes in pure and entrainer-modified supercritical fluids. Specific topics were: Kinetics for solvation in supercritical media, influence on entrainers on solvation, reversibility of solvation, effects of solvation on intramolecular solute-solute interaction kinetics, and impact of fluid density on these processes. Time-resolved fluorescence spectroscopy was used as the main analytical tool. A summary is given of the 2.5 years' research.

  20. Charting the landscape of supercritical string theory.

    Science.gov (United States)

    Hellerman, Simeon; Swanson, Ian

    2007-10-26

    Special solutions of string theory in supercritical dimensions can interpolate in time between theories with different numbers of spacetime dimensions and different amounts of world sheet supersymmetry. These solutions connect supercritical string theories to the more familiar string duality web in ten dimensions and provide a precise link between supersymmetric and purely bosonic string theories. Dimension quenching and c duality appear to be natural concepts in string theory, giving rise to large networks of interconnected theories.

  1. Water in supercritical carbon dioxide dyeing

    Directory of Open Access Journals (Sweden)

    Zheng Lai-Jiu

    2015-01-01

    Full Text Available This paper investigates the effect of water serving as entrainer on the dyeing of wool fabrics in supercritical carbon dioxide. Compared with previous supercritical dyeing methods, addition of water makes the dyeing process more effective under low temperature and low pressure. During dyeing process, dyestuff can be uniformly distributed on fabrics’s surface due to water interaction, as a result coloration is enhanced while color difference is decreased.

  2. Supercritical fluid reverse micelle separation

    Science.gov (United States)

    Fulton, John L.; Smith, Richard D.

    1993-01-01

    A method of separating solute material from a polar fluid in a first polar fluid phase is provided. The method comprises combining a polar fluid, a second fluid that is a gas at standard temperature and pressure and has a critical density, and a surfactant. The solute material is dissolved in the polar fluid to define the first polar fluid phase. The combined polar and second fluids, surfactant, and solute material dissolved in the polar fluid is maintained under near critical or supercritical temperature and pressure conditions such that the density of the second fluid exceeds the critical density thereof. In this way, a reverse micelle system defining a reverse micelle solvent is formed which comprises a continuous phase in the second fluid and a plurality of reverse micelles dispersed in the continuous phase. The solute material is dissolved in the polar fluid and is in chemical equilibrium with the reverse micelles. The first polar fluid phase and the continuous phase are immiscible. The reverse micelles each comprise a dynamic aggregate of surfactant molecules surrounding a core of the polar fluid. The reverse micelle solvent has a polar fluid-to-surfactant molar ratio W, which can vary over a range having a maximum ratio W.sub.o that determines the maximum size of the reverse micelles. The maximum ratio W.sub.o of the reverse micelle solvent is then varied, and the solute material from the first polar fluid phase is transported into the reverse micelles in the continuous phase at an extraction efficiency determined by the critical or supercritical conditions.

  3. Supercritical fluid reverse micelle separation

    Science.gov (United States)

    Fulton, J.L.; Smith, R.D.

    1993-11-30

    A method of separating solute material from a polar fluid in a first polar fluid phase is provided. The method comprises combining a polar fluid, a second fluid that is a gas at standard temperature and pressure and has a critical density, and a surfactant. The solute material is dissolved in the polar fluid to define the first polar fluid phase. The combined polar and second fluids, surfactant, and solute material dissolved in the polar fluid is maintained under near critical or supercritical temperature and pressure conditions such that the density of the second fluid exceeds the critical density thereof. In this way, a reverse micelle system defining a reverse micelle solvent is formed which comprises a continuous phase in the second fluid and a plurality of reverse micelles dispersed in the continuous phase. The solute material is dissolved in the polar fluid and is in chemical equilibrium with the reverse micelles. The first polar fluid phase and the continuous phase are immiscible. The reverse micelles each comprise a dynamic aggregate of surfactant molecules surrounding a core of the polar fluid. The reverse micelle solvent has a polar fluid-to-surfactant molar ratio W, which can vary over a range having a maximum ratio W[sub o] that determines the maximum size of the reverse micelles. The maximum ratio W[sub o] of the reverse micelle solvent is then varied, and the solute material from the first polar fluid phase is transported into the reverse micelles in the continuous phase at an extraction efficiency determined by the critical or supercritical conditions. 27 figures.

  4. [Neurogenic shock].

    Science.gov (United States)

    Meister, Rafael; Pasquier, Mathieu; Clerc, David; Carron, Pierre-Nicolas

    2014-08-13

    The neurogenic shock is a common complication of spinal cord injury, especially when localized at the cervical level. Characterized by a vasoplegia (hypotension) and bradycardia, the neurogenic shock is secondary to the damage of the sympathetic nervous system. The clinical presentation often includes tetraplegia, with or without respiratory failure. Early treatment aims to minimize the occurrence of secondary spinal cord lesions resulting from systemic ischemic injuries. Medical management consists in a standardized ABCDE approach, in order to stabilize vital functions and immobilize the spine. The hospital care includes performing imaging, further measures of neuro-resuscitation, and coordinated surgical assessment and treatment of any other injury.

  5. Supercritical Fluid Facilitated Growth of Copper and Aluminum Oxide Nanoparticles

    Science.gov (United States)

    Williams, Geoffrey L.; Vohs, Jason K.; Brege, Jonathan J.; Fahlman, Bradley D.

    2005-01-01

    Supercritical fluids (SCFs) possess properties that are intermediate between liquids and gases. The combination of supercritical fluid technology with advanced characterization techniques such as electron microscopy provided a practical and rewarding undergraduate laboratory experiment.

  6. Supercritical Extraction of Lycopene from Tomato Industrial Wastes with Ethane

    OpenAIRE

    Mendes, Rui L.; Cristino, Ana F.; Nobre, Beatriz P.; Luisa Gouveia; António F. Palavra; Patricia G. S. Matos

    2012-01-01

    Supercritical fluid extraction of all-E-lycopene from tomato industrial wastes (mixture of skins and seeds) was carried out in a semi-continuous flow apparatus using ethane as supercritical solvent. The effect of pressure, temperature, feed particle size, solvent superficial velocity and matrix initial composition was evaluated. Moreover, the yield of the extraction was compared with that obtained with other supercritical solvents (supercritical CO2...

  7. Supercritical Extraction of Lycopene from Tomato Industrial Waste with Ethane

    OpenAIRE

    Nobre, Beatriz P.; Gouveia, L.; Patricia G. S. Matos; Cristino, Ana F.; António F. Palavra; Mendes, Rui L.

    2012-01-01

    Supercritical fluid extraction of all-E-lycopene from tomato industrial wastes (mixture of skins and seeds) was carried out in a semi-continuous flow apparatus using ethane as supercritical solvent. The effect of pressure, temperature, feed particle size, solvent superficial velocity and matrix initial composition was evaluated. Moreover, the yield of the extraction was compared with that obtained with other supercritical solvents (supercritical CO2 and a near critical mixture of ethane and p...

  8. Drying of supercritical carbon dioxide with membrane processes

    NARCIS (Netherlands)

    Lohaus, Theresa; Scholz, Marco; Koziara, Beata T.; Benes, N.E.; Wessling, Matthias

    2015-01-01

    In supercritical extraction processes regenerating the supercritical fluid represents the main cost constraint. Membrane technology has potential for cost efficient regeneration of water-loaded supercritical carbon dioxide. In this study we have designed membrane-based processes to dehydrate water-l

  9. Advanced Supercritical Carbon Dioxide Brayton Cycle Development

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Mark [Univ. of Wisconsin, Madison, WI (United States); Sienicki, James [Argonne National Lab. (ANL), Argonne, IL (United States); Moisseytsev, Anton [Argonne National Lab. (ANL), Argonne, IL (United States); Nellis, Gregory [Univ. of Wisconsin, Madison, WI (United States); Klein, Sanford [Univ. of Wisconsin, Madison, WI (United States)

    2015-10-21

    Fluids operating in the supercritical state have promising characteristics for future high efficiency power cycles. In order to develop power cycles using supercritical fluids, it is necessary to understand the flow characteristics of fluids under both supercritical and two-phase conditions. In this study, a Computational Fluid Dynamic (CFD) methodology was developed for supercritical fluids flowing through complex geometries. A real fluid property module was implemented to provide properties for different supercritical fluids. However, in each simulation case, there is only one species of fluid. As a result, the fluid property module provides properties for either supercritical CO2 (S-CO2) or supercritical water (SCW). The Homogeneous Equilibrium Model (HEM) was employed to model the two-phase flow. HEM assumes two phases have same velocity, pressure, and temperature, making it only applicable for the dilute dispersed two-phase flow situation. Three example geometries, including orifices, labyrinth seals, and valves, were used to validate this methodology with experimental data. For the first geometry, S-CO2 and SCW flowing through orifices were simulated and compared with experimental data. The maximum difference between the mass flow rate predictions and experimental measurements is less than 5%. This is a significant improvement as previous works can only guarantee 10% error. In this research, several efforts were made to help this improvement. First, an accurate real fluid module was used to provide properties. Second, the upstream condition was determined by pressure and density, which determines supercritical states more precise than using pressure and temperature. For the second geometry, the flow through labyrinth seals was studied. After a successful validation, parametric studies were performed to study geometric effects on the leakage rate. Based on these parametric studies, an optimum design strategy for the see

  10. Pharmaceutical applications of supercritical carbon dioxide.

    Science.gov (United States)

    Kaiser, C S; Römpp, H; Schmidt, P C

    2001-12-01

    The appearance of a supercritical state was already observed at the beginning of the 19th century. Nevertheless, the industrial extraction of plant and other natural materials started about twenty years ago with the decaffeination of coffee. Today carbon dioxide is the most common gas for supercritical fluid extraction in food and pharmaceutical industry. Since pure supercritical carbon dioxide is a lipophilic solvent, mixtures with organic solvents, especially alcohols, are used to increase the polarity of the extraction fluid; more polar compounds can be extracted in this way. The main fields of interest are the extraction of vegetable oils from plant material in analytical and preparative scale, the preparation of essential oils for food and cosmetic industry and the isolation of substances of pharmaceutical relevance. Progress in research was made by the precise measurement of phase equilibria data by means of different methods. Apart from extraction, supercritical fluid chromatography was introduced in the field of analytics, as well as micro- and nanoparticle formation using supercritical fluids as solvent or antisolvent. This review presents pharmaceutical relevant literature of the last twenty years with special emphasis on extraction of natural materials.

  11. Characteristics of compressible flow of supercritical kerosene

    Institute of Scientific and Technical Information of China (English)

    Feng-Quan Zhong; Xue-Jun Fan; Jing Wang; Gong Yu; Jian-Guo Li

    2012-01-01

    In this paper,compressible flow of aviation kerosene at supercritical conditions has been studied both numerically and experimentally.The thermophysical properties of supercritical kerosene are calculated using a 10-species surrogate based on the principle of extended corresponding states (ECS).Isentropic acceleration of supercritical kerosene to subsonic and supersonic speeds has been analyzed numerically.It has been found that the isentropic relationships of supercritical kerosene are significantly different from those of ideal gases.A two-stage fuel heating and delivery system is used to heat the kerosene up to a temperature of 820 K and pressure of 5.5 MPa with a maximum mass flow rate of 100 g/s.The characteristics of supercritical kerosene flows in a converging-diverging nozzle (Laval nozzle) have been studied experimentally.The results show that stable supersonic flows of kerosene could be established in the temperature range of 730 K-820 K and the measurements in the wall pressure agree with the numerical calculation.

  12. Culture Shock

    Institute of Scientific and Technical Information of China (English)

    宋文玲

    2004-01-01

    Specialists say that it is not easy to get used to life in a new culture.“Culture shock”is the term these specialists use when talking about the feelings that people have in a new environment.There are three stages of culture shock,say the specialists.In the first stage,the newcomers like their new environment,Then when the fresh experience

  13. Shock Waves

    CERN Document Server

    Jiang, Z

    2005-01-01

    The International Symposium on Shock Waves (ISSW) is a well established series of conferences held every two years in a different location. A unique feature of the ISSW is the emphasis on bridging the gap between physicists and engineers working in fields as different as gas dynamics, fluid mechanics and materials sciences. The main results presented at these meetings constitute valuable proceedings that offer anyone working in this field an authoritative and comprehensive source of reference.

  14. Enhancing power cycle efficiency for a supercritical Brayton cycle power system using tunable supercritical gas mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Steven A.; Pickard, Paul S.; Vernon, Milton E.; Radel, Ross F.

    2017-08-29

    Various technologies pertaining to tuning composition of a fluid mixture in a supercritical Brayton cycle power generation system are described herein. Compounds, such as Alkanes, are selectively added or removed from an operating fluid of the supercritical Brayton cycle power generation system to cause the critical temperature of the fluid to move up or down, depending upon environmental conditions. As efficiency of the supercritical Brayton cycle power generation system is substantially optimized when heat is rejected near the critical temperature of the fluid, dynamically modifying the critical temperature of the fluid based upon sensed environmental conditions improves efficiency of such a system.

  15. Driving Interconnected Networks to Supercriticality

    Directory of Open Access Journals (Sweden)

    Filippo Radicchi

    2014-04-01

    Full Text Available Networks in the real world do not exist as isolated entities, but they are often part of more complicated structures composed of many interconnected network layers. Recent studies have shown that such mutual dependence makes real networked systems potentially exposed to atypical structural and dynamical behaviors, and thus there is an urgent necessity to better understand the mechanisms at the basis of these anomalies. Previous research has mainly focused on the emergence of atypical properties in relation to the moments of the intra- and interlayer degree distributions. In this paper, we show that an additional ingredient plays a fundamental role for the possible scenario that an interconnected network can face: the correlation between intra- and interlayer degrees. For sufficiently high amounts of correlation, an interconnected network can be tuned, by varying the moments of the intra- and interlayer degree distributions, in distinct topological and dynamical regimes. When instead the correlation between intra- and interlayer degrees is lower than a critical value, the system enters in a supercritical regime where dynamical and topological phases are no longer distinguishable.

  16. Supercritical fluid extraction of hops

    Directory of Open Access Journals (Sweden)

    ZORAN ZEKOVIC

    2007-01-01

    Full Text Available Five cultivars of hop were extracted by the method of supercritical fluid extraction using carbon dioxide (SFE–CO2 as extractant. The extraction (50 g of hop sample using a CO2 flow rate of 97.725 L/h was done in the two steps: 1. extraction at 150 bar and 40°C for 2.5 h (sample of series A was obtained and, after that, the same sample of hop was extracted in the second step: 2. extraction at 300 bar and 40 °C for 2.5 h (sample of series B was obtained. The Magnum cultivar was chosen for the investigation of the extraction kinetics. For the qualitative and quantitative analysis of the obtained hop extracts, the GC-MS method was used. Two of four themost common compounds of hop aroma (a-humulene and b-caryophyllene were detected in samples of series A. In addition, isomerized a-acids and a high content of b-acids were detected. The a-acids content in the samples of series B was the highest in the extract of the Magnum cultivar (it is a bitter variety of hop. The low contents of a-acids in all the other hop samples resulted in extracts with low a-acids content, i.e., that contents were under the prescribed a-acids content.

  17. Supercritical carbon dioxide hop extraction

    Directory of Open Access Journals (Sweden)

    Pfaf-Šovljanski Ivana I.

    2005-01-01

    Full Text Available The hop of Magnum cultivar was extracted using supercritical carbon dioxide (SFE-as extractant. Extraction was carried out in the two steps: the first one being carried out at 150 bar and 40°C for 2.5 h (Extract A, and the second was the extraction of the same hop sample at 300 bar and 40°C for 2.5 h (Extract B. Extraction kinetics of the system hop-SFE-CO2 was investigated. Two of four most common compounds of hop aroma (α-humulene and β-caryophyllene were detected in Extract A. Isomerised α-acids and β-acids were detected too. a-Acid content in Extract B was high (that means it is a bitter variety of hop. Mathematical modeling using empirical model characteristic time model and simple single sphere model has been performed on Magnum cultivar extraction experimental results. Characteristic time model equations, best fitted experimental results. Empirical model equation, fitted results well, while simple single sphere model equation poorly approximated the results.

  18. Supercritical waste oxidation pump investigation

    Energy Technology Data Exchange (ETDEWEB)

    Thurston, G.; Garcia, K.

    1993-02-01

    This report investigates the pumping techniques and pumping equipment that would be appropriate for a 5,000 gallon per day supercritical water oxidation waste disposal facility. The pumps must boost water, waste, and additives from atmospheric pressure to approximately 27.6 MPa (4,000 psia). The required flow ranges from 10 gpm to less than 0.1 gpm. For the higher flows, many commercial piston pumps are available. These pumps have packing and check-valves that will require periodic maintenance; probably at 2 to 6 month intervals. Several commercial diaphragm pumps were also discovered that could pump the higher flow rates. Diaphragm pumps have the advantage of not requiring dynamic seals. For the lower flows associated with the waste and additive materials, commercial diaphragm pumps. are available. Difficult to pump materials that are sticky, radioactive, or contain solids, could be injected with an accumulator using an inert gas as the driving mechanism. The information presented in this report serves as a spring board for trade studies and the development of equipment specifications.

  19. Hydrodynamics and Mass Transfer Performance in Supercritical Fluid Extraction Columns

    Institute of Scientific and Technical Information of China (English)

    石冰洁; 张泽廷; 等

    2002-01-01

    New models for describing hydrodynamics and mass transfer performance in supercritical fluid extraction columns were proposed.Those models were proved by experimental data,which were obtained in supercritical fluid extraction packed column,spray column and sieve tray column respectively.The inner diameter of those columns areΦ25mm,These experimental systems include supercritical carbon dioxideisopropanol-water and supercritical carbon dioxide-ethanol-water,in which supercritical carbon dioxide was dispersed phase,and another was continuous phase.The extraction processes were operated with continuous countercurrent flow.The predicted values are agreed well with experimental data.

  20. DNS of High Pressure Supercritical Combustion

    Science.gov (United States)

    Chong, Shao Teng; Raman, Venkatramanan

    2016-11-01

    Supercritical flows have always been important to rocket motors, and more recently to aircraft engines and stationary gas turbines. The purpose of the present study is to understand effects of differential diffusion on reacting scalars using supercritical isotropic turbulence. Focus is on fuel and oxidant reacting in the transcritical region where density, heat capacity and transport properties are highly sensitive to variations in temperature and pressure. Reynolds and Damkohler number vary as a result and although it is common to neglect differential diffusion effects if Re is sufficiently large, this large variation in temperature with heat release can accentuate molecular transport differences. Direct numerical simulations (DNS) for one step chemistry reaction between fuel and oxidizer are used to examine the differential diffusion effects. A key issue investigated in this paper is if the flamelet progress variable approach, where the Lewis number is usually assumed to be unity and constant for all species, can be accurately applied to simulate supercritical combustion.

  1. Supercritical fluid thermodynamics for coal processing

    Energy Technology Data Exchange (ETDEWEB)

    van Swol, F. (Illinois Univ., Urbana, IL (United States). Dept. of Chemical Engineering); Eckert, C.A. (Georgia Inst. of Tech., Atlanta, GA (United States). School of Chemical Engineering)

    1988-09-15

    The main objective of this research is to develop an equation of state that can be used to predict solubilities and tailor supercritical fluid solvents for the extraction and processing of coal. To meet this objective we have implemented a two-sided. approach. First, we expanded the database of model coal compound solubilities in higher temperature fluids, polar fluids, and fluid mixtures systems. Second, the unique solute/solute, solute/cosolvent and solute/solvent intermolecular interactions in supercritical fluid solutions were investigated using spectroscopic techniques. These results increased our understanding of the molecular phenomena that affect solubility in supercritical fluids and were significant in the development of an equation of state that accurately reflects the true molecular makeup of the solution. (VC)

  2. Supercritical fluid mixing in Diesel Engine Applications

    Science.gov (United States)

    Bravo, Luis; Ma, Peter; Kurman, Matthew; Tess, Michael; Ihme, Matthias; Kweon, Chol-Bum

    2014-11-01

    A numerical framework for simulating supercritical fluids mixing with large density ratios is presented in the context of diesel sprays. Accurate modeling of real fluid effects on the fuel air mixture formation process is critical in characterizing engine combustion. Recent work (Dahms, 2013) has suggested that liquid fuel enters the chamber in a transcritical state and rapidly evolves to supercritical regime where the interface transitions from a distinct liquid/gas interface into a continuous turbulent mixing layer. In this work, the Peng Robinson EoS is invoked as the real fluid model due to an acceptable compromise between accuracy and computational tractability. Measurements at supercritical conditions are reported from the Constant Pressure Flow (CPF) chamber facility at the Army Research Laboratory. Mie and Schlieren optical spray diagnostics are utilized to provide time resolved liquid and vapor penetration length measurement. The quantitative comparison presented is discussed. Oak Ridge Associated Universities (ORAU).

  3. Heat Transfer Phenomena of Supercritical Fluids

    Energy Technology Data Exchange (ETDEWEB)

    Krau, Carmen Isabella; Kuhn, Dietmar; Schulenberg, Thomas [Forschungszentrum Karlsruhe, Institute for Nuclear and Energy Technologies, 76021 Karlsruhe (Germany)

    2008-07-01

    In concepts for supercritical water cooled reactors, the reactor core is cooled and moderated by water at supercritical pressures. The significant temperature dependence of the fluid properties of water requires an exact knowledge of the heat transfer mechanism to avoid fuel pin damages. Near the pseudo-critical point a deterioration of heat transfer might happen. Processes, that take place in this case, are not fully understood and are due to be examined systematically. In this paper a general overview on the properties of supercritical water is given, experimental observations of different authors will be reviewed in order to identify heat transfer phenomena and onset of occurrence. The conceptional design of a test rig to investigate heat transfer in the boundary layer will be discussed. Both, water and carbon dioxide, may serve as operating fluids. The loop, including instrumentation and safety devices, is shown and suitable measuring methods are described. (authors)

  4. Experimental Data from the Benchmark SuperCritical Wing Wind Tunnel Test on an Oscillating Turntable

    Science.gov (United States)

    Heeg, Jennifer; Piatak, David J.

    2013-01-01

    The Benchmark SuperCritical Wing (BSCW) wind tunnel model served as a semi-blind testcase for the 2012 AIAA Aeroelastic Prediction Workshop (AePW). The BSCW was chosen as a testcase due to its geometric simplicity and flow physics complexity. The data sets examined include unforced system information and forced pitching oscillations. The aerodynamic challenges presented by this AePW testcase include a strong shock that was observed to be unsteady for even the unforced system cases, shock-induced separation and trailing edge separation. The current paper quantifies these characteristics at the AePW test condition and at a suggested benchmarking test condition. General characteristics of the model's behavior are examined for the entire available data set.

  5. Adsorption from Experimental Isotherms of Supercritical Gases

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A mathematical method was proposed for the determination of absolute adsorption from experimental isotherms. The method is based on the numerical equality of the absolute and the excess adsorption when either the gas phase density or the amount adsorbed is not quite considerable. The initial part of the experimental isotherms, which represents the absolute adsorption, became linear with some mathematical manipulations. The linear isotherms were reliably formulated. As consequence, either the volume or the density of the supercritical adsorbate could be determined by a non-empirical way. This method was illustrated by the adsorption data of supercritical hydrogen and methane on a superactivated carbon in large ranges of temperature and pressure.

  6. Charting the landscape of supercritical string theory

    CERN Document Server

    Hellerman, Simeon

    2007-01-01

    Special solutions of string theory in supercritical dimensions can interpolate in time between theories with different numbers of spacetime dimensions (via dimension quenching) and different amounts of worldsheet supersymmetry (via c-duality). These solutions connect supercritical string theories to the more familiar string duality web in ten dimensions, and provide a precise link between supersymmetric and purely bosonic string theories. Dimension quenching and c-duality appear to be natural concepts in string theory, giving rise to large networks of interconnected theories. We describe some of these networks in detail and discuss general consistency constraints on the types of transitions that arise in this framework.

  7. [Definition of shock types].

    Science.gov (United States)

    Adams, H A; Baumann, G; Gänsslen, A; Janssens, U; Knoefel, W; Koch, T; Marx, G; Müller-Werdan, U; Pape, H C; Prange, W; Roesner, D; Standl, T; Teske, W; Werner, G; Zander, R

    2001-11-01

    Definitions of shock types. Hypovolaemic shock is a state of insufficient perfusion of vital organs with consecutive imbalance of oxygen supply and demand due to an intravascular volume deficiency with critically impaired cardiac preload. Subtypes are haemorrhagic shock, hypovolaemic shock in the narrow sense, traumatic-haemorrhagic shock and traumatic-hypovolaemic shock. Cardiac shock is caused by a primary critical cardiac pump failure with consecutive inadequate oxygen supply of the organism. Anaphylactic shock is an acute failure of blood volume distribution (distributive shock) and caused by IgE-dependent, type-I-allergic, classical hypersensibility, or a physically, chemically, or osmotically induced IgE-independent anaphylactoid hypersensibility. The septic shock is a sepsis-induced distribution failure of the circulating blood volume in the sense of a distributive shock. The neurogenic shock is a distributive shock induced by generalized and extensive vasodilatation with consecutive hypovolaemia due to an imbalance of sympathetic and parasympathetic regulation of vascular smooth muscles.

  8. Localized shocks

    CERN Document Server

    Roberts, Daniel A; Susskind, Leonard

    2014-01-01

    We study products of precursors of spatially local operators, $W_{x_{n}}(t_{n}) ... W_{x_1}(t_1)$, where $W_x(t) = e^{-iHt} W_x e^{iHt}$. Using chaotic spin-chain numerics and gauge/gravity duality, we show that a single precursor fills a spatial region that grows linearly in $t$. In a lattice system, products of such operators can be represented using tensor networks. In gauge/gravity duality, they are related to Einstein-Rosen bridges supported by localized shock waves. We find a geometrical correspondence between these two descriptions, generalizing earlier work in the spatially homogeneous case.

  9. Supercritical carbondioxide extraction of cypermethrin in different ...

    African Journals Online (AJOL)

    STORAGESEVER

    2010-04-12

    Apr 12, 2010 ... century coincided with the development of industrial methods of cultivation ... though supercritical CO2 is a good solvent only for the extraction of non-polar to ..... 101-111. Lange's Handbook of Chemistry (1985) . ed. Dean JA ...

  10. Destruction of Energetic Materials in Supercritical Water

    Science.gov (United States)

    2002-06-25

    THERMOCHEMISTRY OF ENERGETIC MATERIALS IN SUPERCRITICAL WATER...fringe spacing is 13.5 µm and the acoustic signal period is 28.3 ns. 138 SECTION VI THERMOCHEMISTRY OF ENERGETIC MATERIALS IN...validation calculation studied the solvation free energies of alkali–chloride ion pairs in liquid water. Such information can teach us about the

  11. Supercritical fluid extraction and processing of foods

    Science.gov (United States)

    Consumers are aware of the processing techniques used to manufacture food and health supplements and are concerned about the impact of those processes on their health and the environment. Processes that use supercritical fluids as an alternative to solvents that are used to extract nutrients and bio...

  12. Supercritical-Multiple-Solvent Extraction From Coal

    Science.gov (United States)

    Corcoran, W.; Fong, W.; Pichaichanarong, P.; Chan, P.; Lawson, D.

    1983-01-01

    Large and small molecules dissolve different constituents. Experimental apparatus used to test supercritical extraction of hydrogen rich compounds from coal in various organic solvents. In decreasing order of importance, relevant process parameters were found to be temperature, solvent type, pressure, and residence time.

  13. Improved Supercritical-Solvent Extraction of Coal

    Science.gov (United States)

    Compton, L.

    1982-01-01

    Raw coal upgraded by supercritical-solvent extraction system that uses two materials instead of one. System achieved extraction yields of 20 to 49 weight percent. Single-solvent yields are about 25 weight percent. Experimental results show extraction yields may be timedependent. Observed decreases in weight of coal agreed well with increases in ash content of residue.

  14. Diiodination of Alkynes in supercritical Carbon dioxide

    Institute of Scientific and Technical Information of China (English)

    李金恒; 谢叶香; 尹笃林; 江焕峰

    2003-01-01

    A general,green and efficient method for the synthesis of transdiiodoalkenes in CO2(sc) has been developed.Trans-diiodoalkenes were obtained stereospecifically in quantitative yields via diiodination of both electron-rich and electron-deficient alkynes in the presence of KI,Ce(SO4)2 and water in supercritical carbon dioxide [CO2(sc)]at 40℃.

  15. Petrophysical core characterization at supercritical geothermal conditions

    Science.gov (United States)

    Kummerow, Juliane; Raab, Siegfried

    2015-04-01

    There is a growing scientific interest in the exploitation of supercritical geothermal reservoirs to increase the efficiency of geothermal power plants. The utilisation of geothermal energy requires in any case the detailed knowledge of the reservoir. In reservoir engineering, the characterisation of the geothermal system by electrical resistivity tomography (ERT) is a common geophysical exploration and monitoring strategy. For a realistic interpretation of the field measurements it is necessary to know both, the physical properties of the rock and those of the interacting fluid at defined temperature and pressure conditions. While there have been made great effort in determine the physical and chemical properties of water above its critical point (Tcritical = 374.21° C and pcritical = 221.2 bar), the influence of fluid-rock interactions on petrophysical properties in supercritical aqueous systems is nearly unknown. At supercritical conditions the viscosity of the fluid is low, which enhances the mass transfer and diffusion-controlled chemical reactions. This may have considerable effects on the porosity and hydraulic properties of a rock. To investigate high-enthalpy fluid-rock systems, in the framework of the EU-funded project IMAGE we have built a new percolation set-up, which allows for the measurement of electrical resistivity and permeability of rock samples at controlled supercritical conditions of aqueous fluids (pore pressure = 400 bar and a temperature = 400° C). First results will be presented.

  16. Thermodynamics of Giant Planet Formation: Shocking Hot Surfaces on Circumplanetary Disks

    CERN Document Server

    Szulágyi, J

    2016-01-01

    The luminosity of young giant planets can inform about their formation and accretion history. The directly imaged planets detected so far are consistent with the "hot-start" scenario of high entropy and luminosity. If nebular gas passes through a shock front before being accreted into a protoplanet, the entropy can be substantially altered. To investigate this, we present high resolution, 3D radiative hydrodynamic simulations of accreting giant planets. The accreted gas is found to fall with supersonic speed in the gap from the circumstellar disk's upper layers onto the surface of the circumplanetary disk and polar region of the protoplanet. There it shocks, creating an extended hot supercritical shock surface. This shock front is optically thick, therefore, it can conceal the planet's intrinsic luminosity beneath. The gas in the vertical influx has high entropy which when passing through the shock front decreases significantly while the gas becomes part of the disk and protoplanet. This shows that circumplan...

  17. Recovery of Minerals in Martian Soils Via Supercritical Fluid Extraction

    Science.gov (United States)

    Debelak, Kenneth A.; Roth, John A.

    2001-03-01

    We are investigating the use of supercritical fluids to extract mineral and/or carbonaceous material from Martian surface soils and its igneous crust. Two candidate supercritical fluids are carbon dioxide and water. The Martian atmosphere is composed mostly of carbon dioxide (approx. 95.3%) and could therefore provide an in-situ source of carbon dioxide. Water, although present in the Martian atmosphere at only approx. 0.03%, is also a candidate supercritical solvent. Previous work done with supercritical fluids has focused primarily on their solvating properties with organic compounds. Interestingly, the first work reported by Hannay and Hogarth at a meeting of the Royal Society of London in 1879 observed that increasing or decreasing the pressure caused several inorganic salts e.g., cobalt chloride, potassium iodide, and potassium bromide, to dissolve or precipitate in supercritical ethanol. In high-pressure boilers, silica, present in most boiler feed waters, is dissolved in supercritical steam and transported as dissolved silica to the turbine blades. As the pressure is reduced the silica precipitates onto the turbine blades eventually requiring the shutdown of the generator. In supercritical water oxidation processes for waste treatment, dissolved salts present a similar problem. The solubility of silicon dioxide (SiO2) in supercritical water is shown. The solubility curve has a shape characteristic of supercritical systems. At a high pressure (greater than 1750 atmospheres) increasing the temperature results in an increase in solubility of silica, while at low pressures, less than 400 atm., the solubility decreases as temperature increases. There are only a few studies in the literature where supercritical fluids are used in extractive metallurgy. Bolt modified the Mond process in which supercritical carbon monoxide was used to produce nickel carbonyl (Ni(CO)4). Tolley and Tester studied the solubility of titanium tetrachloride (TiCl4) in supercritical CO2

  18. Bio-oil production from biomass via supercritical fluid extraction

    Energy Technology Data Exchange (ETDEWEB)

    Durak, Halil, E-mail: halildurak@yyu.edu.tr [Yuzuncu Yıl University, Vocational School of Health Services, 65080, Van (Turkey)

    2016-04-18

    Supercritical fluid extraction is used for producing bio-fuel from biomass. Supercritical fluid extraction process under supercritical conditions is the thermally disruption process of the lignocellulose or other organic materials at 250-400 °C temperature range under high pressure (4-5 MPa). Supercritical fluid extraction trials were performed in a cylindrical reactor (75 mL) in organic solvents (acetone, ethanol) under supercritical conditions with (calcium hydroxide, sodium carbonate) and without catalyst at the temperatures of 250, 275 and 300 °C. The produced liquids at 300 °C in supercritical liquefaction were analyzed and characterized by elemental, GC-MS and FT-IR. 36 and 37 different types of compounds were identified by GC-MS obtained in acetone and ethanol respectively.

  19. Supercritical Fluids Processing of Biomass to Chemicals and Fuels

    Energy Technology Data Exchange (ETDEWEB)

    Olson, Norman K. [Iowa State Univ., Ames, IA (United States)

    2011-09-28

    The main objective of this project is to develop and/or enhance cost-effective methodologies for converting biomass into a wide variety of chemicals, fuels, and products using supercritical fluids. Supercritical fluids will be used both to perform reactions of biomass to chemicals and products as well as to perform extractions/separations of bio-based chemicals from non-homogeneous mixtures. This work supports the Biomass Program’s Thermochemical Platform Goals. Supercritical fluids are a thermochemical approach to processing biomass that, while aligned with the Biomass Program’s interests in gasification and pyrolysis, offer the potential for more precise and controllable reactions. Indeed, the literature with respect to the use of water as a supercritical fluid frequently refers to “supercritical water gasification” or “supercritical water pyrolysis.”

  20. Bio-oil production from biomass via supercritical fluid extraction

    Science.gov (United States)

    Durak, Halil

    2016-04-01

    Supercritical fluid extraction is used for producing bio-fuel from biomass. Supercritical fluid extraction process under supercritical conditions is the thermally disruption process of the lignocellulose or other organic materials at 250-400 °C temperature range under high pressure (4-5 MPa). Supercritical fluid extraction trials were performed in a cylindrical reactor (75 mL) in organic solvents (acetone, ethanol) under supercritical conditions with (calcium hydroxide, sodium carbonate) and without catalyst at the temperatures of 250, 275 and 300 °C. The produced liquids at 300 °C in supercritical liquefaction were analyzed and characterized by elemental, GC-MS and FT-IR. 36 and 37 different types of compounds were identified by GC-MS obtained in acetone and ethanol respectively.

  1. Industrial applications and current trends in supercritical fluid technologies

    OpenAIRE

    Gamse Thomas

    2005-01-01

    Supercritical fluids have a great potential for wide fields of processes Although CO2 is still one of the most used supercritical gases, for special purposes propane or even fluorinated-chlorinated fluids have also been tested. The specific characteristics of supercritical fluids behaviour were analyzed such as for example the solubilities of different components and the phase equilibria between the solute and solvent. The application at industrial scale (decaffeinating of tea and coffee, hop...

  2. Solvent adsorption in SFC : Adsorption of methanol under supercritical conditions

    OpenAIRE

    Edström, Emelie

    2015-01-01

    Chromatography is a widely used separation technique including many different modes, for example supercritical fluid chromatography (SFC) which uses a supercritical fluid as mobile phase. A supercritical fluid is achieved when a substance is subjected to a temperature and pressure above the critical point and the boundary between the liquid phase and gas phase is erased. The interest for SFC has increased in recent years, mainly for separation of chiral molecules in the pharmaceutical industr...

  3. Supercritical water oxidation of products of human metabolism

    Science.gov (United States)

    Tester, Jefferson W.; Orge A. achelling, Richard K. ADTHOMASSON; Orge A. achelling, Richard K. ADTHOMASSON

    1986-01-01

    Although the efficient destruction of organic material was demonstrated in the supercritical water oxidation process, the reaction kinetics and mechanisms are unknown. The kinetics and mechanisms of carbon monoxide and ammonia oxidation in and reaction with supercritical water were studied experimentally. Experimental oxidation of urine and feces in a microprocessor controlled system was performed. A minaturized supercritical water oxidation process for space applications was design, including preliminary mass and energy balances, power, space and weight requirements.

  4. Solubility and Phase Behavior of CL20 in Supercritical Fluids

    Science.gov (United States)

    2006-09-01

    supercritical state. The fugacity of the solute in the supercritical fluid can be evaluated using a cubic equation of state such as the Redlich - Kwong ...pro- gram was validated using available literature data for the solubility of naphthalene and of biphenyl in supercritical CO2. The applicability of...promising process using environmentally benign compressed gases as either solvents or anti-solvents is being investi- gated for applications in

  5. Collisionless electrostatic shocks

    DEFF Research Database (Denmark)

    Andersen, H.K.; Andersen, S.A.; Jensen, Vagn Orla

    1970-01-01

    An attempt was made in the laboratory to observe the standing collisionless electrostatic shocks in connection with the bow shock of the earth......An attempt was made in the laboratory to observe the standing collisionless electrostatic shocks in connection with the bow shock of the earth...

  6. Supercritical Water Process for the Chemical Recycling of Waste Plastics

    Science.gov (United States)

    Goto, Motonobu

    2010-11-01

    The development of chemical recycling of waste plastics by decomposition reactions in sub- and supercritical water is reviewed. Decomposition reactions proceed rapidly and selectively using supercritical fluids compared to conventional processes. Condensation polymerization plastics such as PET, nylon, and polyurethane, are relatively easily depolymerized to their monomers in supercritical water. The monomer components are recovered in high yield. Addition polymerization plastics such as phenol resin, epoxy resin, and polyethylene, are also decomposed to monomer components with or without catalysts. Recycling process of fiber reinforced plastics has been studied. Pilot scale or commercial scale plants have been developed and are operating with sub- and supercritical fluids.

  7. Supercritical Water Liquefaction of Coal and Waste Tires

    National Research Council Canada - National Science Library

    Prapan KUCHONTHARA; Yukihiko MATSUMURA

    2001-01-01

      Supercritical water liquefaction of scrap tire rubber and Ishikari coal, separately and in mixtures was investigated to study the possible synergetic effects of coliquefaction between the feedstocks...

  8. Dependence of Reaction Rate Constants on Density in Supercritical Fluids

    Institute of Scientific and Technical Information of China (English)

    WANGTao; SHENZhongyao

    2002-01-01

    A new method,which correlates rate constants of chemical reactions and density or pressure in supercritical fluids,was developed.Based on the transition state theory and thermodynamic principles, the rate constant can be reasonably correlated with the density of the supercritical fluid,and a correlation equation was obtained. Coupled with the equation of state (EOS) of a supercritical solvent,the effect of pressure on reaction rate constant could be represented.Two typical systems were used to test this method.The result indicates that this method is suitable for dilute supercritical fluid solutions.

  9. Reaction Behavior of Unsaturated Compounds in Sub- and Supercritical Water

    Institute of Scientific and Technical Information of China (English)

    K. Kobiro

    2005-01-01

    @@ 1Introduction Much attention has been paid on the chemistry of sub- and supercritical water, because of their unique prosperities such as low viscosity, low polarity, and high solubility to organic compounds[1]. Recently, the unique sub- and supercritical water is applied as reaction media and reaction catalysts for organic reactions[2,3].We herein disclose the unique reaction of unsaturated compounds in sub- and supercritical water with specific interaction between unsaturated bond(s) and high-density and high-energy water molecule(s) in sub- and supercritical water.

  10. Supercritical CO{sub 2} fluid for chip resistor cleaning

    Energy Technology Data Exchange (ETDEWEB)

    Wang, C.W.; Chang, R.T.; Lin, W.K.; Lin, R.D.; Liang, M.T.; Yang, J.F.; Wang, J.B.

    1999-09-01

    The cleaning ability of supercritical CO{sub 2} was examined on chip resistors. Extraction analyses were made by atomic absorption spectroscopy and the extent of surface cleaning observed by scanning electron microscopy. Experimental results showed that the flow-cleaning process of supercritical CO{sub 2} possessed the advantages of having a superior cleaning ability and permitting a nondrying step. These characteristics strongly suggest that supercritical CO{sub 2} is a superior alternative to the traditional deionized water used in rinsing chip resistors. Moreover, a higher pressure and temperature can benefit the cleaning ability of this novel supercritical CO{sub 2} cleaning technique.

  11. Supercritical boiler material selection using fuzzy analytic network process

    Directory of Open Access Journals (Sweden)

    Saikat Ranjan Maity

    2012-08-01

    Full Text Available The recent development of world is being adversely affected by the scarcity of power and energy. To survive in the next generation, it is thus necessary to explore the non-conventional energy sources and efficiently consume the available sources. For efficient exploitation of the existing energy sources, a great scope lies in the use of Rankin cycle-based thermal power plants. Today, the gross efficiency of Rankin cycle-based thermal power plants is less than 28% which has been increased up to 40% with reheating and regenerative cycles. But, it can be further improved up to 47% by using supercritical power plant technology. Supercritical power plants use supercritical boilers which are able to withstand a very high temperature (650-720˚C and pressure (22.1 MPa while producing superheated steam. The thermal efficiency of a supercritical boiler greatly depends on the material of its different components. The supercritical boiler material should possess high creep rupture strength, high thermal conductivity, low thermal expansion, high specific heat and very high temperature withstandability. This paper considers a list of seven supercritical boiler materials whose performance is evaluated based on seven pivotal criteria. Given the intricacy and difficulty of this supercritical boiler material selection problem having interactions and interdependencies between different criteria, this paper applies fuzzy analytic network process to select the most appropriate material for a supercritical boiler. Rene 41 is the best supercritical boiler material, whereas, Haynes 230 is the worst preferred choice.

  12. The pseudocritical regions for supercritical water

    Energy Technology Data Exchange (ETDEWEB)

    Imre, A.R., E-mail: imre.attila@energia.mta.hu [HAS Centre for Energy Research, Thermohydraulics Department, P.O. Box 49, H-1525 Budapest (Hungary); University Cologne, Institute for Physical Chemistry, Luxemburger Str. 116, D-50939 Koeln (Germany); Deiters, U.K.; Kraska, T. [University Cologne, Institute for Physical Chemistry, Luxemburger Str. 116, D-50939 Koeln (Germany); Tiselj, I. [Jozef Stefan Institute, Reactor Engineering Division, Jamova 39, 1000 Ljubljana (Slovenia)

    2012-11-15

    Highlights: Black-Right-Pointing-Pointer Supercritical water behaves anomalously around the Widom lines. Black-Right-Pointing-Pointer We calculated the location of the Widom lines for several thermodynamic functions. Black-Right-Pointing-Pointer Simple quadratic fitting equations are given to describe these lines. - Abstract: Vapour pressure curves and stability lines can be extended beyond the critical points into the supercritical domain by so-called Widom lines, along which some thermodynamic property undergoes a rapid change and liquid-like behaviour turns to vapour-like one. Knowledge about such lines is therefore important for thermohydraulic calculations and design. There are several properties that can be chosen as defining property of a Widom line. In this short note we calculate and compare several kinds of Widom lines for water.

  13. Depolymerization of polyethylene terephthalate in supercritical methanol

    Science.gov (United States)

    Goto, Motonobu; Koyamoto, Hiroshi; Kodama, Akio; Hirose, Tsutomu; Nagaoka, Shoji

    2002-11-01

    The degradation of polyethylene terephthalate (PET) in supercritical methanol was investigated with the aim of developing a process for chemical recycling of waste plastics. A batch reactor was used at temperatures of 573-623 K under an estimated pressure of 20 MPa for a reaction time of 2-120 min. PET was decomposed to its monomers, dimethyl terephthalate and ethylene glycol, by methanolysis in supercritical methanol. The reaction products were analysed using size-exclusion chromatography, gas chromatography-mass spectrometry, and reversed-phase liquid chromatography. The molecular weight distribution of the products was obtained as a function of reaction time. The yields of monomer components of the decomposition products including by-products were measured. Continuous kinetics analysis was performed on the experimental data.

  14. Supercritical separation process for complex organic mixtures

    Science.gov (United States)

    Chum, Helena L.; Filardo, Giuseppe

    1990-01-01

    A process is disclosed for separating low molecular weight components from complex aqueous organic mixtures. The process includes preparing a separation solution of supercritical carbon dioxide with an effective amount of an entrainer to modify the solvation power of the supercritical carbon dioxide and extract preselected low molecular weight components. The separation solution is maintained at a temperature of at least about 70.degree. C. and a pressure of at least about 1,500 psi. The separation solution is then contacted with the organic mixtures while maintaining the temperature and pressure as above until the mixtures and solution reach equilibrium to extract the preselected low molecular weight components from the organic mixtures. Finally, the entrainer/extracted components portion of the equilibrium mixture is isolated from the separation solution.

  15. Supercritical Fluid Extraction of Flavonoids from Dandelion

    Directory of Open Access Journals (Sweden)

    Wu Jun

    2014-01-01

    Full Text Available In this study, the total flavonoids from dandelion was extracted by supercritical CO2 and the total flavonoids content in the extract was investigated by the sodium nitrite-aluminum nitrate method with Rutin as a standard product. Single-factor experiments were carried out to map the effects of extraction pressure, temperature, time and entrainer amount on the yield of flavonoids. The orthogonal experiments on the optimum technology parameters demonstrated that the influence of the experimental conditions over the yield from high to low was: (a pressure, (b temperature, (c entrainer amount, (d time. The optimization result showed that under the conditions of 50°C, 35 MPa, 80 min and 4.0 mL/g entrainer amount, the yield of the preparative supercritical fluid extraction was 4.974%.

  16. Stochastic simulation of supercritical fluid extraction processes

    Directory of Open Access Journals (Sweden)

    Mizutani F. T.

    2000-01-01

    Full Text Available Process simulation involves the evaluation of output variables by the specification of input variables and process parameters. However, in a real process, input data and parameters cannot be known without uncertainty. This fact may limit the utilization of simulation results to predict plant behavior. In order to achieve a more realistic analysis, the procedure of stochastic simulation can be conducted. This technique is based on a large set of simulation runs where input variables and parameters are randomly selected according to adequate probability density functions. The objective of this work is to illustrate the application of a stochastic simulation procedure to the process of fractionation of orange essential oil, using supercritical carbon dioxide in a multistage extraction column. Analysis of the proposed example demonstrates the importance of the stochastic simulation to develop more reliable designs and operating conditions for a supercritical fluid extraction process.

  17. Using supercritical fluids to refine hydrocarbons

    Science.gov (United States)

    Yarbro, Stephen Lee

    2014-11-25

    This is a method to reactively refine hydrocarbons, such as heavy oils with API gravities of less than 20.degree. and bitumen-like hydrocarbons with viscosities greater than 1000 cp at standard temperature and pressure using a selected fluid at supercritical conditions. The reaction portion of the method delivers lighter weight, more volatile hydrocarbons to an attached contacting device that operates in mixed subcritical or supercritical modes. This separates the reaction products into portions that are viable for use or sale without further conventional refining and hydro-processing techniques. This method produces valuable products with fewer processing steps, lower costs, increased worker safety due to less processing and handling, allow greater opportunity for new oil field development and subsequent positive economic impact, reduce related carbon dioxide, and wastes typical with conventional refineries.

  18. Effect of supercritical fluid density on nanoencapsulated drug particle size using the supercritical antisolvent method.

    Science.gov (United States)

    Kalani, Mahshid; Yunus, Robiah

    2012-01-01

    The reported work demonstrates and discusses the effect of supercritical fluid density (pressure and temperature of supercritical fluid carbon dioxide) on particle size and distribution using the supercritical antisolvent (SAS) method in the purpose of drug encapsulation. In this study, paracetamol was encapsulated inside L-polylactic acid, a semicrystalline polymer, with different process parameters, including pressure and temperature, using the SAS process. The morphology and particle size of the prepared nanoparticles were determined by scanning electron microscopy and transmission electron microscopy. The results revealed that increasing temperature enhanced mean particle size due to the plasticizing effect. Furthermore, increasing pressure enhanced molecular interaction and solubility; thus, particle size was reduced. Transmission electron microscopy images defined the internal structure of nanoparticles. Thermal characteristics of nanoparticles were also investigated via differential scanning calorimetry. Furthermore, X-ray diffraction pattern revealed the changes in crystallinity structure during the SAS process. In vitro drug release analysis determined the sustained release of paracetamol in over 4 weeks.

  19. Nonstationarity of a two-dimensional perpendicular shock: Competing mechanisms

    Science.gov (United States)

    Lembège, Bertrand; Savoini, Philippe; Hellinger, Petr; Trávníček, Pavel M.

    2009-03-01

    Two-dimensional particle-in-cell (PIC) simulations are used for analyzing in detail different nonstationary behaviors of a perpendicular supercritical shock. A recent study by Hellinger et al. (2007) has shown that the front of a supercritical shock can be dominated by the emission of large-amplitude whistler waves. These waves inhibit the self-reformation driven by the reflected ions; then, the shock front appears almost ``quasi-stationary.'' The present study stresses new complementary results. First, for a fixed β i value, the whistler waves emission (WWE) persists for high M A above a critical Mach number (i.e., M A >= M A WWE). The quasi-stationarity is only apparent and disappears when considering the full 3-D field profiles. Second, for lower M A , the self-reformation is retrieved and becomes dominant as the amplitude of the whistler waves becomes negligible. Third, there exists a transition regime in M A within which both processes compete each other. Fourth, these results are observed for a strictly perpendicular shock only as B 0 is within the simulation plane. When B 0 is out of the simulation plane, no whistler waves emission is evidenced and only self-reformation is recovered. Fifth, the occurrence and disappearance of the nonlinear whistler waves are well recovered in both 2-D PIC and 2-D hybrid simulations. The impacts on the results of the mass ratio (2-D PIC simulations), of the resistivity and spatial resolution (2-D hybrid simulations), and of the size of the simulation box along the shock front are analyzed in detail.

  20. Dye solubility in supercritical carbon dioxide fluid

    Directory of Open Access Journals (Sweden)

    Yan Jun

    2015-01-01

    Full Text Available Supercritical carbon dioxide fluid is an alternative solvent for the water of the traditional dyeing. The solubility of dyestuff affects greatly the dyeing process. A theoretical model for predicting the dye solubility is proposed and verified experimentally. The paper concludes that the pressure has a greater impact on the dyestuff solubility than temperature, and an optimal dyeing condition is suggested for the highest distribution coefficient of dyestuff.

  1. Computational Modeling of Supercritical and Transcritical Flows

    Science.gov (United States)

    2017-01-09

    reasonably accurate for supercritical and transcritical combustion. 15. SUBJECT TERMS N/A 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF...pr Reduced pressure (p/pc) Tc Critical temperature Tr Reduced temperature (T/Tc) Vm Molar volume Xi Mole fraction of species i Z Compressibility ω...pressure states. A 5.5mm by 0.4064mm domain uses a uniform 256 × 512 Cartesian grid. The code is fifth order accurate in space and a third order

  2. Supercritical fluid extraction of mercury species.

    Science.gov (United States)

    Foy, G P; Pacey, G E

    2003-12-23

    Supercritical fluid extraction was used to recover organic and inorganic mercury species. Variations in pressure, water, methanol, and chelator create methods that allowed separation of inorganic from organic mercury species. When extracted using a compromised set of extraction conditions, the order of extraction was methyl, phenyl and inorganic mercury. For the individually optimized conditions, quantitative recoveries were observed. Level as low as 20 ppb were extracted and then determined using ICP.

  3. Supercritical CO2 Extraction of Ethanol

    OpenAIRE

    GÜVENÇ, A.; MEHMETOĞLU, Ü.; ÇALIMLI, A.

    1999-01-01

    Extraction of ethanol was studied from both synthetic ethanol solution and fermentation broth using supercritical CO2 in an extraction apparatus in ranges of 313 to 333 K and 80 to 160 atmospheres, for varying extraction times. The experimental system consists mainly of four parts: a CO2 storage system, a high-pressure liquid pump, an extractor and a product collection unit. Samples were analyzed by gas chromatography. Effects of temperature, pressure, extraction time, initial ethan...

  4. Geometrical shock dynamics for magnetohydrodynamic fast shocks

    KAUST Repository

    Mostert, W.

    2016-12-12

    We describe a formulation of two-dimensional geometrical shock dynamics (GSD) suitable for ideal magnetohydrodynamic (MHD) fast shocks under magnetic fields of general strength and orientation. The resulting area–Mach-number–shock-angle relation is then incorporated into a numerical method using pseudospectral differentiation. The MHD-GSD model is verified by comparison with results from nonlinear finite-volume solution of the complete ideal MHD equations applied to a shock implosion flow in the presence of an oblique and spatially varying magnetic field ahead of the shock. Results from application of the MHD-GSD equations to the stability of fast MHD shocks in two dimensions are presented. It is shown that the time to formation of triple points for both perturbed MHD and gas-dynamic shocks increases as (Formula presented.), where (Formula presented.) is a measure of the initial Mach-number perturbation. Symmetry breaking in the MHD case is demonstrated. In cylindrical converging geometry, in the presence of an azimuthal field produced by a line current, the MHD shock behaves in the mean as in Pullin et al. (Phys. Fluids, vol. 26, 2014, 097103), but suffers a greater relative pressure fluctuation along the shock than the gas-dynamic shock. © 2016 Cambridge University Press

  5. NUMERICAL COMPUTATIONS OF CO-EXISTING SUPER-CRITICAL AND SUB-CRITICAL FLOWS BASED UPON CRD SCHEMES

    Science.gov (United States)

    Horie, Katsuya; Okamura, Seiji; Kobayashi, Yusuke; Hyodo, Makoto; Hida, Yoshihisa; Nishimoto, Naoshi; Mori, Akio

    Stream flows in steep gradient bed form complicating flow configurations, where co-exist super-critical and sub-critical flows. Computing numerically such flows are the key to successful river management. This study applied CRD schemes to 1D and 2D stream flow computations and proposed genuine ways to eliminate expansion shock waves. Through various cases of computing stream flows conducted, CRD schemes showed that i) conservativeness of discharge and accuracy of four significant figures are ensured, ii) artificial viscosity is not explicitly used for computational stabilization, and thus iii) 1D and 2D computations based upon CRD schemes are applicable to evaluating complicating stream flows for river management.

  6. Advanced Thermal Storage for Central Receivers with Supercritical Coolants

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, Bruce D.

    2010-06-15

    The principal objective of the study is to determine if supercritical heat transport fluids in a central receiver power plant, in combination with ceramic thermocline storage systems, offer a reduction in levelized energy cost over a baseline nitrate salt concept. The baseline concept uses a nitrate salt receiver, two-tank (hot and cold) nitrate salt thermal storage, and a subcritical Rankine cycle. A total of 6 plant designs were analyzed, as follows: Plant Designation Receiver Fluid Thermal Storage Rankine Cycle Subcritical nitrate salt Nitrate salt Two tank nitrate salt Subcritical Supercritical nitrate salt Nitrate salt Two tank nitrate salt Supercritical Low temperature H2O Supercritical H2O Two tank nitrate salt Supercritical High temperature H2O Supercritical H2O Packed bed thermocline Supercritical Low temperature CO2 Supercritical CO2 Two tank nitrate salt Supercritical High temperature CO2 Supercritical CO2 Packed bed thermocline Supercritical Several conclusions have been drawn from the results of the study, as follows: 1) The use of supercritical H2O as the heat transport fluid in a packed bed thermocline is likely not a practical approach. The specific heat of the fluid is a strong function of the temperatures at values near 400 °C, and the temperature profile in the bed during a charging cycle is markedly different than the profile during a discharging cycle. 2) The use of supercritical CO2 as the heat transport fluid in a packed bed thermocline is judged to be technically feasible. Nonetheless, the high operating pressures for the supercritical fluid require the use of pressure vessels to contain the storage inventory. The unit cost of the two-tank nitrate salt system is approximately $24/kWht, while the unit cost of the high pressure thermocline system is nominally 10 times as high. 3) For the supercritical fluids, the outer crown temperatures of the receiver tubes are in the range of 700 to 800 °C. At temperatures of 700 °C and above

  7. Use of supercritical carbon dioxide extraction

    Energy Technology Data Exchange (ETDEWEB)

    Taniguchi, Masayuki (Niigata Univ., Faculty of Engineering, Niigata, (Japan))

    1989-09-25

    Supercritical fluid extraction is a novel diffusion and separation technique which exploits simultaneously the increase of vapor pressure and the difference of chemical affinities of fluids near the critical point. A solvent which is used as the supercritical fluid has the following features: the critical point exists in the position of relatively ease of handling, the solvent is applicable to the extraction of a physiological active substance of thermal instability. Carbon dioxide as the solvent is non-flammable, non-corrosive, non-toxic, cheap, and readily available of high purity. The results of studies on the use of supercritical carbon dioxide (SC-CO{sub 2}) as a solvent for natural products in the fermentation and food industries, were collected. SC-CO{sub 2} extraction are used in many fields, examples for the application are as follows: removal of organic solvents from antibiotics; extraction of vegetable oils contained in wheat germ oil, high quality mustard seeds, rice bran and so on; brewing of sake using rice and rice-koji; use as a non-aqueous medium for the synthesis of precursors of the Aspartame; and use in sterilization. 66 refs., 17 figs., 21 tabs.

  8. Determination of binary diffusion coefficients in supercritical carbon dioxide with supercritical fluid chromatography (SFC)

    Energy Technology Data Exchange (ETDEWEB)

    Dahmen, N.; Duelberg, A.; Schneider, G.M. (Bochum Univ. (Germany, F.R.). Lehrstuhl fuer Physikalische Chemie 2)

    1990-03-01

    Binary diffusion coefficient D{sub 12} in supercritical carbon dioxide were determined in a Supercritical Fluid Chromatography (SFC) apparatus by the peak broadening method (PBM). Some cyclic and linear ketones were investigated as a function of pressure between 9.5 and 18 MPa at about 314 K corresponding to densities form 513 to 820 kg m{sup -3}. The resulting D{sub 12} values are of the order of 10{sup -8} m{sup 2} s{sup -1} and lnD{sub 12} decreases about linearly with increasing density {rho} of the CO{sub 2}. (orig.).

  9. Radiative Shock Waves In Emerging Shocks

    Science.gov (United States)

    Drake, R. Paul; Doss, F.; Visco, A.

    2011-05-01

    In laboratory experiments we produce radiative shock waves having dense, thin shells. These shocks are similar to shocks emerging from optically thick environments in astrophysics in that they are strongly radiative with optically thick shocked layers and optically thin or intermediate downstream layers through which radiation readily escapes. Examples include shocks breaking out of a Type II supernova (SN) and the radiative reverse shock during the early phases of the SN remnant produced by a red supergiant star. We produce these shocks by driving a low-Z plasma piston (Be) at > 100 km/s into Xe gas at 1.1 atm. pressure. The shocked Xe collapses to > 20 times its initial density. Measurements of structure by radiography and temperature by several methods confirm that the shock wave is strongly radiative. We observe small-scale perturbations in the post-shock layer, modulating the shock and material interfaces. We describe a variation of the Vishniac instability theory of decelerating shocks and an analysis of associated scaling relations to account for the growth of these perturbations, identify how they scale to astrophysical systems such as SN 1993J, and consider possible future experiments. Collaborators in this work have included H.F. Robey, J.P. Hughes, C.C. Kuranz, C.M. Huntington, S.H. Glenzer, T. Doeppner, D.H. Froula, M.J. Grosskopf, and D.C. Marion ________________________________ * Supported by the US DOE NNSA under the Predictive Sci. Academic Alliance Program by grant DE-FC52-08NA28616, the Stewardship Sci. Academic Alliances program by grant DE-FG52-04NA00064, and the Nat. Laser User Facility by grant DE-FG03-00SF22021.

  10. Thermodynamic Optimization of Supercritical CO{sub 2} Brayton Cycles

    Energy Technology Data Exchange (ETDEWEB)

    Rhim, Dong-Ryul; Park, Sung-Ho; Kim, Su-Hyun; Yeom, Choong-Sub [Institute for Advanced Engineering, Yongin (Korea, Republic of)

    2015-05-15

    The supercritical CO{sub 2} Brayton cycle has been studied for nuclear applications, mainly for one of the alternative power conversion systems of the sodium cooled fast reactor, since 1960's. Although the supercritical CO{sub 2} Brayton cycle has not been expected to show higher efficiency at lower turbine inlet temperature over the conventional steam Rankine cycle, the higher density of supercritical CO{sub 2} like a liquid in the supercritical region could reduce turbo-machinery sizes, and the potential problem of sodium-water reaction with the sodium cooled fast reactor might be solved with the use of CO{sub 2} instead of water. The supercritical CO{sub 2} recompression Brayton cycle was proposed for the better thermodynamic efficiency than for the simple supercritical CO{sub 2} Brayton cycle. Thus this paper presents the efficiencies of the supercritical CO{sub 2} recompression Brayton cycle along with several decision variables for the thermodynamic optimization of the supercritical CO{sub 2} recompression Brayton cycle. The analytic results in this study show that the system efficiency reaches its maximum value at a compressor outlet pressure of 200 bars and a recycle fraction of 30 %, and the lower minimum temperature approach at the two heat exchangers shows higher system efficiency as expected.

  11. Introduction to supercritical fluids a spreadsheet-based approach

    CERN Document Server

    Smith, Richard; Peters, Cor

    2013-01-01

    This text provides an introduction to supercritical fluids with easy-to-use Excel spreadsheets suitable for both specialized-discipline (chemistry or chemical engineering student) and mixed-discipline (engineering/economic student) classes. Each chapter contains worked examples, tip boxes and end-of-the-chapter problems and projects. Part I covers web-based chemical information resources, applications and simplified theory presented in a way that allows students of all disciplines to delve into the properties of supercritical fluids and to design energy, extraction and materials formation systems for real-world processes that use supercritical water or supercritical carbon dioxide. Part II takes a practical approach and addresses the thermodynamic framework, equations of state, fluid phase equilibria, heat and mass transfer, chemical equilibria and reaction kinetics of supercritical fluids. Spreadsheets are arranged as Visual Basic for Applications (VBA) functions and macros that are completely (source code) ...

  12. Lower hybrid waves at the shock front: a reassessment

    Directory of Open Access Journals (Sweden)

    S. N. Walker

    2008-03-01

    Full Text Available The primary process occurring at a collisionless shock is the redistribution of the bulk upstream energy into other degrees of freedom. One part of this process results in the acceleration of electrons at the shock front. Accelerated electrons are observed at the terrestrial and other planetary shocks, comets, and their effects are observed in astrophysical phenomena such as supernova remnants and jets in the form of X-ray bremsstrahlung radiation. One of the physical models for electron acceleration at supercritical shocks is based on low-hybrid turbulence due to the presence of reflected ions in the foot region. Since lower hybrid waves propagate almost perpendicular to the magnetic field they can be simultaneously in resonance with both the unmagnetised ions (ω=Vik and magnetised electrons (ω=Vek||. In this paper, Cluster observations of the electric field are used to study the occurrence of lower hybrid waves in the front of the terrestrial bow shock. It is shown that the lower hybrid waves exist as isolated wave packets. However, the very low level of the observed lower hybrid turbulence is too small to impart significant energisation to the electron population.

  13. Metal Nanoparticles Preparation In Supercritical Carbon Dioxide Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Harry W. Rollins

    2004-04-01

    The novel optical, electronic, and/or magnetic properties of metal and semiconductor nanoparticles have resulted in extensive research on new methods for their preparation. An ideal preparation method would allow the particle size, size distribution, crystallinity, and particle shape to be easily controlled, and would be applicable to a wide variety of material systems. Numerous preparation methods have been reported, each with its inherent advantages and disadvantages; however, an ideal method has yet to emerge. The most widely applied methods for nanoparticle preparation include the sonochemical reduction of organometallic reagents,(1&2) the solvothermal method of Alivisatos,(3) reactions in microemulsions,(4-6) the polyol method (reduction by alcohols),(7-9) and the use of polymer and solgel materials as hosts.(10-13) In addition to these methods, there are a variety of methods that take advantage of the unique properties of a supercritical fluid.(14&15) Through simple variations of temperature and pressure, the properties of a supercritical fluid can be continuously tuned from gas-like to liquid-like without undergoing a phase change. Nanoparticle preparation methods that utilize supercritical fluids are briefly reviewed below using the following categories: Rapid Expansion of Supercritical Solutions (RESS), Reactive Supercritical Fluid Processing, and Supercritical Fluid Microemulsions. Because of its easily accessible critical temperature and pressure and environmentally benign nature, carbon dioxide is the most widely used supercritical solvent. Supercritical CO2 is unfortunately a poor solvent for many polar or ionic species, which has impeded its use in the preparation of metal and semiconductor nanoparticles. We have developed a reactive supercritical fluid processing method using supercritical carbon dioxide for the preparation of metal and metal sulfide particles and used it to prepare narrowly distributed nanoparticles of silver (Ag) and silver sulfide

  14. DIFFUSIVE SHOCK ACCELERATION AT COSMOLOGICAL SHOCK WAVES

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Hyesung [Department of Earth Sciences, Pusan National University, Pusan 609-735 (Korea, Republic of); Ryu, Dongsu, E-mail: kang@uju.es.pusan.ac.kr, E-mail: ryu@canopus.cnu.ac.kr [Department of Astronomy and Space Science, Chungnam National University, Daejeon 305-764 (Korea, Republic of)

    2013-02-10

    We reexamine nonlinear diffusive shock acceleration (DSA) at cosmological shocks in the large-scale structure of the universe, incorporating wave-particle interactions that are expected to operate in collisionless shocks. Adopting simple phenomenological models for magnetic field amplification (MFA) by cosmic-ray (CR) streaming instabilities and Alfvenic drift, we perform kinetic DSA simulations for a wide range of sonic and Alfvenic Mach numbers and evaluate the CR injection fraction and acceleration efficiency. In our DSA model, the CR acceleration efficiency is determined mainly by the sonic Mach number M{sub s} , while the MFA factor depends on the Alfvenic Mach number and the degree of shock modification by CRs. We show that at strong CR modified shocks, if scattering centers drift with an effective Alfven speed in the amplified magnetic field, the CR energy spectrum is steepened and the acceleration efficiency is reduced significantly, compared to the cases without such effects. As a result, the postshock CR pressure saturates roughly at {approx}20% of the shock ram pressure for strong shocks with M{sub s} {approx}> 10. In the test-particle regime (M{sub s} {approx}< 3), it is expected that the magnetic field is not amplified and the Alfvenic drift effects are insignificant, although relevant plasma physical processes at low Mach number shocks remain largely uncertain.

  15. Streptococcal toxic shock syndrome

    OpenAIRE

    Gvozdenović Ljiljana; Pasternak Janko; Milovanović Stanislav; Ivanov Dejan; Milić Saša

    2010-01-01

    Introduction. Streptococcal toxic shock syndrome is now recognized as a toxin-mediated, multisystem illness. It is characterized by an early onset of shock with multiorgan failure and continues to be associated with high morbidity and mortality, caused by group A Streptococcus pyogenes. The symptoms for staphylococcal and streptococcal toxic shock syndrome are similar. Streptococcal toxic shock syndrome was not well described until 1993, when children who had suffered from varicella pre...

  16. Biomass shock pretreatment

    Science.gov (United States)

    Holtzapple, Mark T.; Madison, Maxine Jones; Ramirez, Rocio Sierra; Deimund, Mark A.; Falls, Matthew; Dunkelman, John J.

    2014-07-01

    Methods and apparatus for treating biomass that may include introducing a biomass to a chamber; exposing the biomass in the chamber to a shock event to produce a shocked biomass; and transferring the shocked biomass from the chamber. In some aspects, the method may include pretreating the biomass with a chemical before introducing the biomass to the chamber and/or after transferring shocked biomass from the chamber.

  17. Supercritical fluids: Reactions, materials and applications

    Energy Technology Data Exchange (ETDEWEB)

    Tumas, W.; Jacobson, G.B.; Josephsohn, N.S.; Brown, G.H.

    1999-04-09

    A number of important processes utilizing supercritical fluids have been either implemented or are emerging for extractions, separations and a wide range of cleaning applications. Supercritical fluids can be reasonable solvents yet share many of the advantages of gases including miscibility with other gases (i.e. hydrogen and oxygen), low viscosities and high diffusivities. Carbon dioxide has the further advantages of being nontoxic, nonflammable, inexpensive and currently unregulated. The use of compressed gases, either as liquids or supercritical fluids, as reaction media offers the opportunity to replace conventional hazardous solvents and also to optimize and potentially control the effect of solvent on chemical and material processing. The last several years has seen a significant growth in advances in chemical synthesis, catalytic transformations and materials synthesis and processing. The authors report on results from an exploratory program at Los Alamos National Laboratory aimed at investigating the use of dense phase fluids, particularly carbon dioxide, as reaction media for homogeneous, heterogeneous and phase-separable catalytic reactions in an effort to develop new, environmentally-friendly methods for chemical synthesis and processing. This approach offers the possibility of opening up substantially different chemical pathways, increasing selectivity at higher reaction rates, facilitating downstream separations and mitigating the need for hazardous solvents. Developing and understanding chemical and catalytic transformations in carbon dioxide could lead to greener chemistry at three levels: (1) Solvent replacement; (2) Better chemistry (e.g. higher reactivity, selectivity, less energy consumption); and (3) New chemistry (e.g. novel separations, use of COP{sub 2} as a C-1 source).

  18. Supercritical Water Oxidation Data Acquisition Testing

    Energy Technology Data Exchange (ETDEWEB)

    K. M. Garcia

    1996-08-01

    Supercritical Water Oxidation (SCWO) is a high pressure oxidation process that blends air, water, and organic waste material in an oxidizer in which where the temperature and pressure in the oxidizer are maintained above the critical point of water. Supercritical water mixed with hydrocarbons, which would be insoluble at subcritical conditions, forms a homogeneous phase which possesses properties associated with both a gas and a liquid. Hydrocarbons in contact with oxygen and SCW are readily oxidized. These properties of SCW make it an attractive means for the destruction of waste streams containing organic materials. SCWO technology holds great promise for treating mixed wastes in an environmentally safe and efficient manner. In the spring of 1994 the U.S. Department of Energy (DOE) initiated a Supercritical Water Oxidation Data Acquisition Testing (SCWODAT) program. The SCWODAT program provided further information and operational data on the effectiveness of treating both simulated mixed waste and typical Navy hazardous waste using the SCWO technology. The program concentrated on the acquisition of data through pilot plant testing. The Phase I DOE testing used a simulated waste stream that contained a complex machine cutting oil and metals, that acted as surrogates for radionuclides. The Phase II Navy testing included pilot testing using hazardous waste materials to demonstrate the effectiveness of the SCWO technology. The SCWODAT program demonstrated that the SCWO process oxidized the simulated waste stream containing complex machine cutting oil, selected by DOE as representative of one of the most difficult of the organic waste streams for which SCWO had been applied. The simulated waste stream with surrogate metals in solution was oxidized, with a high destruction efficiency, on the order of 99.97%, in both the neutralized and unneutralized modes of operation.

  19. Supercritical fluid thermodynamics from equations of state

    Science.gov (United States)

    Giovangigli, Vincent; Matuszewski, Lionel

    2012-03-01

    Supercritical multicomponent fluid thermodynamics are often built from equations of state. We investigate mathematically such a construction of a Gibbsian thermodynamics compatible at low density with that of ideal gas mixtures starting from a pressure law. We further study the structure of chemical production rates obtained from nonequilibrium statistical thermodynamics. As a typical application, we consider the Soave-Redlich-Kwong cubic equation of state and investigate mathematically the corresponding thermodynamics. This thermodynamics is then used to study the stability of H2-O2-N2 mixtures at high pressure and low temperature as well as to illustrate the role of nonidealities in a transcritical H2-O2-N2 flame.

  20. Supercritical-pressure light water cooled reactors

    CERN Document Server

    Oka, Yoshiaki

    2014-01-01

    This book focuses on the latest reactor concepts, single pass core and experimental findings in thermal hydraulics, materials, corrosion, and water chemistry. It highlights research on supercritical-pressure light water cooled reactors (SCWRs), one of the Generation IV reactors that are studied around the world. This book includes cladding material development and experimental findings on heat transfer, corrosion and water chemistry. The work presented here will help readers to understand the fundamental elements of reactor design and analysis methods, thermal hydraulics, materials and water

  1. Generation and Evolution of High-Mach-Number Laser-Driven Magnetized Collisionless Shocks in the Laboratory

    Science.gov (United States)

    Schaeffer, D. B.; Fox, W.; Haberberger, D.; Fiksel, G.; Bhattacharjee, A.; Barnak, D. H.; Hu, S. X.; Germaschewski, K.

    2017-07-01

    We present the first laboratory generation of high-Mach-number magnetized collisionless shocks created through the interaction of an expanding laser-driven plasma with a magnetized ambient plasma. Time-resolved, two-dimensional imaging of plasma density and magnetic fields shows the formation and evolution of a supercritical shock propagating at magnetosonic Mach number Mms≈12 . Particle-in-cell simulations constrained by experimental data further detail the shock formation and separate dynamics of the multi-ion-species ambient plasma. The results show that the shocks form on time scales as fast as one gyroperiod, aided by the efficient coupling of energy, and the generation of a magnetic barrier between the piston and ambient ions. The development of this experimental platform complements present remote sensing and spacecraft observations, and opens the way for controlled laboratory investigations of high-Mach number collisionless shocks, including the mechanisms and efficiency of particle acceleration.

  2. Generation and Evolution of High-Mach Number, Laser-Driven Magnetized Collisionless Shocks in the Laboratory

    CERN Document Server

    Schaeffer, Derek; Haberberger, Dan; Fiksel, Gennady; Bhattacharjee, Amitava; Barnak, Daniel; Hu, Suxing; Germaschewski, Kai

    2016-01-01

    Shocks act to convert incoming supersonic flows to heat, and in collisionless plasmas the shock layer forms on kinetic plasma scales through collective electromagnetic effects. These collisionless shocks have been observed in many space and astrophysical systems [Smith 1975, Smith 1980, Burlaga 2008, Sulaiman 2015], and are believed to accelerate particles, including cosmic rays, to extremely high energies [Kazanas 1986, Loeb 2000, Bamba 2003, Masters 2013, Ackermann 2013]. Of particular importance are the class of high-Mach number, supercritical shocks [Balogh 2013] ($M_A\\gtrsim4$), which must reflect significant numbers of particles back into the upstream to accommodate entropy production, and in doing so seed proposed particle acceleration mechanisms [Blandford 1978, McClements 2001, Caprioli 2014, Matsumoto 2015]. Here we present the first laboratory generation of high-Mach number magnetized collisionless shocks created through the interaction of an expanding laser-driven plasma with a magnetized ambient ...

  3. Simulating radiative shocks in nozzle shock tubes

    Science.gov (United States)

    van der Holst, B.; Tóth, G.; Sokolov, I. V.; Daldorff, L. K. S.; Powell, K. G.; Drake, R. P.

    2012-06-01

    We use the recently developed Center for Radiative Shock Hydrodynamics (CRASH) code to numerically simulate laser-driven radiative shock experiments. These shocks are launched by an ablated beryllium disk and are driven down xenon-filled plastic tubes. The simulations are initialized by the two-dimensional version of the Lagrangian Hyades code which is used to evaluate the laser energy deposition during the first 1.1 ns. Later times are calculated with the CRASH code. CRASH solves for the multi-material hydrodynamics with separate electron and ion temperatures on an Eulerian block-adaptive-mesh and includes a multi-group flux-limited radiation diffusion and electron thermal heat conduction. The goal of the present paper is to demonstrate the capability to simulate radiative shocks of essentially three-dimensional experimental configurations, such as circular and elliptical nozzles. We show that the compound shock structure of the primary and wall shock is captured and verify that the shock properties are consistent with order-of-magnitude estimates. The synthetic radiographs produced can be used for comparison with future nozzle experiments at high-energy-density laser facilities.

  4. Simulating radiative shocks in nozzle shock tubes

    CERN Document Server

    van der Holst, B; Sokolov, I V; Daldorff, L K S; Powell, K G; Drake, R P

    2011-01-01

    We use the recently developed Center for Radiative Shock Hydrodynamics (CRASH) code to numerically simulate laser-driven radiative shock experiments. These shocks are launched by an ablated beryllium disk and are driven down xenon-filled plastic tubes. The simulations are initialized by the two-dimensional version of the Lagrangian Hyades code which is used to evaluate the laser energy deposition during the first 1.1ns. The later times are calculated with the CRASH code. This code solves for the multi-material hydrodynamics with separate electron and ion temperatures on an Eulerian block-adaptive-mesh and includes a multi-group flux-limited radiation diffusion and electron thermal heat conduction. The goal of the present paper is to demonstrate the capability to simulate radiative shocks of essentially three-dimensional experimental configurations, such as circular and elliptical nozzles. We show that the compound shock structure of the primary and wall shock is captured and verify that the shock properties a...

  5. The influence of frequency-dependent radiative transfer on the structures of radiative shocks

    CERN Document Server

    Vaytet, N; Audit, E; Chabrier, G

    2013-01-01

    Radiative shocks are shocks in a gas where the radiative energy and flux coming from the very hot post-shock material are non-negligible in the shock's total energy budget, and are often large enough to heat the material ahead of the shock. Many simulations of radiative shocks, both in the contexts of astrophysics and laboratory experiments, use a grey treatment of radiative transfer coupled to the hydrodynamics. However, the opacities of the gas show large variations as a function of frequency and this needs to be taken into account if one wishes to reproduce the relevant physics. We have performed radiation hydrodynamics simulations of radiative shocks in Ar using multigroup (frequency dependent) radiative transfer with the HERACLES code. The opacities were taken from the ODALISC database. We show the influence of the number of frequency groups used on the dynamics and morphologies of subcritical and supercritical radiative shocks in Ar gas, and in particular on the extent of the radiative precursor. We fin...

  6. Effects of supercritical environment on hydrocarbon-fuel injection

    Science.gov (United States)

    Shin, Bongchul; Kim, Dohun; Son, Min; Koo, Jaye

    2017-04-01

    In this study, the effects of environment conditions on decane were investigated. Decane was injected in subcritical and supercritical ambient conditions. The visualization chamber was pressurized to 1.68 MPa by using nitrogen gas at a temperature of 653 K for subcritical ambient conditions. For supercritical ambient conditions, the visualization chamber was pressurized to 2.52 MPa by using helium at a temperature of 653 K. The decane injection in the pressurized chamber was visualized via a shadowgraph technique and gradient images were obtained by a post processing method. A large variation in density gradient was observed at jet interface in the case of subcritical injection in subcritical ambient conditions. Conversely, for supercritical injection in supercritical ambient conditions, a small density gradient was observed at the jet interface. In a manner similar to that observed in other cases, supercritical injection in subcritical ambient conditions differed from supercritical ambient conditions such as sphere shape liquid. Additionally, there were changes in the interface, and the supercritical injection core width was thicker than that in the subcritical injection. Furthermore, in cases with the same injection conditions, the change in the supercritical ambient normalized core width was smaller than the change in the subcritical ambient normalized core width owing to high specific heat at the supercritical injection and small phase change at the interface. Therefore, the interface was affected by the changing ambient condition. Given that the effect of changing the thermodynamic properties of propellants could be essential for a variable thrust rocket engine, the effects of the ambient conditions were investigated experimentally.

  7. When Shock Waves Collide

    CERN Document Server

    Hartigan, P; Frank, A; Hansen, E; Yirak, K; Liao, A S; Graham, P; Wilde, B; Blue, B; Martinez, D; Rosen, P; Farley, D; Paguio, R

    2016-01-01

    Supersonic outflows from objects as varied as stellar jets, massive stars and novae often exhibit multiple shock waves that overlap one another. When the intersection angle between two shock waves exceeds a critical value, the system reconfigures its geometry to create a normal shock known as a Mach stem where the shocks meet. Mach stems are important for interpreting emission-line images of shocked gas because a normal shock produces higher postshock temperatures and therefore a higher-excitation spectrum than an oblique one does. In this paper we summarize the results of a series of numerical simulations and laboratory experiments designed to quantify how Mach stems behave in supersonic plasmas that are the norm in astrophysical flows. The experiments test analytical predictions for critical angles where Mach stems should form, and quantify how Mach stems grow and decay as intersection angles between the incident shock and a surface change. While small Mach stems are destroyed by surface irregularities and ...

  8. Supercritical Fluid Extraction: Present Status and Prospects

    Energy Technology Data Exchange (ETDEWEB)

    King, J. W.

    2002-07-01

    Supercritical extraction (SFE), using primarily environmentally-benign carbon dioxide (CO{sub 2}) as the extraction agent, is reviewed with respect to its present status and future use. SFE was developed for analytical application in the mid 1980's in response to the desire to reduce the use of organic solvents in the laboratory environment and is becoming a standard method for the preparation and analysis of lipid-containing sample matrices. Currently, analytical SFE is predominately practiced in the off-line mode, using both sequential and parallel extraction modes. Depending on the instrumental configuration, the preparation of up to 24 samples can be accomplished on one instrument on a daily basis. Several other benefits can be achieved using SFE, such as the processing of thermally-sensitive analytes and rapid analyte extraction kinetics relative to extraction with liquid solvents. Examples are provided not only of the analytical SFE of oils and fats, but of volatile solutes from an array of sample types. Finally, the relevance of analytical SFE to processing with supercritical fluids (SFs) is documented using examples from our own research involving a combinatorial approach to optimising processing conditions. (Author) 70 refs.

  9. Performance of supercritical methanol in polyurethane degradation

    Directory of Open Access Journals (Sweden)

    Liu Lu

    2016-01-01

    Full Text Available Polyurethane is a group of block copolymer which is composed of diisocyanate, chain extender, and polyol, including polyurethane foam, polyurethane elastomer, waterborne polyurethane, etc. This research focused on thermoplastic polyurethane elastomer (TPU which is formed with 4,4’-diphenylmethane diisocyanate (MDI, poly(1,4-butanediol-hexanedioic acid diolpolyester(PBA and extended with 1,4-butanediol(BDO.The degradation of TPU was carried out with the help of methanol as the supercritical solvent. The SEM of the reaction residues revealed the process of the depolymerisation. The products were measured by GC-MS and found out to be PBA, BDO and 4,4’-methylene diphenyl carbamate(MDC which is themethylate of MDI.GC-FID, HPLC-UV and GPC were used to further analysis. The experimental results showed that supercritical methanol performed outstandingly in TPU recycling, it needed lower temperature and shorter time than regular methods. At 230°C/70min, over 90% raw materials of TPU could be recovered.

  10. Supercritical extraction of oleaginous: parametric sensitivity analysis

    Directory of Open Access Journals (Sweden)

    Santos M.M.

    2000-01-01

    Full Text Available The economy has become universal and competitive, thus the industries of vegetable oil extraction must advance in the sense of minimising production costs and, at the same time, generating products that obey more rigorous patterns of quality, including solutions that do not damage the environment. The conventional oilseed processing uses hexane as solvent. However, this solvent is toxic and highly flammable. Thus the search of substitutes for hexane in oleaginous extraction process has increased in the last years. The supercritical carbon dioxide is a potential substitute for hexane, but it is necessary more detailed studies to understand the phenomena taking place in such process. Thus, in this work a diffusive model for semi-continuous (batch for the solids and continuous for the solvent isothermal and isobaric extraction process using supercritical carbon dioxide is presented and submitted to a parametric sensitivity analysis by means of a factorial design in two levels. The model parameters were disturbed and their main effects analysed, so that it is possible to propose strategies for high performance operation.

  11. Supercritical fluid chromatography (SFC). Pt. 3. Applications

    Energy Technology Data Exchange (ETDEWEB)

    Leyendecker, D.; Hoefler, F.

    1989-05-01

    During the last few years, Supercritical Fluid Chromatography (SFC) has been emerged from an academic object of research to an important tool for the analytical chemist. Persuasive SFC-applications have been reported analyzing substrates with low volatilities, either due to high molecular weights or to high polarities, thermally or solvatolytically labile molecules, or analytes without chromophores or electroactive groups. Examples are oligomers and polymers up to a molecular weight of 10,000 g/mol, e.g., polysiloxanes, polyethers (nonionic surfactants), polyesters, polystyrenes and other vinyl polymers, polyenes etc. In addition, SFC is applicable to the analysis of several monomers. In the petroleum and coal industries, SFC was employed for the characterization of high boiling hydrocarbon mixtures as well as for group separations of alkanes, olefins, and aromatics. Due to the high solvent strength of supercritical fluids, several pesticides, herbicides, and fungicides can be determined either separately or in combination with polar metabolites. Physiologically active substances often are thermally labile and polar at the same time. SFC has been successfully applied to the analysis of steroids, prostaglandins, cannabinoids and other drugs, flavours, and medicines. It is also well suited for analyzing natural or synthetic mono-, di-, and triglycerides. (orig.).

  12. Toward Better Modeling of Supercritical Turbulent Mixing

    Science.gov (United States)

    Selle, Laurent; Okongo'o, Nora; Bellan, Josette; Harstad, Kenneth

    2008-01-01

    study was done as part of an effort to develop computational models representing turbulent mixing under thermodynamic supercritical (here, high pressure) conditions. The question was whether the large-eddy simulation (LES) approach, developed previously for atmospheric-pressure compressible-perfect-gas and incompressible flows, can be extended to real-gas non-ideal (including supercritical) fluid mixtures. [In LES, the governing equations are approximated such that the flow field is spatially filtered and subgrid-scale (SGS) phenomena are represented by models.] The study included analyses of results from direct numerical simulation (DNS) of several such mixing layers based on the Navier-Stokes, total-energy, and conservation- of-chemical-species governing equations. Comparison of LES and DNS results revealed the need to augment the atmospheric- pressure LES equations with additional SGS momentum and energy terms. These new terms are the direct result of high-density-gradient-magnitude regions found in the DNS and observed experimentally under fully turbulent flow conditions. A model has been derived for the new term in the momentum equation and was found to perform well at small filter size but to deteriorate with increasing filter size. Several alternative models were derived for the new SGS term in the energy equation that would need further investigations to determine if they are too computationally intensive in LES.

  13. Supercritical water oxidation treatment of textile sludge.

    Science.gov (United States)

    Zhang, Jie; Wang, Shuzhong; Li, Yanhui; Lu, Jinling; Chen, Senlin; Luo, XingQi

    2016-10-17

    In this work, we studied the supercritical water oxidation (SCWO) of the textile sludge, the hydrothermal conversion of typical textile compounds and the corrosion properties of stainless steel 316. Moreover, the influence mechanisms of NaOH during these related processes were explored. The results show that decomposition efficiency for organic matter in liquid phase of the textile sludge was improved with the increment of reaction temperature or oxidation coefficient. However, the organic substance in solid phase can be oxidized completely in supercritical water. Serious coking occurred during the high pressure water at 250-450°C for the Reactive Orange 7, while at 300 and 350°C for the polyvinyl alcohol. The addition of NaOH not only accelerated the destruction of organic contaminants in the SCWO reactor, but effectively inhibited the dehydration conversion of textile compounds during the preheating process, which was favorable for the treatment system of textile sludge. The corrosion experiment results indicate that the stainless steel 316 could be competent for the body materials of the reactor and the heat exchangers. Furthermore, there was prominent enhancement of sodium hydroxide for the corrosion resistance of 316 in subcritical water. On the contrary the effect was almost none during SCWO.

  14. Supercritical Fluid Extraction of Palm Carotenoids

    Directory of Open Access Journals (Sweden)

    Puah C. Wei

    2005-01-01

    Full Text Available The extraction of carotenoids from crude palm oil was carried out in a dynamic (flow- through supercritical fluid extraction system. The carotenoids obtained were quantified using off-line UV-visible spectrophotometry. The effects of operating pressure and temperature, flow rate of the supercritical carbon dioxide (SC-CO2, sample size of feed used on the solubility of palm carotenoids were investigated. The results showed that the extraction of carotenoids was governed by its solubility in the SC-CO2 and can be enhanced by increasing pressure at a constant temperature or decreasing temperature at a constant pressure. Increasing the flow rate and decreasing the sample size can reduce the extraction time but do not enhance the solubility. Palm carotenoids have very low solubility in SC-CO2 in the range of 1.31 x 10-4 g kg-1 to 1.58 x 10-3 g kg-1 for the conditions investigated in this study. The experimental data obtained were compared with those published by other workers and correlated by a density-based equation as proposed by Chrastil.

  15. Supercritical fluid extraction of Beauvericin from maize.

    Science.gov (United States)

    Ambrosino, P; Galvano, F; Fogliano, V; Logrieco, A; Fresa, R; Ritieni, A

    2004-02-27

    Beauvericin (BEA), a supercritical fluid extraction with supercritical carbon dioxide from maize was investigated. Extraction efficiencies under several different extraction conditions were examined. Pressure, temperature, extraction time, organic modifier and water matrix content (10%) were investigated. The best extraction conditions were at a temperature of 60 degrees C, 3200psi, for 30min static extraction time and methanol as modifier solvent. Extraction recovery of 36% without modifier by adding water to the matrix in the extraction vessel (reproducibility relative standard deviations (R.S.D.)=3-5%) were recorded. Extraction recovery of 76.9% with methanol as co-solvent (reproducibility R.S.D.=3-5%) was obtained. Data shows that SFE gives a lower BEA recovery compared to conventional extraction protocol with organic solvents while SFE with modifier and conventional extraction yields are comparable. BEA extract contents were determined by high pressure liquid chromatography (HPLC) with a diode array detector (DAD) at 205nm and BEA peak confirmed by LC-MS. Acetonitrile-water as mobile phase and column C-18 were both tested. Instrumental and analytical parameters were optimized in the range linear interval from 1 to 500mgkg(-1) and reached a detection limit of 2ng.

  16. Desorption of toluene from modified clays using supercritical carbon dioxide

    Directory of Open Access Journals (Sweden)

    Carneiro D. G. P.

    2004-01-01

    Full Text Available The main objective of this work is to study the regeneration capacity of modified clays using supercritical fluid. These modified clays are used as organic compound adsorvents. The experimental step was done using a packed column with the clay contaminated by toluene. The results obtained showed the influence of the density of the supercritical CO2 and of the organic modifier in the desorption process. These data were modeled with first- and second-order models. Better results were obtained using the second-order model. This study makes possible the scale-up of the desorption process for regeneration of solid matrices using supercritical fluids.

  17. High Density Thermal Energy Storage with Supercritical Fluids

    Science.gov (United States)

    Ganapathi, Gani B.; Wirz, Richard

    2012-01-01

    A novel approach to storing thermal energy with supercritical fluids is being investigated, which if successful, promises to transform the way thermal energy is captured and utilized. The use of supercritical fluids allows cost-affordable high-density storage with a combination of latent heat and sensible heat in the two-phase as well as the supercritical state. This technology will enhance penetration of several thermal power generation applications and high temperature water for commercial use if the overall cost of the technology can be demonstrated to be lower than the current state-of-the-art molten salt using sodium nitrate and potassium nitrate eutectic mixtures.

  18. Thermodynamic properties of supercritical carbon dioxide: Widom and Frenkel lines

    Science.gov (United States)

    Fomin, Yu. D.; Ryzhov, V. N.; Tsiok, E. N.; Brazhkin, V. V.

    2015-02-01

    Supercritical fluids are widely used in a number of important technological applications, yet the theoretical progress in the field has been rather moderate. Fairly recently, a new understanding of the liquidlike and gaslike properties of supercritical fluids has come to the fore, particularly with the advent of the Widom and Frenkel lines that aim to demarcate different physical properties on the phase diagram. Here, we report the results of a computational study of supercritical carbon dioxide, one of the most important fluids in the chemical industry. We study the response functions of CO2 in the supercritical state and calculate the locations of their maxima (Widom lines). We also report the preliminary calculations of the Frenkel line, the line of crossover of microscopic dynamics of particles. Our insights are relevant to physical processes in the atmosphere of Venus and its evolution.

  19. Supercritical Fluid Extraction of Aflatoxin B 1 from Soil

    Science.gov (United States)

    This research describes the development of a Supercritical Fluid Extraction (SFE) method to recover aflatoxin B1 from fortified soil. The effects of temperature, pressure, modifier (identity and percentage), and extraction type were assessed. Using the optimized SFE conditions, ...

  20. Measurement of Orotic Acid in Urine by Supercritical Fluid Chromatography

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    This work presents a simple, rapid and reliable supercritical fluid chromatography (SFC) method for a sensitive measurement of orotic acid in human urine. The samples were diluted with deionized water and analyzed directly without any pretreatment.

  1. Finite connections for supercritical Bernoulli bond percolation in 2D

    CERN Document Server

    Campanino, Massimo; Louidor, Oren

    2009-01-01

    Two vertices are said to be finitely connected if they belong to the same cluster and this cluster is finite. We derive sharp asymptotics for finite connection probabilities for supercritical Bernoulli bond percolation on Z^2.

  2. Supercritical fluid technology for energy and environmental applications

    CERN Document Server

    Anikeev, Vladimir

    2014-01-01

    Supercritical Fluid Technology for Energy and Environmental Applications covers the fundamental principles involved in the preparation and characterization of supercritical fluids (SCFs) used in the energy production and other environmental applications. Energy production from diversified resources - including renewable materials - using clean processes can be accomplished using technologies like SCFs. This book is focused on critical issues scientists and engineers face in applying SCFs to energy production and environmental protection, the innovative solutions they have found, and the challenges they need to overcome. The book also covers the basics of sub- and supercritical fluids, like the thermodynamics of phase and chemical equilibria, mathematical modeling, and process calculations. A supercritical fluid is any substance at a temperature and pressure above its critical point where distinct liquid and gas phases do not exist. At this state the compound demonstrates unique properties, which can be "fine...

  3. Simultaneous Graphite Exfoliation and N Doping in Supercritical Ammonia.

    Science.gov (United States)

    Sasikala, Suchithra Padmajan; Huang, Kai; Giroire, Baptiste; Prabhakaran, Prem; Henry, Lucile; Penicaud, Alain; Poulin, Philippe; Aymonier, Cyril

    2016-11-16

    We report the exfoliation of graphite and simultaneous N doping of graphene by two methods: supercritical ammonia treatment and liquid-phase exfoliation with NH4OH. While the supercritical ammonia allowed N doping at a level of 6.4 atom % in 2 h, the liquid-phase exfoliation with NH4OH allowed N doping at a level of 2.7 atom % in 6 h. The N doped graphene obtained via the supercritical ammonia route had few layers (supercritical ammonia as an exfoliation agent and N doping precursor for graphene. Notably, the N doped graphene showed electrocatalytic activity toward oxygen reduction reaction with high durability and good methanol tolerance compared to those of commercial Pt/C catalyst.

  4. Supercritical Fluid Extraction of Aflatoxin B 1 from Soil

    Science.gov (United States)

    This research describes the development of a Supercritical Fluid Extraction (SFE) method to recover aflatoxin B1 from fortified soil. The effects of temperature, pressure, modifier (identity and percentage), and extraction type were assessed. Using the optimized SFE conditions, ...

  5. Physical properties of the benchmark models program supercritical wing

    Science.gov (United States)

    Dansberry, Bryan E.; Durham, Michael H.; Bennett, Robert M.; Turnock, David L.; Silva, Walter A.; Rivera, Jose A., Jr.

    1993-01-01

    The goal of the Benchmark Models Program is to provide data useful in the development and evaluation of aeroelastic computational fluid dynamics (CFD) codes. To that end, a series of three similar wing models are being flutter tested in the Langley Transonic Dynamics Tunnel. These models are designed to simultaneously acquire model response data and unsteady surface pressure data during wing flutter conditions. The supercritical wing is the second model of this series. It is a rigid semispan model with a rectangular planform and a NASA SC(2)-0414 supercritical airfoil shape. The supercritical wing model was flutter tested on a flexible mount, called the Pitch and Plunge Apparatus, that provides a well-defined, two-degree-of-freedom dynamic system. The supercritical wing model and associated flutter test apparatus is described and experimentally determined wind-off structural dynamic characteristics of the combined rigid model and flexible mount system are included.

  6. Plasticisation and complexation of certain polymers in supercritical CO2

    CSIR Research Space (South Africa)

    Labuschagne, Philip W

    2004-09-01

    Full Text Available A polymer system (polyvinylpyrrolidone + polyvinyl acetate-co-crotonic acid) was successfully identified for use as encapsulation material for sensitive actives using supercritical CO2 as plasticisation medium, having the following properties: 1...

  7. Determination of solvation kinetics in supercritical fluids. Summary report

    Energy Technology Data Exchange (ETDEWEB)

    Bright, F.V.

    1993-01-01

    Objective was to study solvation processes in pure and entrainer-modified supercritical fluids. Specific topics were: Kinetics for solvation in supercritical media, influence on entrainers on solvation, reversibility of solvation, effects of solvation on intramolecular solute-solute interaction kinetics, and impact of fluid density on these processes. Time-resolved fluorescence spectroscopy was used as the main analytical tool. A summary is given of the 2.5 years` research.

  8. Supercritical hydrogenation and acid-catalysed reactions "without gases".

    Science.gov (United States)

    Hyde, Jason R; Poliakoff, Martyn

    2004-07-07

    The high temperature catalytic decomposition of HCO2H and HCO2Et are used to generate the high pressure H2 and the supercritical fluids needed for micro-scale hydrogenation of organic compounds; our approach overcomes the problems and limitations of handling high pressure gases on a small-scale and opens the way to the widespread use of continuous supercritical reactions in the laboratory.

  9. Research in Supercritical Fuel Properties and Combustion Modeling

    Science.gov (United States)

    2015-09-18

    any significant impact on the normal hydrocarbon oxidation kinetics . These are ethanol, dimethyl ether( DME ), and methyl formate (C2H5OH, CH3OCH3...research are to develop stimulated scattering as a diagnostic for supercritical fluids, and to evaluate reaction kinetics inputs involving 2-4...measurements for refractive index measurements, and tested our supercritical cell. On the reaction kinetics task, review and evaluation of reactions, rate

  10. Fischer-Tropsch synthesis in supercritical fluids. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Akgerman, A.; Bukur, D.B.

    1998-12-31

    The objective of this study was to investigate Fischer-Tropsch Synthesis (FTS) in the supercritical phase employing a commercial precipitated iron catalysts. As the supercritical fluid the authors used propane and n-hexane. The catalyst had a nominal composition of 100 Fe/5 Cu/4.2 K/25 SiO{sub 2} on mass basis and was used in a fixed bed reactor under both normal (conventional) and supercritical conditions. Experimental data were obtained at different temperatures (235 C, 250 C, and 260 C) and synthesis gas feed compositions (H{sub 2}/CO molar feed ratio of 0.67, 1.0 and 2.0) in both modes of operation under steady state conditions. The authors compared the performance of the precipitated iron catalyst in the supercritical phase, with the data obtained in gas phase (fixed bed reactor) and slurry phase (STS reactor). Comparisons were made in terms of bulk catalyst activity and various aspects of product selectivity (e.g. lumped hydrocarbon distribution and olefin content as a function of carbon number). In order to gain better understanding of the role of intraparticle mass transfer during FTS under conventional or supercritical conditions, the authors have measured diffusivities of representative hydrocarbon products in supercritical fluids, as well as their effective diffusion rates into the pores of catalyst at the reaction conditions. They constructed a Taylor dispersion apparatus to measure diffusion coefficients of hydrocarbon products of FTS in sub and supercritical ethane, propane, and hexane. In addition, they developed a tracer response technique to measure the effective diffusivities in the catalyst pores at the same conditions. Based on these results they have developed an equation for prediction of diffusion in supercritical fluids, which is based on the rough hard sphere theory.

  11. Electrochemistry in Near-Critical and Supercritical Fluids. I. Ammonia.

    Science.gov (United States)

    1984-07-18

    in a supercritical fluid containing an electrolyte. We show j here that electrocheical techniques, such as cyclic voltametry and .’ chronocoulametrY...8217,_- Electrochemistry, supercritical, ammonia S&. ASSTRACT. (CGWIU&UI VOWO *fo of Rea@ d 8~ US F &I-*I 81116 Cyclic voltanmetric and chronocoulometric studies of N...Bard 4 Department of Chemi stry, The University of Texas Austin, TX 78712 (Abstract) Cyclic voittuuntric and chronocoulometric studies of NH3

  12. Independent Research and Design of 600-MW Supercritical CFB Boiler

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    In order to further develop and improve the technologies for large-capacity supercritical CFB boiler, the key technologies for large CFB boiler were systematically studied, based on the development of first domestically-made 210-MW and 330-MW CFB boilers. The scheme of 600-MW supercritical CFB boiler was designed, including the furnace structure, key components, steam-water system and auxiliary systems, which laid a technical foundation for the engineering applications.

  13. Isolation of Organochlorine Pesticide from Ginseng with Supercritical CO2

    Institute of Scientific and Technical Information of China (English)

    李淑芬; 王幼君; 全灿; 田松江

    2005-01-01

    The feasibility of removal of the organochlorine pesticides residues of hexachlorocyclohexane(BHC) from radix ginseng with supercritical CO2 was explored. Some factors, such as extraction pressure, extraction temperature, and kinds of co-solvents were investigated. The experimental results indicate that it is possible to reduce BHC residues in radix ginseng to the level of 0.1 × 10-6 with supercritical CO2 in the presence of suitable amount of co-solvent, such as water.

  14. Extraction of olive oil with supercritical carbon dioxide / Ilana Geerdts

    OpenAIRE

    Geerdts, Ilana

    2005-01-01

    The principal objective of this study was to extract olive oil from the fruit of Olea europaea by means of supercritical carbon dioxide (sc-C02) as an alternative to traditional methods. Extractions were performed on a laboratory scale supercritical fluid extractor of the latest design, featuring three mutually independent flow systems and extremely high flow rates. A number of extraction runs based on a statistical design was performed to establish the conditions (time, pressu...

  15. Investigating Vaporization of Silica through Laser Driven Shock Wave Experiments

    Science.gov (United States)

    Kraus, R. G.; Swift, D. C.; Stewart, S. T.; Smith, R.; Bolme, C. A.; Spaulding, D. K.; Hicks, D.; Eggert, J.; Collins, G.

    2010-12-01

    Giant impacts melt and vaporize a significant amount of the bolide and target body. However, our ability to determine how much melt or vapor a given impact creates depends strongly on our understanding of the liquid-vapor phase boundary of geologic materials. Our current knowledge of the liquid-vapor equilibrium for one of the most important minerals, SiO2, is rather limited due to the difficulty of performing experiments in this area of phase space. In this study, we investigate the liquid-vapor coexistence region by shocking quartz into a supercritical fluid state and allowing it to adiabatically expand to a state on the liquid-vapor phase boundary. Although shock compression and release has been used to study the liquid-vapor equilibrium of metals [1], few attempts have been made at studying geologic materials by this method [2]. Shock waves were produced by direct ablation of the quartz sample using the Jupiter Laser Facility of Lawrence Livermore National Laboratory. Steady shock pressures of 120-360 GPa were produced in the quartz samples: high enough to force the quartz into a supercritical fluid state. As the shock wave propagates through the sample, we measure the shock velocity using a line imaging velocity interferometer system for any reflector (VISAR) and shock temperature using a streaked optical pyrometer (SOP). When the shock wave reaches the free surface of the sample, the material adiabatically expands. Upon breakout of the shock at the free surface, the SOP records a distinct drop in radiance due to the lower temperature of the expanded material. For a subset of experiments, a LiF window is positioned downrange of the expanding silica. When the expanding silica impacts the LiF window, the velocity at the interface between the expanding silica and LiF window is measured using the VISAR. From the shock velocity measurements, we accurately determine the shocked state in the quartz. The post-shock radiance measurements are used to constrain the

  16. Toxic Shock Syndrome (For Parents)

    Science.gov (United States)

    ... Feeding Your 1- to 2-Year-Old Toxic Shock Syndrome KidsHealth > For Parents > Toxic Shock Syndrome Print ... en español Síndrome de shock tóxico About Toxic Shock Syndrome Toxic shock syndrome (TSS) is a serious ...

  17. Hydrogenation of diesel aromatic compounds in supercritical solvent environment

    Directory of Open Access Journals (Sweden)

    E.P. Martins

    2000-09-01

    Full Text Available Reactions under supercritical conditions have been employed in many processes. Furthermore, an increasing number of commercial reactions have been conducted under supercritical or near critical conditions. These reaction conditions offer several advantages when compared to conditions in conventional catalytic processes in liquid-phase, gas-liquid interface, or even some gas-phase reactions. Basically, a supercritical solvent can diminish the reactant’s transport resistance from the bulk region to the catalyst surface due to enhancement of liquid diffusivity values and better solubility than those in different phases. Another advantage is that supercritical solvents permit prompt and easy changes in intermolecular properties in order to modify reaction parameters, such as conversion or selectivity, or even proceed with the separation of reaction products. Diesel fractions from petroleum frequently have larger than desirable quantities of aromatic compounds. Diesel hydrogenation is intended to decrease these quantities, i.e., to increase the quantity of paraffin present in this petroleum fraction. In this work, the hydrogenation of tetralin was studied as a model reaction for the aromatic hydrogenation process. A conventional gas-liquid-solid catalytic process was compared with that of supercritical carbon dioxide substrate under similar conditions. Additionally, an equilibrium conversion diagram was calculated for this reaction in a wide range of temperature and reactant ratios, so as to optimize the operational conditions and improve the results of subsequent experiments. An increase in the rate of reaction at 493 K in supercritical fluid, as compared to that in the conventional process, was observed.

  18. Effects of Gravity on Supercritical Water Oxidation (SCWO) Processes

    Science.gov (United States)

    Hegde, Uday; Hicks, Michael

    2013-01-01

    The effects of gravity on the fluid mechanics of supercritical water jets are being studied at NASA to develop a better understanding of flow behaviors for purposes of advancing supercritical water oxidation (SCWO) technologies for applications in reduced gravity environments. These studies provide guidance for the development of future SCWO experiments in new experimental platforms that will extend the current operational range of the DECLIC (Device for the Study of Critical Liquids and Crystallization) Facility on board the International Space Station (ISS). The hydrodynamics of supercritical fluid jets is one of the basic unit processes of a SCWO reactor. These hydrodynamics are often complicated by significant changes in the thermo-physical properties that govern flow behavior (e.g., viscosity, thermal conductivity, specific heat, compressibility, etc), particularly when fluids transition from sub-critical to supercritical conditions. Experiments were conducted in a 150 ml reactor cell under constant pressure with water injections at various flow rates. Flow configurations included supercritical jets injected into either sub-critical or supercritical water. Profound gravitational influences were observed, particularly in the transition to turbulence, for the flow conditions under study. These results will be presented and the parameters of the flow that control jet behavior will be examined and discussed.

  19. Hydrogenation of diesel aromatic compounds in supercritical solvent environment

    Energy Technology Data Exchange (ETDEWEB)

    Martins, E.P.; Aranda, D.A.G.; Pessoa, F.L.P. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Escola de Quimica. Dept. de Engenharia Quimica. E-mail: donato@h2o.eq.ufrj.br; pessoa@h2o.eq.ufrj.br; Zotin, J.L. [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas. E-mail: zotin@cenpes.petrobras.com.br

    2000-09-01

    Reactions under supercritical conditions have been employed in many processes. Furthermore, an increasing number of commercial reactions have been conducted under supercritical or near critical conditions. These reaction conditions offer several advantages when compared to conditions in conventional catalytic processes in liquid-phase, gas-liquid interface., or even some gas-phase reactions. basically, a supercritical solvent can diminish the reactant's transport resistance from the bulk region to the catalyst surface due to enhancement of liquid diffusivity values and better solubility than those in different phases. Another advantage is that supercritical solvents permit prompt and easy changes in intermolecular properties in order to modify reaction parameters, such as conversion or selectivity, or even proceed with the separation of reaction products. Diesel fractions from petroleum frequently have larger than desirable quantities of aromatic compounds. Diesel hydrogenation is intended to decrease these quantities, to increase the quantity of paraffin present in this petroleum fraction. In this work, the hydrogenation of tetralin was studied as a model reaction for the aromatic hydrogenation process. A conventional gas-liquid-solid catalytic process was compared with that of supercritical carbon dioxide substrate under similar conditions. Additionally, an equilibrium conversion diagram was calculated for this reaction in a wide range of temperature and reactant ratios, so as to optimize the operational conditions and improve the results of subsequent experiments. An increase in the rate of reaction at 493 K in supercritical fluid, as compared to that in the conventional process, was observed. (author)

  20. Supercritical extraction of lycopene from tomato industrial wastes with ethane.

    Science.gov (United States)

    Nobre, Beatriz P; Gouveia, Luisa; Matos, Patricia G S; Cristino, Ana F; Palavra, António F; Mendes, Rui L

    2012-07-11

    Supercritical fluid extraction of all-E-lycopene from tomato industrial wastes (mixture of skins and seeds) was carried out in a semi-continuous flow apparatus using ethane as supercritical solvent. The effect of pressure, temperature, feed particle size, solvent superficial velocity and matrix initial composition was evaluated. Moreover, the yield of the extraction was compared with that obtained with other supercritical solvents (supercritical CO₂ and a near critical mixture of ethane and propane). The recovery of all-E-lycopene increased with pressure, decreased with the increase of the particle size in the initial stages of the extraction and was not practically affected by the solvent superficial velocity. The effect of the temperature was more complex. When the temperature increased from 40 to 60 °C the recovery of all-E-lycopene increased from 80 to 90%. However, for a further increase to 80 °C, the recovery remained almost the same, indicating that some E-Z isomerization could have occurred, as well as some degradation of lycopene. The recovery of all-E-lycopene was almost the same for feed samples with different all-E-lycopene content. Furthermore, when a batch with a higher all-E-lycopene content was used, supercritical ethane and a near critical mixture of ethane and propane showed to be better solvents than supercritical CO₂ leading to a faster extraction with a higher recovery of the carotenoid.

  1. High Materials Performance in Supercritical CO2 in Comparison with Atmospheric Pressure CO2 and Supercritical Steam

    Energy Technology Data Exchange (ETDEWEB)

    Holcomb, Gordon [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Tylczak, Joseph [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Carney, Casey [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Dogan, Omer N. [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States)

    2017-02-26

    This presentation covers environments (including advanced ultra-supercritical (A-USC) steam boiler/turbine and sCO2 indirect power cycle), effects of pressure, exposure tests, oxidation results, and mechanical behavior after exposure.

  2. Reactions of supercritical water and supercritical methanol with benzaldehyde; Chorinkaisui oyobi chorinkai methanol to benzaldehyde tono hanno

    Energy Technology Data Exchange (ETDEWEB)

    Yokoyama, C.; Yasuda, T.; Nishi, K.; Takahashi, S. [Tohoku University, Sendai (Japan). Institute for Chemical Reaction Science

    1996-11-01

    The reactions of supercritical water and supercritical methanol with benzaldehyde have been examined in the temperature range from 553 to 693 K, and the reaction pathways have been examined from the temporal variations of the reaction products. For the reaction of benzaldehyde with supercritical water, the major product was benzene, which was formed from the pyrolysis of benzaldehyde. The benzoic acid and benzyl alcohol were the by-products, produced from the Cannizzaro-type disproportionation reaction of benzaldehyde with the hydrate formed from the reaction with water and benzaldehyde. The major product for the reaction of benzaldehyde with supercritical methanol was benzyl alcohol, and the by-product were dimethylacetal, benzene, and methyl benzoic acid. Under the reaction conditions of this study, a significant amount of acetal was produced from benzaldehyde and methanol. The pyrolysis of acetal yielded benzyl alcohol. 29 refs., 6 figs., 4 tabs.

  3. Streptococcal toxic shock syndrome

    Directory of Open Access Journals (Sweden)

    Gvozdenović Ljiljana

    2010-01-01

    Full Text Available Introduction. Streptococcal toxic shock syndrome is now recognized as a toxin-mediated, multisystem illness. It is characterized by an early onset of shock with multiorgan failure and continues to be associated with high morbidity and mortality, caused by group A Streptococcus pyogenes. The symptoms for staphylococcal and streptococcal toxic shock syndrome are similar. Streptococcal toxic shock syndrome was not well described until 1993, when children who had suffered from varicella presented roughly 2-4 weeks later with a clinical syndrome highly suggestive of toxic shock syndrome. Characteristics, complications and therapy. It is characterized by a sudden onset of fever, chills, vomiting, diarrhea, muscle aches and rash. It can rapidly progress to severe and intractable hypotension and multisystem dysfunction. Almost every organ system can be involved. Complications of streptococcal toxic shock syndrome may include kidney failure, liver failure and even death. Crystalloids and inotropic agents are used to treat the hypovolemic shock aggressively, with close monitoring of the patient’s mean arterial pressure and central venous pressure. An immediate and aggressive management of hypovolemic shock is essential in streptococcal toxic shock syndrome. Targeted antibiotics are indicated; penicillin or a betalactam antibiotic is used for treating group A streptococci, and clindamycin has emerged as a key portion of the standard treatment.

  4. When Shock Waves Collide

    Science.gov (United States)

    Hartigan, P.; Foster, J.; Frank, A.; Hansen, E.; Yirak, K.; Liao, A. S.; Graham, P.; Wilde, B.; Blue, B.; Martinez, D.; Rosen, P.; Farley, D.; Paguio, R.

    2016-06-01

    Supersonic outflows from objects as varied as stellar jets, massive stars, and novae often exhibit multiple shock waves that overlap one another. When the intersection angle between two shock waves exceeds a critical value, the system reconfigures its geometry to create a normal shock known as a Mach stem where the shocks meet. Mach stems are important for interpreting emission-line images of shocked gas because a normal shock produces higher postshock temperatures, and therefore a higher-excitation spectrum than does an oblique shock. In this paper, we summarize the results of a series of numerical simulations and laboratory experiments designed to quantify how Mach stems behave in supersonic plasmas that are the norm in astrophysical flows. The experiments test analytical predictions for critical angles where Mach stems should form, and quantify how Mach stems grow and decay as intersection angles between the incident shock and a surface change. While small Mach stems are destroyed by surface irregularities and subcritical angles, larger ones persist in these situations and can regrow if the intersection angle changes to become more favorable. The experimental and numerical results show that although Mach stems occur only over a limited range of intersection angles and size scales, within these ranges they are relatively robust, and hence are a viable explanation for variable bright knots observed in Hubble Space Telescope images at the intersections of some bow shocks in stellar jets.

  5. Anti-Shock Garment

    Science.gov (United States)

    1996-01-01

    Ames Research Center developed a prototype pressure suit for hemophiliac children, based on research of astronauts' physiological responses in microgravity. Zoex Corporation picked up the design and patents and developed an anti-shock garment for paramedic use. Marketed by Dyna Med, the suit reverses the effect of shock on the body's blood distribution by applying counterpressure to the legs and abdomen, returning blood to vital organs and stabilizing body pressure until the patient reaches a hospital. The DMAST (Dyna Med Anti-Shock Trousers) employ lower pressure than other shock garments, and are non-inflatable.

  6. Chiral Shock Waves

    CERN Document Server

    Sen, Srimoyee

    2016-01-01

    We study shock waves in relativistic chiral matter. We argue that the conventional Rankine- Hugoinot relations are modified due to the presence of chiral transport phenomena. We show that the entropy discontinuity in a weak shock wave is linearly proportional to the pressure discontinuity when the effect of chiral transport becomes sufficiently large. We also show that rarefaction shock waves, which do not exist in usual nonchiral fluids, can appear in chiral matter. These features are exemplified by shock propagation in dense neutrino matter in the hydrodynamic regime.

  7. Formation of energetic materials using supercritical fluids

    Energy Technology Data Exchange (ETDEWEB)

    Teipel, U.; Kroeber, H.; Krause, H.H. [Fraunhofer-Institut fuer Chemische Technologie (ICT), Pfinztal (Germany)

    2001-10-01

    A new field of applications of compressed gases is the formation of solid particles with well-defined properties, e.g. the particle size, the particle size distribution, the particle shape, the specific surface area and free of solvent inclusions. It is possible to process moderately solids like energetic materials which are difficult to comminute due to their sensitivity to mechanical or thermal stress. The characteristics of compressed gases allow to vary the morphology of solid particles in a wide range. A pilot plant is presented, which has been built to prepare fine particles by the rapid expansion of supercritical solutions (RESS process) and precipitation by a compressed fluid antisolvent (PCA process). In this contribution the micronization of different energetic materials by the RESS and PCA processes will be under investigation. (orig.)

  8. Thermodynamic properties of superheated and supercritical steam

    Energy Technology Data Exchange (ETDEWEB)

    Malhotra, A. [Indian Inst. of Technology, New Delhi (India). Dept. of Mechanical Engineering; Panda, D.M.R. [Dadri Gas Power Station, NTPC, Gautam Buddha Nagar (India)

    2001-07-01

    An existing formulation for steam properties is due to Irvine and Liley. Their equations are convenient to program and do not require excessive computational time to produce results. The properties computed from these equations compare favourably with standard data. An additional advantage of these equations is that they follow prescribed theoretical trends by reducing to perfect-gas behaviour away from the saturation dome. However, a difficulty with these equations is that, at pressures above 10 MPa and close to the saturation dome, unacceptably large errors (above 10%) are produced. These equations are examined in the present work with a view towards enhancing their range of application through the use of additional functions. It is shown that the errors may be reduced to within 1% over the entire range of pressures (both sub-critical and super-critical pressures) required in steam-plant calculations. (author)

  9. Gasification of cyanobacterial in supercritical water.

    Science.gov (United States)

    Zhang, Huiwen; Zhu, Wei; Xu, Zhirong; Gong, Miao

    2014-01-01

    Cyanobacterial collected from eutrophic freshwater lakes constituted intractable waste with a rich algae biomass content. Supercritical water gasification (SCWG) was proposed to treat the cyanobacterial and to produce hydrogen for energy. The H 2 yield reached 2.92 mol/kg at reaction conditions of 500 °C, 30 min and 22 MPa; this yield accounted for 26% of the total gaseous products. Abundant ammonia and dissolved reactive phosphorous were concentrated in the liquid product, which could be recovered and used as a liquid fertilizer. Solid residue, which accounted only for about 1% of the wet weight, was mainly composed of coke and ash. The efficiency of H 2 production was better than that from other biomass, because of the abundant organic matter in cyanobacterial. Thus, cyanobacterial are an ideal biomass feedstock for H 2 production from SCWG.

  10. Supercritical droplet combustion and related transport phenomena

    Science.gov (United States)

    Yang, Vigor; Hsieh, K. C.; Shuen, J. S.

    1993-01-01

    An overview of recent advances in theoretical analyses of supercritical droplet vaporization and combustion is conducted. Both hydrocarbon and cryogenic liquid droplets over a wide range of thermodynamic states are considered. Various important high-pressure effects on droplet behavior, such as thermodynamic non-ideality, transport anomaly, and property variation, are reviewed. Results indicate that the ambient gas pressure exerts significant control of droplet gasification and burning processes through its influence on fluid transport, gas-liquid interfacial thermodynamics, and chemical reactions. The droplet gasification rate increases progressively with pressure. However, the data for the overall burnout time exhibit a considerable change in the combustion mechanism at the criticl pressure, mainly as a result of reduced mass diffusivity and latent heat of vaporization with increased pressure. The influence of droplet size on the burning characteristics is also noted.

  11. Supercritical Antisolvent Precipitation of Microparticles of Quercetin

    Institute of Scientific and Technical Information of China (English)

    刘学武; 李志义; 韩冰; 苑塔亮

    2005-01-01

    Supercritical antisolvent (SAS) process is a recently developed technology to produce micro- and nanoparticles. This paper presents a continuous apparatus to conduct experiment of SAS process. With the apparatus,the effects of pressure, temperature and flow ratio of CO2 to the solution on the shape and size of particles are studied for the quercetin-ethanol-CO2 system. Spherical quercetin microparticles with diameters ranging form i μm to 6μm can be obtained while ethanol is used as organic solvent. The most effective fact on the shape and size of particles is pressure, the next is temperature and the last is the flow ratio of CO2 to solution.

  12. Etching of glass microchips with supercritical water.

    Science.gov (United States)

    Karásek, Pavel; Grym, Jakub; Roth, Michal; Planeta, Josef; Foret, František

    2015-01-07

    A novel method of etching channels in glass microchips with the most tunable solvent, water, was tested as an alternative to common hydrogen fluoride-containing etchants. The etching properties of water strongly depend on temperature and pressure, especially in the vicinity of the water critical point. The chips were etched at the subcritical, supercritical and critical temperature of water, and the resulting channel shape, width, depth and surface morphology were studied by scanning electron microscopy and 3D laser profilometry. Channels etched with the hot water were compared with the chips etched with standard hydrogen fluoride-containing solution. Depending on the water pressure and temperature, the silicate dissolved from the glass could be re-deposited on the channel surface. This interesting phenomenon is described together with the conditions necessary for its utilization. The results illustrate the versatility of pure water as a glass etching and surface morphing agent.

  13. Gas dynamics of heat-release-induced waves in supercritical fluids: revisiting the Piston Effect

    Science.gov (United States)

    Migliorino, Mario Tindaro; Scalo, Carlo

    2016-11-01

    We investigate a gasdynamic approach to the modeling of heat-release-induced compression waves in supercritical fluids. We rely on highly resolved one-dimensional fully compressible Navier-Stokes simulations of CO2 at pseudo-boiling conditions in a closed duct inspired by the experiments of Miura et al.. Near-critical fluids exhibit anomalous variations of thermodynamic variables taken into account by adopting the Peng-Robinson equation of state and Chung's Method. An idealized heat source is applied, away from the boundaries, resulting in the generation of compression waves followed by contact discontinuities bounding a region of hot expanding fluid. For higher heat-release rates such compressions are coalescent with distinct shock-like features (i.e. non-isentropicity and propagation Mach numbers measurably greater than unity) and a non-uniform post-shock state, not present in ideal gas simulations, caused by the highly nonlinear equation of state. Thermoacoustic effects are limited to: (1) a one-way/one-time thermal-to-acoustic energy conversion, and (2) cumulative non-isentropic bulk heating due to the resonating compression waves, resulting in what is commonly referred to as the Piston Effect.

  14. Supercritical water oxidation of landfill leachate.

    Science.gov (United States)

    Wang, Shuzhong; Guo, Yang; Chen, Chongming; Zhang, Jie; Gong, Yanmeng; Wang, Yuzhen

    2011-01-01

    In this paper, ammonia as an important ingredient in landfill leachate was mainly studied. Based on Peng-Robinson formulations and Gibbs free energy minimization method, the estimation of equilibrium composition and thermodynamic analysis for supercritical water oxidation of ammonia (SCWO) was made. As equilibrium is reached, ammonia could be totally oxidized in SCW. N(2) is the main product, and the formation of NO(2) and NO could be neglected. The investigation on SCWO of landfill leachate was conducted in a batch reactor at temperature of 380-500 °C, reaction time of 50-300s and pressure of 25 MPa. The effect of reaction parameters such as oxidant equivalent ratio, reaction time and temperature were investigated. The results showed that COD and NH(3) conversion improved as temperature, reaction time and oxygen excess increased. Compared to organics, NH(3) is a refractory compound in supercritical water. The conversion of COD and NH(3) were higher in the presence of MnO(2) than that without catalyst. The interaction between reaction temperature and time was analyzed by using response surface method (RSM) and the results showed that its influence on the NH(3) conversion was relatively insignificant in the case without catalyst. A global power-law rate expression was regressed from experimental data to estimate the reaction rate of NH(3). The activation energy with and without catalyst for NH(3) oxidation were 107.07 ± 8.57 kJ/mol and 83.22 ± 15.62 kJ/mol, respectively.

  15. Thermodynamics of giant planet formation: shocking hot surfaces on circumplanetary discs

    Science.gov (United States)

    Szulágyi, J.; Mordasini, C.

    2017-02-01

    The luminosity of young giant planets can inform about their formation and accretion history. The directly imaged planets detected so far are consistent with the `hot-start' scenario of high entropy and luminosity. If nebular gas passes through a shock front before being accreted into a protoplanet, the entropy can be substantially altered. To investigate this, we present high-resolution, three-dimensional radiative hydrodynamic simulations of accreting giant planets. The accreted gas is found to fall with supersonic speed in the gap from the circumstellar disc's upper layers on to the surface of the circumplanetary disc and polar region of the protoplanet. There it shocks, creating an extended hot supercritical shock surface. This shock front is optically thick; therefore, it can conceal the planet's intrinsic luminosity beneath. The gas in the vertical influx has high entropy which when passing through the shock front decreases significantly while the gas becomes part of the disc and protoplanet. This shows that circumplanetary discs play a key role in regulating a planet's thermodynamic state. Our simulations furthermore indicate that around the shock surface extended regions of atomic - sometimes ionized - hydrogen develop. Therefore, circumplanetary disc shock surfaces could influence significantly the observational appearance of forming gas giants.

  16. Diffusive Shock Acceleration at Cosmological Shock Waves

    CERN Document Server

    Kang, Hyesung

    2012-01-01

    We reexamine nonlinear diffusive shock acceleration (DSA) at cosmological shocks in the large scale structure of the Universe, incorporating wave-particle interactions that are expected to operate in collisionless shocks. Adopting simple phenomenological models for magnetic field amplification (MFA) by cosmic-ray (CR) streaming instabilities and Alfv'enic drift, we perform kinetic DSA simulations for a wide range of sonic and Alfv'enic Mach numbers and evaluate the CR injection fraction and acceleration efficiency. In our DSA model the CR acceleration efficiency is determined mainly by the sonic Mach number Ms, while the MFA factor depends on the Alfv'enic Mach number and the degree of shock modification by CRs. We show that at strong CR modified shocks, if scattering centers drift with an effective Alfv'en speed in the amplified magnetic field, the CR energy spectrum is steepened and the acceleration efficiency is reduced significantly, compared to the cases without such effects. As a result, the postshock C...

  17. Toxic Shock Syndrome (For Teens)

    Science.gov (United States)

    ... Surgery? A Week of Healthy Breakfasts Shyness Toxic Shock Syndrome KidsHealth > For Teens > Toxic Shock Syndrome Print ... it, then take some precautions. What Is Toxic Shock Syndrome? If you're a girl who's had ...

  18. Preliminary Design of In-Pile Supercritical Pressurized Water Test Loop

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>Based on two proven technologies, current light water reactors (LWRs) and the supercritical coal-fired power plants, the supercritical water-cooled reactor (SCWR) is one of the six Generation-Ⅳ

  19. SUPERCRITICAL FLUID EXTRACTION OF POLYCYCLIC AROMATIC HYDROCARBON MIXTURES FROM CONTAMINATED SOILS

    Science.gov (United States)

    Highly contaminated (with PAHs) topsoils were extracted with supercritical CO2 to determine the feasibility and mechanism of supercritical fluid extraction (SFE). Effect of SCF density, temperature, cosolvent type and amount, and of slurrying the soil with water were ...

  20. Climate shocks and conflict

    NARCIS (Netherlands)

    Papaioannou, Kostadis J.

    2016-01-01

    This paper offers a historical micro-level analysis of the impact of climate shocks on the incidence of civil conflict in colonial Nigeria (1912-1945). Primary historical sources on court cases, prisoners and homicides are used to capture conflict. To measure climate shocks we use the deviation f

  1. [Historical vision of shock].

    Science.gov (United States)

    Dosne Pasqualini, C

    1998-01-01

    The concept of shock and its close relationship with that of stress dates back to the experiments of Hans Selye initiated in 1936 at McGill University in Montreal, with whom I collaborated between 1939 and 1942. It was demonstrated that the General Adaptation Syndrome begins with an Alarm Reaction, which consists of a Stage of Shock and one of Counter-Shock, followed by a Stage of Adaptation and finally a Stage of Exhaustion. My Ph.D. thesis concluded that shock was due to an adrenal insufficiency postulating that active metabolic processes drain the body of certain essential compounds the lack of which causes shock. My interest in the role of the glucose metabolism in shock led me to work with Bernardo Houssay in 1942 at the Institute of Physiology of the University of Buenos Aires and in 1944 with C.N.H. Long at Yale University. There I developed a method for the induction of hemorrhagic shock in the guinea pig with 94% lethality; curiously, the administration of 200 mg of ascorbic acid prevented death. Upon my return to Buenos Aires, these results were confirmed and moreover, it was demonstrated that the administration of cortisone led to 40% survival of the animals while desoxycorticosterone had no effect. At the time, no explanation was available but to-day, half a century later, this Symposium should be able to explain the mechanisms leading to death by hemorrhagic shock.

  2. [Shock waves in orthopedics].

    Science.gov (United States)

    Haupt, G

    1997-05-01

    Extracorporeal shock waves have revolutionized urological stone treatment. Nowadays shock waves are widely used in orthopedics, too. This article reviews the applications of extracorporeal shock waves on bone and adjacent soft tissue. The osteoneogenetic effect of extracorporeal shock waves has been proven and can be used to treat pseudarthrosis with a success rate of around 75%. Shock waves have a positive effect in tennis and golfer's elbow, calcaneal spur, and the complex called "periarthritis humero-scapularis." The mechanism for this is not yet known, and results from large prospective and randomized studies are still lacking. However, the treatment has been performed many thousands of times. In patients in whom conservative treatment has failed surgery used to be the only choice, but its success rate barely exceeds that of shock wave therapy and surgery can still be done if shock wave therapy fails. Extracorporeal shock waves will have an impact on orthopedics comparable to its effect in urology. Scientific evaluations, professional certifications, quality assurance and reimbursement issues present great challenges.

  3. The Shock Routine

    DEFF Research Database (Denmark)

    van Hooren, Franca; Kaasch, Alexandra; Starke, Peter

    2014-01-01

    in Australia, Belgium, the Netherlands and Sweden over the course of four global economic shocks, we ask whether the notion of critical junctures is useful in understanding the nature of change triggered by crisis. The main empirical finding is that fundamental change in the aftermath of an exogenous shock...

  4. Our Favorite Film Shocks

    DEFF Research Database (Denmark)

    Willerslev, Rane; Suhr, Christian

    2014-01-01

    shocks? In this text we exchange personal experiences of cinematic shocks and ponder over these questions as related to wider theories on human trauma, emancipation, and enlightenment. In conclusion we argue for a revision of anthropological notions of validity in terms of the efficacy of the cinematic...

  5. Reflection of curved shock waves

    Science.gov (United States)

    Mölder, S.

    2017-03-01

    Shock curvatures are related to pressure gradients, streamline curvatures and vorticity in flows with planar and axial symmetry. Explicit expressions, in an influence coefficient format, are used to relate post-shock pressure gradient, streamline curvature and vorticity to pre-shock gradients and shock curvature in steady flow. Using higher order, von Neumann-type, compatibility conditions, curved shock theory is applied to calculate the flow near singly and doubly curved shocks on curved surfaces, in regular shock reflection and in Mach reflection. Theoretical curved shock shapes are in good agreement with computational fluid dynamics calculations and experiment.

  6. Reflection of curved shock waves

    Science.gov (United States)

    Mölder, S.

    2017-09-01

    Shock curvatures are related to pressure gradients, streamline curvatures and vorticity in flows with planar and axial symmetry. Explicit expressions, in an influence coefficient format, are used to relate post-shock pressure gradient, streamline curvature and vorticity to pre-shock gradients and shock curvature in steady flow. Using higher order, von Neumann-type, compatibility conditions, curved shock theory is applied to calculate the flow near singly and doubly curved shocks on curved surfaces, in regular shock reflection and in Mach reflection. Theoretical curved shock shapes are in good agreement with computational fluid dynamics calculations and experiment.

  7. Industrial applications and current trends in supercritical fluid technologies

    Directory of Open Access Journals (Sweden)

    Gamse Thomas

    2005-01-01

    Full Text Available Supercritical fluids have a great potential for wide fields of processes Although CO2 is still one of the most used supercritical gases, for special purposes propane or even fluorinated-chlorinated fluids have also been tested. The specific characteristics of supercritical fluids behaviour were analyzed such as for example the solubilities of different components and the phase equilibria between the solute and solvent. The application at industrial scale (decaffeinating of tea and coffee, hop extraction or removal of pesticides from rice, activity in supercritical extraction producing total extract from the raw material or different fractions by using the fractionated separation of beverages (rum, cognac, whisky, wine, beer cider, of citrus oils and of lipids (fish oils, tall oil were also discussed. The main interest is still for the extraction of natural raw materials producing food ingredients, nutraceuticals and phytopharmaceuticals but also cleaning purposes were tested such as the decontamination of soils the removal of residual solvents from pharmaceutical products, the extraction of flame retardants from electronic waste or precision degreasing and cleaning of mechanical and electronic parts. An increasing interest obviously exists for impregnation purposes based on supercritical fluids behaviour, as well as for the dying of fibres and textiles. The production of fine particles in the micron and submicron range, mainly for pharmaceutical products is another important application of supercritical fluids. Completely new products can be produced which is not possible under normal conditions. Supercritical fluid technology has always had to compete with the widespread opinion that these processes are very expensive due to very high investment costs in comparison with classical low-pressure equipment. Thus the opinion is that these processes should be restricted to high-added value products. A cost estimation for different plant sizes and

  8. Supercritical fluid reactions for coal processing. Quarterly progress report, April 1, 1996--June 30, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Eckert, C.A.

    1996-11-01

    Exciting opportunities exist for the application of supercritical fluid (SCF) reactions for the pre-treatment of coal. Utilizing reactants which resemble the organic nitrogen containing components of coal, we propose to develop a method to tailor chemical reactions in supercritical fluid solvents for the specific application of coal denitrogenation. The tautomeric equilibrium of a Schiff base was chosen as the model system and was investigated in supercritical ethane and cosolvent modified supercritical ethane.

  9. Supercritical fluid reactions for coal processing. Quarterly report, January 1, 1996--March 31, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Eckert, C.A.

    1996-10-01

    Exciting opportunities exist for the application of supercritical fluid (SCF) reactions for the pre-treatment of coal. Utilizing reactants which resemble the organic nitrogen containing components of coal, we propose to develop a method to tailor chemical reactions in supercritical fluid solvents for the specific application of coal denitrogenation. The tautomeric equilibrium of a Schiff base was chosen as the model system and was investigated in supercritical ethane and cosolvent modified supercritical ethane.

  10. Characteristics of Hydraulic Shock Waves in an Inclined Chute Contraction by Using Three Dimensional Numerical Model

    Science.gov (United States)

    Hsiao, Kai-Wen; Hsu, Yu-Chao; Jan, Chyan-Deng; Su, Yu-Wen

    2016-04-01

    The inclined rectangular chute construction is a common structure used in hydraulic engineering for typical reasons such as the increase of bottom slope, the transition from side channel intakes to tunnel spillways, the drainage construction, and the reduction of chute width due to bridges, flood diversion structures or irrigation systems. The converging vertical sidewalls of a chute contraction deflect the supercritical flow to form hydraulic shock waves. Hydraulic shock waves have narrow and locally extreme wavy surfaces, which commonly results in the requirement of higher height of sidewalls. Therefore, predicting the possible height and position of maximum hydraulic shock wave are necessary to design the required height of sidewalls to prevent flow overtopping. In this study, we used a three-dimensional computation fluid dynamics model (i.e., FLOW-3D) to simulate the characteristics of hydraulic shock waves in an inclined chute contraction. For this purpose, the parameters of simulated hydraulic shock wave, such as the shock angle, maximum shock wave height and maximum shock wave position in various conditions are compared with those calculated by the empirical relations obtained from literatures. We showed that the simulated results are extremely close to the experimental results. The numerical results validated the applicability of these empirical relations and extend their applicability to higher approach Froude numbers from 3.51 to 7.27. Furthermore, we also applied the Yuan-Shan-Tsu flood diversion channel under 200-year peak flow condition to FLOW-3D model to simulate the hydraulic shock waves and validate the effect of the installation of a diversion pier in the channel on promoting the stability of flow fluid. The results revealed that a diversion pier installed in the Yuan-Shan-Tsu flood diversion channel is helpful for improving the stability of flow field. In summary, this study demonstrates that FLOW-3D model can be used to simulate the

  11. Topics in Chemical Instrumentation--An Introduction to Supercritical Fluid Chromatography: Part 1: Principles and Instrumentation.

    Science.gov (United States)

    Palmieri, Margo D.

    1988-01-01

    Identifies the properties and characteristics of supercritical fluids. Discusses the methodology for supercritical fluid chromatography including flow rate, plate height, column efficiency, viscosity, and other factors. Reviews instruments, column types, and elution conditions. Lists supercritical fluid data for 22 compounds, mostly organic. (MVL)

  12. Reaction kinetics of cellulose hydrolysis in subcritical and supercritical water

    Science.gov (United States)

    Olanrewaju, Kazeem Bode

    The uncertainties in the continuous supply of fossil fuels from the crisis-ridden oil-rich region of the world is fast shifting focus on the need to utilize cellulosic biomass and develop more efficient technologies for its conversion to fuels and chemicals. One such technology is the rapid degradation of cellulose in supercritical water without the need for an enzyme or inorganic catalyst such as acid. This project focused on the study of reaction kinetics of cellulose hydrolysis in subcritical and supercritical water. Cellulose reactions at hydrothermal conditions can proceed via the homogeneous route involving dissolution and hydrolysis or the heterogeneous path of surface hydrolysis. The work is divided into three main parts. First, the detailed kinetic analysis of cellulose reactions in micro- and tubular reactors was conducted. Reaction kinetics models were applied, and kinetics parameters at both subcritical and supercritical conditions were evaluated. The second major task was the evaluation of yields of water soluble hydrolysates obtained from the hydrolysis of cellulose and starch in hydrothermal reactors. Lastly, changes in molecular weight distribution due to hydrothermolytic degradation of cellulose were investigated. These changes were also simulated based on different modes of scission, and the pattern generated from simulation was compared with the distribution pattern from experiments. For a better understanding of the reaction kinetics of cellulose in subcritical and supercritical water, a series of reactions was conducted in the microreactor. Hydrolysis of cellulose was performed at subcritical temperatures ranging from 270 to 340 °C (tau = 0.40--0.88 s). For the dissolution of cellulose, the reaction was conducted at supercritical temperatures ranging from 375 to 395 °C (tau = 0.27--0.44 s). The operating pressure for the reactions at both subcritical and supercritical conditions was 5000 psig. The results show that the rate-limiting step in

  13. 10 MW Supercritical CO2 Turbine Test

    Energy Technology Data Exchange (ETDEWEB)

    Turchi, Craig

    2014-01-29

    The Supercritical CO2 Turbine Test project was to demonstrate the inherent efficiencies of a supercritical carbon dioxide (s-CO2) power turbine and associated turbomachinery under conditions and at a scale relevant to commercial concentrating solar power (CSP) projects, thereby accelerating the commercial deployment of this new power generation technology. The project involved eight partnering organizations: NREL, Sandia National Laboratories, Echogen Power Systems, Abengoa Solar, University of Wisconsin at Madison, Electric Power Research Institute, Barber-Nichols, and the CSP Program of the U.S. Department of Energy. The multi-year project planned to design, fabricate, and validate an s-CO2 power turbine of nominally 10 MWe that is capable of operation at up to 700°C and operates in a dry-cooled test loop. The project plan consisted of three phases: (1) system design and modeling, (2) fabrication, and (3) testing. The major accomplishments of Phase 1 included: Design of a multistage, axial-flow, s-CO2 power turbine; Design modifications to an existing turbocompressor to provide s-CO2 flow for the test system; Updated equipment and installation costs for the turbomachinery and associated support infrastructure; Development of simulation tools for the test loop itself and for more efficient cycle designs that are of greater commercial interest; Simulation of s-CO2 power cycle integration into molten-nitrate-salt CSP systems indicating a cost benefit of up to 8% in levelized cost of energy; Identification of recuperator cost as a key economic parameter; Corrosion data for multiple alloys at temperatures up to 650ºC in high-pressure CO2 and recommendations for materials-of-construction; and Revised test plan and preliminary operating conditions based on the ongoing tests of related equipment. Phase 1 established that the cost of the facility needed to test the power turbine at its full power and temperature would exceed the planned funding for Phases 2 and 3. Late

  14. Vasogenic shock physiology

    Directory of Open Access Journals (Sweden)

    Sotiria Gkisioti

    2011-01-01

    Full Text Available Sotiria Gkisioti, Spyros D MentzelopoulosDepartment of Intensive Care Medicine, University of Athens Medical School, Evaggelismos General Hospital, Athens, GreeceAbstract: Shock means inadequate tissue perfusion by oxygen-carrying blood. In vasogenic shock, this circulatory failure results from vasodilation and/or vasoplegia. There is vascular hyporeactivity with reduced vascular smooth muscle contraction in response to α1 adrenergic agonists. Considering vasogenic shock, one can understand its utmost importance, not only because of its association with sepsis but also because it can be the common final pathway for long-lasting, severe shock of any cause, even postresuscitation states. The effective management of any patient in shock requires the understanding of its underlying physiology and pathophysiology. Recent studies have provided new insights into vascular physiology by revealing the interaction of rather complicated and multifactorial mechanisms, which have not been fully elucidated yet. Some of these mechanisms, such as the induction of nitric oxide synthases, the activation of adenosine triphosphate-sensitive potassium channels, and vasopressin deficiency, have gained general acceptance and are considered to play an important role in the pathogenesis of vasodilatory shock. The purpose of this review is to provide an update on the pathogenesis of vasogenic shock.Keywords: nitric oxide synthases, KATP channels, vasopressin, H2S, vasoplegic syndrome

  15. Supercritical fluid processing: opportunities for new resist materials and processes

    Science.gov (United States)

    Gallagher-Wetmore, Paula M.; Ober, Christopher K.; Gabor, Allen H.; Allen, Robert D.

    1996-05-01

    Over the past two decades supercritical fluids have been utilized as solvents for carrying out separations of materials as diverse as foods, polymers, pharmaceuticals, petrochemicals, natural products, and explosives. More recently they have been used for non-extractive applications such as recrystallization, deposition, impregnation, surface modification, and as a solvent alternative for precision parts cleaning. Today, supercritical fluid extraction is being practiced in the foods and beverage industries; there are commercial plants for decaffeinating coffee and tea, extracting beer flavoring agents from hops, and separating oils and oleoresins from spices. Interest in supercritical fluid processing of polymers has grown over the last ten years, and many new purification, fractionation, and even polymerization techniques have emerged. One of the most significant motivations for applying this technology to polymers has been increased performance demands. More recently, with increasing scrutiny of traditional solvents, supercritical fluids, and in particular carbon dioxide, are receiving widespread attention as 'environmentally conscious' solvents. This paper describes several examples of polymers applications, including a few involving photoresists, which demonstrate that as next- generation advanced polymer systems emerge, supercritical fluids are certain to offer advantages as cutting edge processing tools.

  16. Experimental study of elliptical jet from sub to supercritical conditions

    Science.gov (United States)

    Muthukumaran, C. K.; Vaidyanathan, Aravind

    2014-04-01

    The jet mixing at supercritical conditions involves fluid dynamics as well as thermodynamic phenomena. All the jet mixing studies at critical conditions to the present date have focused only on axisymmetric jets. When the liquid jet is injected into supercritical environment, the thermodynamic transition could be well understood by considering one of the important fluid properties such as surface tension since it decides the existence of distinct boundary between the liquid and gaseous phase. It is well known that an elliptical liquid jet undergoes axis-switching phenomena under atmospheric conditions due to the presence of surface tension. The experimental investigations were carried out with low speed elliptical jet under supercritical condition. Investigation of the binary component system with fluoroketone jet and N2 gas as environment shows that the surface tension force dominates for a large downstream distance, indicating delayed thermodynamic transition. The increase in pressure to critical state at supercritical temperature is found to expedite the thermodynamic transition. The ligament like structures has been observed rather than droplets for supercritical pressures. However, for the single component system with fluoroketone jet and fluoroketone environment shows that the jet disintegrates into droplets as it is subjected to the chamber conditions even for the subcritical pressures and no axis switching phenomenon is observed. For a single component system, as the pressure is increased to critical state, the liquid jet exhibits gas-gas like mixing behavior and that too without exhibiting axis-switching behavior.

  17. Experimental study of elliptical jet from sub to supercritical conditions

    Energy Technology Data Exchange (ETDEWEB)

    Muthukumaran, C. K.; Vaidyanathan, Aravind, E-mail: aravind7@iist.ac.in [Department of Aerospace Engineering, Indian Institute of Space Science and Technology, Trivandrum, Kerala 695547 (India)

    2014-04-15

    The jet mixing at supercritical conditions involves fluid dynamics as well as thermodynamic phenomena. All the jet mixing studies at critical conditions to the present date have focused only on axisymmetric jets. When the liquid jet is injected into supercritical environment, the thermodynamic transition could be well understood by considering one of the important fluid properties such as surface tension since it decides the existence of distinct boundary between the liquid and gaseous phase. It is well known that an elliptical liquid jet undergoes axis-switching phenomena under atmospheric conditions due to the presence of surface tension. The experimental investigations were carried out with low speed elliptical jet under supercritical condition. Investigation of the binary component system with fluoroketone jet and N{sub 2} gas as environment shows that the surface tension force dominates for a large downstream distance, indicating delayed thermodynamic transition. The increase in pressure to critical state at supercritical temperature is found to expedite the thermodynamic transition. The ligament like structures has been observed rather than droplets for supercritical pressures. However, for the single component system with fluoroketone jet and fluoroketone environment shows that the jet disintegrates into droplets as it is subjected to the chamber conditions even for the subcritical pressures and no axis switching phenomenon is observed. For a single component system, as the pressure is increased to critical state, the liquid jet exhibits gas-gas like mixing behavior and that too without exhibiting axis-switching behavior.

  18. Extraction of metals using supercritical fluid and chelate forming legand

    Science.gov (United States)

    Wai, Chien M.; Laintz, Kenneth E.

    1998-01-01

    A method of extracting metalloid and metal species from a solid or liquid material by exposing the material to a supercritical fluid solvent containing a chelating agent is described. The chelating agent forms chelates that are soluble in the supercritical fluid to allow removal of the species from the material. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is a fluorinated .beta.-diketone. In especially preferred embodiments the extraction solvent is supercritical carbon dioxide, and the chelating agent comprises a fluorinated .beta.-diketone and a trialkyl phosphate, or a fluorinated .beta.-diketone and a trialkylphosphine oxide. Although a trialkyl phosphate can extract lanthanides and actinides from acidic solutions, a binary mixture comprising a fluorinated .beta.-diketone and a trialkyl phosphate or a trialkylphosphine oxide tends to enhance the extraction efficiencies for actinides and lanthanides. The method provides an environmentally benign process for removing contaminants from industrial waste without using acids or biologically harmful solvents. The method is particularly useful for extracting actinides and lanthanides from acidic solutions. The chelate and supercritical fluid can be regenerated, and the contaminant species recovered, to provide an economic, efficient process.

  19. Extraction of metals using supercritical fluid and chelate forming ligand

    Science.gov (United States)

    Wai, C.M.; Laintz, K.E.

    1998-03-24

    A method of extracting metalloid and metal species from a solid or liquid material by exposing the material to a supercritical fluid solvent containing a chelating agent is described. The chelating agent forms chelates that are soluble in the supercritical fluid to allow removal of the species from the material. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is a fluorinated {beta}-diketone. In especially preferred embodiments the extraction solvent is supercritical carbon dioxide, and the chelating agent comprises a fluorinated {beta}-diketone and a trialkyl phosphate, or a fluorinated {beta}-diketone and a trialkylphosphine oxide. Although a trialkyl phosphate can extract lanthanides and actinides from acidic solutions, a binary mixture comprising a fluorinated {beta}-diketone and a trialkyl phosphate or a trialkylphosphine oxide tends to enhance the extraction efficiencies for actinides and lanthanides. The method provides an environmentally benign process for removing contaminants from industrial waste without using acids or biologically harmful solvents. The method is particularly useful for extracting actinides and lanthanides from acidic solutions. The chelate and supercritical fluid can be regenerated, and the contaminant species recovered, to provide an economic, efficient process. 7 figs.

  20. Supercritical fluid extraction: Application in the food industry

    Directory of Open Access Journals (Sweden)

    Skala Dejan U.

    2002-01-01

    Full Text Available Supercritical fluid extraction is an extraction process realized with supercritical fluids, which are at a temperature and pressure above their critical temperature and critical pressure. This process has shown to be very efficient one for the isolation of different substances of medium molecular weights and molecules of relatively low polarity. The solubility of more polar substances in supercritical fluids can be improved by the addition of small amounts of other polar solvents (cosolvent to the supercritical fluids, which is the main solvent in extraction process. The advantage of supercritical extraction compared to other extraction procedures (the application of classical organic solvents hydrodistillation, distillation with steam is that SFE is usually performed at moderate temperature (e.g. with SF CO2 at 40-70°C so it can be applied for the separation of different substances which are thermally unstable and have a larger vapour pressure. All of these facts indicate that SFE is of special interest for the food and pharmaceutical industry.

  1. Oxidation behavior of Incoloy 800 under simulated supercritical water conditions

    Energy Technology Data Exchange (ETDEWEB)

    Fulger, M. [Institute for Nuclear Research Pitesti, POB 78, Campului Street, No. 1, 115400 Mioveni (Romania)], E-mail: manuela.fulger@nuclear.ro; Ohai, D.; Mihalache, M.; Pantiru, M. [Institute for Nuclear Research Pitesti, POB 78, Campului Street, No. 1, 115400 Mioveni (Romania); Malinovschi, V. [University of Pitesti, Research Center for Advanced Materials, Targul din Vale Street, No. 1, 110040 Pitesti (Romania)

    2009-03-31

    For a correct design of supercritical water-cooled reactor (SCWR) components, data regarding the behavior of candidate materials in supercritical water are necessary. Corrosion has been identified as a critical problem because the high temperature and the oxidative nature of supercritical water may accelerate the corrosion kinetics. The goal of this paper is to investigate the oxidation behavior of Incoloy 800 exposed in autoclaves under supercritical water conditions for up to 1440 h. The exposure conditions (thermal deaerated water, temperatures of 723, 773, 823 and 873 K and a pressure of 25 MPa) have been selected as relevant for a supercritical power plant concept. To investigate the structural changes of the oxide films, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX) and electrochemical impedance spectroscopy (EIS) analyses were used. Results show changes in the oxides chemical composition, microstructure and thickness versus testing conditions (pressure, temperature and time). The oxide films are composed of two layers: an outer layer enriched in Fe oxide and an inner layer enriched in Cr and Ni oxides corresponding to small cavities supposedly due to internal oxidation.

  2. A cylindrical converging shock tube for shock-interface studies.

    Science.gov (United States)

    Luo, Xisheng; Si, Ting; Yang, Jiming; Zhai, Zhigang

    2014-01-01

    A shock tube facility for generating a cylindrical converging shock wave is developed in this work. Based on the shock dynamics theory, a specific wall profile is designed for the test section of the shock tube to transfer a planar shock into a cylindrical one. The shock front in the converging part obtained from experiment presents a perfect circular shape, which proves the feasibility and reliability of the method. The time variations of the shock strength obtained from numerical simulation, experiment, and theoretical estimation show the desired converging effect in the shock tube test section. Particular emphasis is then placed on the problem of shock-interface interaction induced by cylindrical converging shock waves. For this purpose, membrane-less gas cylinder is adopted to form the interface between two different fluids while the laser sheet technique to visualize the flow field. The result shows that it is convenient to perform such experiments in this facility.

  3. Lessons Learned in the Selection and Development of Test Cases for the Aeroelastic Prediction Workshop: Rectangular Supercritical Wing

    Science.gov (United States)

    Heeg, Jennifer; Chwalowski, Pawel; Wieseman, Carol D.; Florance, Jennifer P.; Schuster, David M.

    2013-01-01

    The Aeroelastic Prediction Workshop brought together an international community of computational fluid dynamicists as a step in defining the state of the art in computational aeroelasticity. The Rectangular Supercritical Wing (RSW) was chosen as the first configuration to study due to its geometric simplicity, perceived simple flow field at transonic conditions and availability of an experimental data set containing forced oscillation response data. Six teams performed analyses of the RSW; they used Reynolds-Averaged Navier-Stokes flow solvers exercised assuming that the wing had a rigid structure. Both steady-state and forced oscillation computations were performed by each team. The results of these calculations were compared with each other and with the experimental data. The steady-state results from the computations capture many of the flow features of a classical supercritical airfoil pressure distribution. The most dominant feature of the oscillatory results is the upper surface shock dynamics. Substantial variations were observed among the computational solutions as well as differences relative to the experimental data. Contributing issues to these differences include substantial wind tunnel wall effects and diverse choices in the analysis parameters.

  4. Conceptual design of a thermalhydraulic loop for multiple test geometries at supercritical conditions named Supercritical Phenomena Experimental Test Apparatus (SPETA)

    Science.gov (United States)

    Adenariwo, Adepoju

    The efficiency of nuclear reactors can be improved by increasing the operating pressure of current nuclear reactors. Current CANDU-type nuclear reactors use heavy water as coolant at an outlet pressure of up to 11.5 MPa. Conceptual SuperCritical Water Reactors (SCWRs) will operate at a higher coolant outlet pressure of 25 MPa. Supercritical water technology has been used in advanced coal plants and its application proves promising to be employed in nuclear reactors. To better understand how supercritical water technology can be applied in nuclear power plants, supercritical water loops are used to study the heat transfer phenomena as it applies to CANDU-type reactors. A conceptual design of a loop known as the Supercritical Phenomena Experimental Apparatus (SPETA) has been done. This loop has been designed to fit in a 9 m by 2 m by 2.8 m enclosure that will be installed at the University of Ontario Institute of Technology Energy Research Laboratory. The loop include components to safely start up and shut down various test sections, produce a heat source to the test section, and to remove reject heat. It is expected that loop will be able to investigate the behaviour of supercritical water in various geometries including bare tubes, annulus tubes, and multi-element-type bundles. The experimental geometries are designed to match the fluid properties of Canadian SCWR fuel channel designs so that they are representative of a practical application of supercritical water technology in nuclear plants. This loop will investigate various test section orientations which are the horizontal, vertical, and inclined to investigate buoyancy effects. Frictional pressure drop effects and satisfactory methods of estimating hydraulic resistances in supercritical fluid shall also be estimated with the loop. Operating limits for SPETA have been established to be able to capture the important heat transfer phenomena at supercritical conditions. Heat balance and flow calculations have

  5. Chemistry and catalysis in supercritical media

    Energy Technology Data Exchange (ETDEWEB)

    Tumas, W.; Morgenstern, D.; Feng, S. [and others

    1997-07-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The aim of this research is to explore the potential of supercritical fluids as reaction media for stoichiometric and catalytic chemical transformations in an effort to develop new, environmentally-friendly methods for chemical synthesis or processing. This approach offers the possibility of opening up substantially different chemical pathways, increasing selectivity while enhancing reaction rates, facilitating downstream separations and mitigating the need for hazardous solvents. The authors describe investigations into a number of catalytic processes for which carbon dioxide represents a viable solvent replacement. In several cases they have observed significant enhancements in selectivity and/or reactivity relative to conventional organic solvents. They have investigated the following catalytic processes: (a) selective oxidation including dihydroxylation and epoxidation, (b) asymmetric hydrogenation and hydrogen transfer reduction, (c) Lewis acid catalyzed acylation and alkylation, and (c) coupling of amines with carbon dioxide to make isocyanates.

  6. Coal gasification with water under supercritical conditions

    Energy Technology Data Exchange (ETDEWEB)

    A.A. Vostrikov; S.A. Psarov; D.Yu. Dubov; O.N. Fedyaeva; M.Ya. Sokol [Russian Academy of Sciences, Novosibirsk (Russian Federastion). Kutateladze Institute of Thermophysics, Siberian Division

    2007-08-15

    The conversion of an array of coal particles in supercritical water (SCW) was studied in a semibatch reactor at a pressure of 30 MPa, 500-750{sup o}C, and a reaction time of 1-12 min. The bulk conversion, surface conversion, and random pore models were used to describe the conversion. The quantitative composition of reaction products was determined, and the dependence of the rate of reaction on the degree of coal conversion, reaction time, and reaction temperature was obtained on the assumption of a first-order reaction and the Arrhenius function. It was found that the gasification of coal under SCW conditions without the addition of oxidizing agents is a weakly endothermic process. The addition of CO{sub 2} to SCW decreased the rate of conversion and increased the yield of CO. It was found that, at a 90% conversion of the organic matter of coal (OMC) in a flow of SCW in a time of 2 min, the process power was 26 W/g per gram of OMC.

  7. Kinetics of coal conversion in supercritical water

    Energy Technology Data Exchange (ETDEWEB)

    Anatoli A. Vostrikov; Sergey A. Psarov; Dmitri Yu. Dubov; Oxana N. Fedyaeva; Mikhail Ya. Sokol [Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation). Institute of Thermophysics

    2007-09-15

    Conversion of the coal particle pack in supercritical water (SCW) was studied in the semibatch reactor under the pressure of P = 30 MPa, in the temperature range of T = 500-750{sup o}C, and in the reaction time of t = 60-720 s. The experimental results were analyzed within the framework of homogeneous, nonreacted core, and random pore models. The quantitative composition of conversion products was determined. Dependences of the conversion rate on the degree of coal conversion, reaction time, and temperature were described in an assumption of the first-order reaction and Arrhenius dependence. It was found that activation energy of conversion is E = 103 kJ/mol and the pre-exponential factor is A{sub 0} = 1.3 x 10{sup 3.1} s{sup -1}. It was revealed that coal gasification in SCW without oxidants is the weakly endothermic process. The addition of CO{sub 2} into SCW decreases the conversion rate and increases the CO yield. 20 refs., 8 figs.

  8. Supercritical fluids technology for clean biofuel production

    Institute of Scientific and Technical Information of China (English)

    Dongsheng Wen; H.Jiang; Kai Zhang

    2009-01-01

    Biofuels are liquid or gaseous fuels that are predominantly produced from biomass for transport sector applications.As biofuels are renewable,sustainable,carbon neutral and environmentally benign,they have been proposed as promising alternative fuels for gasoline and diesel engines.This paper reviews state-of-the-art application of the supercritical fluid(SCF)technique in biofuels production that includes biodiesel from vegetable oils via the transesterification process,bio-hydrogen from the gasification and bio-oil from the lique-faction of biomass,with biodiesel production as the main focus. The global biofuel situation and biofuel economics are also reviewed.The SCF has been shown to be a promising technique for future large-scale biofuel production,especially for biodiesel production from waster oil and fat.Compared with conventional biofuel production methods,the SCF technology possesses a number of advantages that includes fast inetics,high fuel production rate,ease of continuous operation and elimination of the necessity of catalysts.The harsh operation environment,i.e. the high temperature and high pressure,and its request on the materials and associated cost are the main concerns for its wide application.

  9. Some Organic Reactions in Supercritical Carbon Dioxide

    Institute of Scientific and Technical Information of China (English)

    JIANG Huan-feng; YANG Xiao-yue; LI Guo-ping; ZOU Gang

    2004-01-01

    Organic reactions in supercritical carbon dioxide (scCO2) have facilitated great progress in recent years 1. ScCO2, as an environmentally friendly reaction medium, may be a substitute for volatile and toxic organic solvents and show some special advantages. Firstly, CO2 is inexpensive,nonflammable, nontoxic and chemical inert under many conditions. Secondly, scCO2 possesses hybrid properties of both liquid and gas, to the advantage of some reactions involving gaseous reagents. Control of the solvent density by variation of the temperature and pressure enables the solvent properties to be "tuned" to reactants. Finally, separating of CO2 from the reaction mixture is energy-efficient and simple. Here we disclose our new work on some organic reactions involving small molecules in scCO2.The results showed that the upper reactions in scCO2 could be carried out smoothly and thepressure of CO2 had a remarkable effect on the conversion and selectivity.

  10. Towards Overhauser DNP in supercritical CO2

    Science.gov (United States)

    van Meerten, S. G. J.; Tayler, M. C. D.; Kentgens, A. P. M.; van Bentum, P. J. M.

    2016-06-01

    Overhauser Dynamic Nuclear Polarization (ODNP) is a well known technique to improve NMR sensitivity in the liquid state, where the large polarization of an electron spin is transferred to a nucleus of interest by cross-relaxation. The efficiency of the Overhauser mechanism for dipolar interactions depends critically on fast local translational dynamics at the timescale of the inverse electron Larmor frequency. The maximum polarization enhancement that can be achieved for 1H at high magnetic fields benefits from a low viscosity solvent. In this paper we investigate the option to use supercritical CO2 as a solvent for Overhauser DNP. We have investigated the diffusion constants and longitudinal nuclear relaxation rates of toluene in high pressure CO2. The change in 1H T1 by addition of TEMPO radical was analyzed to determine the Overhauser cross-relaxation in such a mixture, and is compared with calculations based on the Force Free Hard Sphere (FFHS) model. By analyzing the relaxation data within this model we find translational correlation times in the range of 2-4 ps, depending on temperature, pressure and toluene concentration. Such short correlation times may be instrumental for future Overhauser DNP applications at high magnetic fields, as are commonly used in NMR. Preliminary DNP experiments have been performed at 3.4 T on high pressure superheated water and model systems such as toluene in high pressure CO2.

  11. Towards Overhauser DNP in supercritical CO2.

    Science.gov (United States)

    van Meerten, S G J; Tayler, M C D; Kentgens, A P M; van Bentum, P J M

    2016-06-01

    Overhauser Dynamic Nuclear Polarization (ODNP) is a well known technique to improve NMR sensitivity in the liquid state, where the large polarization of an electron spin is transferred to a nucleus of interest by cross-relaxation. The efficiency of the Overhauser mechanism for dipolar interactions depends critically on fast local translational dynamics at the timescale of the inverse electron Larmor frequency. The maximum polarization enhancement that can be achieved for (1)H at high magnetic fields benefits from a low viscosity solvent. In this paper we investigate the option to use supercritical CO2 as a solvent for Overhauser DNP. We have investigated the diffusion constants and longitudinal nuclear relaxation rates of toluene in high pressure CO2. The change in (1)H T1 by addition of TEMPO radical was analyzed to determine the Overhauser cross-relaxation in such a mixture, and is compared with calculations based on the Force Free Hard Sphere (FFHS) model. By analyzing the relaxation data within this model we find translational correlation times in the range of 2-4ps, depending on temperature, pressure and toluene concentration. Such short correlation times may be instrumental for future Overhauser DNP applications at high magnetic fields, as are commonly used in NMR. Preliminary DNP experiments have been performed at 3.4T on high pressure superheated water and model systems such as toluene in high pressure CO2.

  12. Digested sewage sludge gasification in supercritical water.

    Science.gov (United States)

    Zhai, Yunbo; Wang, Chang; Chen, Hongmei; Li, Caiting; Zeng, Guangming; Pang, Daoxiong; Lu, Pei

    2013-04-01

    Digested sewage sludge gasification in supercritical water was studied. Influences of main reaction parameters, including temperature (623-698 K), pressure (25-35 Mpa), residence time (10-15 min) and dry matter content (5-25 wt%), were investigated to optimize the gasification process. The main gas products were methane, carbon monoxide, carbon dioxide and traces of ethene, etc. Results showed that 10 wt% dry matter content digested sewage sludge at a temperature of 698 K and residence time of 50 min, with a pressure of 25 MPa, were the most favorable conditions for the sewage sludge gasification and carbon gasification efficiencies. In addition, potassium carbonate (K2CO3) was also employed as the catalyst to make a comparison between gasification with and without catalyst. When 2.6 g K2CO3 was added, a gasification efficiency of 25.26% and a carbon gasification efficiency of 20.02% were achieved, which were almost four times as much as the efficiencies without catalyst. K2CO3 has been proved to be effective in sewage sludge gasification.

  13. Welding immiscible polymers with a supercritical fluid.

    Science.gov (United States)

    Wang, Xiaochu; Sanchez, Isaac C

    2007-11-20

    Polymer adhesion between two immiscible polymers is usually poor because there is little interpenetration of one polymer into the other at the interface. Increasing the width of the interfacial zone can enhance adhesion and mechanical properties. In principle, this can be accomplished by exposing heterogeneous polymer materials to a high-pressure fluid. The fluid can act as a common solvent and promote interpenetration. It also increases chain mobility at the interface, which helps to promote "welding" of the two polymers. A combination of the gradient theory of inhomogeneous systems and the Sanchez-Lacombe equation of state was used to investigate this phenomenon, especially the effect of the high compressibility of supercritical (SC) fluid on the compatibilization of two incompatible polymers. We calculate the interfacial density profile, interfacial thickness, and interfacial tension between the two polymers with and without the SC fluid. We find that the interfacial tension is decreased and the interfacial thickness is increased with high-pressure SC fluid for the ternary systems we have investigated. As the critical point is approached and the SC compressibility becomes large, no enhancement or deleterious effects on compatibilization were observed.

  14. Synthesis of biodiesel from edible and non-edible oils in supercritical alcohols and enzymatic synthesis in supercritical carbon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Vivek Rathore; Giridhar Madras [Indian Institute of Science, Bangalore (India). Department of Chemical Engineering

    2007-12-15

    Biodiesel is an attractive alternative fuel because it is environmentally friendly and can be synthesized from edible and non-edible oils. The synthesis of biodiesel from edible oils like palm oil and groundnut oil and from crude non-edible oils like Pongamia pinnata and Jatropha curcas was investigated in supercritical methanol and ethanol without using any catalyst from 200 to 400{sup o}C at 200 bar. The variables affecting the conversion during transesterification, such as molar ratio of alcohol to oil, temperature and time were investigated in supercritical methanol and ethanol. Biodiesel was also synthesized enzymatically with Novozym-435 lipase in presence of supercritical carbon dioxide. The effect of reaction variables such as temperature, molar ratio, enzyme loading and kinetics of the reaction was investigated for enzymatic synthesis in supercritical carbon dioxide. Very high conversions (>80%) were obtained within 10 min and nearly complete conversions were obtained at within 40 min for the synthesis of biodiesel in supercritical alcohols. However, conversions of only 60-70% were obtained in the enzymatic synthesis even after 8 h. 48 refs., 8 figs., 1 tab.

  15. Producing Polymer Fibers by Electrospinning in Supercritical Fluids

    Directory of Open Access Journals (Sweden)

    Lu Li

    2013-01-01

    Full Text Available Nanofibers have a wide range of applications, including filtration and biomedical engineering. Porous or hollow fibers with large surface-to-volume ratios are more popular in some fields than the common nanofibers. Porous nanofibers can be obtained through electrospinning with highly volatile solvents or through special treatment following electrospinning. A new process where electrospinning is conducted in supercritical or near-critical CO2 to produce porous or hollow nanofibers has been summarized. In addition, a process entailing compressed N2-assisted electrospinning was attempted to produce PVP nanofibers in this work, but it was proved to be unsuccessful. Since the fiber morphologies are dependent on the phase behavior of organic solvents in supercritical fluids, ASPEN PLUS 2006 was used to simulate the phase equilibrium of the solvent-supercritical fluid system to explain why porous or hollow fibers can be obtained in compressed CO2, but not in compressed N2.

  16. Research Progress on Preparation of Graphene by Supercritical Fluid Exfoliation

    Directory of Open Access Journals (Sweden)

    HU Sheng-fei

    2017-03-01

    Full Text Available As a new type of two-dimensional carbonaceous material, graphene has excellent physical properties and great application potential. The key problem to realize graphene industrialization is to find a large-scale preparing method of graphene with high quality and low cost. In this paper, the advantages and disadvantages of preparation methods for graphene were first reviewed, and then the mechanism, research status and characterization methods of supercritical fluids exfoliated method were introduced in details. And the features of supercritical fluids exfoliated method with the assistance of ultrasonication and pyrene-polymers were summarized. The advantages of supercritical fluids exfoliated method are simple equipment, processing conditions easy to achieve and products with high quality, and a new way of thinking for the industrial production of graphene is provided.

  17. Biodiesel fuel from rapeseed oil as prepared in supercritical methanol

    Energy Technology Data Exchange (ETDEWEB)

    Saka, S.; Kusdiana, D. [Kyoto University, Kyoto (Japan). Dept. of Socio-Environmental Energy Science, Graduate School of Energy Science

    2001-01-01

    Transesterification reaction of rapeseed oil in supercritical methanol was investigated without using any catalyst. An experiment has been carried out in the batch-type reaction vessel preheated at 350 and 400{degree}C and at a pressure of 45-65 MPa, and with a molar ratio of 1:42 of the rapeseed oil to methanol. It was consequently demonstrated that, in a preheating temperature of 350{degree}C, 240 s of supercritical treatment of methanol was sufficient to convert the rapeseed oil to methyl esters and that, although the prepared methyl esters were basically the same as those of the common method with a basic catalyst, the yield of methyl esters by the former was found to be higher than that by the latter. In addition, it was found that this supercritical methanol process requires the shorter reaction time and simpler purification procedure because of the unused catalyst. 16 refs., 9 figs., 2 tabs.

  18. Preparation of drug delivery systems using supercritical fluid technology.

    Science.gov (United States)

    Kompella, U B; Koushik, K

    2001-01-01

    Small changes in temperature and pressure near the critical region induce dramatic changes in the density and solubility of supercritical fluids, thereby facilitating the use of environmentally benign agents such as CO2 for their solvent and antisolvent properties in processing a wide variety of materials. While supercritical fluid technologies have been in commercial use in the food and chromatography industries for several years, only recently has this technology made inroads in the formulation of drug delivery systems. This review summarizes some of the recent applications of supercritical fluid technology in the preparation of drug delivery systems. Drugs containing polymeric particles, plain drug particles, solute-containing liposomes, and inclusion complexes of drug and carrier have been formulated using this technology. Also, polymer separation using this technology is enabling the selection of a pure fraction of a polymer, thereby allowing a more precise control of drug release from polymeric delivery systems.

  19. Application of Neutron Radiography to Flow Visualization in Supercritical Water

    Science.gov (United States)

    Takenaka, N.; Sugimoto, K.; Takami, S.; Sugioka, K.; Tsukada, T.; Adschiri, T.; Saito, Y.

    Supercritical water is used in various chemical reaction processes including hydrothermal synthesis of metal oxide nano-particles, oxidation, chemical conversion of biomass and plastics. Density of the super critical water is much less than that of the sub-critical water. By using neutron radiography, Peterson et al. have studied salt precipitation processes in supercritical water and the flow pattern in a reverse-flow vessel for salt precipitation, and Balasko et al. have revealed the behaviour of supercritical water in a container. The nano-particles were made by mixing the super critical flow and the sub critical water solution. In the present study, neutron radiography was applied to the flow visualization of the super and sub critical water mixture in a T-junction made of stainless steel pipes for high pressure and temperature conditions to investigate their mixing process. Still images by a CCD camera were obtained by using the neutron radiography system at B4 port in KUR.

  20. Application of supercritical antisolvent method in drug encapsulation: a review

    Directory of Open Access Journals (Sweden)

    Kalani M

    2011-07-01

    Full Text Available Mahshid Kalani, Robiah YunusChemical and Environmental Engineering, Faculty of Engineering, University Putra Malaysia, Selangor Darul Ehsan, MalaysiaAbstract: The review focuses on the application of supercritical fluids as antisolvents in the pharmaceutical field and demonstrates the supercritical antisolvent method in the use of drug encapsulation. The main factors for choosing the solvent and biodegradable polymer to produce fine particles to ensure effective drug delivery are emphasized and the effect of polymer structure on drug encapsulation is illustrated. The review also demonstrates the drug release mechanism and polymeric controlled release system, and discusses the effects of the various conditions in the process, such as pressure, temperature, concentration, chemical compositions (organic solvents, drug, and biodegradable polymer, nozzle geometry, CO2 flow rate, and the liquid phase flow rate on particle size and its distribution.Keywords: supercritical antisolvent method, drug encapsulation, particle size, drug release mechanisms, drug delivery

  1. Molecular Dynamics Investigation of Benzene in Supercritical Water

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Microscopic structure and diffusion properties of benzene in ambient water (298 K, 0.1 MPa) and super critical water (673-773 K, 25-35 MPa) are investigated by molecular dynamics simulation with site-site models. It is found that at the ambient condition, the water molecules surrounding a benzene molecule form a hydrogen bond network. The hydrogen bond interaction between supercritical water molecules decreases dramatically under supercritical conditions. The diffusion coefficients of both the solute molecule and solvent molecule at supercritical conditions increase by 30-180 times than those at the ambient condition. With the temperature approaching the critical temperature, the change of diffusion coefficient with pressure becomes pronounced.

  2. A note on the total domination supercritical graphs

    Directory of Open Access Journals (Sweden)

    Abdollah Alimadadi

    2012-09-01

    Full Text Available Let $G$ be a connected spanning subgraph of $K_{s,s}$ and let $H$ be the complement of $G$ relative to $K_{s,s}$. The graph $G$ is {it $k$-supercritical} relative to $K_{s,s}$ if $gamma_t(G=k$ and $gamma_t(G+e=k-2$ for all $ein E(H$. The 2002 paper by T.W. Haynes, M.A. Henning and L.C. van der Merwe, "Total domination supercritical graphs with respect to relative complements" that appeared in Discrete Mathematics, 258 (2002, 361-371, presents a theorem (Theorem 11 to produce $(2k + 2$-supercritical graphs relative to $K_{2k+1, 2k+1}$ of diameter $5$, for each $kgeq 2$. However, the families of graphs in their proof are not the case. We present a correction of this theorem.

  3. The latent heat of vaporization of supercritical fluids

    Science.gov (United States)

    Banuti, Daniel; Raju, Muralikrishna; Hickey, Jean-Pierre; Ihme, Matthias

    2016-11-01

    The enthalpy of vaporization is the energy required to overcome intermolecular attractive forces and to expand the fluid volume against the ambient pressure when transforming a liquid into a gas. It diminishes for rising pressure until it vanishes at the critical point. Counterintuitively, we show that a latent heat is in fact also required to heat a supercritical fluid from a liquid to a gaseous state. Unlike its subcritical counterpart, the supercritical pseudoboiling transition is spread over a finite temperature range. Thus, in addition to overcoming intermolecular attractive forces, added energy simultaneously heats the fluid. Then, considering a transition from a liquid to an ideal gas state, we demonstrate that the required enthalpy is invariant to changes in pressure for 0 intermolecular forces in the real fluid vapor during heating. At supercritical pressures, all of the transition occurs at non-equilibrium; for p -> 0 , all of the transition occurs at equilibrium.

  4. Collisionless parallel shocks

    Science.gov (United States)

    Khabibrakhmanov, I. KH.; Galeev, A. A.; Galinskii, V. L.

    1993-01-01

    Consideration is given to a collisionless parallel shock based on solitary-type solutions of the modified derivative nonlinear Schroedinger equation (MDNLS) for parallel Alfven waves. The standard derivative nonlinear Schroedinger equation is generalized in order to include the possible anisotropy of the plasma distribution and higher-order Korteweg-de Vies-type dispersion. Stationary solutions of MDNLS are discussed. The anisotropic nature of 'adiabatic' reflections leads to the asymmetric particle distribution in the upstream as well as in the downstream regions of the shock. As a result, nonzero heat flux appears near the front of the shock. It is shown that this causes the stochastic behavior of the nonlinear waves, which can significantly contribute to the shock thermalization.

  5. Shock structures of astrospheres

    CERN Document Server

    Scherer, Klaus; Kleimann, Jens; Wiengarten, Tobias; Bomans, Dominik J; Weis, Kerstin

    2015-01-01

    The interaction between a supersonic stellar wind and a (super-)sonic interstellar wind has recently been viewed with new interest. We here first give an overview of the modeling, which includes the heliosphere as an example of a special astrosphere. Then we concentrate on the shock structures of fluid models, especially of hydrodynamic (HD) models. More involved models taking into account radiation transfer and magnetic fields are briefly sketched. Even the relatively simple HD models show a rich shock structure, which might be observable in some objects. We employ a single fluid model to study these complex shock structures, and compare the results obtained including heating and cooling with results obtained without these effects. Furthermore, we show that in the hypersonic case valuable information of the shock structure can be obtained from the Rankine-Hugoniot equations. We solved the Euler equations for the single fluid case and also for a case including cooling and heating. We also discuss the analytic...

  6. Counseling For Future Shock

    Science.gov (United States)

    Morgan, Lewis B.

    1974-01-01

    In this article the author looks at some of the searing prophecies made by Alvin Toffler in his book Future Shock and relates them to the world of the professional counselor and the clientele the counselor attempts to serve. (Author)

  7. Laboratory studies of stagnating plasma flows with applications to inner solar system and stellar bow shocks

    Science.gov (United States)

    Weber, T. E.; Smith, R. J.; Hsu, S. C.

    2016-10-01

    Supercritical magnetized collisionless shocks are thought to play a dominant role in the overall partition of energy throughout the universe by converting flow kinetic energy to other forms such as thermal and supra-thermal populations, magnetic field enhancement, turbulence, and energetic particles. The Magnetized Shock Experiment (MSX) at LANL creates conditions similar to those of inner solar system and stellar bow shocks by accelerating hot (100s of eV during translation) dense (1022 - 1023 m-3) Field Reversed Configuration (FRC) plasmoids to 100s of km/s; resulting in β 1, collisionless plasma flows with Msonic and MAlfvén 10. The drifting FRC can be made to impinge upon a variety of static obstacles including: a strong mirror or cusp magnetic field (mimicking magnetically excited shocks such as the Earth's bow shock), plasma pileup from a solid obstacle (similar to the bow shocks of Mercury and the Moon), and a neural gas puff (bow shocks of Venus or the comets). Characteristic shock length and time scales that are both large enough to observe yet small enough to fit within the experiment, enabling study of the complex interplay of kinetic and fluid processes that mediate cosmic shocks and can generate non-thermal distributions, produce density and magnetic field enhancements much greater than predicted by fluid theory, and accelerate particles. An overview of the experimental program will be presented, including recent results. This work is supported by the U.S. DOE, Office of Science, Office of Fusion Energy Sciences under Contract No. DE-AC52-06NA25369.

  8. Surfactant/Supercritical Fluid Cleaning of Contaminated Substrates

    Science.gov (United States)

    White, Gary L.

    1997-01-01

    CFC's and halogenated hydrocarbon solvents have been the solvents of choice to degrease and otherwise clean precision metal parts to allow proper function. Recent regulations have, however, rendered most of these solvents unacceptable for these purposes. New processes which are being used or which have been proposed to replace these solvents usually either fail to remove water soluble contaminants or produce significant aqueous wastes which must then be disposed of. In this work, a new method for cleaning surfaces will be investigated. Solubility of typical contaminants such as lubricating greases and phosphatizing bath residues will be studied in several surfactant/supercritical fluid solutions. The effect of temperature, pressure, and the composition of the cleaning mixture on the solubility of oily, polar, and ionic contaminants will be investigated. A reverse micellar solution in a supercritical light hydrocarbon solvent will be used to clean samples of industrial wastes. A reverse micellar solution is one where water is dissolved into a non-polar solvent with the aid of a surfactant. The solution will be capable of dissolving both water-soluble contaminants and oil soluble contaminants. Once the contaminants have been dissolved into the solution they will be separated from the light hydrocarbon and precipitated by a relatively small pressure drop and the supercritical solvent will be available for recycle for reuse. The process will be compared to the efficacy of supercritical CO2 cleaning by attempting to clean the same types of substrates and machining wastes with the same contaminants using supercritical CO2. It is anticipated that the supercritical CO2 process will not be capable of removing ionic residues.

  9. Precipitation of fluticasone propionate microparticles using supercritical antisolvent

    Directory of Open Access Journals (Sweden)

    A Vatanara

    2009-03-01

    Full Text Available ABSTRACT Background: The ability of supercritical fluids (SCFs, such as carbon dioxide, to dissolve and expand or extract organic solvents and as result lower their solvation power, makes it possible the use of SCFs for the precipitation of solids from organic solutions. The process could be the injection of a solution of the substrate in an organic solvent into a vessel which is swept by a supercritical fluid. The aim of this study was to ascertain the feasibility of supercritical processing to prepare different particulate forms of fluticasone propionate (FP, and to evaluate the influence of different liquid solvents and precipitation temperatures on the morphology, size and crystal habit of particles. Method: The solution of FP in organic solvents, was precipitated by supercritical carbon dioxide (SCCO2 at two pressure and temperature levels. Effects of process parameters on the physicochemical characteristics of harvested microparticles were evaluated. Results: Particle formation was observed only at the lower selected pressure, whilst at the higher pressure, no precipitation of particles was occurred due to dissolution of FP in supercritical antisolvent. The micrographs of the produced particles showed different morphologies for FP obtained from different conditions. The results of thermal analysis of the resulted particles showed that changes in the processing conditions didn't influence thermal behavior of the precipitated particles. Evaluation of the effect of temperature on the size distribution of particles showed that increase in the temperature from 40 oC to 50 oC, resulted in reduction of the mean particle size from about 30 µm to about 12 μm. ‍Conclusion: From the results of this study it may be concluded that, processing of FP by supercritical antisolvent could be an approach for production of diverse forms of the drug and drastic changes in the physical characteristics of microparticles could be achieved by changing the

  10. Supercritical Extraction of Lycopene from Tomato Industrial Wastes with Ethane

    Directory of Open Access Journals (Sweden)

    Rui L. Mendes

    2012-07-01

    Full Text Available Supercritical fluid extraction of all-E-lycopene from tomato industrial wastes (mixture of skins and seeds was carried out in a semi-continuous flow apparatus using ethane as supercritical solvent. The effect of pressure, temperature, feed particle size, solvent superficial velocity and matrix initial composition was evaluated. Moreover, the yield of the extraction was compared with that obtained with other supercritical solvents (supercritical CO2 and a near critical mixture of ethane and propane. The recovery of all-E-lycopene increased with pressure, decreased with the increase of the particle size in the initial stages of the extraction and was not practically affected by the solvent superficial velocity. The effect of the temperature was more complex. When the temperature increased from 40 to 60 °C the recovery of all-E-lycopene increased from 80 to 90%. However, for a further increase to 80 °C, the recovery remained almost the same, indicating that some E-Z isomerization could have occurred, as well as some degradation of lycopene. The recovery of all-E-lycopene was almost the same for feed samples with different all-E-lycopene content. Furthermore, when a batch with a higher all-E-lycopene content was used, supercritical ethane and a near critical mixture of ethane and propane showed to be better solvents than supercritical CO2 leading to a faster extraction with a higher recovery of the carotenoid.

  11. Destruction of energetic materials by supercritical water oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Beulow, S.J.; Dyer, R.B.; Harradine, D.M.; Robinson, J.M.; Oldenborg, R.C.; Funk, K.A.; McInroy, R.E.; Sanchez, J.A.; Spontarelli, T.

    1993-10-01

    Supercritical water oxidation is a relatively low-temperature process that can give high destruction efficiencies for a variety of hazardous chemical wastes. Results are presented examining the destruction of high explosives and propellants in supercritical water and the use of low temperature, low pressure hydrolysis as a pretreatment process. Reactions of cyclotrimethylene trinitramine (RDX), cyclotetramethylene tetranitramine (HMX), nitroguanidine (NQ), pentaerythritol tetranitrate (PETN), and 2,4,6-trinitrotoluene (TNT) are examined in a flow reactor operated at temperatures between 400{degrees}C and 650{degrees}C. Explosives are introduced into the reactor at concentrations below the solubility limits. For each of the compounds, over 99.9% is destroyed in less than 30 seconds at temperatures above 600{degrees}C. The reactions produce primarily N{sub 2}, N{sub 2}O,CO{sub 2}, and some nitrate and nitrite ions. The distribution of reaction products depends on reactor pressure, temperature, and oxidizer concentration. Kinetics studies of the reactions of nitrate and nitrite ions with various reducing reagents in supercritical water show that they can be rapidly and completely destroyed at temperatures above 525{degrees}C. The use of slurries and hydrolysis to introduce high concentrations of explosives into a supercritical water reactor is examined. For some compounds the rate of reaction depends on particle size. The hydrolysis of explosives at low temperatures (<100{degrees}C) and low pressures (<1 atm) under basic conditions produces water soluble, non-explosive products which are easily destroyed by supercritical water oxidation. Large pieces of explosives (13 cm diameter) have been successfully hydrolyzed. The rate, extent, and products of the hydrolysis depend on the type and concentration of base. Results from the base hydrolysis of triple base propellant M31A1E1 and the subsequent supercritical water oxidation of the hydrolysis products are presented.

  12. [Pathophysiology of hemorragic shock].

    Science.gov (United States)

    Copotoiu, R; Cinca, E; Collange, O; Levy, F; Mertes, P-M

    2016-11-01

    This review addresses the pathophysiology of hemorrhagic shock, a condition produced by rapid and significant loss of intravascular volume, which may lead to hemodynamic instability, decreases in oxygen delivery, decreased tissue perfusion, cellular hypoxia, organ damage, and death. The initial neuroendocrine response is mainly a sympathetic activation. Haemorrhagic shock is associated altered microcirculatory permeability and visceral injury. It is also responsible for a complex inflammatory response associated with hemostasis alteration. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  13. Measurement of flow in supercritical flow regime using cutthroat flumes

    Indian Academy of Sciences (India)

    Shrikant A Tekade; Avinash D Vasudeo; Aniruddha D Ghare; Ramesh N Ingle

    2016-02-01

    Cutthroat flume is commonly used for measurement of subcritical flow in open channel because of its simplicity and ease of construction. No experimental data is available in literature for measurement of flow in supercritical regime using cutthroat flume. The present paper finds the feasibility of cutthroat flume as a measurement device for flow in supercritical regime. Experimental data are generated to develop the relation between discharge and observed head at a specified location on upstream of throat section. Regression analysis for discharge and head indicated a good correlation. Based on all the experimental data generated, a relationship between discharge and head is proposed.

  14. Supercritical CO2 extraction of essential oils from Thymus vulgaris

    Directory of Open Access Journals (Sweden)

    S.A.B. Vieira de Melo

    2000-09-01

    Full Text Available Supercritical CO2 extraction of essential oil from Thymus vulgaris leaves was studied using experimental data recently obtained in the Florys S.p.A. laboratory. Mass transfer coefficients in the supercritical and solid phases from extraction curves at 40°C and 20 MPa were evaluated using a mathematical model based on the local adsorption equilibrium of essential oil on lipid in leaves. The adsorption equilibrium constant was fitted to these experimental data, and internal and external mass transfer resistances were calculated, allowing identification of the mechanism controlling the extraction process.

  15. AN INTERIM THERMODYNAMIC PROPERTY FORMULATION FOR SUPERCRITICAL n-HEXANE

    Directory of Open Access Journals (Sweden)

    Azzedine Abbaci

    2010-07-01

    Full Text Available Accurate information on the thermodynamic properties of supercritical fluids is highly sought for the chemical technology, especially, supercritical extraction technology. The thermodynamic properties of fluids near the critical region are strongly affected by the presence of fluctuations and therefore, can not be described by conventional equation. We have investigated an interim formulation for the behavior of the thermodynamic properties of n-hexane in the vicinity of the critical region. For this reason we have used the so-called “crossover model” to describe the thermodynamic properties of n-hexane in a wide range of temperatures and densities around the critical point.

  16. Supercritical carbon dioxide-based sterilization of decellularized heart valves.

    Science.gov (United States)

    Hennessy, Ryan S; Jana, Soumen; Tefft, Brandon J; Helder, Meghana R; Young, Melissa D; Hennessy, Rebecca R; Stoyles, Nicholas J; Lerman, Amir

    2017-02-01

    The goal of this research project encompasses finding the most efficient and effective method of decellularized tissue sterilization. Aortic tissue grafts have been utilized to repair damaged or diseased valves. Although, the tissues for grafting are collected aseptically, it does not eradicate the risk of contamination nor disease transfer. Thus, sterilization of grafts is mandatory. Several techniques have been applied to sterilize grafts; however, each technique shows drawbacks. In this study, we compared several sterilization techniques: supercritical carbon dioxide, electrolyzed water, gamma radiation, ethanol-peracetic acid, and hydrogen peroxide for impact on the sterility and mechanical integrity of porcine decellularized aortic valves. Valve sterility was characterized by histology, microbe culture, and electron microscopy. Uniaxial tensile testing was conducted on the valve cusps along their circumferential orientation to study these sterilization techniques on their integrity. Ethanol-peracetic acid and supercritical carbon dioxide treated valves were found to be sterile. The tensile strength of supercritical carbon dioxide treated valves (4.28 ± 0.22 MPa) was higher to those valves treated with electrolyzed water, gamma radiation, ethanol-peracetic acid and hydrogen peroxide (1.02 ± 0.15, 1.25 ± 0.25, 3.53 ± 0.41 and 0.37 ± 0.04 MPa, respectively). Superior sterility and integrity were found in the decellularized porcine aortic valves with supercritical carbon dioxide sterilization. This sterilization technique may hold promise for other decellularized soft tissues. Sterilization of grafts is essential. Supercritical carbon dioxide, electrolyzed water, gamma radiation, ethanol-peracetic acid, and hydrogen peroxide techniques were compared for impact on sterility and mechanical integrity of porcine decellularized aortic valves. Ethanol-peracetic acid and supercritical carbon dioxide treated valves were found to be sterile using histology, microbe

  17. Solubilities of triolein in supercritical CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, M.A.; Bernardo-Gil, M.G. [Instituto Superior Tecnico, Lisboa (Portugal). Dept. de Engenharia Quimica

    1995-11-01

    A vegetable oil typically consists of a range of triglycerides, approximately 10% diglycerides, and a small fraction of free fatty acids and other minor constituents. The use of supercritical carbon dioxide for solvent extraction is currently the subject of numerous investigations. The solubilities of triolein in supercritical carbon dioxide were measured over a temperature range of 308--328 K and at pressures between 8 and 20 MPa by the static method. The data were correlated by the model proposed by Chrastil and the modification proposed by Adachi and Lu and Del Valle and Aguilera.

  18. SOLID PHASE TRANSITION OF SYNDIOTACTIC POLYSTYRENE IN SUPERCRITICAL CO2

    Institute of Scientific and Technical Information of China (English)

    Yu-ying Li; Jia-song He

    2002-01-01

    Solid phase transition of the a form crystals to the β form crystals in syndiotactic polystyrene (sPS) samples has occurred in supercritical CO2. This transformation is different from those detected under other conditions. The effects of some factors (e.g. time, temperature, and pressure) on the solid phase transformation of sPS in supercritical CO2 were analyzed in detail. Experimental results show that longer time, higher temperature or higher pressure favors the transformation of the α form crystals to the β form crystals.

  19. Supercritical water oxidation - Concept analysis for evolutionary Space Station application

    Science.gov (United States)

    Hall, John B., Jr.; Brewer, Dana A.

    1986-01-01

    The ability of a supercritical water oxidation (SCWO) concept to reduce the number of processes needed in an evolutionary Space Station design's Environmental Control and Life Support System (ECLSS), while reducing resupply requirements and enhancing the integration of separate ECLSS functions into a single Supercritical Water Oxidation process, is evaluated. While not feasible for an initial operational capability Space Station, the SCWO's application to the evolutionary Space Station configuration would aid the integration of eight ECLSS functions into a single one, thereby significantly reducing program costs.

  20. Neural networks for predicting mass transfer parameters in supercritical extraction

    Directory of Open Access Journals (Sweden)

    A.P. Fonseca

    2000-12-01

    Full Text Available Neural networks have been investigated for predicting mass transfer coefficients from supercritical Carbon Dioxide/Ethanol/Water system. To avoid the difficulties associated with reduce experimental data set available for supercritical extraction in question, it was chosen to use a technique to generate new semi-empirical data. It combines experimental mass transfer coefficient with those obtained from correlation available in literature, producing an extended data set enough for efficient neural network identification. With respect to available experimental data, the results obtained to benefit neural networks in comparing with empirical correlations for predicting mass transfer parameters.

  1. Extraction of oil from wheat germ by supercritical CO2.

    Science.gov (United States)

    Piras, Alessandra; Rosa, Antonella; Falconieri, Danilo; Porcedda, Silvia; Dessì, Maria A; Marongiu, Bruno

    2009-07-15

    This study examined the supercritical fluid extraction of wheat germ oil. The effects of pressure (200-300 bar at 40 degrees C) and extraction time on the oil quality/quantity were studied. A comparison was also made between the relative qualities of material obtained by SFE and by organic solvent extraction. The extracts were analyzed for alpha-tocopherol and polyunsaturated fatty acid content. The maximum wheat germ oil yield at about 9% was obtained with supercritical carbon dioxide extraction at 300 bar, while fatty acid and alpha-tocopherol composition of the extracts was not remarkable affected by either pressure or the extraction method.

  2. [Chemical constituents from supercritical CO2 extraction of Schisandra chinensis].

    Science.gov (United States)

    Zhu, Hong-yan; Lin, Hai-cheng; Wang, Guo-li; Zhang, Lian-xue

    2014-11-01

    To study the chemical constituents from the supercritical CO2 extraction of Schisandra chinensis. The compounds were separated and purified by conventional column chromatography and their structures were identified by spectroscopic methods. Nine compounds were isolated from the supercritical CO2 extraction of Schisandra chinensis, and their structures were identified as chrysophanol(1),schisandrin B(2), β-sitosterol(3), schisandrin C(4),schisandrol A(5), angeloylgomisin H(6), daucosterol(7) 1, 5-dimethyl citrate (8), and shikimic acid (9). Compounds 1, 8 and 9 are isolated from Schisandra chinensis for the first time,and compound 1 as an anthraquinone is isolated from this genus for the first time.

  3. Processing of polyolefin blends in supercritical propane solution

    Science.gov (United States)

    Han, Suh Joon

    New polymer blending methods are developed and studied by processing polyolefins in supercritical propane in this research. Polypropylene and ethylene copolymers were dissolved in supercritical propane, and processed via various paths and reactions, i.e., RESS (rapid expansion of supercritical solution), ICSS (isobaric crystallization from supercritical solution), and thermoplastic vulcanizate (TPV) formation. Each process resulted in a unique morphology of polyolefin blends. The effect of polyolefin microstructure on the solution behavior in supercritical propane was investigated, and the relationship between the morphology of the polyolefin blends and processing paths in supercritical propane solutions was established. To understand the thermodynamic properties of polyolefins in bulk and solutions, the solubility parameter was estimated by measurement of the internal pressure from the experimental P-V-T data for polyolefins in the melt state. As the short chain branch content in the ethylene copolymers increased, the internal pressure decreased. The cloud-point pressures of binary polymer solutions in propane decreased as the extent of short chain branching increased in the ethylene copolymers. At the same degree of branching, the cloud-point pressure decreased slightly with increasing branch length. The cloud-point pressures of a ternary polymer solution in the pressure-temperature phase diagrams were higher than those of binary polymer solutions at the same composition (indicating poorer solubility). Microfibers and microparticles (10 ˜ 50 mum diameter) were precipitated from the RESS process while microcellular foams were obtained from the ICSS process. The phase domains of the ethylene-butene (EB) copolymer in the polypropylene from the RESS process were smaller for highly branched EB copolymer. The surface morphology of ethylene copolymers in the microcelluar foams was also changed by increasing the branch content from microparticles to a viscous layer. New

  4. Generic supercritical water technology; Generic technology to shite no chorinkaisui riyo gijutsu

    Energy Technology Data Exchange (ETDEWEB)

    Arai, K.; Ajiri, M.; Inomata, H.; Smith, R.; Hakuta, Y. [Tohoku University, Sendai (Japan). Faculty of Engineering; Yokoyama, C. [Tohoku University, Sendai (Japan). The Institute forChemical Reaction Science; Chin, L. [New Energy and Industrial Technology Development Organization, Tokyo, (Japan)

    1997-02-01

    This paper describes the measurement and analysis for clarifying solution structure of supercritical water and exhibition mechanism of solvent functions. It also describes the development of new processes using supercritical water as reaction solvent. The PVT measurements were conducted in the supercritical region using pure water and NaCl aqueous solution, to confirm the reduction of molar volume of the electrolyte solution. The hydration structure was examined in the supercritical aqueous solution by the molecular dynamic simulation. As a result, presence of hydrogen bond structure, where the contribution of two branching hydrogen bond can not be ignored, was suggested under the supercritical condition. Characteristics of supercritical aqueous solutions are analyzed through in-situ Raman and scattered X-ray spectral measurements. Moreover, this paper introduces developments of some processes in the supercritical water, such as decomposition of wasted polymers, recovery of chemical materials, reforming of heavy hydrocarbons by contact hydrogenation, and synthesis of fine powders of metal oxide by reaction crystallization.

  5. Molecular dynamics simulation of the key characteristics of the supercritical CO2-pentaerythritol tetraacetate system

    Science.gov (United States)

    Lei, Peiyu; Jin, Zunlong; Liu, Hong; Wang, Dingbiao; Liu, Donglai

    2016-12-01

    Supercritical CO2 is widely used in many fields of industry. Investigation of statistical mechanics of CO2 fluid under quasi critical and supercritical state has great significance. Equilibrium molecular dynamics (EMD) simulations are carried out to investigate the statistical mechanics and macroscopic performance of CO2 fluid under the quasi critical and supercritical state. The results show that the bond length and bond angle distributions for supercritical CO2 are Gaussian distribution basically. The dimers' proportion of supercritical CO2 system changes with pressure increasing. T-type dimer has high share within the system when pressure is higher than 9MPa. It can be inferred that T-type dimer leads to CO2 physical properties changing tempestuously under supercritical state. The effect that lubricating oil has on microstructure and heat transfer of supercritical CO2 is also investigated in the present work. The results show the lubricating oil produces significant effect on the dimers' structure under low pressure.

  6. Treatment of sewage sludge in supercritical water and evaluation of the combined process of supercritical water gasification and oxidation.

    Science.gov (United States)

    Qian, Lili; Wang, Shuzhong; Xu, Donghai; Guo, Yang; Tang, Xingying; Wang, Longfei

    2015-01-01

    Influences of temperature and oxidation coefficient (n) on sewage sludge treatment in supercritical water and its corresponding reaction mechanism were studied. Moreover, the combined process of supercritical water gasification (SCWG) and supercritical water oxidation (SCWO) was also investigated. The results show that ammonia nitrogen, phenols and pyridines are main refractory intermediates. The weight of solid products at 873K and n=4 is only 3.5wt.% of the initial weight, which is lower than that after combustion. Volatile organics in solid phase have almost released at 723K and n=0. Highest yield of combustible gases was obtained at n=0, and H2 yield can reach 11.81mol/kg at 873K. Furthermore, the combination of SCWG at 723K and SCWO at 873K with a total n=1 is feasible for its good effluent quality and low operation costs.

  7. Review of the coal-fired, over-supercritical and ultra-supercritical steam power plants

    Science.gov (United States)

    Tumanovskii, A. G.; Shvarts, A. L.; Somova, E. V.; Verbovetskii, E. Kh.; Avrutskii, G. D.; Ermakova, S. V.; Kalugin, R. N.; Lazarev, M. V.

    2017-02-01

    The article presents a review of developments of modern high-capacity coal-fired over-supercritical (OSC) and ultra-supercritical (USC) steam power plants and their implementation. The basic engineering solutions are reported that ensure the reliability, economic performance, and low atmospheric pollution levels. The net efficiency of the power plants is increased by optimizing the heat balance, improving the primary and auxiliary equipment, and, which is the main thing, by increasing the throttle conditions. As a result of the enhanced efficiency, emissions of hazardous substances into the atmosphere, including carbon dioxide, the "greenhouse" gas, are reduced. To date, the exhaust steam conditions in the world power industry are p 0 ≈ 30 MPa and t 0 = 610/620°C. The efficiency of such power plants reaches 47%. The OSC plants are being operated in Germany, Denmark, Japan, China, and Korea; pilot plants are being developed in Russia. Currently, a project of a power plant for the ultra-supercritical steam conditions p 0 ≈ 35 MPa and t 0 = 700/720°C with efficiency of approximately 50% is being studied in the EU within the framework of the Thermie AD700 program, project AD 700PF. Investigations in this field have also been launched in the United States, Japan, and China. Engineering solutions are also being sought in Russia by the All-Russia Thermal Engineering Research Institute (VTI) and the Moscow Power Engineering Institute. The stated steam parameter level necessitates application of new materials, namely, nickel-base alloys. Taking into consideration high costs of nickel-base alloys and the absence in Russia of technologies for their production and manufacture of products from these materials for steam-turbine power plants, the development of power plants for steam parameters of 32 MPa and 650/650°C should be considered to be the first stage in creating the USC plants as, to achieve the above parameters, no expensive alloys are require. To develop and

  8. Supercritical fluid extraction: Present status and prospects

    Directory of Open Access Journals (Sweden)

    King, Jerry W.

    2002-03-01

    Full Text Available Supercritical extraction (SFE, using primarily environmentally-benign carbon dioxide (CO2 as the extracting agent, is reviewed with respect to its present status and future use. SFE was developed for analytical application in the mid 1980’s in response to the desire to reduce the use of organic solvents in the laboratory environment and is becoming a standard method for the preparation and analysis of lipid-containing sample matrices. Currently, analytical SFE is predominately practiced in the off-line mode, using both sequential and parallel extraction modes. Depending on the instrumental configuration, the preparation of up to 24 samples can be accomplished on one instrument on a daily basis. Several other benefits can be achieved using SFE, such as the processing of thermally-sensitive analytes and rapid analyte extraction kinetics relative to extraction with liquid solvents. Examples are provided not only of the analytical SFE of oils and fats, but of volatile solutes from an array of sample types. Finally, the relevance of analytical SFE to processing with supercritical fluids (SFs is documented using examples from our own research involving a combinatorial approach to optimising processing conditions.Este artículo revisa el presente y el uso futuro de la extracción con fluidos supercríticos (SFE, principalmente dióxido de carbono (CO2 benigno para el ambiente. La extracción con fluidos supercríticos se desarrolló como aplicación analítica a mediados de los años 80 como respuesta al deseo de reducir el uso de disolventes orgánicos en el ambiente del laboratorio, y se está convirtiendo en un método estándar con respecto a la preparación y análisis de muestras conteniendo lípidos. Actualmente, la analítica de SFE es predominantemente aplicada en modo “off-line”, usando modos de extracción secuenciales y paralelos. Dependiendo de la configuración de la instrumentación, se pueden llegar a preparar diariamente

  9. Supercritical water pyrolysis of sewage sludge.

    Science.gov (United States)

    Ma, Wenchao; Du, Guiyue; Li, Jian; Fang, Yuanhao; Hou, Li'an; Chen, Guanyi; Ma, Degang

    2017-01-01

    Municipal sewage sludge (SS) from wastewater treatment plant containing high water content (>85wt.%), lead to the difficulty of co-combustion with MSW or coal due to the high cost of drying. This study explores an alternative method by supercritical water (SCW) pyrolysis of sewage sludge (SS) in a high pressure reaction vessel. The effects of temperature and moisture content of SS on yield and composition of the products (bio-oil, bio char and non-condensable gas) were studied. A temperature of 385°C and moisture content of 85wt.% were found to be the optimum conditions for the maximum bio-oil production of 37.23wt.%, with a higher heating value of 31.08MJ/kg. In the optimum condition, the yields of aliphatic hydrocarbon and phenols were about 29.23wt.% and 12.51wt.%, respectively. The physical and chemical properties of bio-char were analyzed by using XRF and BET. Results of GC analyses of NCG showed that it has the maximum HHV of 13.39MJ/m(3) at 445°C and moisture content of 85wt.%. The reaction path from SS to bio-oil through SCW pyrolysis was given. Moreover, carbon balance was calculated for the optimal condition, and finding out that 64.27wt.% of the carbon content was transferred from SS to bio-oil. Finally, this work demonstrates that the SCW pyrolysis is a promising disposal method for SS. Copyright © 2016. Published by Elsevier Ltd.

  10. Microbial Inactivation by Ultrasound Assisted Supercritical Fluids

    Science.gov (United States)

    Benedito, Jose; Ortuño, Carmen; Castillo-Zamudio, Rosa Isela; Mulet, Antonio

    A method combining supercritical carbon dioxide (SC-CO2) and high power ultrasound (HPU) has been developed and tested for microbial/enzyme inactivation purposes, at different process conditions for both liquid and solid matrices. In culture media, using only SC-CO2, the inactivation rate of E. coli and S. cerevisiae increased with pressure and temperature; and the total inactivation (7-8 log-cycles) was attained after 25 and 140 min of SC-CO2 (350 bar, 36 °C) treatment, respectively. Using SC-CO2+HPU, the time for the total inactivation of both microorganisms was reduced to only 1-2 min, at any condition selected. The SC-CO2+HPU inactivation of both microorganisms was slower in juices (avg. 4.9 min) than in culture media (avg. 1.5 min). In solid samples (chicken, turkey ham and dry-cured pork cured ham) treated with SC-CO2 and SC-CO2+HPU, the inactivation rate of E. coli increased with temperature. The application of HPU to the SC-CO2 treatments accelerated the inactivation rate of E. coli and that effect was more pronounced in treatments with isotonic solution surrounding the solid food samples. The application of HPU enhanced the SC-CO2 inactivation mechanisms of microorganisms, generating a vigorous agitation that facilitated the CO2 solubilization and the mass transfer process. The cavitation generated by HPU could damage the cell walls accelerating the extraction of vital constituents and the microbial death. Thus, using the combined technique, reasonable industrial processing times and mild process conditions could be used which could result into a cost reduction and lead to the minimization in the food nutritional and organoleptic changes.

  11. Relativistic Radiation Mediated Shocks

    CERN Document Server

    Budnik, Ran; Sagiv, Amir; Waxman, Eli

    2010-01-01

    The structure of relativistic radiation mediated shocks (RRMS) propagating into a cold electron-proton plasma is calculated and analyzed. A qualitative discussion of the physics of relativistic and non relativistic shocks, including order of magnitude estimates for the relevant temperature and length scales, is presented. Detailed numerical solutions are derived for shock Lorentz factors $\\Gamma_u$ in the range $6\\le\\Gamma_u\\le30$, using a novel iteration technique solving the hydrodynamics and radiation transport equations (the protons, electrons and positrons are argued to be coupled by collective plasma processes and are treated as a fluid). The shock transition (deceleration) region, where the Lorentz factor $ \\Gamma $ drops from $ \\Gamma_u $ to $ \\sim 1 $, is characterized by high plasma temperatures $ T\\sim \\Gamma m_ec^2 $ and highly anisotropic radiation, with characteristic shock-frame energy of upstream and downstream going photons of a few~$\\times\\, m_ec^2$ and $\\sim \\Gamma^2 m_ec^2$, respectively.P...

  12. Survival Time of a Censored Supercritical Galton-Watson Process

    CERN Document Server

    Couronné, Olivier

    2011-01-01

    We study the asymptotic behavior of the survival time of a supercritical Galton-Watson process censored at a certain level. As a byproduct we obtain the asymptotics for the speed of a particular case of a particle system with branching and selection introduced by B\\'erard and Gou\\'er\\'e (2010).

  13. Research activities on supercritical fluid science in food biotechnology.

    Science.gov (United States)

    Khosravi-Darani, Kianoush

    2010-06-01

    This article serves as an overview, introducing the currently popular area of supercritical fluids and their uses in food biotechnology. Within each application, and wherever possible, the basic principles of the technique, as well as a description of the history, instrumentation, methodology, uses, problems encountered, and advantages over the traditional, non-supercritical methods are given. Most current commercial application of the supercritical extraction involve biologically-produced materials; the technique may be particularly relevant to the extraction of biological compounds in cases where there is a requirement for low-temperature processing, high mass-transfer rates, and negligible carrying over of the solvent into the final product. Special applications to food processing include the decaffeination of green coffee beans, the production of hops extracts, the recovery of aromas and flavors from herbs and spices, the extraction and fractionation of edible oils, and the removal of contaminants, among others. New advances, in which the extraction is combined with reaction or crystallization steps, may further increase the attractiveness of supercritical fluids in the bioprocess industries. To develop and establish a novel and effective alternative to heating treatment, the lethal action of high hydrostatic pressure CO(2) on microorganisms, with none or only a minimal heating process, has recently received a great deal of attention.

  14. Solubilities of sub- and supercritical carbon dioxide in polyester resins

    NARCIS (Netherlands)

    Nalawade, SP; Picchioni, F; Janssen, LPBM; Patil, VE; Keurentjes, JTF; Staudt, R; Nalawade, Sameer P.; Patil, Vishal E.; Keurentjes, Jos T.F.

    In supercritical carbon dioxide (CO2) assisted polymer processes the solubility of CO2 in a polymer plays a vital role. The higher the amount of CO2 dissolved in a polymer the higher is the viscosity reduction of the polymer. Solubilities Of CO2 in polyester resins based on propoxylated bisphenol

  15. Reforming of methanol and glycerol in supercritical water

    NARCIS (Netherlands)

    van Bennekom, J. G.; Venderbosch, R. H.; Assink, D.; Heeres, H. J.

    2011-01-01

    Reforming of pure glycerol, crude glycerin, and methanol (pure and in the presence of Na(2)CO(3)) in supercritical water was investigated. Continuous experiments were carried out at temperatures between 450 and 650 degrees C, residence times between 6 and 173 s, and feed concentrations of 3-20 wt%.

  16. Large Deviation for Supercritical Branching Processes with Immigration

    Institute of Scientific and Technical Information of China (English)

    Jing Ning LIU; Mei ZHANG

    2016-01-01

    In this paper, we study the large deviation for a supercritical branching process with immigration controlled by a sequence of non-negative integer-valued independently identical distributed random variables, improving the previous results for non immigration processes. We rely heavily on the detail description and limit property of the generating function of immigration processes.

  17. Stability of wheat germ oil obtained by supercritical carbon dioxide ...

    African Journals Online (AJOL)

    심정은

    with 1,3-regiospecific lipase at different temperatures (40 to 70°C) to produce diglycerides and ... Key words: Supercritical carbon dioxide, wheat germ oil, ethanolysis, .... Methanol (1 mL), replacing the extract, was used as the blank. The.

  18. Supercritical carbon dioxide process for pasteurization of fruit juices

    Science.gov (United States)

    Supercritical carbon dioxide (SCCO2) nonthermal processing inactivates microorganisms in juices using non-toxic and non-reactive CO2. However, data is lacking on the inactivation of E. coli K12 and L. plantarum in apple cider using pilot plant scale SCCO2 equipment. For this study, pasteurized pres...

  19. Supercritical Fluid Chromatography- A Hybrid of GC and LC

    Directory of Open Access Journals (Sweden)

    Kaushal K Chandrul

    2010-03-01

    Full Text Available

    High performance specifications and unique functionality of chromatographic techniques is a demand of pharmaceutical industry and research. This leads to the origin of Supercritical Fluid Chromatography (SFC. It is a rapidly expanding analytical technique. The main feature that differentiates SFC from other chromatographic techniques is the replacement of either the liquid or gas mobile phase with a supercritical fluid mobile phase. It is considered a hybrid of GC and LC technique. High diffusion coefficient and low viscosity of supercritical fluids is responsible for high speed analysis, high efficiency and high sensitivity. Low mobile-phase flow rate, density programming and compatability with GC and LC detectors make SFC a versatile chromatographic technique in analytical research and development. It has a unique characteristic of analyzing thermo labile or non-volatile substances. This review highlights the role of supercritical fluid chromatography in the separation of polymers, thermally labile pesticides, fatty acids, metal chelates and organometallic compounds, chiral and achiral molecules, identification and analysis of polar samples, explosives, drugs of abuse and application of SFC in forensic science (fingerprinting. 

  20. Supercritical fluid chromatography-A Hybrid of GC and LC

    Directory of Open Access Journals (Sweden)

    Neha Sethi

    2010-01-01

    Full Text Available High performance specifications and unique functionality of chromatographic techniques is a demand of pharmaceutical industry and research. This leads to the origin of Supercritical Fluid Chromatography (SFC. It is a rapidly expanding analytical technique. The main feature that differentiates SFC from other chromatographic techniques is the replacement of either the liquid or gas mobile phase with a supercritical fluid mobile phase. It is considered a hybrid of GC and LC technique. High diffusion coefficient and low viscosity of supercritical fluids is responsible for high speed analysis, high efficiency and high sensitivity. Low mobile-phase flow rate, density programming and compatability with GC and LC detectors make SFC a versatile chromatographic technique in analytical re-search and development. It has a unique characteristic of analyzing thermo labile or non-volatile substances. This review highlights the role of supercritical fluid chromatography in the separation of polymers, thermally labile pesticides, fatty acids, metal chelates and organometallic compounds, chiral and achiral molecules, identification and analysis of polar samples, explosives, drugs of abuse and application of SFC in forensic science (fingerprint-ing.

  1. Preparation of PMMA Foam by Supercritical CO2 with Ethanol

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Supercritical CO2 with ethanol as blowing agent foamed poly(methylmethacrylate) (PMMA) fiber at 308.15K and in the pressure range from 12-15MPa. The foam structure was detected using scanning electron microscope. It was found that the concentration of ethanol in the fluid is a major parameter to affect the foam structure.

  2. WaiGao Qiao: taking supercritical technology to new heights

    Energy Technology Data Exchange (ETDEWEB)

    Kessel, W.; Weiss, G.; Kawa, P. [Alstom, Stuttgart (Germany)

    2006-06-15

    In their first two years of commercial life the two supercritical boilers of Wai Gao Qiao Phase II, at 900 MWe each the largest operating coal fired units in China and the largest tangentially fired bituminous coal fired boilers in the world have performed reliably and efficiently. 11 figs., 1 tab.

  3. Extraction of heavy oil by supercritical carbon dioxide

    DEFF Research Database (Denmark)

    Rudyk, Svetlana Nikolayevna; Spirov, Pavel; Søgaard, Erik Gydesen

    2010-01-01

    The present study deals with the extraction of heavy oil by supercritical carbon dioxide at the pressure values changing from 16 to 56 MPa at the fixed value of temperature: 60oC. The amount of the recovered liquid phase of oil was calculated as a percentage of the extracted amount to the initial...

  4. Solubilities of ferrocene and acetylferrocene in supercritical carbon dioxide

    DEFF Research Database (Denmark)

    Kazemi, Somayeh; Belandria, Veronica; Janssen, Nico

    2012-01-01

    In this work, the solubilities of ferrocene and acetylferrocene in supercritical carbon dioxide (scCO2) were measured using an analytical method in a quasi-flow apparatus. High-performance liquid chromatography was applied through an online sampling procedure to determine the concentration...

  5. Capillary supercritical fluid chromatography-mass spectrometry (SFC-MS)

    Energy Technology Data Exchange (ETDEWEB)

    Kalinoski, H.T.; Udseth, H.R.; Chess, E.K.; Smith, R.D.

    1986-10-01

    The physical and chemical characteristics of supercritical fluids have prompted the development of supercritical fluid chromatography (SFC) for the analysis of labile and less volatile compounds. High resolution chromatographic separations with efficiencies approaching those of gas chromatography and high speed analyses are possible in capillary SFC using pressure programming methods and narrow bore columns. Further refinement of the SFC-mass spectrometry interface (SFC-MS) provides the basis for extension to more polar fluid systems with greater solvating power and the selectivity and sensitivity of mass spectrometric detection. The use of polar modified fluids has been facilitated by advances in understanding of supercritical fluid phase behavior. Fluid mixtures have been prepared for analysis of more polar, higher molecular weight analytes, that allow mild chromatographic temperatures and allow full exploitation of selectivity offered through control of fluid pressure (i.e., density). Continuing development of the SFC-MS interface has led to designs which can be near routinely applied with fluids such as CO/sub 2/, and providing enhanced transport of truly nonvolatile compounds to the mass spectrometer ionization regions. These advances also include an SFC interface to a high resolution, dual electric magnetic sector instrument, allowing supercritical fluid solvents to be explited for on-line extraction-mass spectrometry for characterization of complex, often otherwise intractable, materials. 26 refs., 5 figs., 1 tab.

  6. Manometric determination of supercritical gas sorption in coal

    NARCIS (Netherlands)

    Van Hemert, P.

    2009-01-01

    The characteristics of the manometric method are investigated so that it can be used to obtain accurate data of sorption of supercritical gas in coal. Furthermore, data of the sorption of carbon dioxide, methane and nitrogen in coal at in situ conditions have been determined. Accurate data are req

  7. Statistical mechanical description of supercritical fluid extraction and retrograde condensation

    Science.gov (United States)

    Park, S. J.; Kwak, T. Y.; Mansoori, G. A.

    1987-07-01

    The phenomena of supercritical fluid extraction (SFE) and its reverse effect, which is known as retrograde condensation (RC), have found new and important applications in industrial separation of chemical compounds and recovery and processing of natural products and fossil fuels. Full-scale industrial utilization of SFE/RC processes requires knowledge about thermodynamic and transport characteristics of the asymmetric mixtures involved and the development of predictive modeling and correlation techniques for performance of the SFE/RC system under consideration. In this report, through the application of statistical mechanical techniques, the reasons for the lack of accuracy of existing predictive approaches are described and they are improved. It is demonstrated that these techniques also allow us to study the effect of mixed supercritical solvents on the solubility of heavy solutes (solids) at different compositions of the solvents, pressures, and temperatures. Fluid phase equilibrium algorithms based on the conformal solution van der Waals mixing rules and different equations of state are presented for the prediction of solubilities of heavy liquid in supercritical gases. It is shown that the Peng-Robinson equation of state based on conformal solution theory can predict solubilites of heavy liquid in supercritical gases more accurately than the van der Waals and Redlich-Kwong equations of state.

  8. THE UNIQUENESS OF BIFURCATION TO SEPARATRIX LOOPS IN SUPERCRITICAL CASES

    Institute of Scientific and Technical Information of China (English)

    SUNJIANHUA

    1994-01-01

    In paper[4] the existence of bifurcation to separatrix loops in supercritical cases on the plane is studied.This note is a continuation of [4].The author proves the uniqueness of limit cycles in a neighb-orhood of the separatrix loop,and the results strengthen the relevant conclusions in[1-6].

  9. Promising flame retardant textile in supercritical carbon dioxide

    Science.gov (United States)

    Since carbon dioxide is non-toxic, non-flammable and cost-effective, supercritical carbon dioxide (scCO2) is widely used in textile dyeing applications. Due to its environmentally benign character, scCO2 is considered in green chemistry as a substitute for organic solvents in chemical reactions. O...

  10. Supercritical fluid chromatography for lipid analysis in foodstuffs.

    Science.gov (United States)

    Donato, Paola; Inferrera, Veronica; Sciarrone, Danilo; Mondello, Luigi

    2017-01-01

    The task of lipid analysis has always challenged separation scientists, and new techniques in chromatography were often developed for the separation of lipids; however, no single technique or methodology is yet capable of affording a comprehensive screening of all lipid species and classes. This review acquaints the role of supercritical fluid chromatography within the field of lipid analysis, from the early developed capillary separations based on pure CO2 , to the most recent techniques employing packed columns under subcritical conditions, including the niche multidimensional techniques using supercritical fluids in at least one of the separation dimensions. A short history of supercritical fluid chromatography will be introduced first, from its early popularity in the late 1980s, to the sudden fall and oblivion until the last decade, experiencing a regain of interest within the chromatographic community. Afterwards, the subject of lipid nomenclature and classification will be briefly dealt with, before discussing the main applications of supercritical fluid chromatography for food analysis, according to the specific class of lipids.

  11. Supercritical fluid extraction and bioactivity of cedarwood oil

    Science.gov (United States)

    Supercritical carbon dioxide (70°C, 4,000 psi) was used to extract cedarwood oil from Eastern redcedar, Juniperus virginiana L. The CO2-derived oil was tested for biological activity against several species of arthropods, including mosquitoes, ticks, houseflies, and ants. The cedarwood oil was found...

  12. SUPERCRITICAL WATER OXIDATION MODEL DEVELOPMENT FOR SELECTED EPA PRIORITY POLLUTANTS

    Science.gov (United States)

    Supercritical Water Oxidation (SCWO) evaluated for five compounds: acetic acid, 2,4-dichlorophenol, pentachlorophenol, pyridine, 2,4-dichlorophenoxyacetic acid (methyl ester). inetic models were developed for acetic acid, 2,4-dichlorophenol, and pyridine. he test compounds were e...

  13. Up-Scaled Supercritical Flow Synthesis of Hybrid Materials

    DEFF Research Database (Denmark)

    Hellstern, Henrik Christian; Becker, Jacob; Hald, Peter

    A new, up-scaled supercritical flow synthesis apparatus is currently under construction in Aarhus. A module based system allows for a range of parameter studies with improved parameter control. The dual-reactor setup enables both single phase and core-shell nanoparticle synthesis, and the large...

  14. Treatment of municipal sewage sludge in supercritical water: A review.

    Science.gov (United States)

    Qian, Lili; Wang, Shuzhong; Xu, Donghai; Guo, Yang; Tang, Xingying; Wang, Laisheng

    2016-02-01

    With increasing construction of wastewater treatment plants and stricter policies, municipal sewage sludge (MSS) disposal has become a serious problem. Treatment of MSS in supercritical water (SCW) can avoid the pre-drying procedure and secondary pollution of conventional methods. SCW treatment methods can be divided into supercritical water gasification (SCWG), supercritical water partial oxidation (SCWPO) and supercritical water oxidation (SCWO) technologies with increasing amounts of oxidants. Hydrogen-rich gases can be generated from MSS by SCWG or SCWPO technology using oxidants less than stoichiometric ratio while organic compounds can be completely degraded by SCWO technology with using an oxidant excess. For SCWG and SCWPO technologies, this paper reviews the influences of different process variables (MSS properties, moisture content, temperature, oxidant amount and catalysts) on the production of gases. For SCWO technology, this paper reviews research regarding the removal of organics with or without hydrothermal flames and the changes in heavy metal speciation and risk. Finally, typical systems for handling MSS are summarized and research needs and challenges are proposed.

  15. The solubilities of phosphate and sulfate salts in supercritical water

    NARCIS (Netherlands)

    Leusbrock, Ingo; Metz, Sybrand J.; Rexwinkel, Glenn; Versteeg, Geert F.

    2010-01-01

    Inorganic compounds are regularly present in aqueous streams. To understand their influence and behavior on these streams at supercritical conditions, little to no property data is available, which can be used as starting point for further research or application design. Since inorganic compounds te

  16. Supercritical Water Gasification of Biomass: A Literature and Technology Overview

    NARCIS (Netherlands)

    Yakaboylu, O.; Harinck, J.; Smit, K.G.; De Jong, W.

    2014-01-01

    The supercritical water gasification process is an alternative to both conventional gasification as well as anaerobic digestion as it does not require drying and the process takes place at much shorter residence times; a few minutes at most. The drastic changes in the thermo-physical properties of w

  17. Cobalt carbonyl catalyzed olefin hydroformylation in supercritical carbon dioxide

    Science.gov (United States)

    Rathke, Jerome W.; Klingler, Robert J.

    1993-01-01

    A method of olefin hydroformylation is provided wherein an olefin reacts with a carbonyl catalyst and with reaction gases such as hydrogen and carbon monoxide in the presence of a supercritical reaction solvent, such as carbon dioxide. The invention provides higher yields of n-isomer product without the gas-liquid mixing rate limitation seen in conventional Oxo processes using liquid media.

  18. Green dyeing of cotton fabrics by supercritical carbon dioxide

    Directory of Open Access Journals (Sweden)

    Zhang Juan

    2015-01-01

    Full Text Available Green dyeing process with zero waste water emission is a hot topic recently. This paper reveals that supercritical carbon dioxide is the best candidate for this purpose. Effects of thermodynamic parameters, such as enthalpy and entropy of activation, on dyeing process are studied experimentally.

  19. Supercritical water oxidation data acquisition testing. Final report, Volume I

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-11-01

    This report discusses the phase one testing of a data acquisition system for a supercritical water waste oxidation system. The system is designed to destroy a wide range of organic materials in mixed wastes. The design and testing of the MODAR Oxidizer is discussed. An analysis of the optimized runs is included.

  20. Solubilities of sub- and supercritical carbon dioxide in polyester resins

    NARCIS (Netherlands)

    Nalawade, SP; Picchioni, F; Janssen, LPBM; Patil, VE; Keurentjes, JTF; Staudt, R; Nalawade, Sameer P.; Patil, Vishal E.; Keurentjes, Jos T.F.

    2006-01-01

    In supercritical carbon dioxide (CO2) assisted polymer processes the solubility of CO2 in a polymer plays a vital role. The higher the amount of CO2 dissolved in a polymer the higher is the viscosity reduction of the polymer. Solubilities Of CO2 in polyester resins based on propoxylated bisphenol (P

  1. Aerobic Oxidation of Methyl Vinyl Ketone in Supercritical Carbon Dioxide

    Institute of Scientific and Technical Information of China (English)

    OUYANG,Xiao-Yue(欧阳小月); JIANG,Huan-Feng(江焕峰); CHENG,Jin-Sheng(程金生); ZHANG,Qun-Jian(张群健)

    2002-01-01

    Aerobic oxidation of methyl vinyl ketone to acetal in supercritical carbon dioxide are achieved in high conversion and high selectivity when oxygen pressure reaches 0.5MPa. The effects of cocatalysts,additive, pressure and temperature of the reaction are studied in detail.

  2. Preparation of Aromatic Polycarbonate Nanoparticles using Supercritical Carbon Dioxide

    Science.gov (United States)

    Lee, Jun-Young; Song, Cheong-Hun; Kim, Joong-In; Kim, Jung-Hyun

    2002-04-01

    A novel synthetic process for producing aromatic polycarbonate (PC) nanoparticles using supercritical CO2 was developed. The objective of the present research work was to synthesize high molecular weight PC nanoparticles using transesterification between bisphenol-A (BPA) and diphenyl carbonate (DPC) in supercritical CO2 which is an excellent plasticizing agent and a good solvent for phenol, a by-product of the reaction. Poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) tri-block copolymer with CO2-phobic anchor and CO2-philic tail group was used as a stabilizer for the preparation of stable dispersions of BPA-DPC mixture in a CO2 continuous phase. As the reaction was proceeding, phenol formed from the reaction was dissolved and diffused into supercritical CO2 phase. The PC nanoparticles were isolated by simple venting of the supercritical CO2 from the reactor. Spherical morphology of PC particles was confirmed by scanning electron microscopy. Particle size and morphology of PC particles were modified upon variation of the process conditions. The resulting PC particles with a nano-size of 30-140 nm have a high molecular weight ( M w) of 3.1×105 (g/mol).

  3. Preparing silica aerogel monoliths via a rapid supercritical extraction method.

    Science.gov (United States)

    Carroll, Mary K; Anderson, Ann M; Gorka, Caroline A

    2014-02-28

    A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The procedure requires 15-20 min of preparation time, during which a liquid precursor mixture is prepared and poured into wells of a metal mold that is placed between the platens of a hydraulic hot press, followed by several hours of processing within the hot press. The precursor solution consists of a 1.0:12.0:3.6:3.5 x 10(-3) molar ratio of tetramethylorthosilicate (TMOS):methanol:water:ammonia. In each well of the mold, a porous silica sol-gel matrix forms. As the temperature of the mold and its contents is increased, the pressure within the mold rises. After the temperature/pressure conditions surpass the supercritical point for the solvent within the pores of the matrix (in this case, a methanol/water mixture), the supercritical fluid is released, and monolithic aerogel remains within the wells of the mold. With the mold used in this procedure, cylindrical monoliths of 2.2 cm diameter and 1.9 cm height are produced. Aerogels formed by this rapid method have comparable properties (low bulk and skeletal density, high surface area, mesoporous morphology) to those prepared by other methods that involve either additional reaction steps or solvent extractions (lengthier processes that generate more chemical waste).The rapid supercritical extraction method can also be applied to the fabrication of aerogels based on other precursor recipes.

  4. Synthesis of fatty acid starch esters in supercritical carbon dioxide

    NARCIS (Netherlands)

    Muljana, Henky; van der Knoop, Sjoerd; Keijzer, Danielle; Picchioni, Francesco; Janssen, Leon P. B. M.; Heeres, Hero J.

    2010-01-01

    This manuscript describes an exploratory study on the synthesis of fatty acid/potato starch esters using supercritical carbon dioxide (scCO(2)) as the solvent. The effects of process variables such as pressure (6-25 MPa), temperature (120-150 degrees C) and various basic catalysts and fatty acid der

  5. Supercritical flows past a square cylinder with rounded corners

    Science.gov (United States)

    Cao, Yong; Tamura, Tetsuro

    2017-08-01

    Large-eddy simulations were used to investigate the supercritical aerodynamics of a square cylinder with rounded corners in comparison with those in the subcritical regime. First, the numerical methods, especially the dynamic mixed model, were validated on the basis of their prediction of supercritical flows past a circular cylinder. Then, the supercritical flows past a rounded-corner square cylinder were simulated and systematically clarified. Strong Reynolds number (Re) effects existed in the forces and local pressures as Re increased from o(104) to o(106). Changeover of flow patterns occurred as Re increased. At the supercritical Re, the free stream overall flowed along the cross sections of the cylinder, separated from the leeward corners and generated Karman vortices behind the cylinder. This pattern resulted in a much smaller recirculation region behind the cylinder compared with the subcritical flow. At the micro level, the flow experienced laminar separation and flow reattachment near the frontal corners, followed by the spatial development of turbulent boundary layers (TBLs) on the side faces and turbulent separation near the leeward corners. The feedback by large-scale primary vortex shedding and the small-scale turbulent motions in the high-frequency region with a slope of -5/3 were detected in the TBL. Their interaction affected the spanwise correlations of wall pressure fluctuations. The TBL on the side face differed from the zero-pressure-gradient flat-plate one; it was subjected to pressure gradients varying in space and time.

  6. Shock Detector for SURF model

    Energy Technology Data Exchange (ETDEWEB)

    Menikoff, Ralph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-01-11

    SURF and its extension SURFplus are reactive burn models aimed at shock initiation and propagation of detonation waves in high explosives. A distinctive feature of these models is that the burn rate depends on the lead shock pressure. A key part of the models is an algorithm to detect the lead shock. Typically, shock capturing hydro algorithms have small oscillations behind a shock. Here we investigate how well the shock detection algorithm works for a nearly steady propagating detonation wave in one-dimension using the Eulerian xRage code.

  7. Shock Detector for SURF model

    Energy Technology Data Exchange (ETDEWEB)

    Menikoff, Ralph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-01-11

    SURF and its extension SURFplus are reactive burn models aimed at shock initiation and propagation of detonation waves in high explosives. A distinctive feature of these models is that the burn rate depends on the lead shock pressure. A key part of the models is an algorithm to detect the lead shock. Typically, shock capturing hydro algorithms have small oscillations behind a shock. Here we investigate how well the shock detection algorithm works for a nearly steady propagating detonation wave in one-dimension using the Eulerian xRage code.

  8. Hydrogel Nanoparticles from Supercritical Technology for Pharmaceutical and Seismological Applications

    Science.gov (United States)

    Hemingway, Melinda Graham

    This research focuses on hydrogel nanoparticle formation using miniemulsion polymerization and supercritical carbon dioxide. Hydrogel nanopowder is produced by a novel combination of inverse miniemulsion polymerization and supercritical drying (MPSD) methods. Three drying methods of miniemulsions are examined: (1) a conventional freeze drying technique, and (2) two supercritical drying techniques: (2a) supercritical fluid injection into miniemulsions, and (2b) the polymerized miniemulsion injection into supercritical fluid. Method 2b can produce non-agglomerated hydrogel nanoparticles that are free of solvent or surfactant (Chapter 2). The optimized MPSD method was applied for producing an extended release drug formulation with mucoadhesive properties. Drug nanoparticles of mesalamine, were produced using supercritical antisolvent technology and encapsulation within two hydrogels, polyacrylamide and poly(acrylic acid-co-acrylamide). The encapsulation efficiency and release profile of drug nanoparticles is compared with commercial ground mesalamine particles. The loading efficiency is influenced by morphological compatibility (Chapter 3). The MPSD method was extended for encapsulation of zinc oxide nanoparticles for UV protection in sunscreens (Chapter 4). ZnO was incorporated into the inverse miniemulsion during polymerization. The effect of process parameters are examined on absorbency of ultraviolet light and transparency of visible light. For use of hydrogel nanoparticles in a seismological application, delayed hydration is needed. Supercritical methods extend MPSD so that a hydrophobic coating can be applied on the particle surface (Chapter 5). Multiple analysis methods and coating materials were investigated to elucidate compatibility of coating material to polyacrylamide hydrogel. Coating materials of poly(lactide), poly(sulphone), poly(vinyl acetate), poly(hydroxybutyrate), Geluice 50-13, Span 80, octadecyltrichlorosilane, and perfluorobutane sulfate (PFBS

  9. 超临界氨合成%AMMONIA SYNTHESIS AT SUPERCRITICAL CONDITIONS

    Institute of Scientific and Technical Information of China (English)

    刘化章; 唐浩东; 李小年

    2004-01-01

    Ammonia synthesis at supercritical conditions was first studied over iron and active carbonsupported ruthenium catalysts in a fixed-bed reactor. The influences of 15 kinds of different supercritical media, such as alkanes of C7-C13, 1, 2, 3, 4-tetrahydronaphthalene, cis-decalin, o-xylene,ethylbenzene, quinolin, n-hexane and aniline etc. and reaction conditions (catalyst, temperature, space velocity, particial pressure of media) on ammonia at supercritical condition were investigated.Supercritical medium was decomposed under reaction conditions over Fe and Ru/AC catalysts. The decomposition products deactivated the catalysts. Alkane decomposed the least, and the rate of deactivation was the slowest. Therefore alklane was a relatively good medium. The decomposion of supercritical medium was the key for the deactivation of catalysts. Another important reason for the decrease of ammonia concentration was that the effective pressure of syngas decreased because of the presence of supercritical media. The active temperature of catalyst was the decisive factor in supercritical ammonia synthesis. Supercritical catalytic reaction was viable only at a lower temperature. Ammonia ynthesis at supercritical conditions is possible if a catalyst with active temperature lower than 573 K could e developed and the decomposition of supercritical media could be prevented.

  10. Shock wave reflection phenomena

    CERN Document Server

    Ben-dor, Gabi

    2007-01-01

    This book provides a comprehensive state-of-the-knowledge description of the shock wave reflection phenomena from a phenomenological point of view. The first part is a thorough introduction to oblique shock wave reflections, presenting the two major well-known reflection wave configurations, namely, regular (RR) and Mach (MR) reflections, the corresponding two- and three-shock theories, their analytical and graphical solution and the proposed transition boundaries between these two reflection-wave configurations. The second, third and fourth parts describe the reflection phenomena in steady, pseudo-steady and unsteady flows, respectively. Here, the possible specific types of reflection wave configurations are described, criteria for their formation and termination are presented and their governing equations are solved analytically and graphically and compared with experimental results. The resolution of the well-known von Neumann paradox and a detailed description of two new reflection-wave configurations - t...

  11. Pulsed corona discharge at atmospheric and supercritical conditions

    Science.gov (United States)

    Lock, Evgeniya Hristova

    Pulsed corona discharge is one of the non-equilibrium plasma techniques, by which electrical power is mainly utilized to generate high-energy electrons. These react further with the background gas to produce radicals, which can be further employed in chemically selective reactions. Study of the initiation of pulsed corona discharge in carbon dioxide and air was conducted. Furthermore due to its high removal efficiency, energy yields and good economy, the pulsed corona discharge was employed for removal of methanol and dimethyl sulfide. These compounds are part of the volatile organic compounds (VOC) air pollutants, which are subject of severe environmental regulations due to their toxicity, environmental persistence and intensity of smell. The study provides experimental data for the destruction of methanol and dimethyl sulfide from dry and humid air streams. The effects of the process parameters, including applied voltage, pulse repetition rate, initial concentration of pollutants, temperature and humidity on the destruction and removal efficiency and energy cost are analyzed. Specific consideration is given to the formation of unwanted byproducts. The study on plasma application for pollution control showed that small amounts of dispersed liquid droplets increase the efficiency of the chemical utilization of the high-energy electrons and reduce the required power. So media that could facilitate homogeneous and heterogeneous chemistry at the same time would enhance the efficiency of the removal process. Such medium that has properties intermediate between the gas and liquid phase is the supercritical fluid. Generation of plasma in supercritical fluids is an unexplored area in plasma science. The generation of plasma at elevated pressures usually requires high voltages or small interelectrode distances. The supercritical phase is characterized by extensive cluster formation in the vicinity of the critical point. Typically the clusters have lower ionization

  12. [Traumatic neurogenic shock].

    Science.gov (United States)

    Maurin, O; de Régloix, S; Caballé, D; Arvis, A-M; Perrochon, J-C; Tourtier, J-P

    2013-05-01

    Traumatic neurogenic shock is a rare but serious complication of spinal cord injury. It associates bradycardia and hypotension caused by a medullary trauma. It is life-threatening for the patient and it aggravates the neurological deficit. Strict immobilization and a quick assessment of the gravity of cord injury are necessary as soon as prehospital care has begun. Initial treatment requires vasopressors associated with fluid resuscitation. Steroids are not recommended. Early decompression is recommended for incomplete deficit seen in the first 6 hours. We relate the case of secondary spinal shock to a luxation C6/C7 treated in prehospital care.

  13. [Corticosteroids and septic shock].

    Science.gov (United States)

    Bouletreau, P; Petit, P; Latarjet, J

    1976-01-01

    According to the data in the literature, the authors attempted to sum-up present attitudes on the value of corticoids in the treatment of septic shock. If their cardiovascular effects after a period of enthusiasm, are presently rather controversial, their cellular and sub-cellular actions, on the lysosomal membranes, capillary permeability and perhaps the intimate mechanisms of cellular oxygenation seem to be more real. However, the contra-indications which persist in the results of clinical works have resulted in the fact that the exact place of cortico-steroids in the therapeutic arsenal of septic shock still remains to be specified.

  14. Culture shock and travelers.

    Science.gov (United States)

    Stewart, L; Leggat, P A

    1998-06-01

    As travel has become easier and more affordable, the number of people traveling has risen sharply. People travel for many and varied reasons, from the business person on an overseas assignment to backpackers seeking new and exotic destinations. Others may take up residence in different regions, states or countries for family, business or political reasons. Other people are fleeing religious or political persecution. Wherever they go and for whatever reason they go, people take their culture with them. Culture, like language, is acquired innately in early childhood and is then reinforced through formal and complex informal social education into adulthood. Culture provides a framework for interpersonal and social interactions. Therefore, the contact with a new culture is often not the exciting or pleasurable experience anticipated. When immersed in a different culture, people no longer know how to act when faced with disparate value systems. Contact with the unfamiliar culture can lead to anxiety, stress, mental illness and, in extreme cases, physical illness and suicide. "Culture shock" is a term coined by the anthropologist Oberg. It is the shock of the new. It implies that the experience of the new culture is an unpleasant surprise or shock, partly because it is unexpected and partly because it can lead to a negative evaluation of one's own culture. It is also known as cross-cultural adjustment, being that period of anxiety and confusion experienced when entering a new culture. It affects people intellectually, emotionally, behaviorally and physically and is characterized by symptoms of psychological distress. Culture shock affects both adults and children. In travelers or workers who have prolonged sojourns in foreign countries, culture shock may occur not only as they enter the new culture, but also may occur on their return to their original culture. Children may also experience readjustment problems after returning from leading sheltered lives in expatriate

  15. Characteristics of Weak Interplanetary Shocks and Shock-like Events

    Science.gov (United States)

    Balogh, A.; Gloag, J. M.

    The variation of magnetic and plasma parameters across the discontinuity of a colli- sionless shock wave are clearly understood and presented in MHD theory. The anal- ysis of 116 shock waves appearing on the Ulysses shock list in the period mid 1996 to the end of 1999 show that in the cases of the stronger shock waves, measured by the ratio of downstream to upstream magnetic field magnitudes, this MHD descrip- tion is adequate. However in the case of many of the weaker shocks there are events which are not clearly characterised in MHD terms and in these cases plasma param- eters are particularly difficult to interpret. To explore the issues associated with these very weak shocks further, a set of shock-like events is considered which have shock characteristics in the high frequency wave data measured by the plasma wave inves- tigation(URAP) but are not considered to be clearly shock waves purely considering magnetic and plasma data. These shock-like events are thought to extend the spectrum of interplanetary shocks at the very weakest end and possibly beyond what should be considered a collisionless shock wave.

  16. Solubility of 1:1 Alkali Nitrates and Chlorides in Near-Critical and Supercritical Water : 1 Alkali Nitrates and Chlorides in Near-Critical and Supercritical Water

    NARCIS (Netherlands)

    Leusbrock, Ingo; Metz, Sybrand J.; Rexwinkel, Glenn; Versteeg, Geert F.

    2009-01-01

    To increase the available data oil systems containing supercritical water and inorganic compounds, all experimental setup was designed to investigate the solubilities of inorganic compounds Ill supercritical water, In this work, three alkali chloride salts (LiCl, NaCl, KCl) and three alkali nitrate

  17. Microstructure in two- and three-dimensional hybrid simulations of perpendicular collisionless shocks

    CERN Document Server

    Burgess, David; Gingell, Peter W; Trávníček, Pavel M

    2016-01-01

    Supercritical collisionless perpendicular shocks have an average macrostructure determined primarily by the dynamics of ions specularly reflected at the magnetic ramp. Within the overall macrostructure, instabilities, both linear and nonlinear, generate fluctuations and microstructure. To identify the sources of such microstructure, high-resolution two- and three-dimensional simulations have been carried out using the hybrid method, wherein the ions are treated as particles and the electron response is modelled as a massless fluid. We confirm the results of earlier 2-D simulations showing both field-parallel aligned propagating fluctuations and fluctuations carried by the reflected-gyrating ions. In addition, it is shown that, for 2-D simulations of the shock coplanarity plane, the presence of short-wavelength fluctuations in all magnetic components is associated with the ion Weibel instability driven at the upstream edge of the foot by the reflected-gyrating ions. In 3-D simulations we show for the first tim...

  18. Flow behind concave shock waves

    Science.gov (United States)

    Mölder, S.

    2017-03-01

    Curved shock theory is introduced and applied to calculate the flow behind concave shock waves. For sonic conditions, three characterizing types of flow are identified, based on the orientation of the sonic line, and it is shown that, depending on the ratio of shock curvatures, a continuously curving shock can exist with Type III flow, where the sonic line intercepts the reflected characteristics from the shock, thus preventing the formation of a reflected shock. The necessary shock curvature ratio for a Type III sonic point does not exist for a hyperbolic shock so that it will revert to Mach reflection for all Mach numbers. A demonstration is provided, by CFD calculations, at Mach 1.2 and 3.

  19. Flow behind concave shock waves

    Science.gov (United States)

    Mölder, S.

    2017-09-01

    Curved shock theory is introduced and applied to calculate the flow behind concave shock waves. For sonic conditions, three characterizing types of flow are identified, based on the orientation of the sonic line, and it is shown that, depending on the ratio of shock curvatures, a continuously curving shock can exist with Type III flow, where the sonic line intercepts the reflected characteristics from the shock, thus preventing the formation of a reflected shock. The necessary shock curvature ratio for a Type III sonic point does not exist for a hyperbolic shock so that it will revert to Mach reflection for all Mach numbers. A demonstration is provided, by CFD calculations, at Mach 1.2 and 3.

  20. Shock compression of polyvinyl chloride

    Science.gov (United States)

    Neogi, Anupam; Mitra, Nilanjan

    2016-04-01

    This study presents shock compression simulation of atactic polyvinyl chloride (PVC) using ab-initio and classical molecular dynamics. The manuscript also identifies the limits of applicability of classical molecular dynamics based shock compression simulation for PVC. The mechanism of bond dissociation under shock loading and its progression is demonstrated in this manuscript using the density functional theory based molecular dynamics simulations. The rate of dissociation of different bonds at different shock velocities is also presented in this manuscript.

  1. The special relativistic shock tube

    Science.gov (United States)

    Thompson, Kevin W.

    1986-01-01

    The shock-tube problem has served as a popular test for numerical hydrodynamics codes. The development of relativistic hydrodynamics codes has created a need for a similar test problem in relativistic hydrodynamics. The analytical solution to the special relativistic shock-tube problem is presented here. The relativistic shock-jump conditions and rarefaction solution which make up the shock tube are derived. The Newtonian limit of the calculations is given throughout.

  2. Shock conditions for hypoelastic materials

    Science.gov (United States)

    Renardy, Michael; Rogers, Robert C.

    1993-10-01

    The equations governing the motion of hypoelastic materials (and related models of non-Newtonian fluids) are not in conservation form. Hence there is no obvious formulation of Rankine-Hugoniot jump conditions across a shock. In this paper we demonstrate that a viscosity criterion can be used to obtain meaningful shock conditions. In particular, we discuss shocks of small amplitude. The shock conditions obtained will in general depend on the form of the viscosity term.

  3. Supercritical Water Reactor Cycle for Medium Power Applications

    Energy Technology Data Exchange (ETDEWEB)

    BD Middleton; J Buongiorno

    2007-04-25

    Scoping studies for a power conversion system based on a direct-cycle supercritical water reactor have been conducted. The electric power range of interest is 5-30 MWe with a design point of 20 MWe. The overall design objective is to develop a system that has minimized physical size and performs satisfactorily over a broad range of operating conditions. The design constraints are as follows: Net cycle thermal efficiency {ge}20%; Steam turbine outlet quality {ge}90%; and Pumping power {le}2500 kW (at nominal conditions). Three basic cycle configurations were analyzed. Listed in order of increased plant complexity, they are: (1) Simple supercritical Rankine cycle; (2) All-supercritical Brayton cycle; and (3) Supercritical Rankine cycle with feedwater preheating. The sensitivity of these three configurations to various parameters, such as reactor exit temperature, reactor pressure, condenser pressure, etc., was assessed. The Thermoflex software package was used for this task. The results are as follows: (a) The simple supercritical Rankine cycle offers the greatest hardware simplification, but its high reactor temperature rise and reactor outlet temperature may pose serious problems from the viewpoint of thermal stresses, stability and materials in the core. (b) The all-supercritical Brayton cycle is not a contender, due to its poor thermal efficiency. (c) The supercritical Rankine cycle with feedwater preheating affords acceptable thermal efficiency with lower reactor temperature rise and outlet temperature. (d) The use of a moisture separator improves the performance of the supercritical Rankine cycle with feedwater preheating and allows for a further reduction of the reactor outlet temperature, thus it was selected for the next step. Preliminary engineering design of the supercritical Rankine cycle with feedwater preheating and moisture separation was performed. All major components including the turbine, feedwater heater, feedwater pump, condenser, condenser pump

  4. Remediation of Contaminated Soils By Supercritical Carbon Dioxide Extraction

    Science.gov (United States)

    Ferri, A.; Zanetti, M. C.; Banchero, M.; Fiore, S.; Manna, L.

    The contaminants that can be found in soils are many, inorganic, like heavy metals, as well as organic. Among the organic contaminants, oil and coal refineries are responsi- ble for several cases of soil contamination with PAHs (Polycyclic Aromatic Hydrocar- bons). Polynuclear aromatic hydrocarbons (PAHs) have toxic, carcinogenic and mu- tagenic effects. Limits have been set on the concentration of most contaminants, and growing concern is focusing on soil contamination issues. USA regulations set the maximum acceptable level of contamination by PAHs equal to 40 ppm at residential sites and 270 ppm at industrial sites. Stricter values are usually adopted in European Countries. Supercritical carbon dioxide extraction is a possible alternative technology to remove volatile organic compounds from contaminated soils. Supercritical fluid extraction (SFE) offers many advantages over conventional solvent extraction. Super- critical fluids combine gaseous properties as a high diffusion coefficient, and liquid properties as a high solvent power. The solvent power is strongly pressure-dependent near supercritical conditions: selective extractions are possible without changing the solvent. Solute can be separate from the solvent depressurising the system; therefore, it is possible to recycle the solvent and recover the contaminant. Carbon dioxide is frequently used as supercritical fluid, because it has moderate critical conditions, it is inert and available in pure form. In this work, supercritical fluid extraction technology has been used to remove a polynuclear aromatic hydrocarbon from contaminated soils. The contaminant choice for the experiment has been naphthalene since several data are available in literature. G. A. Montero et al. [1] studied soil remediation with supercrit- ical carbon dioxide extraction technology; these Authors have found that there was a mass-transfer limitation. In the extraction vessel, the mass transfer coefficient in- creases with the

  5. Selective chelation and extraction of lanthanides and actinides with supercritical fluids

    Energy Technology Data Exchange (ETDEWEB)

    Brauer, R.D.; Carleson, T.E.; Harrington, J.D.; Jean, F.; Jiang, H.; Lin, Y.; Wai, C.M.

    1994-01-01

    This report is made up of three independent papers: (1) Supercritical Fluid Extraction of Thorium and Uranium with Fluorinated Beta-Diketones and Tributyl Phosphate, (2) Supercritical Fluid Extraction of Lanthanides with Beta-Diketones and Mixed Ligands, and (3) A Group Contribution Method for Predicting the Solubility of Solid Organic Compounds in Supercritical Carbon Dioxide. Experimental data are presented demonstrating the successful extraction of thorium and uranium using fluorinated beta-diketones to form stable complexes that are extracted with supercritical carbon dioxide. The conditions for extracting the lanthanide ions from liquid and solid materials using supercritical carbon dioxide are presented. In addition, the Peng-Robison equation of state and thermodynamic equilibrium are used to predict the solubilities of organic solids in supercritical carbon dioxide from the sublimation pressure, critical properties, and a centric factor of the solid of interest.

  6. Estimation of the Isotherms of Phenol on Activated Carbons and Polymeric Adsorbents under Supercritical Condition

    Institute of Scientific and Technical Information of China (English)

    奚红霞; 谢兰英; 李祥斌; 李忠

    2003-01-01

    A method named as "volume-expanding and pressure-reducing adsorption" is proposed. It can be used to measure the isotherms under supercritical condition. The adsorption isotherms of phenol on activated carbons and polymeric adsorbents are estimated and compared respectively for the systems of "phenol-activated carbon-supercritical fluid CO2" and "phenol-polymeric adsorbent-supercritical fluid CO2". The results show that the amount of phenol adsorbed on the activated carbons and the polymeric adsorbents under the supercritical condition is much less than that under the general condition, which can be utilized to develop a technology regenerating the activated carbon with supercritical fluid. Moreover, the effects of ethyl alcohol, used as the third component, on the isotherms of phenol on the activated carbons and polymeric adsorbents under the supercritical condition are also investigated.

  7. Application of supercritical fluid carbon dioxide to the extraction and analysis of lipids.

    Science.gov (United States)

    Lee, Jae Won; Fukusaki, Eiichiro; Bamba, Takeshi

    2012-10-01

    Supercritical carbon dioxide (SCCO(2)) is an ecofriendly supercritical fluid that is chemically inert, nontoxic, noninflammable and nonpolluting. As a green material, SCCO(2) has desirable properties such as high density, low viscosity and high diffusivity that make it suitable for use as a solvent in supercritical fluid extraction, an effective and environment-friendly analytical method, and as a mobile phase for supercritical fluid chromatography, which facilitates high-throughput, high-resolution analysis. Furthermore, the low polarity of SCCO(2) is suitable for the extraction and analysis of hydrophobic compounds. The growing concern surrounding environmental pollution has triggered the development of green analysis methods based on the use of SCCO(2) in various laboratories and industries. SCCO(2) is becoming an effective alternative to conventional organic solvents. In this review, the usefulness of SCCO(2) in supercritical fluid extraction and supercritical fluid chromatography for the extraction and analysis of lipids is described.

  8. Teleconnected food supply shocks

    Science.gov (United States)

    Bren d'Amour, Christopher; Wenz, Leonie; Kalkuhl, Matthias; Steckel, Jan Christoph; Creutzig, Felix

    2016-03-01

    The 2008-2010 food crisis might have been a harbinger of fundamental climate-induced food crises with geopolitical implications. Heat-wave-induced yield losses in Russia and resulting export restrictions led to increases in market prices for wheat across the Middle East, likely contributing to the Arab Spring. With ongoing climate change, temperatures and temperature variability will rise, leading to higher uncertainty in yields for major nutritional crops. Here we investigate which countries are most vulnerable to teleconnected supply-shocks, i.e. where diets strongly rely on the import of wheat, maize, or rice, and where a large share of the population is living in poverty. We find that the Middle East is most sensitive to teleconnected supply shocks in wheat, Central America to supply shocks in maize, and Western Africa to supply shocks in rice. Weighing with poverty levels, Sub-Saharan Africa is most affected. Altogether, a simultaneous 10% reduction in exports of wheat, rice, and maize would reduce caloric intake of 55 million people living in poverty by about 5%. Export bans in major producing regions would put up to 200 million people below the poverty line at risk, 90% of which live in Sub-Saharan Africa. Our results suggest that a region-specific combination of national increases in agricultural productivity and diversification of trade partners and diets can effectively decrease future food security risks.

  9. Early Treatment in Shock

    Science.gov (United States)

    2011-06-01

    of L-arginine resuscitation in shock were carried out by An-1 gele , Chaudry, and co-workers. 6-10 They used the rat model, bleeding to 40 mm Hg in...17 14. Preissler G, Lothe F, Ebersberger U, Huff I, Bittmann I, Messmer K, Jauch KW, An-18 gele , MK. Recipient treatment with L-arginine

  10. A Shocking New Pump

    Science.gov (United States)

    2000-01-01

    Hydro Dynamics, Inc. received a technical helping hand from NASA that made their Hydrosonic Pump (HPump) a reality. Marshall engineers resolved a bearing problem in the rotor of the pump and recommended new bearings, housings and mounting hardware as a solution. The resulting HPump is able to heat liquids with greater energy efficiency using shock waves to generate heat.

  11. Planetary Bow Shocks

    CERN Document Server

    Treumann, R A

    2008-01-01

    Our present knowledge of the properties of the various planetary bow shocks is briefly reviewed. We do not follow the astronomical ordering of the planets. We rather distinguish between magnetised and unmagnetised planets which groups Mercury and Earth with the outer giant planets of the solar system, Mars and Moon in a separate group lacking magnetic fields and dense atmospheres, and Venus together with the comets as the atmospheric celestial objects exposed to the solar wind. Asteroids would, in this classification, fall into the group together with the Moon and should behave similarly though being much smaller. Extrasolar planets are not considered as we have only remote information about their behaviour. The presentation is brief in the sense that our in situ knowledge is rather sporadic yet, depending on just a countable number of bow shock crossings from which just some basic conclusions can be drawn about size, stationarity, shape and nature of the respective shock. The only bow shock of which we have ...

  12. Shock compression of nitrobenzene

    Science.gov (United States)

    Kozu, Naoshi; Arai, Mitsuru; Tamura, Masamitsu; Fujihisa, Hiroshi; Aoki, Katsutoshi; Yoshida, Masatake; Kondo, Ken-Ichi

    1999-06-01

    The Hugoniot (4 - 30 GPa) and the isotherm (1 - 7 GPa) of nitrobenzene have been investigated by shock and static compression experiments. Nitrobenzene has the most basic structure of nitro aromatic compounds, which are widely used as energetic materials, but nitrobenzene has been considered not to explode in spite of the fact its calculated heat of detonation is similar to TNT, about 1 kcal/g. Explosive plane-wave generators and diamond anvil cell were used for shock and static compression, respectively. The obtained Hugoniot consists of two linear lines, and the kink exists around 10 GPa. The upper line agrees well with the Hugoniot of detonation products calculated by KHT code, so it is expected that nitrobenzene detonates in that area. Nitrobenzene solidifies under 1 GPa of static compression, and the isotherm of solid nitrobenzene was obtained by X-ray diffraction technique. Comparing the Hugoniot and the isotherm, nitrobenzene is in liquid phase under experimented shock condition. From the expected phase diagram, shocked nitrobenzene seems to remain metastable liquid in solid phase region on that diagram.

  13. Toxic shock syndrome

    Science.gov (United States)

    ... chap 196. Read More Acute kidney failure Heart failure - overview Shock Review Date 4/12/2016 Updated by: Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department ...

  14. Health Shocks and Retirement:

    DEFF Research Database (Denmark)

    Datta Gupta, Nabanita; Larsen, Mona

    benefits in Denmark nor by the promotion of corporate social responsibility initiatives since the mid-1990s. In the late 1990s, however, the retirement rate following a health shock is reduced to 3% with the introduction of the subsidized employment program (fleksjob) but this effect is not strongly...

  15. Supercritical and Transcritical Real-Fluid Mixing in Diesel Engine Applications

    Science.gov (United States)

    2015-09-01

    ARL-RP-0551 ● SEP 2015 US Army Research Laboratory Supercritical and Transcritical Real-Fluid Mixing in Diesel Engine ...ARL-RP-0551 ● SEP 2015 US Army Research Laboratory Supercritical and Transcritical Real-Fluid Mixing in Diesel Engine Applications by...COVERED (From - To) 1 January 2014–30 September 2014 4. TITLE AND SUBTITLE Supercritical and Transcritical Real-Fluid Mixing in Diesel Engine

  16. Preliminary Study on Supercritical Fluid Extraction of Ce(Ⅳ) in Solution

    Institute of Scientific and Technical Information of China (English)

    SONG; Zhi-jun; LIANG; Xiao-hu; DING; You-qian

    2013-01-01

    Supercritical fluid extraction(SFE)has many advantages,such as rapid mass transfer and high solubility.Metal samples can be extracted using supercritical fluid with a small amount of complexant.So in comparison to conventional solvent extraction process,SFE minimizes the amount of secondary waste and the pollution to environment.In order to study the extraction of Pu using supercritical CO2,the

  17. Fixed Bed Adsorption of Drugs on Silica Aerogel from Supercritical Carbon Dioxide Solutions

    OpenAIRE

    Giuseppe Caputo

    2013-01-01

    Supercritical adsorption coupled with the high adsorption capacity of silica aerogel allows the preparation of a new kind of delivery systems of poor water soluble drugs. In order to overcome drawbacks of conventional techniques where the use of liquid solvents can cause the fracture of aerogel porous structure, in this work a new adsorption process of drugs from a supercritical mixture is proposed. Adsorption takes place from a fluid solution of the drug in supercritical CO2 and ethanol as c...

  18. Molecular Dynamics Simulation of Diffusion Coefficients of Oxygen, Nitrogen and Sodium Chloride in Supercritical Water

    Institute of Scientific and Technical Information of China (English)

    肖吉; 陆九芳; 陈健; 李以圭

    2001-01-01

    Molecular dynamics simulation has been performed to determine the infinite-dilution diffusion coefficients of oxygen and nitrogen, and the diffusion coefficients of NaCl in supercritical water from 703.2- 763.2 K and 30-45 MPa.The results obtained show that the diffusion coefficients in supercritical water increase with temperature, while decreasing with pressure. Nevertheless, the diffusion coefficients in supercritical water are much larger than those in normal water.

  19. Development of a Facility for Combustion Stability Experiments at Supercritical Pressure

    Science.gov (United States)

    2013-12-01

    Supercritical Pressure 5a. CONTRACT NUMBER In-House 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Wegener, Leyva, Forliti, Talley 5d... supercritical pressures that are relevant to high-performance liquid rocket engines, accurately-controlled and cryogenically-conditioned propellants, and... Supercritical Pressure Jeffrey L. Wegener1 University of California at Los Angeles, CA 90095 Ivett A. Leyva2 AFRL/RQRE, Edwards AFB, CA 93524

  20. Supercritical Carbon Dioxide Extraction of Benzene in Poly(vinyl acetate) and Polystyrene

    OpenAIRE

    佐々木, 正和; 滝嶌, 繁樹; 舛岡, 弘勝

    1989-01-01

    In order to test the applicability of the supercritical fluid extraction technique to the separation of impurities in polymers, separation of benzene from two polymers of poly(vinyl acetate) and polystyrene was carried out using supercritical carbon dioxide. Figure 1 shows a schematic diagram of the supercritical fluid extraction apparatus. It consists of the following sections: (1) compression of carbon dioxide, (2) extraction, and (3) control and measurement of carbon dioxide flow rates...

  1. [Effect of entrainer on supercritical CO2 for extraction of tradition and herbal drugs].

    Science.gov (United States)

    Xi, Yanbin; Xia, Xiaohui; Jin, Ran; Zhang, Yu; Yang, Liqin; Tang, Shihuan

    2009-06-01

    Type, mode of affiliating, mechanism of action of entrainer in Supercritical CO2 on extraction of Chinese traditional and herbal drugs were briefly reviewed. Application of entrainer in Supercritical CO2 on extraction of flavones, terpenes, sterols, and saponins in Chinese traditional and herbal drugs were recommended in particular. Some problems and directions in research of entrainer in Supercritical CO2 on extraction of Chinese traditional and herbal drugs were shown in this paper.

  2. Applications of Supercritical Fluid Extraction (SFE) of Palm Oil and Oil from Natural Sources

    OpenAIRE

    Mohd Omar Ab Kadir; Sahena Ferdosh; Mohd Yazid Abdul Manap; Nik Norulaini Nik Ab Rahman; Mohammed Jahurul Haque Akanda; Mohammed Zaidul Islam Sarker

    2012-01-01

    Supercritical fluid extraction (SFE), which has received much interest in its use and further development for industrial applications, is a method that offers some advantages over conventional methods, especially for the palm oil industry. SC-CO2 refers to supercritical fluid extraction (SFE) that uses carbon dioxide (CO2) as a solvent which is a nontoxic, inexpensive, nonflammable, and nonpolluting supercritical fluid solvent for the extraction of natural products. Almost 100% oil can be ext...

  3. In situ local shock speed and transit shock speed

    Directory of Open Access Journals (Sweden)

    S. Watari

    Full Text Available A useful index for estimating the transit speeds was derived by analyzing interplanetary shock observations. This index is the ratio of the in situ local shock speed and the transit speed; it is 0.6–0.9 for most observed shocks. The local shock speed and the transit speed calculated for the results of the magnetohydrodynamic simulation show good agreement with the observations. The relation expressed by the index is well explained by a simplified propagation model assuming a blast wave. For several shocks the ratio is approximately 1.2, implying that these shocks accelerated during propagation in slow-speed solar wind. This ratio is similar to that for the background solar wind acceleration.

    Keywords. Interplanetary physics (Flare and stream dynamics; Interplanetary shocks; Solar wind plasma

  4. Shock Dynamics in Stellar Outbursts. I. Shock Formation

    Science.gov (United States)

    Ro, Stephen; Matzner, Christopher D.

    2017-05-01

    Wave-driven outflows and non-disruptive explosions have been implicated in pre-supernova outbursts, supernova impostors, luminous blue variable eruptions, and some narrow-line and superluminous supernovae. To model these events, we investigate the dynamics of stars set in motion by strong acoustic pulses and wave trains, focusing on nonlinear wave propagation, shock formation, and an early phase of the development of a weak shock. We identify the shock formation radius, showing that a heuristic estimate based on crossing characteristics matches an exact expansion around the wave front and verifying both with numerical experiments. Our general analytical condition for shock formation applies to one-dimensional motions within any static environment, including both eruptions and implosions. We also consider the early phase of shock energy dissipation. We find that waves of super-Eddington acoustic luminosity always create shocks, rather than damping by radiative diffusion. Therefore, shock formation is integral to super-Eddington outbursts.

  5. Supercritical CO2 extraction of functional compounds from Spirulina and their biological activity

    National Research Council Canada - National Science Library

    K.G, Mallikarjun Gouda; K, Udaya Sankar; R, Sarada; G.A, Ravishankar

    2015-01-01

    Supercritical carbon dioxide (SCCO2) extraction and fractionation of Spirulina platensis was carried out to obtain functional compounds with antioxidant, antimicrobial and enzyme inhibitory activities...

  6. A finite-dimensional reduction method for slightly supercritical elliptic problems

    Directory of Open Access Journals (Sweden)

    Riccardo Molle

    2004-01-01

    Full Text Available We describe a finite-dimensional reduction method to find solutions for a class of slightly supercritical elliptic problems. A suitable truncation argument allows us to work in the usual Sobolev space even in the presence of supercritical nonlinearities: we modify the supercritical term in such a way to have subcritical approximating problems; for these problems, the finite-dimensional reduction can be obtained applying the methods already developed in the subcritical case; finally, we show that, if the truncation is realized at a sufficiently large level, then the solutions of the approximating problems, given by these methods, also solve the supercritical problems when the parameter is small enough.

  7. Fundamental kinetics and mechanistic pathways for oxidation reactions in supercritical water

    Science.gov (United States)

    Webley, Paul A.; Tester, Jefferson W.

    1988-01-01

    Oxidation of the products of human metabolism in supercritical water has been shown to be an efficient way to accomplish the on-board water/waste recycling in future long-term space flights. Studies of the oxidation kinetics of methane to carbon dioxide in supercritical water are presented in this paper in order to enhance the fundamental understanding of the oxidation of human waste compounds in supercritical water. It is concluded that, although the elementary reaction models remain the best hope for simulating oxidation in supercritical water, several modifications to existing mechanisms need to be made to account for the role of water in the reaction mechanism.

  8. Research and application of multiple model predictive control in Ultra-supercritical boiler-turbine system

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Hengfeng; Yan, Weiwu; Wang, Guoliang; Hu, Yong; Li, Nan [Shanghai Jiao Tong Univ., Shanghai (China). Dept. of Automation; Ministry of Education of China, Shanghai (China). Key Lab. of System Control and Information Processing; Chen, Shihe; Zhang, Xi [Guangdong Electric Power Research Institute, Guangzhou (China)

    2013-07-01

    Based on analyzing the characteristics of Ultra-supercritical unit, this paper introduced a multiple model MCPC (Multivariable Constrained Predictive Control) structure with three inputs and three outputs for coordination control of Ultra-supercritical unit. In the structure, double-layer structure of optimization was used to obtain good steady and dynamic performance, and piecewise linear models at the different operating points of Ultra-supercritical unit were used to deal with nonlinearity. In the real-time simulation, nonlinear model of 1000MW Ultra-supercritical unit in was considered. Finally, the result of real-time simulation was given in the paper.

  9. Preparation and characterization of foxtail millet bran oil using subcritical propane and supercritical carbon dioxide extraction

    National Research Council Canada - National Science Library

    Shi, Yuzhong; Ma, Yuxiang; Zhang, Ruitin; Ma, Hanjun; Liu, Benguo

    2015-01-01

    ...), supercritical carbon dioxide extraction (SCE) and subcritical propane extraction (SPE) and analyzed the yield, physicochemical property, fatty acid profile, tocopherol composition, oil oxidative stability in this study...

  10. Shock detachment from curved wedges

    Science.gov (United States)

    Mölder, S.

    2017-03-01

    Curved shock theory is used to show that the flow behind attached shocks on doubly curved wedges can have either positive or negative post-shock pressure gradients depending on the freestream Mach number, the wedge angle and the two wedge curvatures. Given enough wedge length, the flow near the leading edge can choke to force the shock to detach from the wedge. This local choking can preempt both the maximum deflection and the sonic criteria for shock detachment. Analytical predictions for detachment by local choking are supported by CFD results.

  11. Shock detachment from curved wedges

    Science.gov (United States)

    Mölder, S.

    2017-09-01

    Curved shock theory is used to show that the flow behind attached shocks on doubly curved wedges can have either positive or negative post-shock pressure gradients depending on the freestream Mach number, the wedge angle and the two wedge curvatures. Given enough wedge length, the flow near the leading edge can choke to force the shock to detach from the wedge. This local choking can preempt both the maximum deflection and the sonic criteria for shock detachment. Analytical predictions for detachment by local choking are supported by CFD results.

  12. Experimental study of choking flow of water at supercritical conditions

    Science.gov (United States)

    Muftuoglu, Altan

    Future nuclear reactors will operate at a coolant pressure close to 25 MPa and at outlet temperatures ranging from 500°C to 625°C. As a result, the outlet flow enthalpy in future Supercritical Water-Cooled Reactors (SCWR) will be much higher than those of actual ones which can increase overall nuclear plant efficiencies up to 48%. However, under such flow conditions, the thermal-hydraulic behavior of supercritical water is not fully known, e.g., pressure drop, forced convection and heat transfer deterioration, critical and blowdown flow rate, etc. Up to now, only a very limited number of studies have been performed under supercritical conditions. Moreover, these studies are conducted at conditions that are not representative of future SCWRs. In addition, existing choked flow data have been collected from experiments at atmospheric discharge pressure conditions and in most cases by using working fluids different than water which constrain researchers to analyze the data correctly. In particular, the knowledge of critical (choked) discharge of supercritical fluids is mandatory to perform nuclear reactor safety analyses and to design key mechanical components (e.g., control and safety relief valves, etc.). Hence, an experimental supercritical water facility has been built at Ecole Polytechnique de Montreal which allows researchers to perform choking flow experiments under supercritical conditions. The facility can also be used to carry out heat transfer and pressure drop experiments under supercritical conditions. In this thesis, we present the results obtained at this facility using a test section that contains a 1 mm inside diameter, 3.17 mm long orifice plate with sharp edges. Thus, 545 choking flow of water data points are obtained under supercritical conditions for flow pressures ranging from 22.1 MPa to 32.1 MPa, flow temperatures ranging from 50°C to 502°C and for discharge pressures from 0.1 MPa to 3.6 MPa. Obtained data are compared with the data given in

  13. Shock metamorphism of deformed quartz

    Science.gov (United States)

    Gratz, Andrew J.; Christie, John; Tyburczy, James; Ahrens, Thomas; Pongratz, Peter

    1988-01-01

    The effect produced by shock loading (to peak pressures of 12 and 24) on deformed synthetic quartz containing a dislocation and abundant bubbles and small inclusions was investigated, and the relationships between preexisting dislocation density shock lamellae in the target material were examined. The resultant material was found to be inhomogeneously deformed and extremely fractured. Results of TEM examinations indicate that no change in dislocation density was caused by shock loading except in regions containing shock lamellae, where the dislocation density was lowered. The shock-induced defects tend to nucleate on and be controlled by preexisting stress concentrators; shock lamellae, glassy veins, and most curviplanar defects form in tension, presumably during release. An extremely mobile silica fluid is formed and injected into fractures during release, which forcibly removes crystalline fragments from vein walls. It is concluded that shock deformation in quartz is dominated by fracture and melting.

  14. Bubble Dynamics and Shock Waves

    CERN Document Server

    2013-01-01

    This volume of the Shock Wave Science and Technology Reference Library is concerned with the interplay between bubble dynamics and shock waves. It is divided into four parts containing twelve chapters written by eminent scientists. Topics discussed include shock wave emission by laser generated bubbles (W Lauterborn, A Vogel), pulsating bubbles near boundaries (DM Leppinen, QX Wang, JR Blake), interaction of shock waves with bubble clouds (CD Ohl, SW Ohl), shock propagation in polydispersed bubbly liquids by model equations (K Ando, T Colonius, CE Brennen. T Yano, T Kanagawa,  M Watanabe, S Fujikawa) and by DNS (G Tryggvason, S Dabiri), shocks in cavitating flows (NA Adams, SJ Schmidt, CF Delale, GH Schnerr, S Pasinlioglu) together with applications involving encapsulated bubble dynamics in imaging (AA Doinikov, A Novell, JM Escoffre, A Bouakaz),  shock wave lithotripsy (P Zhong), sterilization of ships’ ballast water (A Abe, H Mimura) and bubbly flow model of volcano eruptions ((VK Kedrinskii, K Takayama...

  15. Near-membrane refractometry using supercritical angle fluorescence

    CERN Document Server

    Brunstein, Maia; Oheim, Martin

    2016-01-01

    Total internal reflection fluorescence (TIRF) microscopy and its variants are key technologies for visualizing the dynamics of single molecules or organelles in live cells. Yet, truely quantitative TIRF remains problematic. One unknown hampering the interpretation of evanescent-wave excited fluorescence intensities is the undetermined cell refractive index (RI). Here, we use a combination of TIRF excitation and supercritical angle fluorescence emission detection to directly mea-sure the average RI in the 'footprint' region of the cell, during imaging. Our RI measurement is based on the determination on a back-focal plane image of the critical angle separating supercritical and undercritial fluorescence emission components. We validate our method by imaging mouse embryonic fibroblasts. By targeting various dyes and fluorescent-protein chimerae to vesicles, the plasma membrane as well as mitochondria and the ER, we demonstrate local RI measurements with subcellular resolution on a standard TIRF microscope with ...

  16. Application of supercritical antisolvent method in drug encapsulation: a review.

    Science.gov (United States)

    Kalani, Mahshid; Yunus, Robiah

    2011-01-01

    The review focuses on the application of supercritical fluids as antisolvents in the pharmaceutical field and demonstrates the supercritical antisolvent method in the use of drug encapsulation. The main factors for choosing the solvent and biodegradable polymer to produce fine particles to ensure effective drug delivery are emphasized and the effect of polymer structure on drug encapsulation is illustrated. The review also demonstrates the drug release mechanism and polymeric controlled release system, and discusses the effects of the various conditions in the process, such as pressure, temperature, concentration, chemical compositions (organic solvents, drug, and biodegradable polymer), nozzle geometry, CO(2) flow rate, and the liquid phase flow rate on particle size and its distribution.

  17. Supercritical Fluid Parameters in Organic Rankine Cycle Applications

    Directory of Open Access Journals (Sweden)

    Andreas Schuster

    2008-09-01

    Full Text Available Nowadays, the use of Organic Rankine Cycle (ORC in decentralised applications is linked with the fact that this process allows to use low temperature heat sources and offers an advantageous efficiency in small-scale applications. Many state of the art applications like geothermal and biomass fired power plants as well as new applications like solar desalination with reverse osmosis, waste heat recovery from biogas digestion plants or micro-Combined Heat and Power (micro-CHP systems can successfully use the ORC process. The investigation of supercritical parameters in ORC applications seems to bring promising results in decentralised energy production. This paper presents the results from the simulation of the ORC process in normal and supercritical fluid parameters and discusses the efficiency variation in various applications.

  18. Supercritical Saltwater Spray for Marine Cloud Brightening (MCB)

    Science.gov (United States)

    Neukermans, A.; Cooper, G. F.; Foster, J.; Galbraith, L. K.; Johnston, D.; Ormond, B.; Wang, Q.

    2012-12-01

    Solar Radiation Management (SRM), including both stratospheric sulfur aerosol delivery and MCB, has emerged as the leading contender for geoengineering. Field research in MCB would require a technique capable of producing 1017 salt nuclei/sec from a single source on a seagoing vessel. Spraying supercritical saltwater has emerged as a viable technology, at least for research purposes. Under optimum conditions a single 50-μm nozzle produces 1014 suitable nuclei/sec. Power consumption is high (1-2 MW), but 95% of the required energy is in the form of heat that can probably be obtained from wasted ship-engine heat. While its implementation is conceptually simple, the corrosive nature of supercritical saltwater makes the material requirements very demanding. Progress on this work is detailed.

  19. The Supercritical Pile Model: Prompt Emission Across the Electromagnetic Spectrum

    Science.gov (United States)

    Kazanas, Demos; Mastichiadis, A.

    2008-01-01

    The "Supercritical Pile" GRB model is an economical model that provides the dissipation necessary to convert explosively the energy stored in relativistic protons in the blast wave of a GRB into radiation; at the same time it produces spectra whose luminosity peaks at 1 MeV in the lab frame, the result of the kinematics of the proton-photon - pair production reaction that effects the conversion of proton energy to radiation. We outline the fundamental notions behind the "Supercritical Pile" model and discuss the resulting spectra of the prompt emission from optical to gamma-ray energies of order Gamma^2 m_ec^2, (Gamma is the Lorentz factor of the blast wave) present even in the absence of an accelerated particle distribution and compare our results to bursts that cover this entire energy range. Particular emphasis is given on the emission at the GLAST energy range both in the prompt and the afterglow stages of the burst.

  20. Solubility of the sesquiterpene alcohol patchoulol in supercritical carbon dioxide.

    Science.gov (United States)

    Hybertson, Brooks M

    2007-01-01

    The solubility of the sesquiterpene alcohol patchoulol in supercritical carbon dioxide was measured at P ranging from 10.0 MPa to 25.0 MPa and T of 40.0 and 50.0 °C using a simple microsampling type apparatus with a 100.5 µL sample loop to remove aliquots for off-line analysis. The system was first validated using vanillin with off-line spectrophotometric analysis, then utilized for patchoulol measurements with off-line GC-MS analysis. The measured solubility of patchoulol in supercritical CO(2) ranged from mole fractions of 0.43 × 10(-3) at 10.0 MPa and 50.0 °C to 9.45 × 10(-3) at 25.0 MPa and 40.0 °C.

  1. Extraction of tannin by Acacia mearnsii with supercritical fluids

    Directory of Open Access Journals (Sweden)

    Marcia Regina Pansera

    2004-11-01

    Full Text Available Studies were carried out on solvent and supercritical extraction to obtain natural tannins. The results showed that the best co-solvent to extract tannin with CO2 supercritical was water with a concentration of 5.0% and the best trap rinse solvent was methanol.Neste trabalho foram utilizados dois processos de extração de tanino vegetal: extração a quente em aparelho Soxhlet e extração com CO2 supercítico. Os resultados mostraram que o melhor co-solvente para extração de taninos com CO2 supercrítico foi a água na concentração de 5% e o melhor solvente para lavagem do trap foi o metanol.

  2. Extraction of copper ions by supercritical carbon dioxide

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Complexation combined with supercritical fluid extraction was used to extract Cu2+ in this study. The effects of pressure, temperature, volume of CO2 on the efficiency of extraction were systematically investigated. At the optimum condition a 57.32% recovery was achieved. Addition of suitable amount of methanol(v/v = 5 % ) to the supercritical CO2 can increase in the extraction of Cu2+ (72.69 %, RSD = 2.12 %, n = 3). And the recovery can further increase in the presence of non-ionic surfactant Triton X-100 because of its function of solubilization. Surfactant was first used in the extraction of metal ions in the present study, and the results are satisfied (90.52%, RSD=2.20%, n =3).

  3. Exploration of the gasification of Spirulina algae in supercritical water.

    Science.gov (United States)

    Miller, Andrew; Hendry, Doug; Wilkinson, Nikolas; Venkitasamy, Chandrasekar; Jacoby, William

    2012-09-01

    This study presents non-catalytic gasification of Spirulina algae in supercritical water using a plug flow reactor and a mechanism for feeding solid carbon streams into high pressure (>25 MPa) environments. A 2(III)(3-1) factorial experimental design explored the effect of concentration, temperature, and residence time on gasification reactions. A positive displacement pump fed algae slurries into the reactor at a temperature range of 550-600°C, and residence times between 4 and 9s. The results indicate that algae gasify efficiently in supercritical water, highlighting the potential for a high throughput process. Additional experiments determined Arrhenius parameters of Spirulina algae. This study also presents a model of the gasification reaction using the estimated activation energy (108 kJ/mol) and other Arrhenius parameters at plug flow conditions. The maximum rate of gasification under the conditions studied of 53 g/Ls is much higher than previously reported.

  4. Operation and analysis of a supercritical CO2 Brayton cycle.

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Steven Alan; Radel, Ross F.; Vernon, Milton E.; Pickard, Paul S.; Rochau, Gary Eugene

    2010-09-01

    Sandia National Laboratories is investigating advanced Brayton cycles using supercritical working fluids for use with solar, nuclear or fossil heat sources. The focus of this work has been on the supercritical CO{sub 2} cycle (S-CO2) which has the potential for high efficiency in the temperature range of interest for these heat sources, and is also very compact, with the potential for lower capital costs. The first step in the development of these advanced cycles was the construction of a small scale Brayton cycle loop, funded by the Laboratory Directed Research & Development program, to study the key issue of compression near the critical point of CO{sub 2}. This document outlines the design of the small scale loop, describes the major components, presents models of system performance, including losses, leakage, windage, compressor performance, and flow map predictions, and finally describes the experimental results that have been generated.

  5. Methanolysis of Poly(ethylene terephthalate) in Supercritical Phase

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The depolymerization of poly(ethylene terephthalate, PET) in supercritical methanol is studied using a stainless stirred autoclave at temperature of 255~260℃, pressure of 8.5~14.0 MPa, and methanol/PET weight ratio of 3~8. Under the optimal conditions, the PET is depolymerized completely to its monomers in 60 min. The main products of the reaction are dimethyl terephthalate and ethylene glycol. There are still some small amounts of byproducts, such as methyl-(2-hydroxyethyl) terephthalate, bis(hydroxyethyl) terephthalate, dimers and oligomers. Reversed-phase high performance liquid chrom- atography and gas chromatography are used to analyze solid products and liquid products respectively. The results of depolymerization show that the yield of dimethyl terephthalate and the degree of PET depolymerization are dependent on the reaction temperature, weight ratio of methanol to PET and reaction time. But the reaction pressure has little influence on the depolymerization as long as methanol is in supercritical state.

  6. The Supercritical Pile Model: Prompt Emission Across the Electromagnetic Spectrum

    Science.gov (United States)

    Kazanas, Demos; Mastichiadis, A.

    2008-01-01

    The "Supercritical Pile" GRB model is an economical model that provides the dissipation necessary to convert explosively the energy stored in relativistic protons in the blast wave of a GRB into radiation; at the same time it produces spectra whose luminosity peaks at 1 MeV in the lab frame, the result of the kinematics of the proton-photon - pair production reaction that effects the conversion of proton energy to radiation. We outline the fundamental notions behind the "Supercritical Pile" model and discuss the resulting spectra of the prompt emission from optical to gamma-ray energies of order Gamma^2 m_ec^2, (Gamma is the Lorentz factor of the blast wave) present even in the absence of an accelerated particle distribution and compare our results to bursts that cover this entire energy range. Particular emphasis is given on the emission at the GLAST energy range both in the prompt and the afterglow stages of the burst.

  7. Modeling supercritical fluid extraction process involving solute-solid interaction

    Energy Technology Data Exchange (ETDEWEB)

    Goto, M.; Roy, B. Kodama, A.; Hirose, T. [Kumamoto Univ., Kumamoto (Japan)

    1998-04-01

    Extraction or leaching of solute from natural solid material is a mass transfer process involving dissolution or release of solutes from a solid matrix. Interaction between the solute and solid matrix often influences the supercritical fluid extraction process. A model accounting for the solute-solid interaction as well as mass transfer is developed. The BET equation is used to incorporate the interaction and the solubility of solutes into the local equilibrium in the model. Experimental data for the supercritical extraction of essential oil and cuticular wax from peppermint leaves are successfully analyzed by the model. The effects of parameters on the extraction behavior are demonstrated to illustrate the concept of the model. 18 refs., 5 figs., 1 tab.

  8. Prediction of the viscosity of supercritical fluid mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Vesovic, V. [Imperial Coll., London (United Kingdom). T.H. Huxley School of Environment, Earth Sciences and Engineering; Assael, M.J.; Gallis, Z.A. [Aristotle Univ., Thessaloniki (Greece). Faculty of Chemical Engineering

    1998-09-01

    A method for predicting the viscosity of supercritical, multicomponent fluid mixtures, at any density, from the zero-density viscosity of pure components is presented. The method is based upon the results for a rigid-sphere model, suitably interpreted to apply to real fluids, and on the finding that the excess viscosity of pure supercritical fluids can be adequately described by a density function independent of temperature. The density range of the method extends to twice the critical density of the pure component with the smallest critical density. The only exception is for the methane-rich mixtures where the mixture density should not exceed 12000 mol{center_dot}m{sup {minus}3}. The uncertainty ascribed to the predictions made by this method is of the order of {+-}5%.

  9. Supercritical fluid extraction of all-trans-lycopene from tomato.

    Science.gov (United States)

    Gómez-Prieto, M Salud; Caja, M Mar; Herraiz, Marta; Santa-María, Guillermo

    2003-01-01

    A procedure is proposed for the supercritical fluid extraction of all-trans-lycopene from tomato using carbon dioxide at 40 degrees C without modifier. The present method minimizes the risk of degradation via isomerization and oxidation of health-promoting ingredients, such as lycopene. The effect of different experimental variables on the solvating power of the supercritical fluid was evaluated in terms of both the selectivity achievable in the process and the yield of the extraction of all-trans-lycopene. Satisfactory separations of the all-trans-lycopene isomers from the cis counterparts were achieved using a C(30) column. The obtained extract contained 88% all-trans-lycopene and 12% cis-lycopene.

  10. [Extraction of lobetyolin from codonopsis with supercritical CO2].

    Science.gov (United States)

    Liu, Tongju; Li, Shufen; Min, Jiang; Bao, Xiaomei

    2009-03-01

    To develop a green and rapid method for extraction of lobetyolin from C. pilosula. Extraction of lobetyolin from C. pilosula with supercritical carbon dioxide in the presence of ethanol was studied. The effects of pressure, temperature, volume of cosolvent and extraction time on efficiency and their interactive relationships were discussed, based on central composite design and response surface methodology (RSM). The key effect factor was volume of cosolvent. The extraction yield of lobetyolin was 0.078 6 mg x g(-1) when C. pilosula (40-60 mesh) was extracted at 30 MPa, 60 degrees C and 2 L x min(-1) (as CO2 in normal pressure and temperature) for 100 minutes with supercritical CO2 and 1 mL x min(-1) ethanol as dynamic cosolvent. This result is better than that obtained from traditional method. Therefore, the optimized process is valuable for extraction of lobetyolin from C. pilosula.

  11. Design of Supercritical Carbon Dioxide Compressor Testing Loop

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seong Gu; Lee, Jeong Ik; Ahn, Yoon Han; Lee, Je Kyoung [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Yoon, Ho Joon; Addad, Yacine [KUSTAR, Abu Dhabi (United Arab Emirates)

    2012-05-15

    For small and medium-sized reactors and Generation IV reactors such as sodium-cooled fast reactor are recently under development actively. The supercritical CO{sub 2} Brayton cycle is considered as an attractive cycle for the above mentioned nuclear systems. This is because the supercritical CO{sub 2} Brayton cycle (S-CO{sub 2} cycle) is especially effective to reduce the volume of power generation system, which occupies 1.5{approx}2 times more space than the primary nuclear system in general. Comparing to traditional water-vapor cycle and helium cycle, the S-CO{sub 2} system has relatively much less volume and component size. Therefore, S-CO{sub 2} cycle can be used for many purposes such as nuclear ship propulsion where volume requirement is strict, or a small nuclear reactor when it is constructed on geographically limited area

  12. Modification and processing of polymers using supercritical fluids

    CERN Document Server

    Webb, P B

    2000-01-01

    This thesis describes the application of supercritical CO sub 2 to the modification and processing of polymeric materials. Chapter 1 begins by outlining the physical properties of supercritical fluids (SCF's) and the characteristic signatures of critical point phase transitions. This chapter then goes on to describe some of the current applications of SCF's and the advantages that can be gained by working in such media with particular reference to applications involving polymers. Whilst SCF's may offer several advantages compared to conventional liquid solvents, the switch to a SCF process is by no means a straightforward task and requires consideration of several factors in its development. Such considerations are discussed in the first part of chapter 2, again with particular reference to the modification and processing of polymers. Chapter 3 details the preliminary results obtained from experiments performed with the new high-pressure IR cell; initial experiments were carried out to study the effectiveness...

  13. Homogeneous catalysis of valeronitrile hydrolysis under supercritical conditions.

    Science.gov (United States)

    Sarlea, Michael; Kohl, Sabine; Blickhan, Nina; Vogel, Herbert

    2012-01-01

    Supercritical nitrile hydrolysis can be used for both, amide and acid production as well as waste water treatment, as the hydrolysis products show good biodegradability. The conventional process at ambient conditions requires large amounts of mineral acid or base. Approaches that use supercritical water as a green solvent without a catalyst have been investigated over recent years. Findings for valeronitrile hydrolysis presented recently showed promising reaction rates and valeric acid yields. In an attempt to further maximize product yield and to better understand the impact of the pH, reactions in dilute sulfuric acid (0.01 mol L(-1)) were performed in a continuous high-pressure laboratory-scale apparatus at 400-500 °C, 30 MPa, and a maximum residence time of 100 s. Results from both reaction media were compared with regard to productivity and sustainability.

  14. Simulations of Relativistic Collisionless Shocks: Shock Structure and Particle Acceleration

    Energy Technology Data Exchange (ETDEWEB)

    Spitkovsky, Anatoly; /KIPAC, Menlo Park

    2006-04-10

    We discuss 3D simulations of relativistic collisionless shocks in electron-positron pair plasmas using the particle-in-cell (PIC) method. The shock structure is mainly controlled by the shock's magnetization (''sigma'' parameter). We demonstrate how the structure of the shock varies as a function of sigma for perpendicular shocks. At low magnetizations the shock is mediated mainly by the Weibel instability which generates transient magnetic fields that can exceed the initial field. At larger magnetizations the shock is dominated by magnetic reflections. We demonstrate where the transition occurs and argue that it is impossible to have very low magnetization collisionless shocks in nature (in more than one spatial dimension). We further discuss the acceleration properties of these shocks, and show that higher magnetization perpendicular shocks do not efficiently accelerate nonthermal particles in 3D. Among other astrophysical applications, this may pose a restriction on the structure and composition of gamma-ray bursts and pulsar wind outflows.

  15. Carbon dioxide-based supercritical fluids as IC manufacturing solvents

    Energy Technology Data Exchange (ETDEWEB)

    Rubin, J.B.; Davenhall, L.B.; Taylor, C.M.V.; Sivils, L.D.; Pierce, T.; Tiefert, K.

    1999-05-11

    The production of integrated circuits (IC's) involves a number of discrete steps which utilize hazardous or regulated solvents and generate large waste streams. ES&H considerations associated with these chemicals have prompted a search for alternative, more environmentally benign solvent systems. An emerging technology for conventional solvent replacement is the use of supercritical fluids based on carbon dioxide (CO{sub 2}). Research work, conducted at Los Alamos in conjunction with the Hewlett-Packard Company, has lead to the development of a CO{sub 2}-based supercritical fluid treatment system for the stripping of hard-baked photoresists. This treatment system, known as Supercritical CO{sub 2} Resist Remover, or CORR, uses a two-component solvent composed of a nonhazardous, non-regulated compound, dissolved in supercritical CO{sub 2}. The solvent/treatment system has been successfully tested on metallized Si wafers coated with negative and positive photoresist, the latter both before and after ion-implantation. A description of the experimental data will be presented. Based on the initial laboratory results, the project has progressed to the design and construction of prototype, single-wafer photoresist-stripping equipment. The integrated system involves a closed-loop, recirculating cycle which continuously cleans and regenerates the CO{sub 2}, recycles the dissolved solvent, and separates and concentrates the spent resist. The status of the current design and implementation strategy of a treatment system to existing IC fabrication facilities will be discussed. Additional remarks will be made on the use of a SCORR-type system for the cleaning of wafers prior to processing.

  16. Ultra-Supercritical Pressure CFB Boiler Conceptual Design Study

    Energy Technology Data Exchange (ETDEWEB)

    Zhen Fan; Steve Goidich; Archie Robertson; Song Wu

    2006-06-30

    Electric utility interest in supercritical pressure steam cycles has revived in the United States after waning in the 1980s. Since supercritical cycles yield higher plant efficiencies than subcritical plants along with a proportional reduction in traditional stack gas pollutants and CO{sub 2} release rates, the interest is to pursue even more advanced steam conditions. The advantages of supercritical (SC) and ultra supercritical (USC) pressure steam conditions have been demonstrated in the high gas temperature, high heat flux environment of large pulverized coal-fired (PC) boilers. Interest in circulating fluidized bed (CFB) combustion, as an alternative to PC combustion, has been steadily increasing. Although CFB boilers as large as 300 MWe are now in operation, they are drum type, subcritical pressure units. With their sizes being much smaller than and their combustion temperatures much lower than those of PC boilers (300 MWe versus 1,000 MWe and 1600 F versus 3500 F), a conceptual design study was conducted herein to investigate the technical feasibility and economics of USC CFB boilers. The conceptual study was conducted at 400 MWe and 800 MWe nominal plant sizes with high sulfur Illinois No. 6 coal used as the fuel. The USC CFB plants had higher heating value efficiencies of 40.6 and 41.3 percent respectively and their CFB boilers, which reflect conventional design practices, can be built without the need for an R&D effort. Assuming construction at a generic Ohio River Valley site with union labor, total plant costs in January 2006 dollars were estimated to be $1,551/kW and $1,244/kW with costs of electricity of $52.21/MWhr and $44.08/MWhr, respectively. Based on the above, this study has shown that large USC CFB boilers are feasible and that they can operate with performance and costs that are competitive with comparable USC PC boilers.

  17. Supercritical carbon dioxide: a solvent like no other

    Directory of Open Access Journals (Sweden)

    Jocelyn Peach

    2014-08-01

    Full Text Available Supercritical carbon dioxide (scCO2 could be one aspect of a significant and necessary movement towards green chemistry, being a potential replacement for volatile organic compounds (VOCs. Unfortunately, carbon dioxide has a notoriously poor solubilising power and is famously difficult to handle. This review examines attempts and breakthroughs in enhancing the physicochemical properties of carbon dioxide, focusing primarily on factors that impact solubility of polar and ionic species and attempts to enhance scCO2 viscosity.

  18. Valorization of horse manure through catalytic supercritical water gasification.

    Science.gov (United States)

    Nanda, Sonil; Dalai, Ajay K; Gökalp, Iskender; Kozinski, Janusz A

    2016-06-01

    The organic wastes such as lignocellulosic biomass, municipal solid waste, sewage sludge and livestock manure have attracted attention as alternative sources of energy. Cattle manure, a waste generated in surplus amounts from the feedlot, has always been a chief environmental concern. This study is focused on identifying the candidacy of horse manure as a next generation feedstock for biofuel production through supercritical water gasification. The horse manure was gasified in supercritical water to examine the effects of temperature (400-600°C), biomass-to-water ratio (1:5 and 1:10) and reaction time (15-45min) at a pressure range of 23-25MPa. The horse manure and resulting biochar were characterized through carbon-hydrogen-nitrogen-sulfur (CHNS), inductively coupled plasma-mass spectrometry (ICP-MS), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and scanning electron microscopy (SEM). The effects of alkali catalysts such as NaOH, Na2CO3 and K2CO3 at variable concentrations (1-2wt%) were investigated to maximize the hydrogen yields. Supercritical water gasification of horse manure with 2wt% Na2CO3 at 600°C and 1:10 biomass-to-water ratio for 45min revealed maximum hydrogen yields (5.31mmol/g), total gas yields (20.8mmol/g) with greater carbon conversion efficiency (43.1%) and enhanced lower heating value of gas products (2920kJ/Nm(3)). The manure-derived biochars generated at temperatures higher than 500°C also demonstrated higher thermal stability (weight loss 70wt%) suggesting their application in enhancing soil fertility and carbon sequestration. The results propose that supercritical water gasification could be a proficient remediation technology for horse manure to generate hydrogen-rich gas products.

  19. Destruction of Navy Hazardous Wastes by Supercritical Water Oxidation

    Science.gov (United States)

    1994-08-01

    voltmeters and scanning thermocouple meters. The data are acquired, analyzed, filed, and displayed using software written for the LabWindows data...acquisition software from National Instruments Corporation. The code was written by NFESC in the C computer language and compiled to achieve rapid program...Hazards and operability ( HAZOP ) study of a supercritical water oxidation (SCWO) bench scale system. Cambridge, MA, Aug 1992. 8. Arthur D. Little, Inc

  20. Supercritical water oxidation of wastewater and sludges - design considerations

    Energy Technology Data Exchange (ETDEWEB)

    Alonso, M.J.C.; Sanchez, E.A.; Fernandez-Polanco, F. [Dept. Ingenieria Quimica, Univ. de Valladolid, Valladolid (Spain)

    2002-07-01

    The supercritical water oxidation (SCWO) process is a promising technology for the treatment of industrial wastewaters and sludges. It has been shown to be effective in destroying recalcitrant, xenobiotic or nonbiodegradable compounds and is an interesting alternative to conventional chemical and biological oxidation processes. This paper describes the basic concepts and state of the art of the SCWO technology and presents the flow sheets and energy and mass balances for diluted wastewater and sludge treatment. (orig.)

  1. Droplet turbulence interactions under subcritical and supercritical conditions

    Science.gov (United States)

    Coy, E. B.; Greenfield, S. C.; Ondas, M. S.; Song, Y.-H.; Spegar, T. D.; Santavicca, D. A.

    1993-01-01

    The goal of this research is to experimentally characterize the behavior of droplets in vaporizing liquid sprays under conditions typical of those encountered in high pressure combustion systems such as liquid fueled rocket engines. Of particular interest are measurements of droplet drag, droplet heating, droplet vaporization, droplet distortion, and secondary droplet breakup, under both subcritical and supercritical conditions. The paper presents a brief description of the specific accomplishments which have been made over the past year.

  2. Heat Transfer Phenomena in Supercritical Water Nuclear Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Mark H. Anderson; MichaelL. Corradini; Riccardo Bonazza; Jeremy R. Licht

    2007-10-03

    A supercritical water heat transfer facility has been built at the University of Wisconsin to study heat transfer in ancircular and square annular flow channel. A series of integral heat transfer measurements has been carried out over a wide range of heat flux, mas velocity and bulk water temperatures at a pressure of 25 MPa. The circular annular test section geometry is a 1.07 cm diameter heater rod within a 4.29 diameter flow channel.

  3. Supercritical Flow Synthesis of TiO2

    DEFF Research Database (Denmark)

    Hellstern, Henrik Christian; Becker, Jacob; Hald, Peter

    2014-01-01

    A new, up-scaled supercritical flow synthesis apparatus has been constructed in Aarhus. A module based system allows for a range of parameter studies with improved parameter control. The dual-reactor setup enables both single phase and core-shell nanoparticle synthesis. TiO2 is a well......-known material and has been synthesized to evaluate the performance of the new super critical reactor setup. TiO2 will form the basis for planned core-shell syntheses....

  4. Desalination shocks in microstructures

    CERN Document Server

    Mani, Ali

    2011-01-01

    Salt transport in bulk electrolytes is limited by diffusion and convection, but in microstructures with charged surfaces (e.g. microfluidic devices, porous media, soils, or biological tissues) surface conduction and electro-osmotic flow also contribute to ionic fluxes. For small applied voltages, these effects lead to well known linear electrokinetic phenomena. In this paper, we predict some surprising nonlinear dynamics that can result from the competition between bulk and interfacial transport at higher voltages. When counter-ions are selectively removed by a membrane or electrode, a "desalination shock" can propagate through the microstructure, leaving in its wake an ultrapure solution, nearly devoid of co-ions and colloidal impurities. We elucidate the basic physics of desalination shocks and develop a mathematical theory of their existence, structure, and stability, allowing for slow variations in surface charge or channel geometry. Via asymptotic approximations and similarity solutions, we show that des...

  5. Bow shock data analysis

    Science.gov (United States)

    Zipf, Edward C.; Erdman, Peeter W.

    1994-08-01

    The University of Pittsburgh Space Physics Group in collaboration with the Army Research Office (ARO) modeling team has completed a systematic organization of the shock and plume spectral data and the electron temperature and density measurements obtained during the BowShock I and II rocket flights which have been submitted to the AEDC Data Center, has verified the presence of CO Cameron band emission during the Antares engine burn and for an extended period of time in the post-burn plume, and have adapted 3-D radiation entrapment codes developed by the University of Pittsburgh to study aurora and other atmospheric phenomena that involve significant spatial effects to investigate the vacuum ultraviolet (VUV) and extreme ultraviolet (EUV) envelope surrounding the re-entry that create an extensive plasma cloud by photoionization.

  6. SUPERDIFFUSIVE SHOCK ACCELERATION

    Energy Technology Data Exchange (ETDEWEB)

    Perri, S.; Zimbardo, G. [Dipartimento di Fisica, Universita della Calabria, Ponte P. Bucci Cubo 31C, I-87036 Rende (Italy)

    2012-05-10

    The theory of diffusive shock acceleration is extended to the case of superdiffusive transport, i.e., when the mean square deviation grows proportionally to t{sup {alpha}}, with {alpha} > 1. Superdiffusion can be described by a statistical process called Levy random walk, in which the propagator is not a Gaussian but it exhibits power-law tails. By using the propagator appropriate for Levy random walk, it is found that the indices of energy spectra of particles are harder than those obtained where a normal diffusion is envisaged, with the spectral index decreasing with the increase of {alpha}. A new scaling for the acceleration time is also found, allowing substantially shorter times than in the case of normal diffusion. Within this framework we can explain a number of observations of flat spectra in various astrophysical and heliospheric contexts, for instance, for the Crab Nebula and the termination shock of the solar wind.

  7. Spontaneous Ignition of Hydrothermal Flames in Supercritical Ethanol Water Solutions

    Science.gov (United States)

    Hicks, Michael C.; Hegde, Uday G.; Kojima, Jun J.

    2017-01-01

    Results are reported from recent tests where hydrothermal flames spontaneously ignited in a Supercritical Water Oxidation (SCWO) Test Cell. Hydrothermal flames are generally categorized as flames that occur when appropriate concentrations of fuel and oxidizer are present in supercritical water (SCW); i.e., water at conditions above its critical point (218 atm and 374 C). A co-flow injector was used to inject fuel, comprising an aqueous solution of 30-vol to 50-vol ethanol, and air into a reactor held at constant pressure and filled with supercritical water at approximately 240 atm and 425 C. Hydrothermal flames auto-ignited and quickly stabilized as either laminar or turbulent diffusion flames, depending on the injection velocities and test cell conditions. Two orthogonal views, one of which provided a backlit shadowgraphic image, provided visual observations. Optical emission measurements of the steady state flame were made over a spectral range spanning the ultraviolet (UV) to the near infrared (NIR) using a high-resolution, high-dynamic-range spectrometer. Depending on the fuel air flow ratios varying degrees of sooting were observed and are qualitatively compared using light absorption comparisons from backlit images.

  8. Supercritical extraction of carqueja essential oil: experiments and modeling

    Directory of Open Access Journals (Sweden)

    R. M. F. Vargas

    2006-09-01

    Full Text Available Baccharis trimera is a native Brazilian plant which has medicinal properties. In this work a method of supercritical extraction was studied to obtain the popularly essential oil from Baccharis trimera, known as carqueja. The aim was to obtain experimental data and to compare two mathematical models used in the simulation of carqueja (Baccharis trimera oil extraction by supercritical CO2. The two mathematical models are based on mass transfer. One of the models, proposed by Reverchon, is solved numerically and requires two adjustable parameters from the experimental data. The other model chosen is the one proposed by Sovová. This model is solved analytically and requires four adjustable parameters. Numerical results are presented and discussed for the adjusted parameters. The experimental results are obtained in a temperature range of 313.15 K to 343.15 K at 90 bar. The extraction yield of carqueja essential oil using supercritical carbon dioxide ranged between 1.72 % (w/w at 323.15 K and 2.34 % (w/w at 343.15 K, 90 bar with a CO2 flow rate of 3.34.10-8 m³/s for a 0.0015 kg sample of Baccharis trimera.

  9. Subchannel analysis with turbulent mixing rate of supercritical pressure fluid

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jianhui, E-mail: wjianhui1985@gmail.com [Department of Applied Physics, Waseda University, Tokyo 169-8555 (Japan); Oka, Yoshiaki [Emeritus Professor the University of Tokyo, Tokyo (Japan)

    2015-06-15

    Highlights: • Subchannel analysis with turbulent mixing rate law of supercritical pressure fluid (SPF) is carried out. • Turbulent mixing rate is enhanced, compared with that calculated by the law of pressurized water reactor (PWR). • Increase in maximum cladding surface temperature (MCST) is smaller comparing with PWR model. • The sensitivities of MCST on non-uniformity of subchannel area and power peaking are reduced by using SPF model. - Abstract: The subchannel analysis with turbulent mixing rate law of supercritical pressure fluid (SPF) is carried out for supercritical-pressurized light water cooled and moderated reactor (Super LWR). It is different from the turbulent mixing rate law of pressurized water reactor (PWR), which is widely adopted in Super LWR subchannel analysis study, the density difference between adjacent subchannels is taken into account for turbulent mixing rate law of SPF. MCSTs are evaluated on three kinds of fuel assemblies with different pin power distribution patterns, gap spacings and mass flow rates. Compared with that calculated by employing turbulent mixing rate law of PWR, the increase in MCST is smaller even when peaking factor is large and gap spacing is uneven. The sensitivities of MCST on non-uniformity of the subchannel area and power peaking are reduced.

  10. Solubility in supercritical solvents: A comparison of theory and simulation

    Science.gov (United States)

    Tomberli, Bruno Luca

    1998-12-01

    Solubility at supercritical conditions is studied using thermodynamics and statistical mechanics. The Redlich- Kwong equation of state, virial equation of state and fluctuation theory are used to predict the chemical potential for pure and mixed Lennard-Jones fluids. Where literature results are unavailable, Monte Carlo simulations employing the Widom particle insertion method are also carried out to determine the chemical potential at the same conditions. Several methods are shown to achieve an accuracy on the order of five percent. Based on the success of these theories, qualitative studies of cavity-interaction contributions to the chemical potential and the effect of clustering in supercritical solvation are conducted. Finally, fluctuation theory is shown to be the only available method suitable for ab initio calculations of the chemical potential involving anisotropic potentials. A suitable potential for naphthalene-carbon dioxide systems is developed from existing multi-site exp-6-1 potentials and predictions of the chemical potential of infinitely- dilute naphthalene in supercritical carbon dioxide are made as an example of a possible application of this method.

  11. Biodiesel production from rice bran oil and supercritical methanol.

    Science.gov (United States)

    Kasim, Novy Srihartati; Tsai, Tsung-Han; Gunawan, Setiyo; Ju, Yi-Hsu

    2009-04-01

    In this study, production of biodiesel from low cost raw materials, such as rice bran and dewaxed-degummed rice bran oil (DDRBO), under supercritical condition was carried out. Carbon dioxide (CO2) was employed as co-solvent to decrease the supercritical temperature and pressure of methanol. The effects of different raw materials on the yield of biodiesel production were investigated. In situ transesterification of rice bran with supercritical methanol at 30MPa and 300 degrees C for 5 min was not a promising way to produce biodiesel because the purity and yield of fatty acid methyl esters (FAMEs) obtained were 52.52% and 51.28%, respectively. When DDRBO was reacted, the purity and yield were 89.25% and 94.84%, respectively. Trans-FAMEs, which constituted about 16% of biodiesel, were found. They were identified as methyl elaidate [trans-9], methyl linoleaidate [trans-9, trans-12], methyl linoleaidate [cis-9, trans-12], and methyl linoleaidate [trans-9, cis-12]. Hydrocarbons, which constituted about 3% of the reaction product, were also detected.

  12. Supercritical fluids technology in bioprocess industries: A review

    Directory of Open Access Journals (Sweden)

    Kianoush Khosravi Darani

    2009-12-01

    Full Text Available This article reviews the fundamentals of supercritical fluid (SCF science and moves on to the biotechnological applications of them e.g. removal of biostatic agents from fermentation broths, SCF disruption of microorganisms, destruction of industrial waste, the gas-antisolvent crystallization and micron-size particle formation. Also gaining ground is enzymatic catalysis in supercritical carbon dioxide (SC-CO2, which offers the possibility of integrated synthesis product recovery processes. The paper is structured as follows: first, the effects of dense SC-CO2 on the extraction of biomaterials and disruption of cells are thoroughly reported and discussed. Then the application of SC-CO2 in particle formation and modifications of biopolymers and enzymes are described. In general, the article is focused on potential bio-industrial applications and future research needs of the SCF technology. Keywords: Biotechnology, Supercritical Fluids (SCF, disruption, inactivation, extraction, downstream, particle formation Received: 10 October 2009 / Received in revised form: 30 January 2010, Accepted: 30 January 2010, Published online: 10 March 2010

  13. Supercritical Fluid Extraction of Plutonium and Americium from Soil

    Energy Technology Data Exchange (ETDEWEB)

    Fox, R.V.; Mincher, B.J.

    2002-05-23

    Supercritical fluid extraction (SFE) of plutonium and americium from soil was successfully demonstrated using supercritical fluid carbon dioxide solvent augmented with organophosphorus and beta-diketone complexants. Spiked Idaho soils were chemically and radiologically characterized, then extracted with supercritical fluid carbon dioxide at 2,900 psi and 65 C containing varying concentrations of tributyl phosphate (TBP) and thenoyltrifluoroacetone (TTA). A single 45 minute SFE with 2.7 mol% TBP and 3.2 mol% TTA provided as much as 88% {+-} 6.0 extraction of americium and 69% {+-} 5.0 extraction of plutonium. Use of 5.3 mol% TBP with 6.8 mol% of the more acidic beta-diketone hexafluoroacetylacetone (HFA) provided 95% {+-} 3.0 extraction of americium and 83% {+-} 5.0 extraction of plutonium in a single 45 minute SFE at 3,750 psi and 95 C. Sequential chemical extraction techniques were used to chemically characterize soil partitioning of plutonium and americium in pre-SFE soil samples. Sequential chemical extraction techniques demonstrated that spiked plutonium resides primarily (76.6%) in the sesquioxide fraction with minor amounts being absorbed by the oxidizable fraction (10.6%) and residual fractions (12.8%). Post-SFE soils subjected to sequential chemical extraction characterization demonstrated that 97% of the oxidizable, 78% of the sesquioxide and 80% of the residual plutonium could be removed using SFE. These preliminary results show that SFE may be an effective solvent extraction technique for removal of actinide contaminants from soil.

  14. Thermodynamic Analysis of a Supercritical Mercury Power Cycle

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, A.S. Jr.

    1969-04-15

    An heat engine is considered which employs supercritical mercury as the working fluid and a magnetohydrodynamic (MHD) generator for thermal to electrical energy conversion. The main thrust of the paper is power cycle thermodynamics, where constraints are imposed by utilizing a MHD generator operating between supercritical, electrically conducting states of the working fluid; and, pump work is accomplished with liquid mercury. The temperature range is approximately 300 to 2200 K and system pressure is > 1,500 atm. Equilibrium and transport properties are carefully considered since these are known to vary radically in the vicinity of the critical point, which is found near the supercritical states of interest. A maximum gross plant efficiency is 20% with a regenerator effectiveness of 90% and greater, a cycle pressure ratio of two, and with highly efficient pump and generator. Certain specified cycle irreversibilities and others such as heat losses and heat exchanger pressure drops, which are not accounted for explicitly, reduce the gross plant efficiency to a few per cent. Experimental efforts aimed at practical application of the power cycle are discouraged by the marginal thermodynamic performance predicted by this study, unless such applications are insensitive to gross cycle efficiency.

  15. Supercritical nitrogen processing for the purification of reactive porous materials.

    Science.gov (United States)

    Stadie, Nicholas P; Callini, Elsa; Mauron, Philippe; Borgschulte, Andreas; Züttel, Andreas

    2015-05-15

    Supercritical fluid extraction and drying methods are well established in numerous applications for the synthesis and processing of porous materials. Herein, nitrogen is presented as a novel supercritical drying fluid for specialized applications such as in the processing of reactive porous materials, where carbon dioxide and other fluids are not appropriate due to their higher chemical reactivity. Nitrogen exhibits similar physical properties in the near-critical region of its phase diagram as compared to carbon dioxide: a widely tunable density up to ~1 g ml(-1), modest critical pressure (3.4 MPa), and small molecular diameter of ~3.6 Å. The key to achieving a high solvation power of nitrogen is to apply a processing temperature in the range of 80-150 K, where the density of nitrogen is an order of magnitude higher than at similar pressures near ambient temperature. The detailed solvation properties of nitrogen, and especially its selectivity, across a wide range of common target species of extraction still require further investigation. Herein we describe a protocol for the supercritical nitrogen processing of porous magnesium borohydride.

  16. Phase behaviour of sterols and vitamins in supercritical CO2

    Directory of Open Access Journals (Sweden)

    Gerszt R.

    2000-01-01

    Full Text Available Extraction with supercritical solvents has been used in different areas, such as petroleum desasphaltation, descaffeination of coffee and tea and in the separation of other types of natural products. The supercritical solvent most frequently utilized in the extraction of natural products is carbon dioxide (CO2 due to its several advantages over other solvents such as low cost, atoxicity and volatility. The design, evaluation and optimization of a supercritical extraction that is based on phase equilibrium require phase equilibrium data. This type of data is very scarce for natural compounds like sterols and vitamins. These natural compounds are produced synthetically, but nowadays interest in their extraction from natural sources is increasing. Therefore, the objective of this work is to study the thermodynamic modelling equilibrium of systems containing vitamins A, D, E and K, using the predictive LCVM model. The sensitivity of critical properties in the calculation of the phase behavior was also studied. This study proved that the choice of a group contribution method to calculate thermodynamic properties is very important for obtaining good results in the phase equilibrium calculations.

  17. Supercritical Fluid Extraction of Metal Chelate: A Review.

    Science.gov (United States)

    Ding, Xin; Liu, Qinli; Hou, Xiongpo; Fang, Tao

    2017-03-04

    Supercritical fluid extraction (SFE), as a new green extraction technology, has been used in extracting various metal species. The solubilities of chelating agents and corresponding metal chelates are the key factors which influence the efficiency of SFE. Other main properties of them such as stability and selectivity are also reviewed. The extraction mechanisms of mainly used chelating agents are explained by typical examples in this paper. This is the important aspect of SFE of metal ions. Moreover, the extraction efficiencies of metal species also depend on other factors such as temperature, pressure, extraction time and matrix effect. The two main complexation methods namely in-situ and on-line chelating SFE are described in detail. As an efficient chelating agent, tributyl phosphate-nitric acid (TBP-HNO3) complex attracts much attention. The SFE of metal ions, lanthanides and actinides as well as organometallic compounds are also summarized. With the proper selection of ligands, high efficient extraction of metal species can be obtained. As an efficient sample analysis method, supercritical fluid chromatography (SFC) is introduced in this paper. Recently, the extraction method combining ionic liquids (ILs) with supercritical fluid has been becoming a novel technology for treating metal ions. The kinetics related to SFE of metal species is discussed with some specific examples.

  18. Intermolecular interactions and the thermodynamic properties of supercritical fluids.

    Science.gov (United States)

    Yigzawe, Tesfaye M; Sadus, Richard J

    2013-05-21

    The role of different contributions to intermolecular interactions on the thermodynamic properties of supercritical fluids is investigated. Molecular dynamics simulation results are reported for the energy, pressure, thermal pressure coefficient, thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, Joule-Thomson coefficient, and speed of sound of fluids interacting via both the Lennard-Jones and Weeks-Chandler-Andersen potentials. These properties were obtained for a wide range of temperatures, pressures, and densities. For each thermodynamic property, an excess value is determined to distinguish between attraction and repulsion. It is found that the contributions of intermolecular interactions have varying effects depending on the thermodynamic property. The maxima exhibited by the isochoric and isobaric heat capacities, isothermal compressibilities, and thermal expansion coefficient are attributed to interactions in the Lennard-Jones well. Repulsion is required to obtain physically realistic speeds of sound and both repulsion and attraction are necessary to observe a Joule-Thomson inversion curve. Significantly, both maxima and minima are observed for the isobaric and isochoric heat capacities of the supercritical Lennard-Jones fluid. It is postulated that the loci of these maxima and minima converge to a common point via the same power law relationship as the phase coexistence curve with an exponent of β = 0.32. This provides an explanation for the terminal isobaric heat capacity maximum in supercritical fluids.

  19. The Shock and Vibration Bulletin. Part 1. Invited Papers, Submarine Shock Testing, Shock Analysis, Shock Testing

    Science.gov (United States)

    1973-06-01

    P. White, Jr., Rochester Applied Science Associates, Inc., Rochester, New York MATHEMATICAL MODEL OF A TYPICAL FLOATING SHOCK PLATFORM SUBJECTED TO...our offer. standardization projects as well as in the This asrect of cuantitive railroad technology various technical societies. This multi...Analysis of a Gravity phenomena which my education had kept care- Dam," using gelatin models . The stimulation fully hidden from me until that time. It’s

  20. Shock breakout theory

    CERN Document Server

    Waxman, Eli

    2016-01-01

    The earliest supernova (SN) emission is produced when the optical depth of the plasma lying ahead of the shock, which ejects the envelope, drops below c/v, where v is the shock velocity. This "breakout" may occur when the shock reaches the edge of the star, producing a bright X-ray/UV flash on time scales of seconds to a fraction of an hour, followed by UV/optical "cooling" emission from the expanding cooling envelope on a day time-scale. If the optical depth of circumstellar material (CSM) ejected from the progenitor star prior to the explosion is larger than c/v, the breakout will take place at larger radii, within the CSM, extending its duration to days time scale. The properties of the early, breakout and cooling, emission carry unique signatures of the structure of the progenitor star (e.g. its radius and surface composition) and of its mass-loss history. The recent progress of wide-field transient surveys enable SN detections on a day time scale, and are being used to set unique constraints on the proge...

  1. Characterization of shocked beryllium

    Directory of Open Access Journals (Sweden)

    Papin P.A.

    2012-08-01

    Full Text Available While numerous studies have investigated the low-strain-rate constitutive response of beryllium, the combined influence of high strain rate and temperature on the mechanical behavior and microstructure of beryllium has received limited attention over the last 40 years. In the current work, high strain rate tests were conducted using both explosive drive and a gas gun to accelerate the material. Prior studies have focused on tensile loading behavior, or limited conditions of dynamic strain rate and/or temperature. Two constitutive strength (plasticity models, the Preston-Tonks-Wallace (PTW and Mechanical Threshold Stress (MTS models, were calibrated using common quasi-static and Hopkinson bar data. However, simulations with the two models give noticeably different results when compared with the measured experimental wave profiles. The experimental results indicate that, even if fractured by the initial shock loading, the Be remains sufficiently intact to support a shear stress following partial release and subsequent shock re-loading. Additional “arrested” drive shots were designed and tested to minimize the reflected tensile pulse in the sample. These tests were done to both validate the model and to put large shock induced compressive loads into the beryllium sample.

  2. Radiative effects in radiative shocks in shock tubes

    Science.gov (United States)

    Drake, R. P.; Doss, F. W.; McClarren, R. G.; Adams, M. L.; Amato, N.; Bingham, D.; Chou, C. C.; DiStefano, C.; Fidkowski, K.; Fryxell, B.; Gombosi, T. I.; Grosskopf, M. J.; Holloway, J. P.; van der Holst, B.; Huntington, C. M.; Karni, S.; Krauland, C. M.; Kuranz, C. C.; Larsen, E.; van Leer, B.; Mallick, B.; Marion, D.; Martin, W.; Morel, J. E.; Myra, E. S.; Nair, V.; Powell, K. G.; Rauchwerger, L.; Roe, P.; Rutter, E.; Sokolov, I. V.; Stout, Q.; Torralva, B. R.; Toth, G.; Thornton, K.; Visco, A. J.

    2011-09-01

    Using modern high-energy-density facilities it is straightforward to produce radiative shock waves in which the transfer of energy by radiation controls the hydrodynamic structure of the system. Some of these experiments use shock tubes. This paper discusses such experiments, with an emphasis on the simple physical relations that determine the primary features of such shocks and on the details and impact of radiative energy transfer in such systems. Notable aspects include the creation of high-density shocked layers, the flow of radiative energy toward regions of higher energy density, and the creation of secondary shocks by ablation of the tube walls ahead of the primary shock front. Simulations of one such experimental system are also shown.

  3. Fundamentals of collisionless shocks for astrophysical application, 2. Relativistic shocks

    CERN Document Server

    Bykov, A M

    2011-01-01

    We review recent progress on collisionless relativistic shocks. Kinetic instability theory is briefed including its predictions and limitations. The main focus is on numerical experiments in (i) pair and (ii) electron-nucleon plasmas. The main results are: (i) confirmation of shock evolution in non-magnetised relativistic plasma in 3D due to either the lepton-Weibel instability or the ion-Weibel instability; (ii) sensitive dependence on upstream magnetisation ; (iii) the sensitive dependence of particle dynamics on the upstream magnetic inclination angle $\\thetabn$, where particles of $\\thetabn>34^\\circ$ cannot escape upstream, leading to the distinction between `sub-luminal' and `super-luminal' shocks; (iv) particles in ultra-relativistic shocks can hardly overturn the shock and escape to upstream; they may oscillate around the shock ramp for a long time, so to speak `surfing it' and thereby becoming accelerated by a kind of SDA; (v) these particles form a power law tail on the downstream distribution; their...

  4. Shock wave treatment in medicine

    Indian Academy of Sciences (India)

    S K Shrivastava; Kailash

    2005-03-01

    Extracorporeal shock wave therapy in orthopedics and traumatology is still a young therapy method. Since the last few years the development of shock wave therapy has progressed rapidly. Shock waves have changed the treatment of urolithiasis substantially. Today shock waves are the first choice to treat kidney and urethral stones. Urology has long been the only medical field for shock waves in medicine. Meanwhile shock waves have been used in orthopedics and traumatology to treat insertion tendinitis, avascular necrosis of the head of femur and other necrotic bone alterations. Another field of shock wave application is the treatment of tendons, ligaments and bones on horses in veterinary medicine. In the present paper we discuss the basic theory and application of shock waves and its history in medicine. The idea behind using shock wave therapy for orthopedic diseases is the stimulation of healing in tendons, surrounding tissue and bones. This is a completely different approach compared to urology where shock waves are used for disintegration.

  5. Can supercritical oxidation of sewage sludge be an alternative for supercritical gasification?; Kan superkritische oxidatie van zuiveringsslib een alternatief zijn voor superkritische vergassing?

    Energy Technology Data Exchange (ETDEWEB)

    Rulkens, W. [Wageningen UR, Wageningen (Netherlands); Wentink, J. [Horizon Solutions, Leiden (Netherlands)

    2013-05-15

    In the context of the development of The Energy Factory a number of technologies has been identified that may be interesting to develop further. Two of these techniques relate to the conversion of sludge in supercritical water: supercritical gasification of sludge and supercritical oxidation of sludge [Dutch] In het kader van de ontwikkeling van De Energiefabriek is een aantal technologieen geidentificeerd die mogelijk interessant zijn om verder te ontwikkelen. Twee van deze technieken hebben betrekking op de conversie van slib in superkritisch water: superkritische slibvergassing en superkritische sliboxidatie.

  6. Inhibition of AKT signaling by supercritical CO2 extract of mango ginger (Curcuma amada Roxb.) in human glioblastoma cells.

    Science.gov (United States)

    Ramachandran, Cheppail; Portalatin, Gilda; Quirin, Karl-W; Escalon, Enrique; Khatib, Ziad; Melnick, Steven J

    2015-12-01

    Mango ginger (Curcuma amada Roxb.) is a less-investigated herb for anticancer properties than other related Curcuma species. AKT (a serine/threonine protein kinase B, originally identified as an oncogene in the transforming retrovirus AKT8) plays a central role in the development and promotion of cancer. In this investigation, we have analyzed the effect of supercritical CO2 extract of mango ginger (CA) on the genetic pathways associated with AKT signaling in human glioblastoma cells. The inhibitory effect of supercritical CO2 extract of mango ginger (Curcuma amada) on AKT signaling was investigated in U-87MG glioblastoma cells. CA was highly cytotoxic to glioblastoma cell line (IC50=4.92±0.81 µg/mL) compared to mHypoE-N1 normal mouse hypothalamus cell line (IC50=40.57±0.06 µg/mL). CA inhibits AKT (protein Kinase B) and adenosine monophophate -activated protein kinase α (AMPKα) phosphorylation significantly in a dose-dependent manner. The cell migration which is necessary for invasion and metastasis was also inhibited by CA treatment, with about 43% reduction at 20 µg/mL concentration. Analysis of mRNA and protein expression of genes associated with apoptosis, cell proliferation and angiogenesis showed that CA modulates expression of genes associated with apoptosis (Bax, Bcl-2, Bcl-X, BNIP3, caspase-3, mutant p53 and p21), cell proliferation (Ki67) and angiogenesis vascular endothelial growth factor (VEGF). Additionally, heat shock protein 90 (HSP90) and AMPKα genes interacting with the AKT signaling pathway were also downregulated by CA treatment. These results indicate the molecular targets and mechanisms underlying the anticancer effect of CA in human glioblastoma cells.

  7. Polarization and spectral shift of benzophenone in supercritical water.

    Science.gov (United States)

    Fonseca, T L; Georg, H C; Coutinho, K; Canuto, S

    2009-04-30

    Monte Carlo simulation and quantum mechanics calculations based on the INDO/CIS and TD-DFT methods were utilized to study the solvatochromic shift of benzophenone when changing the environment from normal water to supercritical (P = 340.2 atm and T = 673 K) condition. Solute polarization increases the dipole moment of benzophenone, compared to gas phase, by 88 and 35% in normal and supercritical conditions, giving the in-solvent dipole value of 5.8 and 4.2 D, respectively. The average number of solute-solvent hydrogen bonds was analyzed, and a large decrease of 2.3 in normal water to only 0.8 in the supercritical environment was found. By using these polarized models of benzophenone in the two different conditions of water, we performed MC simulations to generate statistically uncorrelated configurations of the solute surrounded by the solvent molecules and subsequent quantum mechanics calculations on these configurations. When changing from normal to supercritical water environment, INDO/CIS calculations explicitly considering all valence electrons of the 235 solvent water molecules resulted in a solvatochromic shift of 1425 cm(-1) for the most intense pi-pi* transition of benzophenone, that is, slightly underestimated in comparison with the experimentally inferred result of 1700 cm(-1). TD-B3LYP/6-311+G(2d,p) calculations on the same configurations but with benzophenone electrostatically embedded in the 320 water molecules resulted in a solvatochromic shift of 1715 cm(-1) for this transition, in very good agreement with the experimental result. When using the unpolarized model of the benzophenone, this calculated solvatochromic shift was only 640 cm(-1). Additional calculations were also made by using BHandHLYP/6-311+G(2d,p) to analyze the effect of the asymptotic decay of the exchange functional. This study indicates that, contrary to the general expectation, there is a sizable solute polarization even in the low-density regime of supercritical condition and

  8. Development of supercritical fluid extraction and supercritical fluid chromatography purification methods using rapid solubility screening with multiple solubility chambers.

    Science.gov (United States)

    Gahm, Kyung H; Huang, Ke; Barnhart, Wesley W; Goetzinger, Wolfgang

    2011-01-01

    Rapid solubility screening in diverse supercritical fluids (SCFs) was carried out via multiple solubility chambers with a trapping device and online ultraviolet (UV) detection. With this device, it was possible to rapidly study the solubility variations of multiple components in a mixture. Results from solubility studies have been used to develop efficient supercritical fluid extraction (SFE) and supercritical fluid chromatography (SFC) methods. After the investigation of solubilities of theophylline and caffeine in several neat organic solvents and SCFs, advantages of SFE over conventional organic solvent extraction were demonstrated with a model mixture of theophylline and caffeine. The highest solubility ratio of 1:40 (theophylline:caffeine) was observed in the SCF with 20% acetonitrile (MeCN), where a ratio of 1:11 was the highest in the neat organic solvents. A model mixture of theophylline:caffeine (85:15 w/w, caffeine as an impurity) was successfully purified by SFE by leveraging the highest solubility difference. The SCF with 20% MeCN selectively removed caffeine and left theophylline largely intact. Rapid SCF solubility screening was applied to development of SFE and SFC methods in a drug discovery environment. Two successful applications were demonstrated with proprietary Amgen compounds to either remove an achiral impurity before chiral purification or enhance chiral chromatographic throughput.

  9. CMEs as a Shock Structure

    Science.gov (United States)

    Muñoz Martínez, Guadalupe; Becerril, Carlos; Lopez-Lopez, Jose Luis

    Interplanetary shocks are associated to approximately one third of the CMEs detected in the interplanetary medium. Even though they have been associated to fast CMEs (V>1000 km/s) it has been shown that some slow ones (V 300 km/s) presented shocks at 1 AU. The structure of the features observed in coronograph images can be hardly compared to the ones detected beyond the coronograph field of view, where the shock is clearly identify. For a few cases, the shock in front of the CME has been distinguish in white light images, but, is there a real visual difference between the CME itself and the considered shock? In this work we compare the optical characteristics of CMEs and some hydrodynamic parameters of ICMEs to show that the feature observed in white light images can be considered as a shock structure.

  10. MALEIC ANHYDRIDE HYDROGENATION OF PD/AL2O3 CATALYST UNDER SUPERCRITICAL CO2 MEDIUM

    Science.gov (United States)

    Hydrogenation of maleic anhydride (MA) to either y-butyrolactone of succinic anhydride over simple Pd/Al2O3 impregnated catalyst in supercritical CO2 medium has been studied at different temperatures and pressures. A comparison of the supercritical CO2 medium reaction with the c...

  11. Supercritical Fluid Extraction and Chromatography Using a Lee Scientific Series 600 SFE/SFC System

    Science.gov (United States)

    1992-05-01

    Dioxide and Ethylene. Journal of Chemical Engineering Data , 26:47. Lee, M.L. and K.E. Markides 1987 Chromatography with Supercritical Fluids. Science...Publishers, Stoneham, MA. McHugh, M.A., and M.E. Paulaitis 1980 Solid Solubilities of Naphthalene and Biphenyle in Supercritical Carbon Dioxide. Journal of Chemical Engineering Data , 25

  12. Application of Parallel Processing to the Investigation of Supercritical Droplet Evaporation and Combustion Using Molecular Dynamics

    Science.gov (United States)

    2007-11-02

    Molecular dynamics (MD) implemented on parallel processors was used to model supercritical droplet phenomena occurring in combustion devices. The use...of molecular dynamics allows the modeling of supercritical phenomena without an a priori knowledge of the equation of state or transport properties

  13. Experimental study of elliptical jet from supercritical to subcritical conditions using planar laser induced fluorescence

    Science.gov (United States)

    Muthukumaran, C. K.; Vaidyanathan, Aravind

    2015-03-01

    The study of fluid jet dynamics at supercritical conditions involves strong coupling between fluid dynamic and thermodynamic phenomena. Beyond the critical point, the liquid-vapor coexistence ceases to exist, and the fluid exists as a single phase known as supercritical fluid with its properties that are entirely different from liquids and gases. At the critical point, the liquids do not possess surface tension and latent heat of evaporation. Around the critical point, the fluid undergoes large changes in density and possesses thermodynamic anomaly like enhancement in thermal conductivity and specific heat. In the present work, the transition of the supercritical and near-critical elliptical jet into subcritical as well as supercritical environment is investigated experimentally with nitrogen and helium as the surrounding environment. Under atmospheric condition, a liquid jet injected from the elliptical orifice exhibits axis switching phenomena. As the injection temperature increases, the axis switching length also increases. Beyond the critical temperature, the axis switching is not observed. The investigation also revealed that pressure plays a major role in determining the thermodynamic transition of the elliptical jet only for the case of supercritical jet injected into subcritical chamber conditions. At larger pressures, the supercritical jet undergoes disintegration and formation of droplets in the subcritical environment is observed. However, for supercritical jet injection into supercritical environment, the gas-gas like mixing behavior is observed.

  14. Experimental study of elliptical jet from supercritical to subcritical conditions using planar laser induced fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Muthukumaran, C. K.; Vaidyanathan, Aravind, E-mail: aravind7@iist.ac.in [Department of Aerospace Engineering, Indian Institute of Space Science and Technology, Trivandrum, Kerala 695547 (India)

    2015-03-15

    The study of fluid jet dynamics at supercritical conditions involves strong coupling between fluid dynamic and thermodynamic phenomena. Beyond the critical point, the liquid-vapor coexistence ceases to exist, and the fluid exists as a single phase known as supercritical fluid with its properties that are entirely different from liquids and gases. At the critical point, the liquids do not possess surface tension and latent heat of evaporation. Around the critical point, the fluid undergoes large changes in density and possesses thermodynamic anomaly like enhancement in thermal conductivity and specific heat. In the present work, the transition of the supercritical and near-critical elliptical jet into subcritical as well as supercritical environment is investigated experimentally with nitrogen and helium as the surrounding environment. Under atmospheric condition, a liquid jet injected from the elliptical orifice exhibits axis switching phenomena. As the injection temperature increases, the axis switching length also increases. Beyond the critical temperature, the axis switching is not observed. The investigation also revealed that pressure plays a major role in determining the thermodynamic transition of the elliptical jet only for the case of supercritical jet injected into subcritical chamber conditions. At larger pressures, the supercritical jet undergoes disintegration and formation of droplets in the subcritical environment is observed. However, for supercritical jet injection into supercritical environment, the gas-gas like mixing behavior is observed.

  15. Use of liquid/supercritical CO2 extraction process for butanol recovery from fermentation broth

    Science.gov (United States)

    In order for butanol fermentation to be a viable option, it is essential to recover it from fermentation broth using economical alternate in-situ product recovery techniques such as liquid/supercritical CO2 extraction as compared to distillation. This technique (liquid CO2 extraction & supercritical...

  16. Study on Supercritical Fluid Extraction of Pu(Ⅳ)in Simulative Contaminated Soils

    Institute of Scientific and Technical Information of China (English)

    SONG; Zhi-jun; DING; You-qian; ZHOU; Li-qiang

    2015-01-01

    Supercritical fluid has advantages of rapid mass transfer and high solubility,which can extract different substance through changing the extracting temperature and pressure.So in comparison to conventional solvent extraction process,supercritical fluid extraction do not need to pretreatment of the matrix,minimizes the amount of secondary waste,and the extraction

  17. Improved manometric setup for the accurate determination of supercritical carbon dioxide sorption

    NARCIS (Netherlands)

    Van Hemert, P.; Bruining, H.; Rudolph, E.S.J.; Wolf, K.H.A.A.; Maas, J.G.

    2009-01-01

    An improved version of the manometric apparatus and its procedures for measuring excess sorption of supercritical carbon dioxide are presented in detail with a comprehensive error analysis. An improved manometric apparatus is necessary for accurate excess sorption measurements with supercritical car

  18. Improved manometric setup for the accurate determination of supercritical carbon dioxide sorption

    NARCIS (Netherlands)

    Van Hemert, P.; Bruining, H.; Rudolph, E.S.J.; Wolf, K.H.A.A.; Maas, J.G.

    2009-01-01

    An improved version of the manometric apparatus and its procedures for measuring excess sorption of supercritical carbon dioxide are presented in detail with a comprehensive error analysis. An improved manometric apparatus is necessary for accurate excess sorption measurements with supercritical car

  19. On-line coupling of supercritical fluid extraction and chromatographic techniques.

    Science.gov (United States)

    Sánchez-Camargo, Andrea Del Pilar; Parada-Alfonso, Fabián; Ibáñez, Elena; Cifuentes, Alejandro

    2017-01-01

    This review summarizes and discusses recent advances and applications of on-line supercritical fluid extraction coupled to liquid chromatography, gas chromatography, and supercritical fluid chromatographic techniques. Supercritical fluids, due to their exceptional physical properties, provide unique opportunities not only during the extraction step but also in the separation process. Although supercritical fluid extraction is especially suitable for recovery of non-polar organic compounds, this technique can also be successfully applied to the extraction of polar analytes by the aid of modifiers. Supercritical fluid extraction process can be performed following "off-line" or "on-line" approaches and their main features are contrasted herein. Besides, the parameters affecting the supercritical fluid extraction process are explained and a "decision tree" is for the first time presented in this review work as a guide tool for method development. The general principles (instrumental and methodological) of the different on-line couplings of supercritical fluid extraction with chromatographic techniques are described. Advantages and shortcomings of supercritical fluid extraction as hyphenated technique are discussed. Besides, an update of the most recent applications (from 2005 up to now) of the mentioned couplings is also presented in this review.

  20. System model for gasification of biomass model compounds in supercritical water – a thermodynamic analysis

    NARCIS (Netherlands)

    Withag, Jan A.M.; Smeets, Jules R.; Bramer, Eddy A.; Brem, Gerrit

    2012-01-01

    This article presents a system model for the process of gasification of biomass model compounds in supercritical water. Supercritical water gasification of wet biomass (water content of 70 wt% or more) has as the main advantage that conversion may take place without the costly drying step. The therm

  1. System model for gasification of biomass model compounds in supercritical water - A thermodynamic analysis

    NARCIS (Netherlands)

    Withag, J.A.M.; Smeets, Jules R.; Bramer, E.A.; Brem, G.

    2012-01-01

    This article presents a system model for the process of gasification of biomass model compounds in supercritical water. Supercritical water gasification of wet biomass (water content of 70 wt% or more) has as the main advantage that conversion may take place without the costly drying step. The therm

  2. Supercritical water gasification of biomass: an experimental study of model compounds and potential biomass feeds

    NARCIS (Netherlands)

    Chakinala, Anand Gupta

    2013-01-01

    Gasification of biomass in supercritical water is a complex process. In supercritical water ideally the biomass structure and the larger molecules are broken down into smaller, gaseous components under the influence of radicals. However, the biomass is normally fed to the system at low temperature a

  3. Lewis-acid catalyzed depolymerization of Protobind lignin in supercritical water and ethanol

    NARCIS (Netherlands)

    Guvenatam, Burcu; Heeres, Erik H.J.; Pidko, Evgeny A.; Hensen, Ernie J. M.

    2016-01-01

    The use of metal acetates, metal chlorides and metal triflates as Lewis acid catalysts for the depolymerization of soda lignin under supercritical conditions was investigated. The reactions were carried out at 400 degrees C in water and ethanol. Lignin conversion in supercritical water led to format

  4. Improvement of dissolution property of poorly water-soluble drug by supercritical freeze granulation.

    Science.gov (United States)

    Sonoda, Ryoichi; Hara, Yuko; Iwasaki, Tomohiro; Watano, Satoru

    2009-10-01

    The dissolution property of the poorly water-soluble drug, flurbiprofen (FP) was improved by a novel supercritical freeze granulation using supercritical carbon dioxide. Supercritical freeze granulation was defined as a production method of the granulated substances by using the dry ice to generate intentionally for the rapid atomization of the supercritical carbon dioxide to the atmospheric pressure. This process utilized a rapid expansion of supercritical solutions (RESS) process with the mixture of the drug and lactose. In the supercritical freeze granulation, needle-like FP fine particles were obtained which adhered to the surface of lactose particles, which did not dissolve in supercritical carbon dioxide. The number of FP particles that adhered to the surface of particles decreased with an increase in the ratio of lactose added, leading to markedly improve the dissolution rate. This improvement was caused not only by the increase in the specific surface area but also the improvement of the dispersibility of FP in water. It is thus concluded that the supercritical freeze granulation is a useful technique to improve the dissolution property of the poorly water-soluble flurbiprofen.

  5. Modeling the outflow of liquid with initial supercritical parameters using the relaxation model for condensation

    Directory of Open Access Journals (Sweden)

    Lezhnin Sergey

    2017-01-01

    Full Text Available The two-temperature model of the outflow from a vessel with initial supercritical parameters of medium has been realized. The model uses thermodynamic non-equilibrium relaxation approach to describe phase transitions. Based on a new asymptotic model for computing the relaxation time, the outflow of water with supercritical initial pressure and super- and subcritical temperatures has been calculated.

  6. Palladium-Catalyzed Carbonylation of Primary Amines in Supercritical Carbon Dioxide

    Institute of Scientific and Technical Information of China (English)

    李金恒; 江焕峰; 陈鸣才

    2001-01-01

    The chemoselectity of the palladimm-catalyzed carbonylation of amines was affected by the addition of MeOH in supercritical carbon dioxide. The results show different selectivity in supercritical carbon dioxide CO2(sc) from that in alcohol.Methyl carbamate and its derivatives were obtained in high yields in CO2(sc).

  7. Metal Ions Extraction with Glucose Derivatives as Chelating Reagents in Supercritical Carbon Dioxide

    Institute of Scientific and Technical Information of China (English)

    Guo Chen YANG; Hai Jian YANG

    2006-01-01

    A series of glucose derivatives have been used as chelating reagents to extract metal ions in supercritical carbon dioxide. With perfluoro-1-octanesulfonic acid tetraethylammonium salt as additive, glucose derivatives were selective for Sr2+ and Pb2+ extraction in supercritical carbon dioxide.

  8. Morphodynamics and sedimentary structures of bedforms under supercritical-flow conditions: new insights from flume experiments

    NARCIS (Netherlands)

    Cartigny, M.J.B.; Ventra, D.; Postma, G.; Berg, J.H. van den

    2012-01-01

    Particulate density currents, such as pyroclastic flows and turbidity currents, are prone to flow in a supercritical state, due to their small density difference in relation to the ambient fluid. Facies deposited in supercritical-flow conditions are therefore likely to be common, yet their recogniti

  9. Lewis-acid catalyzed depolymerization of Protobind lignin in supercritical water and ethanol

    NARCIS (Netherlands)

    Guvenatam, Burcu; Heeres, Erik H.J.; Pidko, Evgeny A.; Hensen, Ernie J. M.

    2016-01-01

    The use of metal acetates, metal chlorides and metal triflates as Lewis acid catalysts for the depolymerization of soda lignin under supercritical conditions was investigated. The reactions were carried out at 400 degrees C in water and ethanol. Lignin conversion in supercritical water led to

  10. Physics of collisionless shocks - theory and simulation

    CERN Document Server

    Novo, A Stockem; Fonseca, R A; Silva, L O

    2015-01-01

    Collisionless shocks occur in various fields of physics. In the context of space and astrophysics they have been investigated for many decades. However, a thorough understanding of shock formation and particle acceleration is still missing. Collisionless shocks can be distinguished into electromagnetic and electrostatic shocks. Electromagnetic shocks are of importance mainly in astrophysical environments and they are mediated by the Weibel or filamentation instability. In such shocks, charged particles gain energy by diffusive shock acceleration. Electrostatic shocks are characterized by a strong electrostatic field, which leads to electron trapping. Ions are accelerated by reflection from the electrostatic potential. Shock formation and particle acceleration will be discussed in theory and simulations.

  11. Stability of oblique shock front

    Institute of Scientific and Technical Information of China (English)

    CHEN; Shuxing(陈恕行)

    2002-01-01

    The stability of the weak planar oblique shock front with respect to the perturbation of the wall is discussed. By the analysis of the formation and the global construction of shock and its asymptotic behaviour for stationary supersonic flow along a smooth rigid wall we obtain the stability of the solution containing a weak planar shock front. The stability can be used to single out a physically reasonable solution together with the entropy condition.

  12. Grain Destruction in Interstellar Shocks

    OpenAIRE

    1995-01-01

    Interstellar shock waves can erode and destroy grains present in the shocked gas, primarily as the result of sputtering and grain-grain collisions. Uncertainties in current estimates of sputtering yields are reviewed. Results are presented for the simple case of sputtering of fast grains being stopped in cold gas. An upper limit is derived for sputtering of refractory grains in C-type MHD shocks: shock speeds $v_s \\gtrsim 50 \\kms$ are required for return of more than 30\\% of the silicate to t...

  13. Management of refractory cardiogenic shock.

    Science.gov (United States)

    Reyentovich, Alex; Barghash, Maya H; Hochman, Judith S

    2016-08-01

    Cardiogenic shock is a life-threatening condition that occurs in response to reduced cardiac output in the presence of adequate intravascular volume and results in tissue hypoxia. Cardiogenic shock has several underlying aetiologies, with the most common being acute myocardial infarction (AMI). Refractory cardiogenic shock presents as persistent tissue hypoperfusion despite administration of adequate doses of two vasoactive medications and treatment of the underlying aetiology. Investigators of the SHOCK trial reported a long-term mortality benefit of emergency revascularization for shock complicating AMI. Since the publication of the SHOCK trial and subsequent guideline recommendations, the increase in community-based use of percutaneous coronary intervention for this condition has resulted in a significant decline in mortality. Despite these successes in the past 15 years, mortality still remains exceptionally high, particularly in patients with refractory cardiogenic shock. In this Review, we discuss the aetiology and pathophysiology of cardiogenic shock and summarize the data on the available therapeutics and their limitations. Although new mechanical circulatory support devices have been shown to improve haemodynamic variables in patients with shock complicating AMI, they did not improve clinical outcomes and are associated with high costs and complications.

  14. Synthesis of niobium pentoxide nanoparticles in single-flow supercritical water

    Science.gov (United States)

    Fuchigami, Teruaki; Kakimoto, Ken-ichi

    2016-10-01

    The development of a new synthesis method is still required for very fine oxide nanoparticles. In this study, a single-flow supercritical fluid system has been developed for the synthesis of highly crystalline nanosized oxide particles. Niobium oxide particles were synthesized by single-flow supercritical water treatment, batch-type supercritical water treatment and subcritical water treatment. Niobium pentoxide nanoparticles synthesized by single-flow supercritical water treatment at 673 K, 24.5 MPa, and 15 ml min-1 flow rate had a pseudohexagonal structure. The morphology of the nanoparticle was a rod, and it has a smaller particle size and larger crystallite size than those of the oxide particles synthesized by the other methods, because the particle growth and the decomposition of surfactant were rapidly suppressed in the single-flow supercritical water treatment. The nanosized niobium pentoxide is useful as a catalyst in harsh environments and as a precursor powder of lead-free piezoelectric materials.

  15. Prospects of Supercritical Fluids in Realizing Graphene-Based Functional Materials.

    Science.gov (United States)

    Padmajan Sasikala, Suchithra; Poulin, Philippe; Aymonier, Cyril

    2016-04-13

    Supercritical-fluids science and technology predate all the approaches that are currently established for graphene production by several decades in advanced materials design. However, it has only recently been proposed as a plausible approach for graphene processing. Since then, supercritical fluids have emerged into contention as an alternative to existing technologies because of their scalability and versatility in processing graphene materials, which include composites, aerogels, and foams. Here, an overview is presented of such materials prepared through supercritical fluids from an advanced materials science standpoint, with a discussion on their fundamental properties and technological applications. The benefits of supercritical-fluid processing over conventional liquid-phase processing are presented. The benefits include not only better performances for advanced applications but also environmental issues associated with the synthesis process. Nevertheless, the limitations of supercritical-fluid processing are also stressed, along with challenges that are still faced toward the achievement of the great expectations from graphene materials.

  16. On the cluster composition of supercritical water combining molecular modeling and vibrational spectroscopic data.

    Science.gov (United States)

    Tassaing, T; Garrain, P A; Bégué, D; Baraille, I

    2010-07-21

    The present study is aimed at a detailed analysis of supercritical water structure based on the combination of experimental vibrational spectra as well as molecular modeling calculations of isolated water clusters. We propose an equilibrium cluster composition model where supercritical water is considered as an ideal mixture of small water clusters (n=1-3) at the chemical equilibrium and the vibrational spectra are expected to result from the superposition of the spectra of the individual clusters, Thus, it was possible to extract from the decomposition of the midinfrared spectra the evolution of the partition of clusters in supercritical water as a function of density. The cluster composition predicted by this model was found to be quantitatively consistent with the near infrared and Raman spectra of supercritical water analyzed using the same procedure. We emphasize that such methodology could be applied to determine the portion of cluster in water in a wider thermodynamic range as well as in more complex aqueous supercritical solutions.

  17. Successively separation method of uranium and rare earth element having supercritical fluid as extracting medium

    Energy Technology Data Exchange (ETDEWEB)

    Iso, Shuichi; Meguro, Yoshihiro; Yoshida, Yoshiyuki

    1996-08-30

    In a method of separating by extraction of coolants uranium and rare earth elements by using supercritical fluid in a supercritical state and a hydrophobic organic chelating agent, a plurality of extraction steps having different extraction efficiencies are provided. As the fluid in the supercritical state, carbon dioxide, carbon monoxide, ammonia, sulfur tetrafluoride and nitrogen are mentioned. A hydrophobic organic chelating agent can form a chelating compound with uranium and rare earth elements, and the formed complex compounds are easily dissolved into the supercritical fluid thereby enabling to provide an excellent extraction effect. A suitable hydrophobic organic chelating agent includes organic phosphor compounds, {beta}-diketone compounds and microcyclic compounds. Then, there can be provided an extraction method using a supercritical liquid as an extraction medium capable of successively separating uranium and rare earth elements selectively having high safety and performed safely and also performed in a case where a plurality of rare earth elements exist together. (N.H.)

  18. Supercritical fluid (SCF) technologies: Assessment of applicability to installation restoration processes

    Science.gov (United States)

    1994-03-01

    USAEC has conducted an evaluation of supercritical fluid (SCF) technologies for their applicability to treatment of explosives, chlorinated hydrocarbons, and metals in soils, water, and/or waste sludge media. Off-specification explosives and propellants that have traditionally been open burned or openly detonated were also examined. Supercritical fluids are substances which have been heated and compressed to above their critical temperatures and pressures and which possess unique transport and mass transfer properties. Supercritical fluid extraction (SFE) uses the solvating properties of supercritical fluids to extract one or more organic components from a mixture into a supercritical solvent (commonly CO2). The concentrated extract stream may then be recycled, reclaimed, or destroyed by other methods.

  19. [Toxic shock syndrome].

    Science.gov (United States)

    Tyll, T; Bílková, M; Revinová, A; Müller, M; Čurdová, M; Zlámal, M; Holub, M

    2015-10-01

    The authors present an up-to-date review of toxic shock syndrome (TSS) - a life-threatening condition where toxins of the Gram-positive bacteria Staphyloccocus aureus and Streptococcus pyogenes play a key role in the pathogenesis. The authors provide insight into the epidemiology and pathogenesis of the disease and point out the relevant patient history data and clinical signs and symptoms that may indicate progression of TSS. Last but not least, the state of the art diagnostic and therapeutic approaches to early and full blown TSS are summarized. Case reports are presented to illustrate two different etiological forms of this relatively rare nosological entity.

  20. A shocking experiment

    Directory of Open Access Journals (Sweden)

    Gregory S. Berns

    2007-08-01

    Full Text Available We study whether probability weighting is observed when individuals are presented with a series of choices between lotteries consisting of real non-monetary adverse outcomes, electric shocks. Our estimation of the parameters of the probability weighting function proposed by Tversky and Kahneman (1992 are similar to those obtained in previous studies of lottery choice for negative monetary payoffs and negative hypothetical payoffs. In addition, common ratio violations in choice behavior are widespread. Our results provide evidence that probability weighting is a general phenomenon, independent of the source of disutility.