The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform

E Vasiliev - One of the best experts on this subject based on the ideXlab platform.

Denis Roizard - One of the best experts on this subject based on the ideXlab platform.

  • separation of binary mixtures by dense membrane processes influence of inert gas entrance under variable Downstream Pressure conditions
    Chemical Engineering Science, 2003
    Co-Authors: Cecile Vallieres, Eric Favre, Xavier Arnold, Denis Roizard
    Abstract:

    The influence of an inert gas on the separation performances of a dense polymeric membrane module working under partial vacuum on the Downstream side, such as possibly encountered in gas permeation, vapor permeation or pervaporation, has been investigated through an experimental and theoretical study. A whole range of situations on the Downstream side, covering ideal vacuum pumping (i.e. zero Downstream Pressure under leak free conditions) to inert gas sweeping under atmospheric Pressure has been tested. A theoretical framework, previously developed for single permeant situation has been extended to the multicomponent case. The separation of methanol and 2-propanol by a dense silicone rubber membrane confirms the ability of this simple modelling strategy to offer quantitative predictions of the permeate composition under variable Downstream Pressure and inert gas flowrate conditions. Based on this observation, the implications of an inert gas contribution on pervaporation or gas separation operation are discussed, particularly in relationship to the global energy consumption of the system or to analytical devices making use of a gas sweep.

  • new insights into pervaporation mass transport under increasing Downstream Pressure conditions critical role of inert gas entrance
    Industrial & Engineering Chemistry Research, 2001
    Co-Authors: Cecile Vallieres, Eric Favre, Denis Roizard, Jerome Bindelle, Daniel Sacco
    Abstract:

    The influence of the total Downstream Pressure on the pervaporation flux of a pure compound through a dense polymer membrane has been the subject to controversial debates recently. Experimental arguments in favor of either the solution−diffusion model or the newly proposed pore-flow model are alternatively reported on different systems. To critically reexamine this debate, an experimental study under controlled Downstream conditions has been performed for pure methanol and pure 2-propanol pervaporation through a poly(dimethylsiloxane) film, the latter having been previously reported to follow pore-flow model predictions. It is shown that a rational analysis of the effects of the Downstream Pressure on the results can be achieved according to the classical solution−diffusion model, provided that the influence of air leaks in the installation is properly taken into account. Based on this observation, the implications of an inert gas contribution, generally speaking, on pervaporation operation are discussed.

H Sonntag - One of the best experts on this subject based on the ideXlab platform.

  • cerebrovascular tone rather than intracranial Pressure determines the effective Downstream Pressure of the cerebral circulation in the absence of intracranial hypertension
    Journal of Neurosurgical Anesthesiology, 2000
    Co-Authors: A Weyland, Wolfgang F Buhre, Stephan Grund, Hans Ludwig, S Kazmaier, W Weyland, H Sonntag
    Abstract:

    : Cerebral perfusion Pressure is commonly calculated from the difference between mean arterial Pressure and intracranial Pressure because intracranial Pressure is known to represent the effective Downstream Pressure of the cerebral circulation. Studies of other organs, however, have shown that effective Downstream Pressure is determined by a critical closing Pressure located at the arteriolar level. This study was designed to investigate the effects of PCO2-induced variations in cerebrovascular tone on the effective Downstream Pressure of the cerebral circulation. Sixteen patients recovering from head injury were studied. Intracranial Pressure was assessed by epidural Pressure transducers. Blood flow velocity in the middle cerebral artery was monitored by transcranial Doppler sonography. Effective Downstream Pressure was derived from the zero flow Pressure as extrapolated by regression analysis of instantaneous arterial Pressure/middle cerebral artery flow velocity relationships. PaCO2 was varied between 30 and 47 mm Hg in randomized sequence. Intracranial Pressure decreased from 18.5+/-5.2 mm Hg during hypercapnia to 9.9+/-3.1 mm Hg during hypocapnia. In contrast, effective Downstream Pressure increased from 13.7+/-9.6 mm Hg to 23.4+/-8.6 mm Hg and exceeded intracranial Pressure at hypocapnic PaCO2 levels. Our results demonstrate that, in the absence of intracranial hypertension, intracranial Pressure does not necessarily represent the effective Downstream Pressure of the cerebral circulation. Instead, the tone of cerebral resistance vessels seems to determine effective Downstream Pressure. This suggests a modified model of the cerebral circulation based on the existence of two Starling resistors in a series connection.

  • cerebrovascular tone rather than intracranial Pressure determines the effective Downstream Pressure of the cerebral circulation in the absence of intracranial hypertension
    Journal of Neurosurgical Anesthesiology, 1997
    Co-Authors: A Weyland, Wolfgang F Buhre, Stephan Grund, Hans Ludwig, S Kazmaier, W Weyland, H Sonntag
    Abstract:

    Summary:Cerebral perfusion Pressure is commonly calculated from the difference between mean arterial Pressure and intracranial Pressure because intracranial Pressure is known to represent the effective Downstream Pressure of the cerebral circulation. Studies of other organs, however, have shown that

G Bendor - One of the best experts on this subject based on the ideXlab platform.

  • the influence of the Downstream Pressure on the shock wave reflection phenomenon in steady flows
    Journal of Fluid Mechanics, 1999
    Co-Authors: G Bendor, T Elperin, H Li, E Vasiliev
    Abstract:

    The eect of the Downstream Pressure (dened here as the wake Pressure behind the tail of the reflecting wedge) on shock wave reflection in steady flows is investigated both numerically and analytically. The dependence of the shock wave congurations on the Downstream Pressure is studied. In addition to the incident-shock-waveangle-induced hysteresis, which was discovered a few years ago, a new DownstreamPressure-induced hysteresis has been found to exist. The numerical study reveals that when the Downstream Pressure is suciently high, an inverse-Mach reflection wave conguration, which has so far been observed only in unsteady flows, can be also established in steady flows. Very good agreement between the analytical predictions and the numerical results is found.

Cecile Vallieres - One of the best experts on this subject based on the ideXlab platform.

  • separation of binary mixtures by dense membrane processes influence of inert gas entrance under variable Downstream Pressure conditions
    Chemical Engineering Science, 2003
    Co-Authors: Cecile Vallieres, Eric Favre, Xavier Arnold, Denis Roizard
    Abstract:

    The influence of an inert gas on the separation performances of a dense polymeric membrane module working under partial vacuum on the Downstream side, such as possibly encountered in gas permeation, vapor permeation or pervaporation, has been investigated through an experimental and theoretical study. A whole range of situations on the Downstream side, covering ideal vacuum pumping (i.e. zero Downstream Pressure under leak free conditions) to inert gas sweeping under atmospheric Pressure has been tested. A theoretical framework, previously developed for single permeant situation has been extended to the multicomponent case. The separation of methanol and 2-propanol by a dense silicone rubber membrane confirms the ability of this simple modelling strategy to offer quantitative predictions of the permeate composition under variable Downstream Pressure and inert gas flowrate conditions. Based on this observation, the implications of an inert gas contribution on pervaporation or gas separation operation are discussed, particularly in relationship to the global energy consumption of the system or to analytical devices making use of a gas sweep.

  • new insights into pervaporation mass transport under increasing Downstream Pressure conditions critical role of inert gas entrance
    Industrial & Engineering Chemistry Research, 2001
    Co-Authors: Cecile Vallieres, Eric Favre, Denis Roizard, Jerome Bindelle, Daniel Sacco
    Abstract:

    The influence of the total Downstream Pressure on the pervaporation flux of a pure compound through a dense polymer membrane has been the subject to controversial debates recently. Experimental arguments in favor of either the solution−diffusion model or the newly proposed pore-flow model are alternatively reported on different systems. To critically reexamine this debate, an experimental study under controlled Downstream conditions has been performed for pure methanol and pure 2-propanol pervaporation through a poly(dimethylsiloxane) film, the latter having been previously reported to follow pore-flow model predictions. It is shown that a rational analysis of the effects of the Downstream Pressure on the results can be achieved according to the classical solution−diffusion model, provided that the influence of air leaks in the installation is properly taken into account. Based on this observation, the implications of an inert gas contribution, generally speaking, on pervaporation operation are discussed.