Self-diffusion of supercritical water in extremely low-density region

Yoshida, Ken; Matubayasi, Nobuyuki; Nakahara, Masaru

doi:10.1063/1.2333511

Cited by 35 publications

(21 citation statements)

References 49 publications

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“…IV C 3͒, there are very few measurements of self-diffusion in low-density water vapor. We are aware of only two: a relatively old measurement by Swinton 59 in 1971 of the diffusion of tritiated water, HTO, in H 2 O and a more recent measurement in 2006 using the NMR spin-echo method by Yoshida et al 60,61 Swinton 59 measured self-diffusion at five temperatures between 363 and 517 K with pressures of 0.01-0.3 bar. The precision of his results ranged from Ϯ1.5% at 363 K to Ϯ4% at 517 K. There was no discussion of any pressure dependence of the diffusion coefficients.…”

Section: B Self-diffusionmentioning

confidence: 99%

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Calculation of the transport and relaxation properties of dilute water vapor

Hellmann

Bich

Vogel

et al. 2009

The Journal of Chemical Physics

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Transport properties of dilute water vapor have been calculated in the rigid-rotor approximation using four different potential energy hypersurfaces and the classical-trajectory method. Results are reported for shear viscosity, self-diffusion, thermal conductivity, and volume viscosity in the dilute-gas limit for the temperature range of 250-2500 K. Of these four surfaces the CC-pol surface of Bukowski et al. [J. Chem. Phys. 128, 094314 (2008)] is in best accord with the available measurements. Very good agreement is found with the most accurate results for viscosity in the whole temperature range of the experiments. For thermal conductivity the deviations of the calculated values from the experimental data increase systematically with increasing temperature to around 5% at 1100 K. For both self-diffusion and volume viscosity, the much more limited number of available measurements are generally consistent with the calculated values, apart from the lower temperature isotopically labeled diffusion measurements.

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Section: B Self-diffusionmentioning

confidence: 99%

“…The spin-echo measurements 60,61 were taken at 473, 573, and 673 K and the results at the two higher temperatures were extrapolated to the zero-density limit. However, measurements at just two pressures were available at 473 K and the value at the lower density ͑0.0041 g cm −3 ͒ was taken as the zero-density limit.…”

Section: B Self-diffusionmentioning

confidence: 99%

Calculation of the transport and relaxation properties of dilute water vapor

Hellmann

Bich

Vogel

et al. 2009

The Journal of Chemical Physics

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“…The results in §2 and numerous papers by Gamache et al make us confident in the accuracy of such predictions. From these, the dependencies on the absolute radiator speed v are straightforwardly obtained by Maxwell-Boltzmann averages over the perturber velocity v p through [30] and Fokin & Kalashnikov [31], respectively, whereas the line gives direct results of molecular dynamics simulations with the intermolecular potential of Mas et al [29].…”

Section: The Limits Of the Voigt Profile And 'Velocity Effects'mentioning

confidence: 99%

Pressure effects on water vapour lines: beyond the Voigt profile

Ngo

Tran

Gamache

et al. 2012

Phil. Trans. R. Soc. A.

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A short overview of recent results on the effects of pressure (collisions) regarding the shape of isolated infrared lines of water vapour is presented. The first part of this study considers the basic collisional quantities, which are the pressure-broadening and -shifting coefficients, central parameters of the Lorentzian (and Voigt) profile and thus of any sophisticated line-shape model. Through comparisons of measured values with semi-classical calculations, the influences of the molecular states (both rotational and vibrational) involved and of the temperature are analysed. This shows the relatively unusual behaviour of H 2 O broadening, with evidence of a significant vibrational dependence and the fact that the broadening coefficient (in cm −1 atm −1 ) of some lines increases with temperature. In the second part of this study, line shapes beyond the Voigt model are considered, thus now taking 'velocity effects' into account. These include both the influence of collisionally induced velocity changes that lead to the so-called Dicke narrowing and the influence of the dependence of collisional parameters on the speed of the radiating molecule. Experimental evidence of deviations from the Voigt shape is presented and analysed. The interest of classical molecular dynamics simulations, to model velocity changes, together with semi-classical calculations of the speed-dependent collisional parameters for line-shape predictions from 'first principles', are discussed.

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“…The parameters D vvST and α vv relate to the self-diffusion of water vapor and their numerical values were determined from a synthesis of results from Hellmann et al (2009) and Yoshida et al (2006Yoshida et al ( , 2007. The uncertainty associated with this value for D vvST is at least ±15 % and possibly more, e.g., Miles et al (2012).…”

Section: Thermophysical Properties Of Water Vapor and Moist Airmentioning

confidence: 99%

A non-equilibrium model for soil heating and moisture transport during extreme surface heating: the soil (heat–moisture–vapor) HMV-Model Version 1

Massman

2015

Geosci. Model Dev.

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Abstract. Increased use of prescribed fire by land managers and the increasing likelihood of wildfires due to climate change require an improved modeling capability of extreme heating of soils during fires. This issue is addressed here by developing and testing the soil (heat-moisture-vapor) HMVmodel, a 1-D (one-dimensional) non-equilibrium (liquidvapor phase change) model of soil evaporation that simulates the coupled simultaneous transport of heat, soil moisture, and water vapor. This model is intended for use with surface forcing ranging from daily solar cycles to extreme conditions encountered during fires. It employs a linearized Crank-Nicolson scheme for the conservation equations of energy and mass and its performance is evaluated against dynamic soil temperature and moisture observations, which were obtained during laboratory experiments on soil samples exposed to surface heat fluxes ranging between 10 000 and 50 000 W m −2 . The Hertz-Knudsen equation is the basis for constructing the model's non-equilibrium evaporative source term. Some unusual aspects of the model that were found to be extremely important to the model's performance include (1) a dynamic (temperature and moisture potential dependent) condensation coefficient associated with the evaporative source term, (2) an infrared radiation component to the soil's thermal conductivity, and (3) a dynamic residual soil moisture. This last term, which is parameterized as a function of temperature and soil water potential, is incorporated into the water retention curve and hydraulic conductivity functions in order to improve the model's ability to capture the evaporative dynamics of the strongly bound soil moisture, which requires temperatures well beyond 150 • C to fully evaporate. The model also includes film flow, although this phenomenon did not contribute much to the model's overall performance. In general, the model simulates the laboratoryobserved temperature dynamics quite well, but is less precise (but still good) at capturing the moisture dynamics. The model emulates the observed increase in soil moisture ahead of the drying front and the hiatus in the soil temperature rise during the strongly evaporative stage of drying. It also captures the observed rapid evaporation of soil moisture that occurs at relatively low temperatures (50-90 • C), and can provide quite accurate predictions of the total amount of soil moisture evaporated during the laboratory experiments. The model's solution for water vapor density (and vapor pressure), which can exceed 1 standard atmosphere, cannot be experimentally verified, but they are supported by results from (earlier and very different) models developed for somewhat different purposes and for different porous media. Overall, this non-equilibrium model provides a much more physically realistic simulation over a previous equilibrium model developed for the same purpose. Current model performance strongly suggests that it is now ready for testing under field conditions.

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Self-diffusion of supercritical water in extremely low-density region

Cited by 35 publications

References 49 publications

Calculation of the transport and relaxation properties of dilute water vapor

Calculation of the transport and relaxation properties of dilute water vapor

Pressure effects on water vapour lines: beyond the Voigt profile

A non-equilibrium model for soil heating and moisture transport during extreme surface heating: the soil (heat–moisture–vapor) HMV-Model Version 1

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