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Тема: ТЕПЛОФИЗИЧЕСКИЕ СВОЙСТВА ВЕЩЕСТВ
Категория:НАУКА
Transport Coefficients for the NASA Lewis Chemical Equilibrium Program. Roger A. Svehla. April 1995
This report documents the new transport property data that will be used in the NASA Lewis Research Centers Chemical Equilibrium and Applications Program (CEA). It complements a previous publication that documented the thermodynamic and transport property data then in use. Sources of the data and a brief description of the method by which the data were obtained are given. Coefficients to calculate the viscosity, thermal conductivity, and binary interactions are given for either one, or usually, two temperature intervals, typically 300 to 1000 K and 1000 to 5000 K. The form of the transport equation is the same as used previously. The number of species was reduced from the previous database. Many species for which the data were estimated were eliminated from the database. Some ion-neutral interactions were added.
Available electronically at http://gltrs.grc.nasa.gov/GLTRS
Категория: НАУКА /3. Депозитарий научных работ
The Viscosity and Self-Diffusion of Rarefied Steam:Refinement of Reference Data. L. R. Fokin and A. N. Kalashnikov
Авторы публикации – Фокин Л.Р., Калашников А.Н.
Новые экспериментальные данные по вязкости разреженного водяного пара подтверждают предсказательную способность использования модифицированного (m:6:3) потенциала Штокмайера. Проведена совместная обработка данных по вязкости и коэффициенту самодиффузии пара в диапазоне температур от 280 до 1400 К и рассчитаны уточненные таблицы справочных данных для указанных свойств.
Категория: НАУКА /3. Депозитарий научных работ
S.Ganesh Prakash, R.Ravi, R.P.Chhabra Corresponding states theory and transport coefficients of liquid metals
A study of the applicability of CST towards predicting transport coefficients in liquid metals has been undertaken with particular
emphasis on alkali metals. Characteristic parameters were obtained from six different first principles calculations of inter-ionic
potentials of simple metals reported in the literature. A wide variation was observed in the characteristic parameters as reported by
various authors. Among these, the potential parameters of Shyu et al. provided the best correlation of experimental diffusivity and
viscosity data for alkali metals over moderate temperature ranges. However, use of the Goldschmidt diameter as the characteristic
distance parameter and kBTm, where Tm is the melting temperature, as the characteristic energy parameter gave as good, if not better,
results for alkali metals. This parameter set was not found to be satisfactory when non-alkali metals were also included. Chapman’s
characteristic parameters, obtained from a fit to the viscosity data, provided a reasonable correlation of the diffusivity data to most,
but not all metals studied. Fundamental issues associated with attempting to group all liquid metals under a single corresponding
states theory as well with the conventional use of the potential well-depth and the distance at which the potential becomes zero as
characteristic parameters for liquid metals have been pointed out. A preliminary statistical analysis has been performed to assess the
reliability of our predictions in view of the experimental uncertainties in viscosity and diffusivity data.
Категория: НАУКА /3. Депозитарий научных работ
Review of Techniques for Thermophysical Property. Kenneth C. MiIls, Lee Courtney, Robert F. Brooks and Brian J. Monaghan
The methods available for the measurements of the following thermophysical properties of high temperature melts are reviewed viz. density, viscosity, surface tension, heat capacity, enthalpy, thermal diffusivity and conductivity, electrical conductivity and emissivity. The methods are illustrated with reference to work carried out on molten silicon. In order to combat contamination of the melt from container/sample reactions there has been a gradual switch to the use of (i) containerless methods employing various forms of levitation or microgravity (drop towers, parabolic flights and space experiments) and (ii) sub-second rapid heating and other non-intrusive techniques. However, there are other equally-important conditions which must be addressed to obtain accurate property values, e.g. the control of oxygen partial pressure in surface tension measurements and the selection of the most reliable method to analyse data. It is our contention that equal attention should be given to these problems.
Категория: НАУКА /3. Депозитарий научных работ
Radim Mares and Jana Kalova . Thermophysical Properties Converted from Data and Equations Based on Old Temperature Scales
Доклад на 15 Международной конференции по свойствам воды и водяного пара
Thermophysical properties measured before 1990 are based on obsolete temperature scales. In spite of great progress of experimental technique, there are data measured before 1990 that are still considered as very precious. In similar way it is with correlations of old but reliable thermophysical data. The only change of a parameter, as critical temperature, does not guarantee a correct approach to the right conversion. Comparison of values from an equation based on obsolete temperature scale with a new equation calculated for the same numerical values of temperature gives comparison at two different thermal states. There are thermophysical properties the temperature conversion of which depends on derivatives of equation converting an old temperature scale to the new one. Specific heat capacity, coefficient of thermal conductivity etc. could serve as examples of such properties. Complicated situation is with such properties as entropy and properties derived from it. The paper brings discussion of examples of temperature conversion of experimental data and equations as well.
Категория: НАУКА /3. Депозитарий научных работ
New International Formulation for the Thermal Conductivity of H2O
Международная ассоциация по свойствам воды и водяного пара (IAPWS) провела интенсивную работу по ревизии прежних документов по теплопроводности, что завершилось принятием формуляции 2011 года. Статья в последнем выпуске журнала J. Phys. Chem. Ref. Data детально описывает разработку формуляции, которая содержит корреляционные уравнения для воды от температуры плавления до 1173 К при давлении до 1000 МПа. Неопределенность данных колеблется от 1 до 6% в зависимости от области параметров.
Текст статьи из журнала
Формуляция IAPWS от 2011
Категория: НАУКА /3. Депозитарий научных работ
Fundamental Equations of State for Parahydrogen, Normal Hydrogen, and Orthohydrogen
(J. Phys. Chem. Ref. Data, Vol. 38, No. 3, 2009)
J. W. Leachman, R. T Jacobsen, S. G. Penoncello, E. W. Lemmon
If the potential for a boom in the global hydrogen economy is realized, there will be an increase in the need for accurate hydrogen thermodynamic property standards. Based on current and anticipated needs, new fundamental equations of state for parahydrogen, normal hydrogen, and orthohydrogen were developed to replace the existing property models. To accurately predict thermophysical properties near the critical region and in liquid states, the quantum law of corresponding states was applied to improve the normal hydrogen and orthohydrogen formulations in the absence of available experimental data. All three equations of state have the same maximum pressure of 2000 MPa and upper temperature limit of 1000 K. Uncertainty estimates in this paper can be considered to be estimates of a combined expanded uncertainty with a coverage factor of 2 for primary data sets. The uncertainty in density is 0.04% in the region between 250 and 450 K and at pressures up to 300 MPa. The uncertainties of vapor pressures and saturated liquid densities vary from 0.1% to 0.2%. Heat capacities are generally estimated to be accurate to within 1%, while speed-of-sound values are accurate to within 0.5% below 100 MPa.
текст статьи
Категория: НАУКА /3. Депозитарий научных работ
Eric W. Lemmona, Richard T Jacobsen and Steven G. Penoncello, Daniel G. Friend Thermodynamic Properties of Air and Mixtures of Nitrogen, Argon, and Oxygen From 60 to 2000 K at Pressures to 2000 MPa
A thermodynamic property formulation for standard dry air based upon available experimental
p –r – T, heat capacity, speed of sound, and vapor–liquid equilibrium data is
presented. This formulation is valid for liquid, vapor, and supercritical air at temperatures
from the solidification point on the bubble-point curve ~59.75 K! to 2000 K at pressures
up to 2000 MPa.
Категория: НАУКА /3. Депозитарий научных работ
DIRECT OBSERVATION OF AN ABRUPT INSULATOR-TO-METAL TRANSITION IN DENSE LIQUID DEUTERIUM
DIRECT OBSERVATION OF AN ABRUPT
INSULATOR-TO-METAL TRANSITION IN
DENSE LIQUID DEUTERIUM
M. D. Knudson, M. P. Desjarlais, A. Becker, R. W. Lemke, K. R. Cochrane,
M. E. Savage, D. E. Bliss, T. R. Mattsson, R. Redmer
Eighty years ago, it was proposed that solid hydrogen would becomemetallic at sufficiently high
density. Despite numerous investigations, this transition has not yet been experimentally observed. More recently, there has been much interest in the analog of this predicted metallic transition in the dense liquid, due to its relevance to planetary science. Here, we show direct observation of an abrupt insulator-to-metal transition in dense liquid deuterium. Experimental determination of the location of this transition provides a much-needed benchmark for theory and may constrain the region of hydrogen-helium immiscibility and the boundary-layer pressure in standard models of the internal structure of gas-giant planets.
Download from www.scincemag.org on June 29, 2015
Текст статьи
Краткое популярное обсуждение нового результата
можно найти на российском сайте Lenta.ru,
http://lenta.ru/news/2015/06/27/deuterium/
Категория: НАУКА /3. Депозитарий научных работ
DATA QUALITY - MORE IMPORTANT THAN EVER IN THE INTERNET AGE
В журнале Data Science Journal опубликована методическая заметка д-ра Лайда (David R. Lide), который долгие годы был главным редактором справочника CRC Handbook of Chemistry and Physics, о качестве и надежности физико-химических данных, распространяемых в сети Интернет. На ряде примеров д-р Лайд показывает, что старая «болезнь» - распространение в литературе ненадежных и плохо документированных данных, лишь усилилась в эру Интернета, заполненного плохо контролируемой информацией. Автор дает ряд советов, какой стратегии надо придерживаться при поиске в сети данных по свойствам веществ.
Методическая заметка
Категория: НАУКА /3. Депозитарий научных работ
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