Browsing by Author "Ramires, Maria de Lurdes V."
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- Reacting Mixtures at Low Density - Alkali Metal VapoursPublication . Fialho, Paulo; Ramires, Maria de Lurdes V.; Nieto de Castro, Carlos A.; Fareleira, João M.N.A."Previous chapters of this volume dealt with the transport properties of nonreacting mixtures. However, there are several systems of scientific and industrial interest that involve chemical reactions between some of the atoms or molecules present. This fact modifies the values of the transport properties of these systems because there are additional processes of heat and mass transfer caused by the existence of the chemical reaction. The simplest kind of system where chemical reaction is present is an alkali metal vapour, where dimerization of atoms takes place, with a temperature- and pressuredependent composition. This fact, allied to the high-temperature domain of the application of these vapors, makes the determination of the transport properties of these systems very challenging from a theoretical point of view. […]".
- Thermophysical properties of alkali metal vapours. Part I.A - prediction and correlation of transport properties for monatomic systemsPublication . Fialho, Paulo; Ramires, Maria de Lurdes V.; Fareleira, João M.N.A.; Nieto de Castro, Carlos A.New calculations of the collision integrals for the singlet potential functions involved in the determination of viscosity, thermal conductivity and self-diffusion coefficients of the monatomic alkali metal vapours are presented. An interpolation procedure for the calculation of the monatomic systems transport coefficients in a large temperature range is provided. This is based on temperature correlations of the collision integrals for the singlet and triplet potential functions. The calculations have been carried out using a new potential function for the ground singlet state of the alkali diatomics. This is a recent version of the Extended Hartree-Fock Approximate Correlation Energy (EHFACE2U), proposed by Varandas et al., which is believed to give a correct description of the potential energy to vanishing internuclear distances. The results which are compared with previous calculations, are intended to be utilized in Part II of this paper in order to assess available experimental data on the viscosity and thermal conductivity coefficients of the alkali metal vapours.
- Thermophysical properties of alkali metal vapours. Part II - assessment of experimental data on thermal conductivity and viscosityPublication . Fialho, Paulo; Ramires, Maria de Lurdes V.; Nieto de Castro, Carlos A.; Fareleira, João M.N.A.; Mardolcar, Umesh V.An analysis of the available data on the viscosity and thermal conductivity coefficients of the alkali metal vapours is presented. The analysis is based upon theoretical calculations of the properties of the monatomic systems, described in the preceding parts I and I.A of the present paper, and making use of the kinetic theory of a binary gas reacting mixture. A summary of the measurement techniques used, including, whenever possible, the magnitude of the corrections performed on the raw data and the nominal precision of the results, complements the analysis. It is concluded that it is possible to select precise and mutually consistent sets of experimental results for both viscosity and thermal conductivity coefficients of lithium, sodium and potassium vapours among the available literature data and to classify all the data in uncertainty classes. Regarding rubidium and cesium no systematic discussion is possible due to a lack of experimental data with sufficient precision.
- Viscosity, Thermal Conductivity and Thermal Diffusion Ratio of the Alkali Metal Vapours.Publication . Fialho, Paulo; Ramires, Maria de Lurdes V.; Fareleira, João M.N.A.; Nieto de Castro, Carlos A.The Subcommittee of Transport Properties of IUP AC started in 1982 a project with the objective of correlating and predicting the transport properties of the alkali metal vapours, in the temperature and pressure zones that are useful to the scientific and industrial uses. In a recent paper [1] the authors suggested a new approach to assess the available experimental data, based in the kinetic theory of gas mixtures, which is a modification of the method developed by Vargaftik and Yargin[2]. In the present communication, we present the surfaces for the viscosity and thermal conductivity, and thermal diffusion ratio which have been developed for lithium, sodium and potassium with average uncertainties of 1%, 0.5% and 0.5%, respectively, for temperature ranges 800-2000 K (lithium) and 700-1500 K (sodium and potassium). . For rubidium and cesium, the available data does not allow a similar development of the corresponding surfaces. It is interesting to note that no clear evidence for the presence of dimers was found for cesium within experimental uncertainty.