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Subject: search.filters.subject.Thermal Conductivities

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    Thermal Conductivities of Ethene and its Fluorocarbon Analogues and of their Binary Mixtures with Argon
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Gray, Peter; Parkinson, Christopher
    The thermal conductivities of the five pure gases CH2CH2, CHFCH2, CF2CH2, CF2CHF and CF2CF2 together with their binary mixtures with argon, have been measured at both 50 and 100°C. At 50°C, negative deviations below the molar average value occur in the conductivity against composition curves for all five systems, and minima or signs of minima at intermediate compositions develop in the mixtures of CF2CH2, CF2CHF and CF2CF2 with argon. At 100°C, the latter three systems again show negative deviations, and minima are once more displayed by the mixtures of CF2CHF and CF2CF2 with argon. The system CHFCH2 plus argon exhibits evidence for a point of inflexion in the curve. This is the first time that minima have been observed in binary mixtures of a polar and a monatomic gas, though minima have been found with non-polar mixtures. Where minima develop, the formal condition AijAji[gt-or-equal]λj/λi is fulfilled, where Aij and Aji are coefficients of the Sutherland–Wassil-jewa equation, subscript i denoting the component with the lower thermal conductivity. The predictions of the empirical equation of Lindsay and Bronley are compared with experiment: the agreement is markedly less good than normally found, discrepancies being greatest in mixtures containing the most polar constituents. Outline comparisons with the Hirschfelder–Eucken approximation to rigorous theory are satisfactory.
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    Thermal Conductivities of Gaseous Mixtures Containing Hydrocarbons: Part 2.—Cyclopropane, Propene, But-l-ene and trans-But-2-ene, and Their Binary Mixtures with Argon
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (6), 1972) Parkinson, C.; Mukhopadhyay, P.; Gray, P.
    Thermal conductivities of the four pure gases cyclopropane, propene, but-l-ene and trans-but-2- ene and their binary mixtures with argon have been measured at both 50 and 100°C. The thermal conductivities of the pure polyatomic gases lie close together and strong similarities exist in the conductivity versus composition curves for each binary mixture. At 50°C thermal conductivities of the mixtures arc less than the molar average values and a broad minimum results in each case. At 100°C negative deviations are much reduced and only the trans- but-2-cne with argon system displays a minimum. Points of inflexion develop for the cyclopropane, propene and but-l-enc mixtures at this temperature and thermal conductivities slightly above molar average values arc seen in regions of high hydrocarbon concentration. Thermal conductivities of the binary mixtures calculated on the basis of an empirical equation and from approximations to rigorous kinetic theory (Hirschfelder-Euckcn and Monchick, Pereira and Mason) arc compared with the experimental results. All three methods of calculation are found to give reasonably good agreement with experiment, but the Hirschfcldcr-Eucken approximation is the most satisfactory (mean deviation 0.89 % from 72 compositions) for these mixtures.
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    Thermal Conductivities of Gaseous Mixtures Containing Hydrocarbons: Part 1.—n-Butane, iso-Butane, iso-Pentane and neo-Pentane, and Their Binary Mixtures With Argon
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (6), 1972) Parkinson, C.; Gray, P.
    Thermal conductivities of the four pure gases n-butane, iso-butane, iso-pentanc and nco-pentane and of their binary mixtures with argon have been measured at 50 and 100°C. The thermal conductivities of all four polyatomic gases lie close together and there arc marked similarities in the conductivity against composition curves for their binary mixtures with argon. Thermal conductivities less than molar average values are found at both 50 and 100 C for each mixture. These “ negative deviations ” arc greatest at 50nC and result in broad minima in each case. At 100 C minima arc less pronounced and arc confined to the n-butane, iso-pentane and neo-pcntanc mixtures. Points of inflexion develop in all the conductivity against composition curves at this temperature. We believe that negative deviations are generally to be associated with binary mixtures of a monatomic with a non-polar polyatomic gas, and minima can be manifested when the ratio of thermal conductivities for the pure components (Xj/X/) is not far from unity. The formal condition is AjjAji > where Ay and Aji arc coefficients of the Suthcrland-Wassiljcwa equation and subscript i denotes the component with the lower thermal conductivity. The data arc used to test predictions of thermal conductivities of gas mixtures both by approximations to rigorous kinetic theory (Hirschfelder-Eucken, and Monchick, Pereira and Mason) and by the empirical relationship of Lindsay and Bromley. All three methods predict thermal conductivities which arc in reasonable agreement with experimental measurements, but the Hirschfelder-Eucken approximation is found to be most satisfactory (mean deviation 1.27 % from 74 compositions) for these mixtures.