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The thermophysical properties of gases determined using an annular acoustic resonator

Buxton, A.J.; (1997) The thermophysical properties of gases determined using an annular acoustic resonator. Doctoral thesis, University of London. Green open access

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Abstract

A novel annular acoustic resonator was constructed for measurements of the speed of sound in gases at pressures below 1 MPa. The resonator was designed to allow measurements of the speed and absorption of sound at low pressure in gases with large bulk viscosities. Measurements in propene, for which the speed of sound is known, served to characterise the geometry of the resonator and provide a test of the acoustic model for the system. A detailed description of the resonator which has an outer radius of 140 mm is given. The large radius provides low frequency resonance modes that minimise acoustic losses in the bulk of the gas. Three substances were studied: trifluoromethane, sulfur hexafluoride and a binary mixture consisting of methane and ethane with mole fraction composition {0.85 CH₄ + 0.15 C₂H₆}. Measurements were conducted over the temperature range 230 to 350 K, and the results analysed to obtain perfect gas heat capacities and second acoustic virial coefficients. The heat capacity data are compared to literature sources. Values for the second (p,V,T) virial coefficients were obtained from the second acoustic virial coefficients and the results are compared with previous determinations. Analysis of the acoustic loss mechanisms allows the shear viscosity, thermal conductivity and bulk viscosity of the gas to be estimated. The values obtained do not have the accuracy that may be achieved using specialised techniques and a comparison is made where data is available. The estimates of the thermal conductivity and shear and bulk viscosities provide a new self consistent method for the analysis of the acoustic results which does not rely on literature values for the transport coefficients. Where possible vibrational relaxation times are evaluated from the bulk viscosity and are compared with results from other sources.

Type:Thesis (Doctoral)
Title:The thermophysical properties of gases determined using an annular acoustic resonator
Open access status:An open access version is available from UCL Discovery
Language:English
Additional information:Thesis digitised by British Library EThOS
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry

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