Perturbation viscometer to measure the viscosity gradients of gas mixtures

P.A. Russell, B.A. Buffham, G. Mason, M. Heslop

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Perturbation viscometry measures the logarithmic viscosity gradient of the viscosity-composition curve for gas mixtures. The flow and composition of a gas mixture flowing through a capillary are perturbed by adding a small flow of gas, normally one of the pure components of the gas mixture. Two pressure changes are seen at the capillary, the first due to the change in flow rate and the second, a short time later, due to the change in viscosity. The logarithmic viscosity gradient can be calculated from the ratio of these two pressure changes. Integration of logarithmic viscosity gradients measured over the full composition range gives the mixture viscosity relative to the viscosity of one of the pure components of the gas mixture. This method is attractive because, for measurements of equal precision, integration of the gradients is potentially an order of magnitude more precise than conventional methods that measure viscosities directly. It can also work at high and low temperatures and perhaps high pressures. The potential of this technique was previously demonstrated with a rudimentary apparatus, but its advantages and potential flaws need to be more closely examined. A fully thermostatted apparatus is detailed, including all modifications incorporated from experience operating the original apparatus. Experimental data for the helium-nitrogen mixture at 360°C, the practical upper operating limit of the apparatus, are presented. Integral consistency checks performed on the measured data show that high-quality data produced compare well (less than 1% deviation) with the best literature data available.
LanguageEnglish
Pages1986-1994
Number of pages8
JournalAIChE Journal
Volume49
Issue number8
DOIs
Publication statusPublished - 2003

Fingerprint

Viscometers
Viscosity
Gas mixtures
Gases
Pressure
Chemical analysis
Helium
Viscosity measurement
Flow of gases
Nitrogen
Flow rate
Defects
Temperature

Keywords

  • gas
  • chemical engineering
  • chemistry
  • viscosity
  • perturbation viscometry

Cite this

Russell, P.A. ; Buffham, B.A. ; Mason, G. ; Heslop, M. / Perturbation viscometer to measure the viscosity gradients of gas mixtures. In: AIChE Journal. 2003 ; Vol. 49, No. 8. pp. 1986-1994.
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Perturbation viscometer to measure the viscosity gradients of gas mixtures. / Russell, P.A.; Buffham, B.A.; Mason, G.; Heslop, M.

In: AIChE Journal, Vol. 49, No. 8, 2003, p. 1986-1994.

Research output: Contribution to journalArticle

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AB - Perturbation viscometry measures the logarithmic viscosity gradient of the viscosity-composition curve for gas mixtures. The flow and composition of a gas mixture flowing through a capillary are perturbed by adding a small flow of gas, normally one of the pure components of the gas mixture. Two pressure changes are seen at the capillary, the first due to the change in flow rate and the second, a short time later, due to the change in viscosity. The logarithmic viscosity gradient can be calculated from the ratio of these two pressure changes. Integration of logarithmic viscosity gradients measured over the full composition range gives the mixture viscosity relative to the viscosity of one of the pure components of the gas mixture. This method is attractive because, for measurements of equal precision, integration of the gradients is potentially an order of magnitude more precise than conventional methods that measure viscosities directly. It can also work at high and low temperatures and perhaps high pressures. The potential of this technique was previously demonstrated with a rudimentary apparatus, but its advantages and potential flaws need to be more closely examined. A fully thermostatted apparatus is detailed, including all modifications incorporated from experience operating the original apparatus. Experimental data for the helium-nitrogen mixture at 360°C, the practical upper operating limit of the apparatus, are presented. Integral consistency checks performed on the measured data show that high-quality data produced compare well (less than 1% deviation) with the best literature data available.

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