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Viscosity - Fluids

   Method employed  


  • The technique employed for the measurement of the viscosity of fluids, is the Vibrating-Wire technique (VBW). According to this technique, a thin vertical wire, constrained not to move at its two ends, is placed in the fluid. If an oscillation is initiated by the displacement of the wire from its equilibrium position then, following a short-lived initial transient, the motion will conform to a damped, simple harmonic motion, characteristic of the viscosity of the fluid. The motion resembles the movement of a quitar string. The technique is applied to liquids and gases (with thinner wire).

thw

 An actual instrument employs a 100μm-diameter 50mm-length tungsten wire. Constant tensioning is accomplished by a two-weights assembly at its bottom. The volumes of the two weights (the inner one is made from tungsten and the outer one from stainless steel), are chosen so that the net effect of changing the density of the surrounding liquid results in a negligible effect upon the frequency of oscillation. This arrangement also ensures that wire oscillations occur in only one plane of oscillation (in the case of gases, the non-boyancy mechanism is replaced by a small weight). Two permanent samarium-cobalt magnets, placed around the wire, are employed for the electromagnetic initiation of the oscillations as well as for their detection.
     Following initiation of the motion, the signal induced in the vibrating wire is observed with a bridge in which the wire forms one arm. The out-of-balance signal, amplified by 30,000 times, is then observed with an A/D converter coupled to a microcomputer at a rate of 50 kHz with a resolution of 12 bits.
     The logarithmic decrement and the frequency of oscillation, are then obtained from the recorded data with the aid of a non-linear least squares fitting procedure, and from them the viscosity is obtained by a full theoretical analysis. Work currently is concentrated in the measurement of the viscosity of high-viscosity fluids over extended temperatures and pressures.  

 From left to right:
  a) Vibrating wire for liquids
  b) Vibrating wire for gases.

   Ranges & uncertainties  

 

  • Liquids - Present instruments cover the following ranges:
    - Pressure: 0.1 to 400 bars
    - Temperature: -70 to +100 'C
    - Uncertainty: 0.5%
  • Gases (or vapours) - Present instruments cover the following ranges:
    - Pressure: 0.1 to 400 bars
    - Temperature: -20 to +200 'C
    - Uncertainty: 0.5 - 1%


Both electrically conducting and non-conducting fluids have been studied

   Systems sudied so far  


  • Hydrocarbons - Selected papers:
    Santos F.J.V., Nieto de Castro C.A., Dymond J.H., Dalaouti N.K., Assael M.J., Nagashima A., “Standard Reference Data for the Viscosity of Toluene”, J. Phys. Chem. Ref. Data 35:1-8 (2006)..
    Langelandsvik L.I., Solvang S., Rousseler M., Metaxa I., and Assael M.J., ”Dynamic Viscosity Measurements of Three Natural Gas Mixtures - Comparison against Prediction Models”, Int. J. Thermophys. (in press)
    Assael M.J., Bauer H., Dalaouti N.K. and Harris K.R., "Reference Correlation for the Viscosity of Liquid Cyclopentane from 220 to 310 K at Pressures up to 25 MPa", Int. J. Thermophys. 25:13-20 (2004).
    Assael M.J., Dalaouti N.K., and Vesovic V., "Viscosity of Natural-Gas Mixtures: Measurements and Prediction", Int. J. Thermophys. 22:61-71 (2001).
    Assael M.J., Dalaouti N.K., and Dymond J.H., "Viscosity of Toluene+Cyclopentane Mixtures: Measurements and Prediction", Int. J. Thermophys. 21:621-637 (2000).
    Assael M.J., Dalaouti N.K., and Dymond J.H., "The Viscosity of Toluene in the Temperature Range 210 to 370 K", Int. J. Thermophys. 21:291-299 (2000).
    Assael M.J., Dalaouti N.K., and Polimatidou S., "The Viscosity of Toluene in the Temperature Range 210 to 370 K and Pressures up to 30 MPa", Int. J. Thermophys. 20:1367-1377 (1999).
    Hendl S., Millat J., Vogel E., Vesovic V., Wakeham W.A., Luettmer-Strathmann J., Sengers J.V., and Assael M.J. "The Transport Properties of Ethane. I.Viscosity", Int. J. Thermophys. 15:1-31 (1994).
    Assael M.J., Dymond J.H., Polimatidou S.K. and Vogel E., "Measurements of the Viscosity of Toluene and Mesitylene Mixtures at Pressures up to 55 MPa", Int.J.Thermophys. 13:791-800 (1992).
    Assael M.J., Dymond J.H. and Papadaki M., "Viscosity Coefficients of Binary n-Heptane and n-Alkane Mixtures", Fluid Phase Equilib. 75:287-297 (1992).
    Assael M.J, Papadaki M., Richardson S.M., Oliveira C. and Wakeham W.A. "Vibrating-wire Viscometry on Liquid Hydrocarbons at High Pressure", High Temp. High Press. 23:561-568 (1991).
    Assael M.J., Papadaki M. and Wakeham W.A., "Measurement of the Viscosity of Benzene, Toluene and m-Xylene at Pressures up to 80 MPa", Int.J.Thermophys. 12:449-457 (1991).
    Assael M.J., Karagiannidis L. and Papadaki M., "Measurements of the Viscosity of n-Heptane and n-Undecane Mixtures at Pressures up to 75 MPa", Int.J.Thermophys. 12:811-820 (1991).
    Assael M.J. and Papadaki M., "Measurements of the Viscosity of n-Heptane, n-Nonane and n-Undecane at Pressures up to 80 MPa", Int.J.Thermophys. 12:801-810 (1991).
    Assael M.J., Papadaki M., Dix M., Richardson S.M. and Wakeham W.A. "An Absolute Vibrating-Wire Viscometer for Liquids at High Pressures", Int.J.Thermophys. 12:231-244 (1991).
    Assael M.J., Charitidou E., Dymond J.H., and Papadaki M., "Viscosity and Thermal Conductivity of Binary n-Heptane+n-Alkane Mixtures", Int. J. Thermophys. 13:237-249 (1992).
    Assael M.J. and Dalaouti N.K., "Measurement of the Viscosity of Cyclopentane from 200-300K up to 25 MPa", High Temp.- High Press. 32:179-185 (2000).
    Langelandsvik L.I., Solvang S., Rousselet M., Metaxa I., and Assael M.J., ”Dynamic Viscosity Measurements of Three Natural Gas Mixtures - Comparison against Prediction Models”, Int. J. Thermophys. 28:1120-1130 (2007).

  • Alcohols and water - Selected papers:
    Assael M.J. and Polimatidou S.K., "Measurements of the Viscosity of Alcohols in the Temperature Range 290-340 K at Pressures up to 30 MPa", Int.J.Thermophys. 15:95-107 (1994).
    Assael M.J., Polimatidou S.K. and Wakeham W.A., "The Viscosity of Liquid Water at Pressures up to 32 MPa", Int. J. Thermophys. 14:795-803 (1993).

  • Polyatomic Gases and mixtures - Selected papers:
    Assael M.J., Dalaouti N.K., and Vesovic V., "Viscosity of Natural-Gas Mixtures: Measurements and Prediction", Int. J. Thermophys. 22:61-71 (2001).
    Assael M.J, Polimatidou S.K., Vesovic V. and Wakeham W.A., "The Viscosity of Gaseous Binary Mixtures Containing Water Vapour", High Temp. High Press. 29:514-524 (1997).
    Assael M.J., Bich E. and Vogel E., "Temperature and Initial Density Dependence of Experimental Viscosity and Calculated Diffusion Coefficients for Binary Vapour Mixtures of Benzene+Phenol", J.Non Equil.Thermod. 19:1-14 (1994).

  • Refrigerant Liquid and Gases - Selected papers:
    Assael M.J., Oliveira C., Wakeham W.A. "Towards the Viscosity of Refrigerant/Oil Mixtures", Fluid Phase Equil. 210:5-19 (2003).
    Assael M.J., Leipertz A., MacPherson E., Nagasaka Y., Nieto de Castro C.A., Perkins R.A., Strom K., Vogel E. and Wakeham W.A., "Transport Property Measurements on the IUPAC Sample of R134a", Int. J. Thermophys. 21:1-22 (2000)
    Gao X., Assael M.J., Nagasaka Y., and Nagashima A., "Estimation & Prediction of Thermal Conductivity and Viscosity of Binary and Ternary HFC Refrigerant Mixtures", Int. J. Thermophys. 21:23-34 (2000).
    Assael M.J., Gialou K.E, and Dalaouti N.K., "Viscosity and Thermal Conductivity of Methane, Ethane and Propane Halogenated Refrigerants", Fluid Phase Equil. 174:203-211 (2000).
    Assael M.J., Dalaouti N.K., Dymond J.H., and Feleki E.P., "The Viscosity and Thermal Conductivity of Liquid Halogenated Ethane Refrigerants", Int. J. Thermophys. 21:367-375 (2000).
    Assael M.J., Dalaouti N.K., Griva A.A., and Dymond J.H., "Viscosity and Thermal Conductivity of Halogenated Methane and Ethane Refrigerants", Int. J. Refrig. 22:525-535 (1999).
    Assael M.J. and Polimatidou S.K., "Viscosity Measurements of the New Refrigerants in the Vapour Phase", Int. J. Thermophys. 18:353-366 (1997).
    Assael M.J., Karagiannidis E. and Polimatidou S.K., "Measurements of the Viscosity of New Refrigerants in the Temperature Range 290-340 K at Pressures up to 20 MPa", Int.J.Thermophys. 16:133-143 (1995).
    Assael M.J. and Polimatidou S.K., "Measurements of the Viscosity of Liquid R22, R124 and R125 in the Temperature Range 273-333 K at Pressures up to 17 MPa", Int.J.Thermophys. 15:779-790(1994).
    Assael M.J., Dymond J.H. and Polimatidou S.K. "Measurements of the Viscosity of R134a and R32 in the Temperature Range 270-340 K at Pressures up to 20 MPa", Int.J.Thermophys. 15:591-601 (1994).
    Assael M.J., Polimatidou S.K., Vogel E. and Wakeham W.A., "The Viscosity of R11, R12, R141b and R152a in the Temperature Range 270-340 K at Pressures up to 20 MPa", Int.J.Thermophys. 15:575-589 (1994).
    Assael M.J. and Polimatidou S.K., "Measurements of the Viscosity of Liquid R22, R124 and R125 in the Temperature Range 273-333 K at Pressures up to 17 MPa", Int. J. Thermophys. 15:779-790 (1994).
 
 
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