Apparatus for determining physical properties of fluids

Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – By vibration

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73 6179, 310322, 310348, G01N 2900

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active

055092993

DESCRIPTION:

BRIEF SUMMARY
FIELD OF ART

The present invention relates to instrument engineering and can be utilized for precision measurements of physical properties of fluids at high pressures in oil and gas industries, mechanical engineering, medicine, biology, ect.


PRIOR ART

Known in the prior art is a high-pressure apparatus (V. N. Belonenko "Ultrasonics" 1991, vol 29, March, p. 108) comprising an acoustic chamber with a variable base and a press with a piston combined in a single hydraulic unit. Connecting the piston with a displacement indicator permits determining the distance covered by the piston, the changes in the volume of test fluid under pressure, its density and isothermal compressibility. Said apparatus is deficient in its low accuracy of determination of said characteristics.
The closest apparatus in its essence to the claimed one is the apparatus for testing the parameters of fluids (USSR Invertor's Certificate No. 1,226,279, G OI N 29/02, 1986). Said apparatus comprises a high-pressure chamber with a piston, and ultrasonic piezotransducers disposed outside of the casing, a load unit, a displacement meter, and an electronic unit for excitation of pulse signals, their reception, processing and recording of data.
A disadvantage of said apparatus lies in a low accuracy of determining acoustic parameters, density and compressibility.
An essential disadvantage of the above-quoted apparatuses is a low accuracy in determining the coefficient of isothermal compressibility. This reduces radically the efficiency of acoustic methods and prevents their reliable use for determining the thermophysical properties of fluids, such as isobaric C.sub.p and isochoric C.sub.v heat capacities, since the relation C.sub.p /C.sub.v =.beta..sub.T /.beta..sub.S
where .beta..sub.T -coefficient of isothermal compressibility, .beta..sub.S =I/.rho..c.sup.2 --coefficient of adiabatic compressibility, .rho.--density, and c--sound velocity. With highly accurate determination of the ultrasound velocity, the accuracy of determining the coefficient of compressibility and heat capacities depends on the accuracy of determining the density and volume and their changes under the effect of pressure and temperature.


DISCLOSURE OF THE INVENTION

The main object of the invention resides in raising the accuracy and resolving power when measuring the physical properties of fluids under varying PVT (P--pressure, V--volume, T--temperature).
This object is attained by providing an apparatus comprising a chamber with fluid, a piston, a casing, a thermostat, an oscillation transducer and a unit for excitation and reception of signals, recording and processing of data wherein the oscillation transducer is accommodated inside the chamber parallel to the end surface of the piston so as to form two measuring cells, having constant and variable acoustic paths, respectively.
Radiation of the piezocrystal into the cell with a permanent acoustic base provides for measuring the velocity and absorption of sound while its radiation into the variable acoustic path cell gives a notion of piston displacement. The distance covered by the piston is found either by the signal transmission time or by the wavelength and frequency and/or by counting the number of half-waves that fit into the distance between the crystal and the reflecting surface of the piston. Such an arrangement of the oscillation transducer makes it possible by the use of the piston to combine the pressure-producing function with precision measurement of piston travel and change of volume; density; isothermal compressibility; velocity and absorption of ultrasound; determining isobaric and isochoric heat capacities; coefficient of thermal expansion and other thermophysical properties, thermodynamic functions and potentials, etc. Besides, the piston is used to compensate for changes of volume under various PVT conditions.
The concurrent use of the constant acoustic path and variable acoustic path cells also broadens substantially the capabilities of the apparatus in measuring the sound attenuation coefficient. I

REFERENCES:
patent: 2711646 (1955-06-01), Mendousse
patent: 2833142 (1958-05-01), Runquist et al.
patent: 4098128 (1978-07-01), Baumert
patent: 4249422 (1981-02-01), Gaunaurd et al.
patent: 4325255 (1982-04-01), Howard et al.
patent: 4936143 (1990-06-01), Schutten et al.
patent: 4969362 (1990-11-01), Zacharias et al.
Tribological problems: V. N. Beloneko (Ultrasonics 1991 vol. 29 Mar. pp. 107-118.
"Role of Bulk Viscosity . . . ", V. N. Beloneko (Ultrasonics 1991, vol. 29, Mar. pp. 101-106.
"Development of Methods of Precise Ultrasonic Measurements . . . " A. P. Sarvazyan (Ultrasonics Jul. 1982) pp. 151-154.
Translation entitled, "Interferometers", 1988 translation of portion of: "Der Ultraschall Und Seine Anwendung in Wissenschaft und Technik" von Dr. Ludwig Bergmann, Zurich, 1954.
Role of Bulk Viscosity and Acoustic Parameters In Tribological Problems--Ultrasonics, vol. 29, Mar. 1991, pp. 101 & 108.

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