DEVICE AND METHOD TO DETERMINE THE VISCOSITY OR VISCOELASTICITY OF A LIQUID FROM THE TORQUE OF A RIMMING FLOW

Abstract

The invention discloses a device for viscosity or viscoelasticity measurement comprising: a horizontal rotatable cylinder-shaped section for receiving a liquid whose viscosity or viscoelasticity is to be measured, and a torque meter for measuring the torque from said liquid while in rotation. It also discloses a method of measuring viscosity or viscoelasticity of a liquid comprising the following steps: placing a liquid into a horizontal rotatable cylinder-shaped section, said liquid partially filling said structure; rotating said structure at a speed such that a quasi-cylindrical inner free surface of the liquid is obtained; determining the torque from said liquid when rotating said partially filled structure and calculating the viscosity or viscoelasticity of the liquid from the torque determined in the previous step.

Claims

1. Device for viscosity or viscoelasticity measurement of a liquid comprising: a structure comprising a horizontal rotatable cylinder-shaped section for receiving a liquid whose viscosity or viscoelasticity is to be measured; a transducer, particularly a torque meter, an electric motor or any other means for measuring the torque from said liquid and for producing an output signal based on the torque measurement; wherein said torque measurement is dependent on the rotation speed of said structure.

2. Device according to claim 1, further comprising a liquid whose viscosity or viscoelasticity is to be measured and air, a second fluid, a floating material and/or a rigid float.

3. Device according to claim 1, wherein the liquid is in the flow regime of rimming flow.

4. Device according to claim 1, having means for controlling rotation speed.

5. Device according to claim 1, wherein the structure has a variable diameter, in particular the structure is tapered towards one or both ends, or where said structure is partially open at one or both ends.

6. Device according to claim 1, wherein said structure is made of polymethyl methacrylate, ceramics, glass, hard plastic, steel or combinations thereof, or wherein said structure comprises an inner surface having an antioxidant and/or antimicrobial coating.

7. Device according to claim 1, wherein said structure has an inner diameter from 60 mm to 300 mm, preferably from 64 mm to 200 mm, particularly 120 mm.

8. Device according to claim 1, wherein said structure has a length from 150 to 1000 mm, preferably from 200 mm to 600 mm, particularly 300 mm.

9. Device according to claim 1, further comprising an outer case around the horizontal rotatable cylinder for monitoring the temperature during viscosity or viscoelasticity measurement.

10. Device according to claim 1, wherein the structure comprises at least one ball bearing or at least one air bearing.

11. Device according to claim 1, further comprising means for determining the weight of the liquid while it is inside of said structure.

12. Device according to claim 1, further comprising means for measuring the thickness of said liquid, wherein said means are optical means which may comprise a light source in a position in the central area of the horizontal rotatable cylinder.

13. Method of measuring viscosity or viscoelasticity of a liquid comprising the following steps: placing a liquid into a structure comprising a horizontal rotatable cylinder-shaped section, said liquid partially filling said structure; rotating said structure at a speed such that a quasi-cylindrical free surface of the liquid is obtained; determining the torque from said liquid when rotating said partially filled structure with a torque meter or an electric motor or any other means for measuring the torque from a liquid; wherein the quasi-cylindrical free surface of the said liquid is kept; and calculating the viscosity or viscoelasticity of the liquid from the torque determined in the previous step.

14. Method according to claim 13, comprising the steps of: repeating such measurement for said speed with different levels of filling and/or different diameters of said cylinder and/or different lengths of said structure to obtain additional data about the viscoelastic parameters or to increase the precision of the structure.

15. Method according to claim 13 wherein the liquid is selected from the following list: liquid with no impurities, liquid with impurities, untransparent liquid, non-reflecting liquid, liquid with inhomogeneities, liquid with dirt particles, liquid with metal spheres or balls, liquid with foam, liquid with nanoparticles and mixtures thereof.

16. Method according to claim 13 wherein the liquid is in the flow regime of rimming flow.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0073] The following figures provide particular embodiments of the present invention and shall not be interpreted as limiting the scope of the disclosure.

[0074] FIG. 1 represents an embodiment of the present invention. Rimming flow occurs when the horizontal rotatable cylinder 101 rotates sufficiently fast. The flow field of the liquid 102 is driven by the rotation of said cylinder and gravity g. In rimming flow, the free surface 103 of the liquid has the shape of a near circular tube around the axis of the cylinder.

[0075] FIG. 2 is a side view of the device in an embodiment with the rotatable horizontal cylinder 201 partially filled with the test liquid 202. The test liquid forms an inner free surface 203 due to the flow field induced by the rotation and the centrifugal force. In the embodiment shown the two end-pieces 204 and 205 are closed. The cylinder is driven by a motor 206 and the rotating torque from the liquid is measured by a torque meter 207. The torque meter can be mounted at either side of the motor.

[0076] FIG. 3 represents an embodiment of the present invention. Said device with the horizontal rotatable cylinder 301 is combined with an optical measurement of the thickness of the rotating liquid. The configuration is similar as in FIG. 2, but the left end-piece 305 is partially open. This allows placing a light source 308 in a position near the center of the horizontal rotatable cylinder 301. A light sensor 309 is rotated independently from said cylinder 301 and, together with the light source it is moved in the axial direction of said cylinder 301. The light absorbed by the liquid on its path through the liquid, from the light source to the sensor, is a measure of the liquid thickness at the respective position. In this embodiment, the cylinder 301 is transparent and the liquid absorbs a certain amount of light.

DETAILED DESCRIPTION OF THE INVENTION

[0077] The proposed device is a horizontal rotatable cylinder with means for measuring the torque from a liquid, or that produces an output based on the torque, applied for rotating the said cylinder.

[0078] The cylinder is rotatable around its natural rotation axis.

[0079] In an embodiment the cylinder contains a liquid sample. The end pieces of the cylinder keep the liquid from flowing out of the cylinder when the cylinder rotates at sufficient speed. In an embodiment, the end pieces are completely closed or partially open.

[0080] In an embodiment, the liquid inside the device is in a quantity such that it fills the cylinder partially. The cylinder is rotatable at sufficient speed so that the liquid adheres to the inner wall of the cylinder, rotating with the cylinder and forming a circular or near-circular inner free surface leaving an annual open space around the rotation axis of the cylinder.

[0081] At high rotation speeds, from around 300 rpm, the liquid is in a near rigid rotation due the predominance of centrifugal forces. Measurements are performed at lower rotation speeds, when gravity affects the liquid flow and the torque applied for rotating the liquid has increased.

[0082] The algorithm for deducing the viscoelastic properties is based on a valid flow model that relates the viscoelastic properties to the rotation speed of the measurement and the measure torque.

[0083] In an embodiment, the device's performance is based on the measured torque or an equivalent to the torque without using the torque value itself, but calibrating the instrument directly for the viscoelastic parameters. This may be done for specific liquids by previous measurements or by measurements made with other type of instruments. The latter may be especially convenient when repeating measurements for the same liquid in a repetitive industrial application.

[0084] In a further embodiment, said cylinder is encapsulated in a heat shield. This would facilitate controlling the temperature of the measured liquid.

[0085] In a further embodiment, for liquids with uniform light absorption, said device comprises means for measuring the liquid thickness by the light shining through the liquid at different angles and different positions along the axis of the cylinder. The absorbed light is a measure of the thickness of the liquid layer at the respective position as shown in FIG. 3.

[0086] In a further embodiment, the proposed device measures viscoelastic properties of some other material, especially of liquid with no impurities, liquid with impurities, untransparent liquid, non-reflecting liquid, liquid with inhomogeneities, liquid with dirt particles, liquid with metal spheres or balls, liquid with foam, liquid with nanoparticles and mixtures thereof.

[0087] The meaning of “horizontal cylinder” is not restricted to the definition of a mathematical cylinder shape. It shall enclose any similar shape with the function as described for the cylinder above. In a particular embodiment, the horizontal cylinder is tapered towards its ends.

[0088] The meaning of “viscoelastic properties” comprises “viscosity” for Newtonian liquids as a special case.

[0089] The term “comprising” whenever used in this document is intended to indicate the presence of stated features, integers, steps, components, but not to preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0090] The disclosure is of course not in any way restricted to the embodiments described and a person with ordinary skill in the art will foresee many possibilities to modifications thereof without departing from the basic idea of the disclosure as defined in the appended claims.

[0091] The above-described embodiments are obviously combinable.

[0092] The following dependent claims set out particular embodiments of the disclosure.

REFERENCES

[0093] [1] J. Sanders, D. D. Joseph and G. S. Beavers, Rimming Flow of a Viscoelastic Liquid Inside a Rotating Horizontal Cylinder, Journal of Non-Newtonian Fluid Mechanics, 9 (1981) 269-300. [0094] [2] J. Sanders, “Device and method for viscosity or viscoelasticity measurement”, International patent application PCT/IB2020/061097. [0095] [3] Ch. Macosko, “Rheology: Principles, Measurements and Applications”, Wiley-VCH, 1994.