Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Viscosity
Reexamination Certificate
2002-05-28
2003-02-25
Williams, Hezron (Department: 2856)
Measuring and testing
Liquid analysis or analysis of the suspension of solids in a...
Viscosity
Reexamination Certificate
active
06523396
ABSTRACT:
SPECIFICATION
BACKGROUND OF THE INVENTION
A capillary viscometer is commonly used because of its inherent features such as simplicity, accuracy, similarity to process flows like extrusion dies, no free surface, etc. Viscous flow in capillary viscometry is firmly established both theoretically and experimentally. C. W. Macosko, Rheology:
Principles, Measurements, and Applications
(VCH, 1993). In fact, the capillary viscometer was the first viscometer and this device remains the most common for measuring viscosity for polymer solutions and other non-Newtonian fluids. However, most existing capillary viscometers produce viscosity measurement a shear rate at a time. In the case of Newtonian fluids the observation of the rate of flow at a single pressure drop is sufficient to define the flow behavior. However, in the case of non-Newtonian fluids, viscosity measurements need to be performed over a range of shear rates. In order to measure viscosity over a range of shear rates, it is necessary to repeat the measurement by varying either the driving pressure head or the capillary tube diameter, which leads to a time-consuming measurement requiring intensive labor. Hence, these methods are not suited for measuring the rheology of polymer fluids that may exhibit shear-dependent viscosities. Furthermore, application of such techniques often requires relatively large volumes of the test fluids. Therefore, there has been a need to develop a simple and labor-free viscometer which can measure the viscosity of fluids over shear rates at a time.
In U.S. Pat. Nos. 6,019,735 (Kensey et al.) and U.S. Pat. No. 6,077,234 (Kensey et al.), which are assigned to the same Assignee, namely Visco Technologies, Inc., of the present invention, there is disclosed a scanning-capillary-tube viscometer for measuring the viscosity of a fluid, e.g., circulating blood of a living being. Among other things, this scanning capillary tube viscometer discloses an apparatus that monitors the changing height of a column of fluid versus time in a riser that is in fluid communication with a living being's circulating blood. A further improvement of this type of scanning capillary tube viscometer is disclosed in application Ser. No. 09/439,735 entitled DUAL RISER/SINGLE CAPILLARY VISCOMETER, which is assigned to the same Assignee as the present invention, namely, Visco Technologies, Inc. and whose entire disclosure is incorporated by reference herein. In that application, a U-shaped tube structure is utilized that generates a falling and rising column of test fluid that is driven by a decreasing pressure differential for moving these columns of fluid through a plurality of shear rates, which is necessary for non-Newtonian fluid (e.g., blood) viscosity determinations. Such an apparatus can produce viscosity data in a low shear range (e.g., approximately 0.02 s
−1
).
However, there is a need for an alternative mechanism of monitoring the changing column of fluid over time, such as detecting the changing mass of the column of fluid or the changing height of the column of fluid, as set forth in the present application. The key principle of the single riser/single capillary viscometer is that both flow rate and pressure drop at a capillary tube can be determined by the monitoring of collected fluid mass variation with time using a load cell, or by the monitoring of the changing height with time of the fluid column height. Thus, there also remains a need to develop a viscosity determination in a quasi-steady capillary flow and to measure the viscosity of non-Newtonian fluids (e.g., polymer solutions, circulating blood of a living being, etc.) over a range of shear rates.
SUMMARY OF THE INVENTION
An apparatus for detecting the movement of a fluid at plural shear rates caused by a decreasing pressure differential. The apparatus comprises: a lumen (e.g., a riser tube) having a first end and a second end and being positioned at an angle to a horizontal reference greater than zero degrees; a flow restrictor (e.g., a capillary tube) having an inlet and an outlet wherein the inlet is in fluid communication with the second end and wherein the outlet is arranged to deliver any fluid that passes therethrough to a collector; the lumen and the flow restrictor being initially occupied by a continuous, non-moving sample of fluid therein; a sensor (e.g., a precision balance, load cell, or level detector) for detecting the movement of the fluid over time once the sample of fluid begins moving and passes from the outlet into the collector; and the first end being exposed to atmospheric pressure creating a pressure differential between the first end and the outlet, whereby the sample of fluid moves through the lumen and the flow restrictor at a first shear rate caused by the pressure differential and wherein the movement of fluid causes the pressure differential to decrease from the first shear rate for generating the plural shear rates.
An apparatus for determining the viscosity of a fluid over plural shear rates using a decreasing pressure differential. The apparatus comprises: a lumen (e.g., a riser tube) having a first end and a second end and is positioned at an angle to a horizontal reference greater than zero degrees and wherein the lumen has a first known dimension; a flow restrictor (e.g., a capillary tube) having an inlet and an outlet and wherein the inlet is in fluid communication with the second end and wherein the outlet is arranged to deliver any fluid that passes therethrough to a collector, and wherein the flow restrictor includes some known dimensions; wherein the lumen and the flow restrictor are initially occupied by a continuous, non-moving sample of fluid therein; a sensor (e.g., a precision balance, load cell or a level detector) for detecting the movement of the fluid over time once the sample of fluid begins moving and passes from the outlet into the collector, and wherein the sensor generates data relating to the movement of the fluid over time; the first end is then exposed to atmospheric pressure which creates a pressure differential between the first end and the outlet, and wherein the sample of fluid moves through the lumen and the flow restrictor at a first shear rate caused by the pressure differential, and wherein the movement of fluid causes the pressure differential to decrease from the first shear rate for generating the plural shear rates; and a computer, coupled to the sensor, for calculating the viscosity of the fluid based on the data relating to the movement of the fluid over time, the first known dimension of the lumen and the some known dimensions of the flow restrictor.
A method for detecting the movement a fluid at plural shear rates caused by a decreasing pressure differential. The method comprises the steps of: (a) providing a lumen (e.g., a riser tube) having a first end and a second end and positioned at an angle to a horizontal reference greater than zero degrees; (b) coupling an inlet of a flow restrictor (e.g., a capillary tube), having an outlet, to the second end of the lumen; (c) positioning the outlet to deliver any fluid flowing through the outlet into the collector; (d) coupling a suction source to the first end and activating the source to draw up a sample of the fluid from the collector to form a continuous sample of fluid that occupies the lumen and the flow restrictor, thereby establishing a pressure differential between the first end and the outlet; (e) exposing the first end to atmospheric pressure to cause the sample of fluid to move through the lumen and the flow restrictor at a first shear rate caused by the pressure differential, wherein the movement of fluid causes the pressure differential to decrease from the first shear rate for generating the plural shear rates; and (f) providing a sensor (e.g., a precision balance, a load cell, or a level detector) for detecting the movement of fluid over time as the sample of fluid moves and passes through the outlet into the collector.
A method for determining the viscosity of a fluid over plural shear rates caused by a decr
Cho Young
Hogenauer William N.
Kensey Kenneth
Kim Sangho
Shin Sehyun
Caesar Rivise Bernstein Cohen & Pokotilow Ltd.
Politzer Jay L
Rheologics, Inc.
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