WO2024039500A1

WO2024039500A1 - System and method for determining in-line rheology measurement of slipping flow of fluid

Info

Publication number: WO2024039500A1
Application number: PCT/US2023/028684
Authority: WO
Inventors: Garrett R. SWINDLEHURST
Original assignee: General Mills, Inc.
Priority date: 2022-08-17
Filing date: 2023-07-26
Publication date: 2024-02-22

Abstract

A measurement system (100) for determining in-line rheology measurement of slipping flow of fluid (130) is provided for measuring the in-line rheology of material including fluids (305) exhibiting "plug flow" behavior due to significant fluid wall slip and/or high yield stress. The system (100) adds a second shearing surface (330, 500, 630) in addition to a wall (120) forming a standard pipe configuration (110) so that significant total shear is generated. The shear is then detected and quantified by Ultrasound Velocimetry Profiling with Pressure Drop (UVP-PD) technology to construct an in-process rheogram of the material or fluid (305). An apparatus (100) and method for conducting a UVP-PD measurement on a slipping flow is arranged such that the characteristic shear rheogram (740) of the fluid or semisolid material (305) can be obtained.

Description

SYSTEM AND METHOD FOR DETERMINING IN-LINE RHEOLOGY MEASUREMENT OF SLIPPING FLOW OF FLUID

FIELD OF THE INVENTION

[0001] The invention generally pertains to a measurement system and method for determining inline rheology of slipping flow of fluid employing an ultrasound technique for measuring fluid dynamics in a pipe, such as the Ultrasound Velocity Profiling and Pressure Drop technique (UVP-PD). More specifically, the technique employs inline rheology measurement of a slipping flow in a hollow pipe including a shearing surface in addition to the inner wall of the pipe.

BACKGROUND OF THE INVENTION

[0002] A wide range of ingredients is employed in industrial food production, including concentrated starch suspensions and semisolid fats or oils, among others. These ingredients are processed as fluids in an overall process system when making food products. The fluids are pumped through the system under pressure. The fluids generally have a shear rheology that can be adjusted. Often, the organoleptic properties of such fluids are very desirable as these organoleptic properties lead to good mouthfeel of the food products. The quality of mouthfeel is highly dependent on the shear rheology. As the fluids move through a pipe during food product manufacture, the fluids interact with an inner wall of the pipe. Some fluids are slowed down by the wall so that the fluid near the wall forms a shearing fluid layer that moves slower than the fluid in the center of the pipe. The shearing fluid layer will slow the fluid flow and cause an unacceptable pressure drop in the overall process system. However, other fluids, such as semisolid fats or oils, often display near complete “plug flow” behavior. “Plug flow” refers to apparent slip at the wall of the pipe between a non-deforming mass of fluid (the “plug”) and the enclosing pipe. This slip is true slip at the molecular level, which occurs with polymeric food fluids and, therefore, does not result in a shearing fluid layer. Plug flow more commonly occurs in fluids exhibiting an external lubrication layer due to a phase change or physical separation. Plug flow is desirable since less pressure drop will occur in the overall process system.

[0003] Rheology is the study of how fluid and semisolid materials deform in response to stress. As a discipline, rheology lies in the space between deformation mechanics of perfectly elastic (Hookean) solids and those of perfectly viscous (Newtonian) fluids. A rheogram is a plot showing the characteristic deformation response of a material to applied stress, in the fluid perspective. More specifically, a rheogram is a plot of stress vs. strain rate of the material. For fluids, one of the most important stresses is the shear stress, which is typically measured versus shear strain rate to develop a shear rheogram. There are numerous ways in which information used to produce a shear rheogram can be collected. One method of particular interest is capillary rheometry. In this method, a reservoir of fluid is pressurized and then allowed to depressurize at steady flow conditions through a small diameter capillary. Capillary rheometry, therefore, is similar to a typical steady flow of a process fluid in a pipe.

[0004] Often, the shear rheology of a process fluid is either dynamic (changing with time or length along a flow process) or sensitive to processing conditions to which the fluid is subjected. As such, it is desirable to leverage rheometric methods that can measure the shear rheology directly in the process context. Once the shear rheology of a food is measured, the rheology can be adjusted to improve the overall mouthfeel of food products being produced. An emergent method of the last few decades, and only recently accessible commercially, is known as Ultrasound Velocity Profiling with Pressure Drop (UVP-PD).

[0005] A UVP-PD system 100 is shown in Figure 1, wherein a pipe 110 has a wall 120 for containing a flow of fluid 130. Fluid 130 forms a radial velocity flow profile 132 with a nominal speed 140 towards the center of pipe 110 and a slower speed 145 towards wall 120. Flow 130 is shown with flowing particles 131 in pipe 100. A pressure drop measurement system constituted by differential pressure sensor 150 is provided with an upstream pressure sensor 160 and a downstream pressure sensor 170 and used to determine the shear stress distribution in pipe 110. A first ultrasonic transducer 180 and a second ultrasonic transducer 190 are employed to measure radial velocity flow profile 132 in pipe 110 with an ultrasound doppler technique applied to flowing particles 131. In use, the two eponymous measurements collect both a shear stress (by pressure drop) and a shear rate (calculated from velocity profile 132 across pipe 110). From these two measurements a shear rheogram can be constructed for the fluid. An exemplary shear rheogram 200 is shown in Figure 2. Rheogram 200 is a complete multipoint rheogram showing shear stress vs. shear rate which is determined from flow profile 132 and the differential pressure measurement. The max shear rate depends on nominal speed 140 for the flow rate in pipe 110.

[0006] UVP-PD is a useful technique for obtaining an in-context shear rheogram as long as the radial velocity profile of the fluid can be measured by the ultrasound doppler method. However, some foods are highly viscoelastic fluids, or colloidal fluids with strong and/or hierarchical interparticle interactions, which are difficult to measure with UVP-PD since these fluids exhibit the plug flow. For example, shortenings and other bakery fats are conveyed as near-plug flows in heat-jacketed pipes. In these processes, the heated fluid of the jacket melts the outer layer of the shortening to a liquid oil, which then lubricates the surface of the plug, permitting conveyance at an acceptable pressure drop. This lubrication layer, which exhibits a much lower viscosity than the fluid in the center of the pipe, internalizes all the shear stress of the pressure driving force for pipe flow. The flow regime characterizing these fluids is described as “slipping flow.”

[0007] An example of plug flow is shown in Figure 3. The arrangement of Figure 1 is modified to show a plug flow 240 with a constant velocity profile 245 that extends close to wall 120 of pipe 110. The fluids relevant to industrial food production, such as semisolid fats or oils, exhibit high yield stresses or phase change behavior, making collection of a shear rheogram with a conventional UVP-PD apparatus difficult to obtain or making the results useless in the case of the shear rate range being too small to be useful. For reliable industrial production of such fluid food ingredients, an in-context shear rheometiy system is needed for quality control. There also exists a need in the art for a UVP-PD methodology or apparatus for this class of desirable food fluids in order to determine the shear rheology of the fluids used in food production when the fluids exhibit plug flow. SUMMARY OF THE INVENTION

[0008] According to a first aspect of the invention, a measurement system for determining in-line rheology measurement of slipping flow of fluid material is described for measuring fluids exhibiting “plug flow” behavior due to significant fluid wall slip and/or high yield stress. The system adds a second shearing surface in addition to a wall forming a standard pipe configuration so that significant total shear is generated. The shear is then detected and quantified, such as by Ultrasound Velocimetry Profiling with Pressure Drop (UVP-PD) technology, to construct an in-process rheogram of the material. An apparatus and method for conducting a shear measurement on a slipping flow is arranged such that the characteristic shear rheogram of the fluid or semisolid material can be obtained.

[0009] In a preferred embodiment, the system includes a measuring tube formed with an upstream portion, a downstream portion, and a wall having a low friction interior surface forming a passageway configured to allow passage of a fluid flowing through the measuring tube. The wall is also configured to allow the fluid to slip relative to the low friction interior surface. A shearing device is mounted in the passageway between the upstream portion and the downstream portion. The shearing device is formed with a shearing surface having a higher friction coefficient than the low friction interior surface and is configured to shear the fluid. A first ultrasonic transducer is mounted to the wall in the upstream portion and configured to transmit and/or receive an ultrasonic wave. A second ultrasonic transducer is mounted to the wall in the downstream portion and also configured to transmit and/or receive an ultrasonic wave. The transducers measure information about the ultrasonic wave and, correspondingly, the fluid. A first pressure sensor is configured to measure a first pressure of the fluid in the upstream portion and a second pressure sensor is configured to measure the pressure of the fluid in the downstream portion. A differential pressure sensor is connected to the first and second pressure sensors to provide a signal indicating a pressure differential. A control unit is configured to receive the information regarding pressure in the upstream portion and the pressure in the downstream portion to determine a shear stress distribution in the measuring tube. The control unit is also configured to receive information from the ultrasonic transducers to determine the shear rate distribution in the measuring tube.

[0010] The shearing device may have several aspects which may be employed independently or in combination. In one preferred embodiment, the shearing device extends across the tube and splits the passageway into two symmetrical flow paths having the same cross section. The shearing device is formed as a flat plate. In another preferred embodiment, the shearing device is formed with a conical shape. Multiple shearing surfaces may be employed together.

[0011] Preferably, the measuring tube is part of a pipe. The pipe may be split to form a gap, with the shearing device having an outer wall configured to removably engage the pipe and fit in the gap. When changing the shearing force is considered desirable, one shearing device with a first shearing surface configuration can be replaced with a second shearing device having a different shearing surface configuration.

[0012] In another embodiment, the shearing surface is adjustable. In a particularly preferred embodiment, the shearing surface has a conical shape and can translate along the axis of the measuring tube. When the shearing surface is moved between the ultrasonic transducers, the amount of shearing surface between the transducers is initially small with only the point of the conical shape being between the ultrasonic transducers. The shearing surface between the transducers increases as the surface is moved so that a wider portion of the conical shape is between the transducers.

[0013] The fluid may be shortening or other materials that have a viscosity affected by heat. In yet another preferred embodiment, a utility tube is located within the measurement tube. The utility tube is configured to contain a utility fluid for heating the fluid material being measured. The heat from the utility fluid is controlled to regulate the viscosity of the measured fluid.

[0014] In-line rheology of slipping flow is conducted by sending a flow of fluid through the measuring tube while transmitting an ultrasonic wave into the fluid with the ultrasonic transducers mounted on the wall. The method also includes measuring a first pressure of the fluid in the upstream portion with a first pressure sensor; measuring a second pressure of the fluid in the downstream portion with a second pressure sensor, and determining a shear stress distribution in the measuring tube. The method includes receiving the information from the ultrasonic transducers to determine the shear rate distribution in the measuring tube and developing a rheogram of the fluid.

[0015] The method also contemplates splitting the passageway into symmetrical flow paths having the same cross section or splitting the passageway into flow paths of different cross section. In order to adjust for differing fluids, the method includes replacing the shearing device with a second shearing device having a different shearing surface. Alternatively, the method includes dynamically changing the shearing surface during measuring or heating the fluid within the measurement tube to change the viscosity of the fluid being measured.

[0016] By adding an additional shearing surface to the interior of the pipe section along which PD measurements are conducted, the fluid is subject to additional shearing, and the shear stress is measured between the differential pressure transducers. The additional shearing surface fundamentally disrupts the plug flow condition and probes the shear rheologic response of the material. This non-zero shear rate zone has a radial velocity gradient which was not previously present in the plug flow scenario. The velocity gradient can be measured, such as by UVP-PD, so the shear rate regime of the fluid can be directly measured. Improved quality of complex fluid food products or ingredients is obtained by quantifying the relationship between processing conditions and the shear rheology of such fluids.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure l is a cross-sectional schematic view of fluid flow, with a standard flow velocity profile, in a pipe with an ultrasound velocimetry profiling with pressure drop (UVP-PD) measuring arrangement according to the prior art.

[0018] Figure 2 is a multipoint rheogram showing shear stress versus shear of the fluid flow in the prior art arrangement of Figure 1. [0019] Figure 3 shows the prior art arrangement of Figure 1 with a fluid flow having a plug velocity profile and slipping flow.

[0020] Figure 4 is a cross-sectional schematic view of a measuring system for measuring fluid flow, with a plug velocity profile, in a pipe with ultrasound sensors for measuring shear rate distribution and pressure sensors measuring shear stress distribution in the pipe with an extra shearing surface applying shearing to the fluid flow according to a preferred embodiment of the invention.

[0021] Figure 5 schematically illustrates a control system of the measuring system of Figure 4.

[0022] Figure 6 shows a cross-section of the pipe in Figure 4, focusing on the additional shearing surface located on a blade having opposed flat surfaces forming two symmetrical passageways

[0023] Figure 7 shows an alternative additional shearing surface located on a solid cylinder.

[0024] Figure 8 shows an alternative additional shearing surface located on a hollow cylinder with an internal channel for passing a utility fluid.

[0025] Figure 9 shows an alternative additional shearing surface formed by filling a pipe half full of solid material.

[0026] Figure 10 is a cross-sectional schematic view of a measuring system for measuring fluid flow, similar to the one shown in Figure 4, modified with a shearing surface which can move axially to change the amount of shearing surface in an area of pipe being measured.

[0027] Figure 11 shows an alternative additional surface located on a blade having opposed flat surfaces forming two asymmetrical passageways.

[0028] Figure 12 is a flow chart showing a method of measuring fluid with the arrangement shown in Figure 4. DETAILED DESCRIPTION OF INVENTION

[0029] Initially, it should be noted that the embodiments of the present invention described below are not intended to be exhaustive or limit the invention to the precise forms disclosed in the following detailed description. Rather, a purpose of the embodiments chosen and described is so that the appreciation and understanding by others skilled in the art of the principles and practices of the present invention can be facilitated. Also, it should be realized that the embodiments described in the below paragraphs for the inventive process, system and/or product are not mutually exclusive and therefore can be combined in connection with other embodiments.

[0030] Referring to Figure 4 of the drawings, a measurement system 300 for determining in-line rheology measurement of slipping flow of a fluid in accordance with the invention is shown. Measurement system 300 generally makes use of the UVP-PD methodology which allows the determination of rheological parameters by combining Ultrasonic Velocity Profiling UVP with Pressure Difference PD measurements. Measurement system 300 is configured to be placed in an overall fluid network 310 or process with fluid 305 being processed. Fluid 305 enters measurement system 300 through line 315 and leaves through line 316. Fluid 305 travels through a measuring tube 320 from an upstream portion 321 through a passageway 322, where fluid 305 forms a fluid flow profile 325, and then to a downstream portion 326 before flowing through line 316 to fluid network 340. Preferably, the fluid network is represented by two boxes (310, 340). Typically, the fluid network (310, 304) is used in a process for producing food products and, more particularly, oils and fats which are processed while being continually measured by system 300. Fluid network 310 preferably has pumps (not shown) to supply fluid 305 with a certain flow rate and pressure. Fluid 305 therefore forms fluid flow profile 325 as represented by arrows with the length of each arrow representing the speed of fluid 305 and showing how the fluid speed changes based on radial position. Fluid 305 is contained by wall 120 of pipe 110. Pipe 110 may be cylindrical, however, the invention is not so limited.

Therefore, the term “pipe” is intended to cover various geometric hollow shapes and should simply to be considered a hollow conduit that allows for the passage of fluid. [0031] Wall 120 has a low friction surface 341 forming passageway 322 configured to allow the fluid to slip relative to low friction surface 341. A differential pressure sensor 150 is provided with an upstream portion with first pressure sensor 160 for producing a first pressure signal indicative of a first pressure at first sensor and a downstream portion with second pressure sensor 170 for producing a second pressure signal indicative of a second pressure at second sensor 170, which is used to determine the shear stress distribution in pipe 110. Differential pressure sensor 150 is also configured to make wall shear stress measurements. More specifically, differential pressure sensor 150 is configured to measure a pressure differential between two points along measuring tube 320. A fluid velocity sensor includes a first ultrasonic transducer 180 and a second ultrasonic transducer 190 which are employed to measure fluid 305 in pipe 110 with an ultrasound doppler technique. These sensors are preferably connected to a dedicated PVD-DP unit 342 which is connected by wire 343 to a PC 344, both of which are commercially available. First ultrasonic transducer 180 fits snugly into pipe wall 126, while second ultrasonic transducer 190 also fits snugly into pipe wall 126. Preferably, first ultrasonic transducer 180 is designed to transmit an ultrasonic signal to second ultrasonic transducer 190 which acts as a receiver and produces information about the ultrasonic wave. As shown, transducers 180 and 190 are set back from surface 341, which advantageously avoids a potential issue with the transducers having trouble sensing the space directly in front of them.

[0032] With transducers 180 and 190 connected to PVD-DP unit 342, PVD-DP unit 342 can send signals to drive transducers 180, 190 to send ultrasonic pulses and send back sensed signals from transducers 180, 190. First pressure sensor 160 and second pressure sensor 170 are connected to the PVD-DP unit by a cable 350 and, more particularly, by wires 360 and 361, respectively. Likewise, first ultrasonic transducer 180 and second ultrasonic transducer 190 are also connected to PVD-DP unit 342 by wires 370 and 380, respectively.

[0033] Turning to Figure 5, there is schematically shown more details of PVD-DP unit 342. Sensors 160, 170 and ultrasonic transducers 180, 190 are connected to an input/output unit 410 which, in turn, is connected to a processor 440 acting as a control unit for PVD-DP unit 342 such that processor 440 is configured to receive pressure signals from first and second pressure sensors 160, 170 to determine a shear stress distribution and receive information from first and second ultrasonic transducers 180, 190 to determine a shear rate distribution in measuring tube 320. A memory 420 is provided for storing data and several modules 450 are provided to process information provided by the sensors 160, 170 and ultrasonic transducers 180, 190. PVD- DP unit 342 is connected to PC 344, which provides a convenient way for a user to control system 300. A communications unit 430 is provided to send information to and from PC 344. More details on such a PVD-DP unit can be found in U.S. patent No. 9,383,237, incorporated herein by reference.

[0034] At this point, it should be noted that measuring system 300 differs from the system of Figure 1 in some important respects. Specifically, measuring system 300 is provided with an additional shear surface 330 (see cross-section of Figure 6) having a coefficient of friction, i.e., a higher friction surface than low friction surface 341. Shear surface 330 is located on a flat plate 460 which extends across measuring tube 320 and divides the interior of pipe 110 into two passages 461 and 462. Shear surface 330 is constituted by multiple shearing surfaces, one on each side of the plate 460. By adding additional shearing surface 330 to the interior of pipe 110 along which pressure differential measurements are conducted, fluid 305 is sheared, and the shear stress caused by surface 330 is measured between ultrasonic transducers 180, 190 and between differential pressure sensors 160, 170. Added shearing surface 330 fundamentally disrupts the plug flow condition, as best represented in Figure 4. More specifically, note the shape of flow profile 325 which slows down near surface 330. Surface 330 also probes the shear rheologic response of the material which forms fluid 305. This non-zero shear rate zone has a radial velocity gradient which forms fluid flow profile 325 and which was not previously present in the plug flow scenario shown in flow profile 245 of Figure 3. The velocity gradient can be measured by UVP so the shear rate regime of fluid 305 can be directly measured. Several apparatus designs may achieve this end so the present disclosure is not intended to be limited to the specific embodiment shown but rather encompasses any added shear surface(s) to disrupt the plug flow condition in conjunction with a UVP-PD measurement conducted within the section of flow wherein such additional surfaces are included.

[0035] In connection with the application for characterizing the shear rheology of bakery shortenings, adding plate 460 of Figure 6 is akin to continuously cutting the shortening flow with a fixed knife edge. Such a flat plate surface is especially attractive as the entire surface has no curvature relative to the ultrasound transducer positioning, which should facilitate accounting for ultrasound reflection from the shearing surface in velocity profile measurements. The thickness of shearing plate 460 can be adjusted to change the cross-section of the pipe section, and thus the amount of pressure drop and additional shear stress applied to the fluid, and therefore can be designed to probe a specific shear rate regime.

[0036] Another useful shearing surface design is a cylindrical surface 500 as best seen in Figure 7. Surface 500 presents curvature relative to the ultrasound transducer position, which may cause complications for ultrasound reflectivity from shearing surface 500. However, the use of an annular flow region 510 for fluid 305 facilitates the calculation of shear stress from the pressure drop, as well as the construction of the shear rheogram from the UVP-PD measurement. [0037] Instead of being established by a solid cylinder, shear surface 500 can be formed by a hollow cylinder filled with a utility fluid 520 of variable temperature for heating fluid 305, as best seen in Figure 8. Such an arrangement is particularly useful for probing the shear rheology of laminating bakery shortenings with the art of the current disclosure. Because these shortenings have a wide melting range from their various fat ingredients, cooling may need to be applied to the shearing surface 500 to prevent the formation of a lubrication layer due to low- melting components separating from the shortening plug flow. Additionally, varying the temperature of utility fluid 520 could be used to approach the formation of a lubrication layer and perhaps even generate lubrication layers of different thicknesses. These thicknesses could then be measured by UVP to potentially quantify the melting behavior (solid fat content) of the shortening.

[0038] It is also possible to establish an added shear surface 540 on a plate taking the form of a solid semicylinder, thus creating a semi-circular flow path 550 as shown in Figure 9. Such asymmetric designs could be useful for achieving different shear rate regimes at a given flowrate, such as the asymmetric flat plate shown in Figure 9.

[0039] In other embodiments, the shear surface can be adjustable such that different shear rate regimes can be probed. In one simple embodiment, the surface can be removable from the pipe section so that surfaces yielding different fluid cross-section can be generated by exchange of parts. For instance, the shearing device of Figure 4 could be replaced with a shearing device with a different shearing surface, such as the shearing surface in shown in Figure 7, 8 or 9. Figure 4 shows a coupling mechanism 556 that can be used for replacing shearing devices. Measuring tube 320 is split at coupling mechanism 556, which has two parts, such that a gap is formed when the shearing device is removed. Another shearing device having a wall configured to engage measuring tube 320 may then be placed in the gap and fastened with coupling mechanism 556. While a flange is shown, any pipe coupling mechanism would be acceptable.

[0040J Reference will now be made to Figure 10 in describing another potential insert for use in the overall invention. As shown, a shear surface 555 is established by an insertable section of a conical member having different cross-sections along its length. During use, the conical member can be shifted, as represented by arrows 560, to create varying diametric fluid flow regions. Note how shear surface 555 affects a fluid flow profile 506. Correspondingly, varying shear rate regimes will be presented to the UVP measurement zone. In a more complex embodiment, not separately illustrated, the shear surface could be comprised of two or more adjustable surfaces which can be relatively shifted by mechanical action, or an elastic or wound surface with variable exposed surface area, such that the surfaces of the mechanical system create an occluding body in the pipe with variable volume. Although the varying surface regime can be useful, such a shear surface generating a gradient of fluid cross-section along the pipe section for DP measurement will lead to a nonlinear shear stress gradient which does complicate the calculation of the shear rheogram versus a shear surface of constant fluid cross-section along the pipe length. Therefore, employing a shear surface of constant fluid cross-section may be more desirable, particularly given the ease of rapidly exchanging parts, such as with coupling mechanism 556.

[0041] The added shear surfaces can additionally have different leading-edge geometry to facilitate the faster development of a steady shear profile. For example, a leading edge 570 could be flat as shown in Figures 4 and 6 or a leading edge 580 can be sharp as shown in Figure 10. The rapid approach to a steady shear profile along the length of the pipe is advantageous because it permits the use of a shorter total length of the measurement device. This would lead to an overall lower pressure drop for the process fluid conveying system, which is advantageous for cost and reliability.

[0042] The additional shear surface may not be symmetric with regard to the centerline of the process flow piping. Such a scenario is exemplified in Figure 11 wherein different cross sections 610 and 620 are separated by a surface 630 to establish multiple, non-symmetrical fluid flow paths having different flow rates. Since the shear stress regime for each path is equal, as long as the material has a constant rheology along each flow path, the probed shear rate regime will also be equal.

[0043] Each shearing surface 330, 500, 630 must be a surface that will not allow fluid slip in the same way that wall 120 does. For many high-viscosity fluids, a lubricating layer or true molecular slip at the surface of pipe 110 is highly attractive, or often essential, to convey fluid 305 through fluid network 310, 340 at an acceptable pressure drop. To remove slip at wall 120 and generate a shear zone, a textured pipe surface can be used to disrupt molecular slip. If the slip is due to melting or phase separation of the plug flow fluid and generation of a slip layer, as is the case in laminating bakery shortenings, a shear surface of reduced temperature caused by utility fluid 520 relative to the fluid flow can be used to freeze this liquid layer or prevent its formation. By adding a shearing surface to the interior of the pipe, the resulting arrangement creates a pressure drop to the fluid conveying system, which is presented as shear stress dissipated by the fluid in the shearing zone. However, this additional pressure drop is required to probe the material rheology in-context, and therefore must be managed in overall fluid network 310, 340. Employing an additional shearing surface while preserving slip at the containing pipe surface is more effective than just causing slip at the containing pipe surface due to the smaller surface area of the additional shearing surface. The pressure drop additional to the process fluid flow conveyance system is much reduced by the smaller shearing surface area, which is desirable for the overall process.

[0044] Turning now to Figure 12, there is shown a flow chart setting forth the basic operation of the system. Fluid is supplied to measuring system 300 at step 710 while food processing is occurring. The pressure drop of the fluid is measured at step 720. Sensors 160, 170 measure a pressure differential along at least two points in fluid flow profile 325 to determine the shear stress at surface 330 (and hence also the distribution) from the pressure drop over a fixed distance, knowing also the diameter of pipe 100.

[0045] The velocity of fluid 305 is measured at step 730. Preferably a pulsed ultrasound velocity profiling technique (UVP) determines velocity profiles of fluid flow. This technique relies on determination of the frequency shift or time-domain shift of backscattered signals reflecting of particles 131 in fluid 305. This shift is obtained in real-time as a function of spatial range for a large number of spatial positions/times. From these measurements, flow profile 325 of fluid 305 is determined with modules 450 shown in Figure 5. It will be appreciated that from a single velocity profile at a simultaneously measured pressure gradient, system 300 may determine fluid rheological properties over shear rates ranging from zero at pipe wall 120 to the maximum shear rate at shear surface 330. When the ultrasound pulse hits a small particle 130 in fluid 305, part of the ultrasound energy scatters on particle 130 and echoes back. The echo or reflection signal reaches the receiving transducer 190 after a time delay. If scattering particle 130 is moving with a non-zero velocity component into the acoustic axis of transducer 190, a Doppler shift of the echoed frequency takes place, and the received signal frequency becomes ‘Doppler-shifted’ by the frequency equal to the Doppler shift frequency, and the velocity may be determined.

[0046] The information from transducers 180, 190 is processed at step 740 to determine shear rate distribution substantially simultaneously from a measurement of the pressure difference from pressure sensors 160, 170. In particular, the modules 450 may be configured to use the pressure difference in combination with the velocity profile to determine shear viscosities and rheological model parameters. More details on the PVD-DP method can be found in U.S. Patent No. 9,383,237, incorporated herein by reference. The results may be shown on the PC 344 in a visual format including a rheogram similar to the one shown in Figure 2. The information is provided in real time so that the process for producing the food may be adjusted based on the information.

[0047] As referenced above, the present invention has particular applicability in connection with quantifying the relationship between process conditions and shear rheology in real time as foods are produced. The processing results can be used to improve the quality of complex fluid food products or ingredients resulting from quantifying the relationship between processing conditions and the shear rheology of such fluids. The processing conditions are preferably changed based on the quantified relationship to produce foods with better mouthfeel and overall quality.

Claims

1. A measurement system for determining in-line rheology measurement of slipping flow of fluid, comprising: a measuring tube having an upstream portion, a downstream portion, and a wall having a low friction surface forming a passageway configured to allow passage of a fluid flowing through the measuring tube, and configured to allow the fluid to slip relative to the low friction surface; a shearing device mounted in the passageway between the upstream portion and downstream portion, and having a shearing surface with a higher coefficient of friction than the low friction surface, the shearing device being configured to shear the fluid; a fluid velocity sensor including a first ultrasonic transducer mounted on the wall in the upstream portion and configured to transmit an ultrasonic wave, a second ultrasonic transducer mounted on the wall in the downstream portion and configured to measure information about the ultrasonic wave; a differential pressure sensor including a first pressure sensor located in the upstream portion and configured to measure a first pressure of the fluid and produce a first pressure signal indicative of the first pressure and a second pressure sensor located in the downstream portion and configured to measure a second pressure of the fluid and produce a second pressure signal indicative of the second pressure; and a control unit configured to receive the first pressure signal and the second pressure signal to determine a shear stress distribution in the measuring tube and to receive the information from the first ultrasonic transducer and the second ultrasonic transducer to determine a shear rate distribution in the measuring tube.

2. The measurement system according to claim 1, wherein the measuring tube is a pipe.

3. The measurement system according to claim 1, wherein the shearing device extends across the measuring tube and splits the passageway into symmetrical flow paths.

4. The measurement system according to claim 1, wherein the shearing device extends across the measuring tube and splits the passageway into non-symmetrical flow paths.

5. The measurement system according to claim 1, wherein the shearing device constitutes a first shearing device, said measurement system further comprising a second shearing device having a different shearing surface than the first shearing device wherein the tube is split to form a gap and the first shearing device is removable and has an outer wall configured to engage the tube and fit in the gap and the second shearing device is configured to replace the first shearing device.

6. The measurement system according to claim 1, wherein the shearing device is formed with multiple shearing surfaces.

7. The measurement system according to claim 1, wherein the shearing surface is flat.

8. The measurement system according to claim 1, wherein the shearing surface is conical.

9. The measurement system according to claim 1, wherein the shearing surface is adjustable.

10. The measurement system according to claim 1, further comprising a utility tube located within the measuring tube, the utility tube configured to contain a utility fluid for heating the fluid.

11. The measurement system according to claim 1, wherein the fluid is shortening.

12. A method of measuring in-line rheology of slipping flow, said method comprising: sending a flow of fluid through a measuring tube formed having an upstream portion, a downstream portion, and a wall having a low friction surface forming a passageway configured figured to allow the fluid to slip relative to the low friction surface with a shearing device mounted in the passageway between the upstream portion and downstream portion and formed with a shearing surface, the shearing surface having a higher coefficient of friction than the low friction surface and being configured to shear the fluid; transmitting an ultrasonic wave into the fluid with an ultrasonic transducer mounted on the wall in the upstream portion; measuring information about the ultrasonic wave with an ultrasonic sensor; mounted on the wall in the downstream portion; measuring a first pressure of the fluid in the upstream portion with a first pressure sensor to produce a first pressure signal; measuring a second pressure of the fluid in the downstream portion a second pressure sensor to produce a second pressure signal; determining a shear stress distribution in the measuring tube; and receiving the information from the ultrasonic sensor and first and second pressure signals to determine, with a control unit, a shear rate distribution in the measuring tube.

13. The method according to claim 12 including splitting the passageway into symmetrical flow paths.

14. The method according to claim 12 including splitting the passageway into non- symmetrical flow paths.

15. The method according to claim 12 wherein the shearing device constitutes a first shearing device, and the method first comprises replacing the first shearing device with a second shearing device having a different shearing surface than the first shearing device.

16. The method according to claim 15 wherein replacing the first shearing device further includes engaging the measuring tube with edges of the second shearing device.

17. The method according to claim 12 including adjusting the shearing surface of the shearing device.

18. The method according to claim 12 including heating the fluid within the measuring tube.

19. The method according to claim 12 including disrupting a plug flow condition in the measuring tube.