Method and equipment for measuring critical density of fluid
By using solid particles with different density in a closed container, combining the critical temperature and pressure of the fluid, the critical density of the fluid is determined, and the problem of cumbersome and low accuracy in measuring the critical density of the fluid in the prior art is solved, thereby achieving higher accuracy measurements.
Patent Information
- Application Number
- CN202510372642.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-27
- Publication Date
- 2025-06-17
AI Technical Summary
When measuring the critical density of a fluid, the process is cumbersome and difficult to regulate, and the accuracy is limited.
The density of the solid particles at the critical pressure position is determined by selecting multiple solid particles with different density intervals in the solid density range, and in the closed container, the density of the solid particles at the critical pressure position is determined according to the critical temperature and pressure of the fluid to be measured.
Accurate and reliable measurement of the critical density of the fluid is achieved and the measurement accuracy is improved.
Smart Images
Figure CN120160937A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of fluid critical parameter measurement, and particularly to a method and device for measuring the critical density of a fluid. Background Art
[0002] Any substance exists in three phases - gas phase, solid phase, and liquid phase; the point where the three phases coexist in equilibrium is called the triple point. The point where the liquid and gas phases are in equilibrium is called the critical point. The temperature and pressure at the critical point are called the critical temperature and critical pressure. Accurately measuring the critical parameters of a substance in the equilibrium critical state between the gaseous and liquid states has important guiding significance for the practical application of fluids in the critical state.
[0003] The critical density of a fluid is the density of the fluid in the critical state, which is one of the important critical parameters of fluid substances. Currently, there are many methods for measuring the critical density of a fluid, but essentially, they all measure the mass and volume of the fluid under critical pressure and critical temperature conditions, and determine the critical density through the ratio between the mass and the volume. This measurement method is not only cumbersome and difficult to control during the measurement process, but also has limited accuracy in measuring the critical density of the fluid. Summary of the Invention
[0004] The purpose of the present invention is to provide a method and device for measuring the critical density of a fluid, so as to achieve accurate and reliable measurement of the critical density of the fluid.
[0005] To solve the above technical problems, the present invention provides a method for measuring the critical density of a fluid, including:
[0006] According to the theoretical critical density of the fluid to be measured, a plurality of solid particles with different densities in the solid density range are selected; wherein, the density difference between any two adjacent solid particles is not greater than the set density difference; the theoretical critical density is within the solid density range;
[0007] Put each of the solid particles into a closed container;
[0008] At the critical temperature of the fluid to be measured, fill the closed container with the fluid to be measured and pressurize the fluid to be measured until the closed container filled with the fluid to be measured has a top pressure less than the critical pressure of the fluid to be measured and a bottom pressure greater than the critical pressure;
[0009] Identify and determine the solid particles at the position in the closed container where the pressure is equal to the critical pressure, and determine the critical density of the fluid to be measured with the density of the solid particles at the position of the critical pressure.
[0010] In an optional embodiment of the present application, selecting a plurality of solid particles with different densities in the solid density range includes:
[0011] Select a plurality of the solid particles with equal density differences changing in sequence within the solid density range; and the density difference between two adjacent solid particles is not greater than 3% of the theoretical critical density of the fluid to be measured.
[0012] In an optional embodiment of the present application, identifying the solid particles located at the position where the pressure in the closed container is equal to the critical pressure includes:
[0013] Determine a reference solid particle at the position where the solid particles are most densely suspended and distributed in the closed container, and determine the critical density of the fluid to be measured according to the density of the reference solid particle.
[0014] In an optional embodiment of the present application, determining a reference solid particle at the position where the solid particles are most densely suspended and distributed in the closed container, and determining the critical density of the fluid to be measured according to the density of the reference solid particle includes:
[0015] Collect the height data of the distribution of each of the solid particles in the closed container;
[0016] According to the height difference between two adjacent solid particles in the distribution;
[0017] If the height difference between two adjacent solid particles is the smallest in the middle region of the closed container, then use the two solid particles with the smallest height difference as the reference solid particles;
[0018] Determine the critical density of the fluid to be measured according to the average density of the two reference solid particles;
[0019] If there are two equal height differences corresponding to three adjacent solid particles in the middle region of the closed container, and the two height differences are the smallest among all the height difference data, then use the solid particle located in the middle position among the three solid particles as the reference solid particle;
[0020] Use the density of the reference solid particle as the critical density of the fluid to be measured.
[0021] In an optional embodiment of the present application, collecting the height data of the distribution of each of the solid particles in the closed container includes:
[0022] Use X-ray to scan the solid particles from at least two different directions to obtain the height data of each of the solid particles in the closed container.
[0023] In an alternative embodiment of the present application, the top pressure is less than the critical pressure of the fluid to be measured and the bottom pressure is greater than the critical pressure, including:
[0024] The pressure difference between the critical pressure and the top pressure, and the pressure difference between the bottom pressure and the critical pressure are both not less than 100 Pa.
[0025] In an alternative embodiment of the present application, at the critical temperature of the fluid to be measured, after filling the fluid to be measured into the closed container and pressurizing the fluid to be measured, before determining the reference solid particles at the position where the solid particles are most densely suspended in the closed container, it further includes:
[0026] Collect the height data of the distribution of each of the solid particles in the closed container, and determine the height difference between any two adjacent solid particles in the distribution;
[0027] According to each of the height differences, determine the highest solid particle and the lowest solid particle among a plurality of successively adjacent solid particles distributed in the middle section of the closed container and with a corresponding height difference not greater than a preset height difference threshold;
[0028] Take the density range between the density of the highest solid particle and the density of the lowest solid particle as the new solid density range;
[0029] According to the new solid density range, reselect a plurality of solid particles with different densities and within the solid density range;
[0030] Re-execute the step of putting each of the solid particles into the closed container, filling the fluid to be measured into the closed container at the critical temperature of the fluid to be measured, and pressurizing the fluid to be measured; to execute the step of determining the reference solid particles at the position where the solid particles are most densely suspended in the closed container.
[0031] A measuring device for the critical density of a fluid, which is used to implement the method for measuring the critical density of a fluid as described in any one of the above, and the measuring device includes:
[0032] A closed container for containing the fluid to be measured;
[0033] An injection device for injecting the fluid to be measured into the closed container;
[0034] A plurality of solid particles with different densities within the solid density range; wherein, the density difference between any one of the solid particles and the adjacent solid particle with the smallest density difference is not greater than a set density difference; the theoretical critical density of the fluid to be measured is within the solid density range
[0035] A constant temperature device for controlling the fluid to be measured in the closed container to maintain at the critical temperature;
[0036] A pressure measuring device for monitoring the top pressure and bottom pressure of the closed container;
[0037] A detection device for identifying and determining solid particles located at the position where the pressure in the closed container is equal to the critical pressure;
[0038] A controller connected to the detection device for determining the critical density of the fluid to be measured according to the density of the solid particles located at the position of the critical pressure.
[0039] In an alternative embodiment of the present application, the solid particles are solid spheres with a diameter between 1 mm and 5 mm; and each solid particle is provided with a corresponding particle identifier;
[0040] The set density difference is 0.001 g / L;
[0041] Each of the solid particles has a particle structure with density changing in equal density differences in a set solid density range.
[0042] In an alternative embodiment of the present application, each of the solid particles has a particle structure with different densities prepared by mixing at least two different material substances, namely a first material substance and a second material substance, in different proportions; wherein, the density of the first material substance is greater than the theoretical critical density, and the second material substance is less than the critical density;
[0043] And / or, the solid particles have a particle structure with different densities prepared by filling different volume ratios of air bubbles into a material substance with a density greater than the theoretical critical density.
[0044] A method and device for measuring the critical density of a fluid provided by the present invention. The method for measuring the critical density of a fluid includes selecting a plurality of solid particles with different densities in a solid density range according to the theoretical critical density of the fluid to be measured; wherein, the density difference between any one solid particle and the adjacent solid particle in density is not greater than the set density difference; the theoretical critical density is within the solid density range; putting each solid particle into a closed container; at the critical temperature of the fluid to be measured, filling the fluid to be measured into the closed container and pressurizing the fluid to be measured until the closed container filled with the fluid to be measured has a top pressure less than the critical pressure of the fluid to be measured and a bottom pressure greater than the critical pressure; determining a reference solid particle at the position where the solid particles are most densely suspended and distributed in the closed container, and determining the critical density of the fluid to be measured according to the density of the reference solid particle.
[0045] In this application, the characteristic that the pressure of a fluid changes gradually in the vertical direction in a gravitational field is utilized. As a result, the pressure at the top of the fluid in a closed container is less than the critical pressure and the pressure at the bottom is greater than the critical pressure at the critical temperature. This makes it inevitable that the pressure of the fluid at a certain position in the closed container is equal to the critical pressure. And along with the gradual change of the fluid pressure in the vertical direction within the closed container, the density of the fluid also changes gradually in the vertical direction. Thus, in this application, multiple solid particles with different densities are mixed and placed in the fluid. Based on the suspension characteristics of the solid particles, each solid particle will ultimately be suspended at the height position in the fluid where its density is the same. Therefore, the density of the solid particle that is exactly suspended at the position of the critical pressure in the fluid must be the same as the critical density of the fluid. Based on this, the solid particle located at the position in the fluid where the pressure is equal to the critical pressure can be identified and determined. Based on the density of this solid particle, the critical density of the fluid can be determined. Compared with the traditional method of measuring the critical density of a fluid, the critical density of the fluid measured in this application is more accurate, and the measurement result is more accurate and reliable. BRIEF DESCRIPTION OF THE DRAWINGS
[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.
[0047] Figure 1 It is a schematic flowchart of the method for measuring the critical density of a fluid provided by an embodiment of this application;
[0048] Figure 2 It is a schematic diagram of the framework structure of the device for measuring the critical density of a fluid provided by an embodiment of this application;
[0049] Figure 3 It is another schematic flowchart of the method for measuring the critical density of a fluid provided by an embodiment of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0050] The core of the present invention is to provide a method and device for measuring the critical density of a fluid, which can achieve more accurate measurement of the critical density of the fluid.
[0051] In order to enable those skilled in the art to better understand the solution of the present invention, the following will further elaborate on the present invention in combination with the drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.
[0052] As Figure 1 and Figure 2 shown, Figure 1 FIG. is a schematic flowchart of a method for measuring the critical density of a fluid provided by an embodiment of the present application; Figure 2 FIG. is a schematic diagram of the frame structure of a device for measuring the critical density of a fluid provided by an embodiment of the present application.
[0053] In an alternative embodiment of the present application, the method for measuring the critical density of the fluid may include:
[0054] S11: According to the theoretical critical density of the fluid to be measured, select a plurality of solid particles with different densities in the solid density range; wherein, the density difference between any two adjacent solid particles is not greater than the set density difference; the theoretical critical density is within the solid density range.
[0055] It can be understood that the theoretical critical density in this embodiment may be a generally known approximate theoretical critical density of the fluid to be measured 2 in the industry, or determined by other rough means, and there is no high requirement for its accuracy, as long as it roughly reflects the critical density of the fluid to be measured 2.
[0056] In this embodiment, the middle value of the solid density range where the density of each selected solid particle 3 is located may be equal to or close to the theoretical critical density.
[0057] In addition, in the process of selecting each solid particle 3 in this embodiment, two adjacent solid particles 3 in terms of density refer to that if each solid particle 3 is sorted in ascending order of density, any two adjacent solid particles 3 are two adjacent solid particles 3 in terms of density.
[0058] On this basis, the density difference between any two adjacent solid particles 3 in this embodiment is not greater than the set density difference, that is, to ensure that the density change gradient of each solid particle 3 is not too large, thereby ensuring the accuracy of the critical density of the fluid to be measured 2 measured by the density of each solid particle 3. Obviously, the density difference between each adjacent solid particle 3 is also the maximum error of the finally measured critical density of the fluid to be measured 2; therefore, in practical applications, the density difference between adjacent solid particles 3 is not greater than the set density difference, and the set density difference can be set to 3% of the theoretical critical density, that is, to ensure that the accuracy of the measured critical density reaches three percent, or it can be 0.001 g / L.
[0059] In addition, the densities of the selected solid particles 3 in this embodiment may change at equal density differences within the solid density range; that is, the density difference between any two adjacent solid particles 3 is equal.
[0060] Of course, in practical applications, it is not ruled out that the density between each solid particle 3 does not change with an equal density difference. For example, one-third of the solid particles 3 whose density is closer to the theoretical critical density can have a smaller equal density difference, while the remaining two-thirds of the solid particles 3 can have a larger equal density difference. For example, the density difference between solid particles 3 with adjacent densities in each solid particle 3 changes gradually, and the closer the density is to the theoretical critical density, the smaller the density difference between the adjacent solid particles 3. Conversely, the greater the difference between the density and the theoretical critical density, the greater the density difference between the adjacent solid particles 3. The technical solution in the present application can also be implemented, and this will not be repeated in the present application.
[0061] In addition, in order to obtain the solid particles 3 that meet the requirements, each solid particle 3 may be a particle structure with different densities formed by mixing at least two different materials, a first material and a second material, in different proportions; wherein the density of the first material is greater than the theoretical critical density, and the density of the second material is less than the critical density;
[0062] And / or, the solid particles 3 may be a particle structure with different densities formed by filling a material having a density greater than a theoretical critical density with bubbles of different volume proportions.
[0063] In addition, the solid particles 3 may preferably be solid spheres to reduce the resistance of the solid particles 3 moving up and down in the fluid 2 to be measured as much as possible. The diameter of the solid particles 3 may be 1 mm to 5 mm.
[0064] S12: Put each solid particle into a closed container.
[0065] S13: At the critical temperature of the fluid to be measured, the fluid to be measured is filled into a closed container and pressurized until the closed container is filled with the fluid to be measured, and the top pressure is less than the critical pressure of the fluid to be measured and the bottom pressure is greater than the critical pressure.
[0066] It should be noted that the closed container 1 in this embodiment can be placed in a heat preservation device, such as a constant temperature water tank or a constant temperature box, and the temperature of the constant temperature water tank or the constant temperature box is adopted.
[0067] In addition, the closed container 1 in this embodiment can be a container with a fixed volume or a container with a compressible volume, which is not specifically limited in this embodiment. In addition, the closed container 1 is provided with a pressure sensor at least at its top and bottom, and then the top pressure and the bottom pressure of the closed container 1 are measured as the fluid 2 to be measured is filled into the closed container 1.
[0068] Taking the closed container 1 with a fixed volume as an example, when the fluid 2 to be measured at the critical temperature is filled into the closed container 1, as the filling amount of the fluid 2 to be measured increases, when the closed container 1 is completely filled with the fluid 2 to be measured, and then the fluid 2 to be measured is continuously filled, the pressure of the fluid 2 to be measured in the closed container 1 will increase as the filling amount of the fluid 2 to be measured increases, until the top pressure measured at the top of the closed container 1 is less than the critical pressure of the fluid 2 to be measured, and the pressure at the bottom of the closed container 1 is greater than the pressure of the fluid 2 to be measured, then the filling of the fluid 2 to be measured can be stopped.
[0069] Taking the closed container 1 with a compressible volume as an example, after the closed container 1 is filled with a certain mass of the fluid 2 to be measured, the closed container 1 can be compressed, thereby increasing the pressure of the fluid 2 to be measured in the closed container 1 until the top pressure measured at the top of the closed container 1 is less than the critical pressure of the fluid 2 to be measured, and the pressure at the bottom of the closed container 1 is greater than the pressure of the fluid 2 to be measured.
[0070] Whether the closed container 1 is a container with a fixed volume or a container with a compressible volume, when injecting the fluid 2 to be measured into the closed container 1 or compressing the volume of the closed container 1, the pressure of the fluid 2 to be measured in the closed container 1 will inevitably undergo a fluctuating change process; in this embodiment, as long as the top pressure is less than the critical pressure and the bottom pressure is greater than the critical pressure in the final stable state of the fluid 2 to be measured in the closed container 1, specifically, the pressure differences between the top pressure and the bottom pressure and the critical pressure can both be not less than 100 Pa.
[0071] In practical applications, after injecting the fluid 2 to be measured into the closed container 1 or after compressing the closed container 1, the closed container 1 should be kept at the critical temperature condition and left standing for at least 1 h in a state where the top pressure is greater than the critical pressure and the bottom pressure is greater than the critical pressure.
[0072] In addition, whether the closed container 1 is a container with a fixed volume or a container with a compressible volume, only the single substance of the fluid 2 to be measured should be filled in the closed container 1, and no impurities such as air should be included. Specifically, the inside of the closed container 1 can be evacuated before the fluid 2 to be measured is filled into the closed container 1.
[0073] S14: Identify and determine the solid particles at the position in the closed container where the pressure is equal to the critical pressure, and determine the critical density of the fluid to be measured based on the density of the solid particles at the position of the critical pressure.
[0074] As described above, for the closed container 1 in the gravitational field, when the closed container 1 is filled with the fluid 2 to be measured, and the pressure at the top of the closed container 1 is less than the critical pressure while the pressure at the bottom is greater than the critical pressure, the fluid pressure in the vertical direction inside the closed container 1 gradually increases from top to bottom; moreover, the change gradient of the fluid pressure in the vertical direction is greater at positions closer to the critical pressure, and smaller at positions farther away from the critical pressure; correspondingly, the fluid density in the closed container 1 also obviously increases gradually from top to bottom in the vertical direction, and the change gradient of the fluid density is greater at positions closer to the critical pressure, and smaller at positions farther away from the critical pressure. And the suspension position of each solid in the fluid 2 to be measured is at the position where the fluid density is the same as the density of the solid particles 3. Based on this, this application can utilize this characteristic to identify the solid particles 3 at the position of the critical pressure.
[0075] Taking the example where the density of each solid particle 3 in the closed container 1 changes with equal density difference within the set solid density range, obviously, at positions closer to the critical pressure in the closed container 1, the distribution positions of the solid particles 3 are more concentrated. Therefore, in this embodiment, the reference solid particle 3 at the position where the solid particles 3 are most densely suspended in the closed container 1 can be determined, and the critical density of the fluid 2 to be measured can be determined according to the density of the reference solid particle to be measured.
[0076] In an optional implementation manner of this embodiment, the process of identifying the reference solid particle 3 and determining the critical density may further include:
[0077] S141: Collect the height data of the distribution of each solid particle in the closed container;
[0078] S142: According to the height difference between two adjacent solid particles in the distribution;
[0079] S143: If there is a minimum height difference between two adjacent solid particles in the middle area of the closed container, then use the two solid particles 3 with the minimum height difference as the reference solid particles;
[0080] S144: Determine the critical density of the fluid to be measured according to the average density of the two reference solid particles;
[0081] S145: If there are two equal height differences corresponding to three successively adjacent solid particles in the middle area of the closed container, and these two height differences are the smallest compared to the other height difference data, then use the solid particle at the middle position among the three solid particles as the reference solid particle;
[0082] S146: Use the density of the reference solid particle as the critical density of the fluid to be measured.
[0083] In this embodiment, considering that the fluid 2 to be measured may exhibit critical opalescence under the critical state of critical temperature and critical pressure, which may lead to the non-transmission of the fluid 2 to be measured for visible light, and thus the position of the solid particles 3 is not visible. Therefore, in this embodiment, X-ray can be used to scan the solid particles 3 from at least two different directions to obtain the height data of each solid particle 3 in the closed container 1. In practical applications, the X-ray can scan each solid particle 3 around the closed container 1 for one circle, and finally identify the positions of each solid particle 3.
[0084] In addition, particle identifiers should also be provided on the solid particles 3. When the X-ray scans and identifies the height data of each solid particle 3, the particle identifiers of each solid particle 3 should also be identified.
[0085] On this basis, the height differences between two adjacent solid particles 3 among each solid particle 3 are determined in sequence. Obviously, the smaller the height difference between two adjacent solid particles 3, that is, the denser the distribution of the solid particles 3. Thus, when there are two adjacent solid particles 3 with the smallest height difference among each solid particle 3, they can be used as the two reference solid particles 3 with the densest distribution. The position of the critical pressure in the fluid 2 to be measured is approximately located between the two reference solid particles 3. Thus, the average density of the two reference solid particles 3 can be used as the density of the fluid 2 to be measured.
[0086] However, in practical applications, there may also be three continuously distributed solid particles 3, where the height differences between the solid particle 3 in the middle position and the two solid particles 3 above and below it are the same and the smallest among all the height difference data. Thus, the solid particle 3 in the middle position among the three solid particles 3 can be used as the reference solid particle 3, and the density of this reference solid particle 3 can be used as the critical density of the fluid 2 to be measured.
[0087] In addition, it should also be noted that in this embodiment, during the process of calculating the height differences of each solid particle 3, only the height difference data of the solid particles 3 located in the middle region of the closed container 1 can be calculated, so as to avoid the problem that there are a large number of solid particles 3 accumulating at the top and bottom of the closed container 1 due to the relatively small pressure change range from the top to the bottom of the closed container 1 compared to the solid density range of the solid particles 3. In practical applications, the height difference data corresponding to the solid particles 3 in the section at the top of the closed container 1 accounting for one-fourth of the total height of the closed container 1, and the height data corresponding to the solid particles 3 in the section at the bottom of the closed container 1 accounting for one-fourth of the total height of the closed container 1 can be excluded. Finally, only the solid particles 3 with the densest distribution need to be identified in the middle half section of the closed container 1.
[0088] Of course, the present application does not necessarily identify the solid particles 3 located at the position where the pressure is equal to the critical pressure in the closed container 1 by identifying the height difference data between each adjacent solid particle 3. For example, a series of pressure gauges are arranged in sequence along the height direction in the closed container 1, and the height where the critical pressure is located is measured by the pressure gauges, and then the solid particles 3 located at this height position are determined. In addition, in practical applications, the fluid 2 to be tested in the closed container 1 whose pressure is equal to or lower than the fluid pressure will present a supercritical state. For some special fluids, an obvious critical line will be shown in the closed container 1 at the position where the pressure is equal to the critical pressure. Therefore, the solid particles 3 at the position where the fluid pressure is equal to the critical pressure can be directly determined based on the critical line, and the technical solution of the present application can also be realized.
[0089] Based on the above, in the method for measuring the critical density of a fluid in the present application, a large number of solid particles 3 can be placed in the closed container 1 at one time according to the above embodiment, for example, the number of the solid particles 3 is not less than 100, and the density difference between the solid particles 3 with adjacent densities is as small as possible, thereby minimizing the error of the critical density of the fluid 2 to be measured that is finally measured.
[0090] However, in order to reduce the difficulty of identifying the positions of the solid particles 3 , only a few solid particles 3 may be selected each time, and repeated measurements may be performed multiple times to finally determine the particles of the fluid 2 to be measured.
[0091] Specifically, refer to Figure 3 In an optional embodiment of the present application, the method for measuring the critical density of the fluid may include:
[0092] S21: According to the theoretical critical density of the fluid to be measured, multiple solid particles with different densities in the solid density range are selected; wherein the density difference between any two solid particles with adjacent densities is not greater than the set density difference; and the theoretical critical density is within the solid density range;
[0093] S22: putting each solid particle into a closed container;
[0094] S23: at the critical temperature of the fluid to be measured, the fluid to be measured is filled into a closed container and pressurized until the closed container is filled with the fluid to be measured, and the top pressure is less than the critical pressure of the fluid to be measured and the bottom pressure is greater than the critical pressure;
[0095] S24: collecting height data of each solid particle distributed in the closed container, and determining the height difference between any two adjacent solid particles;
[0096] S25: Determine the highest and lowest solid particles among multiple successively adjacent solid particles distributed in the middle section of the closed container and with corresponding height differences not greater than a preset height difference threshold according to each height difference;
[0097] S26: Judge whether the size of the density interval between the density of the highest solid particle and the density of the lowest solid particle is less than a set interval threshold. If not, proceed to S27; if so, proceed to S28;
[0098] S27: Take the density interval between the density of the highest solid particle and the density of the lowest solid particle as the new solid density interval, select multiple solid particles with different densities and within the solid density interval, and proceed to S22;
[0099] S28: Identify and determine the solid particles located at the position in the closed container where the pressure is equal to the critical pressure, and determine the critical density of the fluid to be measured based on the density of the solid particles at the position of the critical pressure.
[0100] In this embodiment, the solid density interval of the solid particles 3 is gradually reduced by repeating the measurement in multiple times, so that a group of solid particles 3 with densities relatively close to the critical density of the fluid to be measured 2 are finally selected; the method for measuring the critical density of the fluid to be measured 2 in this embodiment reduces the number of solid particles 3 selected each time on the basis of ensuring the accuracy of the measured critical density, and the closed container 1 used is also relatively small, thereby being able to ensure to a certain extent the difficulty of controlling the fluid to be measured 2 in the closed container 1 at the critical temperature and critical pressure.
[0101] In summary, in this application, the characteristic that the pressure of the fluid in the gravitational field gradually changes in the vertical direction is utilized, so that the pressure at the top of the closed container is less than the critical pressure and the pressure at the bottom is greater than the critical pressure at the critical temperature of the fluid, which makes the pressure of the fluid at a certain position in the closed container necessarily equal to the critical pressure, and along with the gradual change of the fluid pressure in the vertical direction in the closed container, the density of the fluid also gradually changes in the vertical direction; thus, in this application, multiple solid particles with different densities are mixed and placed in the fluid. Based on the suspension characteristics of the solid particles, each solid particle will ultimately be suspended in the fluid at the height position with the same density as it in sequence. Therefore, the density of the solid particle that is exactly suspended at the position of the critical pressure in the fluid must be the same as the critical density of the fluid; on this basis, the greater the change gradient of the pressure of the fluid in the closed container in the height direction near the critical pressure, based on this, the solid particles located at the position in the fluid where the pressure is equal to the critical pressure can be identified and determined, and the critical density of the fluid can be determined based on the density of the solid particle. Compared with the traditional method for measuring the critical density of the fluid, the critical density of the fluid measured in this application is more accurate, and the measurement result is more accurate and reliable.
[0102] This application also provides a measurement device for the critical density of a fluid, which is characterized in that it is used to implement the measurement method for the critical density of a fluid as described in any one of the above, and the measurement device for the critical density of a fluid may include:
[0103] A closed container 1 for containing the fluid 2 to be measured;
[0104] An injection device for injecting the fluid 2 to be measured into the closed container 1;
[0105] Multiple solid particles 3 with different densities in the solid density range; among them, the density difference between any two adjacent solid particles 3 is not greater than the set density difference; the theoretical critical density of the fluid 2 to be measured is within the solid density range
[0106] A constant temperature device 5 for controlling the fluid 2 to be measured in the closed container 1 to maintain at the critical temperature;
[0107] A pressure measuring device for monitoring the top pressure and bottom pressure of the closed container 1;
[0108] A detection device 6 for identifying and determining the solid particle 3 at the position in the closed container 1 where the pressure is equal to the critical pressure;
[0109] And a controller 7 connected to the detection device, which is used to determine the critical density of the fluid to be measured according to the density of the solid particle 3 at the position of the critical pressure.
[0110] The closed container 1 in this embodiment may be an equilibrium still; and the constant temperature device 5 for controlling the fluid 2 to be measured at the critical temperature may be a constant temperature box filled with a constant temperature medium, and the equilibrium still may be built inside the constant temperature box; in addition, the pressure measuring device may be a thin film pressure sensor arranged at the top and bottom of the closed container 1; this thin film pressure sensor may be wirelessly communicatively connected to the controller 7 outside the closed container 1 and output the pressure to the controller 7 in real time; the detection device 6 for detecting and determining the distribution position of the solid particle 3 may be an X-ray scanning device, which can measure each solid particle 3 through the fluid 2 to be measured with critical opalescence phenomenon.
[0111] It can be understood that in the embodiment where the densities of the solid particles 3 change in equal density differences within the solid density range, the detection device 6 can be used to detect and determine the distribution positions of the solid particles 3 in the closed container 1, and then determine the reference solid particle 3 at the position where the solid particles 3 are most densely suspended and distributed in the closed container 1, and determine the critical density of the fluid 2 to be measured according to the density of the reference solid particle 3.
[0112] Further optionally, the solid particle 3 in this embodiment may be a solid sphere with a diameter between 1 mm and 5 mm; and each solid particle 3 is provided with a corresponding particle identification;
[0113] Each solid particle 3 has a particle structure with equal density differences changing in sequence within a set solid density range; the set density difference is 0.001 g / L.
[0114] In another alternative embodiment of the present application, each solid particle 3 has a particle structure with different densities prepared by mixing at least two different material substances, namely a first material substance and a second material substance, in different proportions; wherein, the density of the first material substance is greater than the theoretical critical density, and the second material substance is less than the critical density.
[0115] And / or, the solid particle 3 has a particle structure with different densities prepared by filling different volume ratios of air bubbles into a material substance with a density greater than the theoretical critical density.
[0116] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes the inherent elements thereof. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element. In addition, the parts of the above technical solutions provided in the embodiments of the present application that are consistent with the corresponding technical solutions in the prior art in terms of implementation principles are not described in detail to avoid excessive elaboration.
[0117] Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the present invention.
Claims
1. A method for measuring the critical density of a fluid, characterized in that: include: According to the theoretical critical density of the fluid to be measured, multiple solid particles with different densities in the solid density range are selected; wherein the density difference between any two solid particles with adjacent densities is not greater than the set density difference; and the theoretical critical density is within the solid density range; Putting each of the solid particles into a closed container; At the critical temperature of the fluid to be measured, the fluid to be measured is filled into the closed container and the fluid to be measured is pressurized until the closed container is filled with the fluid to be measured, the top pressure is less than the critical pressure of the fluid to be measured and the bottom pressure is greater than the critical pressure; Solid particles located at a position in the closed container where the pressure is equal to the critical pressure are identified and determined, and the critical density of the fluid to be measured is determined based on the density of the solid particles located at the position of the critical pressure.
2. The method for measuring the critical density of a fluid as claimed in claim 1, characterized in that: Select multiple solid particles with different densities in the solid density range, including: A plurality of solid particles whose densities vary in sequence with equal density differences are selected within the solid density interval; and the density difference between two solid particles with adjacent densities is not greater than 3% of the theoretical critical density of the fluid to be measured.
3. The method for measuring the critical density of a fluid as claimed in claim 2, characterized in that: Identifying and determining a solid particle located at a position in the closed container where the pressure is equal to the critical pressure, comprising: A reference solid particle at a position where the solid particles are most densely distributed in the closed container is determined, and a critical density of the fluid to be measured is determined according to the density of the reference solid particle.
4. The method for measuring the critical density of a fluid as claimed in claim 2, characterized in that: Determining a reference solid particle at a position where the solid particles are most densely distributed in the closed container, and determining a critical density of the fluid to be measured according to the density of the reference solid particle, comprising: Collecting height data of each solid particle distributed in the closed container; According to the height difference between two adjacently distributed solid particles; If there are two adjacent solid particles in the middle area of the closed container with the smallest height difference, the two solid particles with the smallest height difference are taken as the reference solid particles; Determining the critical density of the fluid to be measured according to the average density of the two reference solid particles; If there are three solid particles adjacent to each other in the middle area of the closed container, and two of the height differences are equal and the height difference is the smallest among all the height difference data, then the solid particle located in the middle position among the three solid particles is used as the reference solid particle; The density of the reference solid particles is used as the critical density of the fluid to be measured.
5. The method for measuring the critical density of a fluid as claimed in claim 4, characterized in that: Collecting height data of each solid particle distribution in the closed container, including: The solid particles are scanned from at least two different directions using X-rays to obtain height data of each of the solid particles in the closed container.
6. The method for measuring the critical density of a fluid according to claim 1, characterized in that: The top pressure is less than the critical pressure of the fluid to be measured and the bottom pressure is greater than the critical pressure, including: The pressure difference between the critical pressure and the top pressure, and the pressure difference between the bottom pressure and the critical pressure are both not less than 100 Pa.
7. The method for measuring the critical density of a fluid according to any one of claims 1 to 6, characterized in that: After the fluid to be measured is filled into the closed container and pressurized at the critical temperature of the fluid to be measured, and before the reference solid particles at the position where the solid particles are most densely distributed in the closed container are determined, the method further includes: Collecting height data of each solid particle distributed in the closed container, and determining the height difference between any two adjacent solid particles; According to each of the height differences, determining the highest solid particle and the lowest solid particle among a plurality of sequentially adjacent solid particles distributed in the middle section of the closed container and corresponding to a height difference not greater than a preset height difference threshold; Taking the density interval between the density of the highest solid particles and the density of the lowest solid particles as a new solid density interval; According to the new solid density range, reselecting a plurality of solid particles with different densities within the solid density range; The steps of placing each of the solid particles into a closed container, filling the fluid to be tested into the closed container and pressurizing the fluid to be tested at the critical temperature of the fluid to be tested are repeated; and the step of determining the reference solid particles at the position where the solid particles are most densely suspended in the closed container is performed.
8. A device for measuring critical density of a fluid, characterized in that: A method for measuring the critical density of a fluid according to any one of claims 1 to 7, wherein the measuring device comprises: A closed container for containing the fluid to be tested; An injection device for injecting the fluid to be tested into the closed container; A plurality of solid particles having different densities in a solid density range; wherein the density difference between any of the solid particles and an adjacent solid particle having the smallest density difference is not greater than a set density difference; and the theoretical critical density of the fluid to be measured is within the solid density range; A thermostatic device for controlling the fluid to be measured in the closed container to maintain a critical temperature; A pressure measuring device for monitoring the top pressure and the bottom pressure of the closed container; A detection device for identifying and determining solid particles located at a position in the closed container where the pressure is equal to the critical pressure; The controller connected to the detection device is used to determine the critical density of the fluid to be measured according to the density of the solid particles located at the position of the critical pressure.
9. The fluid critical density measuring device according to claim 8, characterized in that: The solid particles are solid spheres with a diameter between 1 mm and 5 mm; and each of the solid particles is provided with a corresponding particle identification; The set density difference is 0.001 g / L; Each of the solid particles is a particle structure whose density changes sequentially with equal density difference within a set solid density range.
10. The fluid critical density measuring device according to claim 8, characterized in that: Each of the solid particles is a particle structure with different densities formed by mixing at least two different materials, a first material and a second material, in different proportions; wherein the density of the first material is greater than the theoretical critical density, and the density of the second material is less than the critical density; And / or, the solid particles are particle structures with different densities formed by filling a material having a density greater than the theoretical critical density with bubbles of different volume proportions.