CN110174335B - Fiber material equivalent maximum aperture obtaining system and method based on measurement - Google Patents
Fiber material equivalent maximum aperture obtaining system and method based on measurement Download PDFInfo
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- CN110174335B CN110174335B CN201910183144.8A CN201910183144A CN110174335B CN 110174335 B CN110174335 B CN 110174335B CN 201910183144 A CN201910183144 A CN 201910183144A CN 110174335 B CN110174335 B CN 110174335B
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/088—Investigating volume, surface area, size or distribution of pores; Porosimetry
- G01N15/0893—Investigating volume, surface area, size or distribution of pores; Porosimetry by measuring weight or volume of sorbed fluid, e.g. B.E.T. method
Abstract
The invention provides a system and a method for obtaining equivalent maximum pore diameter of a fiber material based on measurement, wherein the system comprises a measuring chamber 28, an air processing system, an image control system 11 and a central processing system 12, a fractal model is established by adjusting a constant temperature and humidity environment, acquiring a water absorption image of the porous material, measuring the weight change of water and the like and combining factors such as the evaporation rate of water on the surface of the material, and the equivalent maximum pore diameter of the porous material is finally calculated. The invention utilizes a system combining real-time dynamic image acquisition and weight acquisition to quickly, continuously, automatically and synchronously observe the water absorption process of the material and obtain the porosity and permeability of the material. And establishing a relation between the macroscopic water absorption characteristic (water absorption height/weight) of the material and the microstructure parameters of the material by virtue of a fractal theory, further obtaining the microstructure characteristics of the material, improving the experimental accuracy, introducing the surface evaporation rate obtained by the experiment, and improving the prediction precision of the model.
Description
Technical Field
The invention belongs to the technical field of research on micro-scale macro parameters of porous materials by utilizing a fractal theory and a dynamic image processing and weight acquisition technology, and particularly relates to a system and a method for acquiring equivalent maximum pore diameter of a fiber material based on measurement.
Background
Evaporative cooling is a natural cooling method that absorbs latent heat of vaporization in air by using water evaporation. Because a compressor of the traditional vapor compression type air conditioning system is not used, the power consumption is very low, the pollution to the environment is very small, and the air conditioning system is an energy-saving and environment-friendly cooling mode. Typical evaporative cooling means include both direct and indirect evaporative cooling. Compared with direct evaporative cooling, the indirect evaporative cooling mode does not increase the moisture content of the supplied air, the comfort level of the indoor environment is better, and the indirect evaporative cooling mode is more and more applied to building cooling. The indirect evaporation cooling device realizes heat and mass transfer through an evaporation material, the capillary water absorption of the material directly influences the efficiency of the cooling device, and the water absorption of the material is mainly determined by the pore microstructure parameters, so that the research on how to measure the microstructure macro parameters of the porous material reflecting the water absorption is necessary.
At present, the traditional method for directly measuring the pore diameter of the porous material comprises a microscopic measurement method, the method for indirectly measuring the pore diameter comprises a bubble pressure method, a mercury pressing method, a penetration method and the like, the method for measuring the porosity comprises a penetration method based on Darcy's law, but the method is limited by factors such as instruments, environments, technical conditions and the like, and the measurement methods cannot rapidly and directly obtain macroscopic parameters reflecting the integral microstructure of the material and cannot intuitively observe the physical process concerned by people. Secondly, the traditional instruments for observing the physical process of water absorption of the porous material are a gram absorption tester (for measuring the water absorption height) and a precision balance (for measuring the water absorption weight), the gram absorption tester adopts a static measurement method (an observer observes the water absorption height at different moments through a ruler), and the dynamic change of the water absorption height cannot be rapidly, continuously and accurately obtained. In addition, the conventional precision balance for measuring the water absorption change of the porous material is not synchronous with the water absorption height measurement, so that the micro-structural parameters such as the pore diameter, the porosity, the permeability and the like of the material cannot be quickly and directly obtained, and the relation between the micro-structural parameters and the macroscopic water absorption (water absorption height and water absorption weight) is established.
Before the present invention was proposed, we made some relevant research work on water absorption of evaporation materials (Ener gyandBuildings148(2017) 199-210, http:// dx. doi. org/10.1016/j. enbuild.2017.04.012). The absorption heights of various fibrous materials were tested at various times using a conventional klemm absorptiometer. And the mass change of the material before and after water absorption is measured by adopting a precision balance, so that the water absorption capacity of the material is obtained. However, this test method is still a discontinuous static measurement and cannot indirectly acquire the microstructure of the material.
Fractal is an emerging method for characterizing the complex pore microstructure of porous materials, which makes it possible to quantitatively describe the microstructure and macroscopic properties of porous materials. The microstructure of the porous material shows self-similarity characteristics in a certain range, so that the fractal geometry can be used for quantitative characterization. Although the existing fractal theory can establish the relationship between the microscopic parameters such as the fractal dimension, the fractal coefficient, the pore diameter and the like of the pore structure and the macroscopic water absorption performance, various microscopic and macroscopic measuring instruments are required to determine the microscopic structure parameters such as the pore size distribution, the porosity, the permeability and the like of the material in advance, and the relationship between the microscopic structure of the material and the water absorption performance cannot be established quickly and directly. In addition, the existing fractal model does not consider the influence of the water evaporation rate of the material surface on the water absorption of the material.
In summary, the following steps:
1. the traditional bubble pressure method, mercury pressing method and infiltration method for obtaining material aperture and the equipment such as Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM) for analyzing material microstructure are limited by the factors such as instruments, environment and technical conditions, cannot rapidly and directly obtain macroscopic parameters reflecting the whole microstructure, and cannot intuitively observe the water absorption physical process concerned by people.
2. The traditional instrument for measuring the water absorption height of the porous fiber material is a gram absorption determinator, which is a static method for measuring the water absorption height, cannot realize accuracy (especially in the initial stage of experiment, the measurement error of manual observation height and reading is large, and rapid change of the water absorption height cannot be accurately obtained), rapid and continuous measurement, and cannot obtain parameters such as porosity, permeability, pore microstructure and the like of the material.
3. The traditional method for researching the water absorption height and the fractal theory of the porous material does not consider the influence of the water on the surface of the material on the natural evaporation of the ambient environment. Under different ambient air temperature, humidity and water temperature conditions, the evaporation rate of the water on the surface of the material is different, and the water absorption height/performance of the material is directly influenced. In conventional methods, these factors are uncontrollable, resulting in less accurate experimental and theoretical methods.
For the above reasons, it is desirable to develop a system and method for obtaining equivalent maximum pore size of fiber material based on measurement, which can solve the above problems.
Disclosure of Invention
The invention provides a system for acquiring equivalent maximum aperture of a fiber material based on measurement by utilizing physical phenomenon experiments and fractal theory, which has the specific technical scheme that:
the system for obtaining the equivalent maximum aperture of the fiber material based on measurement comprises a measuring chamber, an air processing system, an image control system and a central processing system, wherein the air processing system is connected with the measuring chamber through a ventilating pipeline, the image control system and the central processing system are respectively and electrically connected with the measuring chamber, the measuring chamber comprises a partition plate, an air distribution pore plate, a background plate, a horizontal sliding rail, a measuring unit, a light-emitting unit and an image acquisition unit, the horizontal sliding rail is arranged at the bottom of the measuring chamber, the image acquisition unit, the light-emitting unit and the measuring unit are sequentially arranged on the horizontal sliding rail in parallel, and the air distribution pore plate is arranged on the upper part of the background plate on the side wall of the partition plate of the background plate; the image acquisition unit is respectively and electrically connected with the image control system and the central processing system, and the measurement unit is respectively and electrically connected with the image control system and the central processing system;
furthermore, the measuring unit comprises a protective cover, a vertical slide rail, a weight measuring device, a liquid containing device, an experimental material clamping device, a liquid temperature testing probe and an environment temperature and humidity sensor, wherein the protective cover is arranged at the periphery of the measuring unit, the vertical slide rail is arranged on the horizontal slide rail, the weight measuring device is arranged at the bottom of the measuring unit, the liquid containing device is arranged above the weight measuring device, the fixed end of the experimental material clamping device is arranged on the vertical slide rail, the material clamping end is suspended above the liquid containing device, a porous material can be extended into or out of the liquid containing device through the vertical slide rail, the liquid temperature testing probe is arranged in the liquid containing device and is electrically connected with the central processing system, and the environment temperature and humidity sensor is arranged at the top of the inner side of the protective cover and is electrically connected with the central processing system;
further, the measuring unit further comprises a temperature adjusting device;
furthermore, the measuring unit also comprises a temperature controller which is connected with the temperature adjusting device;
further, the air treatment system comprises an air supply unit, a high-efficiency filtering unit, a fan unit, a humidifying unit, a heating unit, a cooling unit, a coarse-effect filtering unit and an air mixing unit which are sequentially connected, wherein the air supply unit is connected with an air supply outlet at the top end of the measuring chamber through a ventilation pipeline, and the air mixing unit is connected with an air return inlet at the bottom end of the measuring chamber through the ventilation pipeline;
preferably, the image acquisition unit comprises an image acquisition support and an image acquisition device arranged on the image acquisition support, and the image acquisition support is arranged on the horizontal slide rail and can slide back and forth relative to the background plate;
the invention also provides a method for obtaining the equivalent maximum aperture of the fiber material based on measurement, which has the specific technical scheme that:
clamping a porous material to be tested on a vertical slide rail through an experiment clamping device, extending a liquid temperature testing probe into the middle lower part of a liquid containing device, and placing the liquid temperature testing probe on a weight measuring device after the liquid containing device is filled with liquid;
adjusting the water temperature in the liquid containing device to enable the water temperature to reach a set value and keeping the water temperature constant; the air conditioning processing system is used for processing fresh air and indoor return air and then sending the processed fresh air and indoor return air into the measuring room;
adjusting the experiment clamping device to enable the porous material to slowly descend, and starting the automatic water absorption capacity measurement and image acquisition functions of a water absorption area by the central processing system when the bottom of the porous material is about to contact the water surface; along with the slow descending and immersion of the porous material in water, the image acquisition unit acquires time-by-time dynamic images of the water absorption height of the porous material at regular intervals and automatically stores the images; meanwhile, the weight measuring device transmits signals to the central processing system, and real-time data of the weight and corresponding time are automatically stored; the central processing system automatically and synchronously records dynamic images and water absorption weight change data of the water migration process;
step four, processing the pictures acquired by the image acquisition unit in batches through a central processing system to obtain the water absorption areas of the porous material at different moments, wherein the average water absorption height of the porous material is the ratio of the water absorption area to the width of the porous material;
measuring the water absorption weight and the water absorption height synchronously with data acquisition, measuring the mass change of the liquid containing device through a weight measuring device, wherein the weight reduced by the liquid containing device is the sum of the water absorption capacity and the surface evaporation capacity of the porous material, and the weight measuring device is connected with a central processing system, and acquires and automatically stores data through the central processing system;
measuring the surface evaporation rate of the porous material in a water absorption saturation state through a weight measuring device;
step seven, obtaining the porosity and permeability of the porous material through experimental data of the water absorption weight and the water absorption height, and establishing the maximum water absorption height h in the porous material by utilizing a fractal modelmaxThe relation among the equivalent maximum aperture lambda max, the porosity phi, the permeability K, the density rho of the immersion liquid, the viscosity coefficient mu, the surface tension sigma, the solid-liquid contact angle theta and the surface evaporation rate me of the porous material;
step eight, obtaining the maximum water absorption height of the porous material through an experiment, and substituting the parameters obtained through the experiment into the relation so as to obtain the equivalent maximum pore diameter of the porous material;
preferably, the fractal model in the step seven is a formula (3) for obtaining the water migration rate according to a Hagen-Poiseulle equation and a fractal theory:
wherein the content of the first and second substances,
Dffractal dimension of pore volume, DTFractal dimension of tortuosity.
Preferably, when DTWhen 1, the formula (3) can be simplified to formula (4):
preferably, the water absorption height will reach a maximum value when dh/dt is 0, which is set to hmaxFrom said formula (4), formula (5) can be solved:
the invention has the following advantages:
1. according to the invention, by combining a physical phenomenon experiment with a fractal model, a macroscopic parameter reflecting the microstructure of the material, namely the equivalent maximum pore diameter, can be rapidly and directly obtained, and microscopic observation and analysis are not required by means of microscopy;
2. the method adopts automatic dynamic image processing and weight acquisition technology, can quickly, accurately and synchronously measure the water absorption height and weight change of the material, and can obtain macroscopic structure parameters (porosity and permeability) reflecting the material;
3. the experimental and theoretical methods (fractal models) adopted by the invention all consider the influence of the evaporation rate of the water on the surface of the material. In the experiment, the temperature, the humidity and the water temperature of the surrounding environment of the sample to be tested are controllable, and the accuracy of the experiment is improved. In addition, the influence of the surface evaporation rate is considered in the fractal model, the surface evaporation rate obtained by the experiment is introduced into the model, and the prediction precision of the model is improved.
Drawings
FIG. 1 is a schematic view of a measuring structure of the present invention (the temperature adjusting means is a radiation plate disposed at the periphery of the liquid containing device);
FIG. 2 is a schematic view of a measuring structure of the present invention (the temperature adjusting means is a heater provided in the liquid containing means);
figure 3 is a graph of the results of an example of a measurement performed using the present invention,
in the figure: 1-a horizontal sliding rail; 1' -a vertical slide; 2-background plate; 3-a porous material; 4-a liquid holding device; 5-temperature regulating means (radiant panel); 5' -temperature regulating means (heater); 6-liquid temperature test probe; 7-a weight measuring device; 8-temperature controller; 9-a light emitting unit; 10-an image acquisition support; 11-an image control system; 12-a central processing system; 13-air distribution pore plate; 14-an image acquisition device; 15-ambient temperature and humidity sensor; 16-an air supply unit; 17-a high efficiency filtration unit; 18-a fan unit; 19-a humidifying unit; 20-a heating unit; 21-a cooling unit; 22-coarse filtration unit; 23-a wind mixing unit; 24-fresh air; 25-return air channel of ventilating duct; 26-air supply channel of ventilation pipeline; 27-a protective cover; 28-a measurement chamber; 29-experimental clamping device; 30-a measurement unit; 31-a separator; 32-exhaust duct of ventilation duct.
Detailed Description
In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.
As shown in fig. 1, the measurement-based fiber material equivalent maximum pore size acquisition system of the present invention comprises a measurement chamber 28, an air handling system, an image control system 11, a central processing system 12, wherein,
the measuring chamber 28 is a constant temperature and humidity measuring chamber, which is enclosed by a partition plate 31 and comprises an air distribution hole plate 13, a background plate 2, a horizontal slide rail 1, a measuring unit 30, a light-emitting unit 9 and an image collecting unit, wherein the image collecting unit consists of an image collecting device 14, namely a CCD camera, and an image collecting bracket 10, the image collecting bracket 10 is arranged on the horizontal slide rail 1, the light-emitting unit 9 is an LED cold light source and is also arranged on the horizontal slide rail 1, the measuring unit 30 comprises a protective cover 27, a vertical slide rail 1 ', a weight measuring device 7, a liquid containing device 4, an experimental material clamping device 29, a liquid temperature testing probe 6 and an environmental temperature and humidity sensor 15, wherein the protective cover 27 is made of organic glass material, the weight measuring device 7, namely a precision analytical balance, is arranged on the horizontal slide rail 1, the liquid containing device 4, namely a beaker, is arranged on the weight measuring device 7, the fixed end of the experimental material clamping device 29 is arranged on the vertical slide rail 1', the clamping end of the device is used for clamping the porous material 3 for the experiment, and the position of the experiment material clamping device 29 on the vertical slide rail 1' is controlled by the image control system 11, so that the porous material 3 can be immersed in the water of the liquid containing device 4 or extend out of the water;
the air processing system is used for controlling the environmental temperature and humidity of the measuring chamber 28, and comprises an air supply unit 16, a high-efficiency filtering unit 17, a fan unit 18, a humidifying unit 19, a heating unit 20, a cooling unit 21, a coarse filtering unit 22 and an air mixing unit 23 which are sequentially connected, wherein the air supply unit 16 is connected with an air supply outlet at the top end of the measuring chamber 28 through an air supply channel 26 of a ventilating duct, the air mixing unit 23 is connected with an air return outlet at the bottom end of the measuring chamber 28 through an air return channel 25 of the ventilating duct, fresh air 24 enters the air processing system through the air mixing unit 23, sequentially passes through the air mixing unit 23, the coarse filtering unit 22, the cooling unit 21, the heating unit 20, the humidifying unit 19, the fan unit 18 and the high-efficiency filtering unit 17 to enable the humidity and the temperature of the air to reach preset values, and is supplied to the air supply outlet at the top end of the measuring chamber 28 through the air return channel 25 of the ventilating duct through the air return outlet at the bottom end of the measuring chamber 28, one part is discharged from an exhaust pipeline 32 of the ventilation pipeline, and the other part enters the air mixing unit 23 to be mixed with the fresh air 24;
the image control system 11 is a controller for horizontal sliding of the CCD camera and vertical sliding of the porous material, and is responsible for the position of the image acquisition unit 14, namely the CCD camera, on the horizontal slide rail and the position of the experiment clamping device 29 on the vertical slide rail;
the central processing system 12 is an electronic computer, and is electrically connected to the CCD camera 14, the environmental temperature and humidity sensor 15, and the liquid temperature test probe 6, respectively, and is configured to collect a water absorption image of the porous material 3, an environmental temperature and humidity of the measurement unit 30, and a water temperature in the liquid containing device 4.
The specific implementation method of the invention is as follows:
firstly, a test preparation stage:
the measured porous material 3 is clamped on a vertical slide rail 1' through an experiment clamping device 29 (the porous material is ensured to be vertical to the horizontal plane), the experiment clamping device 29 is adjusted through an image control system 11, the bottom of the porous material 3 is kept at about 5 cm above a liquid containing device 4 and a beaker, a liquid temperature testing probe 6 extends into the middle lower part of the beaker 4 and does not touch the wall and the bottom of the beaker, and the beaker is placed on a weight measuring device 7, namely a tray of a precision analytical balance, after being filled with liquid. The temperature controller 8 is turned on to set the temperature of the temperature adjusting device 5 or 5', the light emitting unit 9, namely the LED cold light source, is turned on and adjusted to be perpendicular to the background plate 2, the CCD camera 14 is turned on to adjust the visual field, the whole porous material 3 to be measured is displayed in the visual field range of the CCD camera 14, the porous material 3 to be measured is arranged in the protective cover 27 of the measuring chamber 28, the temperature and humidity sensor 15 is arranged at a proper position in the protective cover 27, the air processing system is adjusted according to the environmental temperature and humidity required by the test, the fresh air 24 and the indoor return air are mixed, the mixed air is sent into the partition plate 31 of the measuring chamber 28 after being processed, the air is uniformly supplied by the air distribution pore plate 13, the central processing system 12, namely the electronic computer, reads the data of the environmental temperature and humidity sensor 15 and the liquid temperature sensor 6, and the test can be started after the data meet the test requirement and are stable for 15 minutes.
II, a testing stage:
two persons are needed to complete the experiment operation in the test process, the first person adjusts the experiment clamping device 29 through the image control system 11 to enable the porous material 3 to slowly descend, the second person operates the central processing system 12, namely the electronic computer, opens the analytical balance data acquisition software and the image processing software, sets the image acquisition parameters of the CCD camera, and prepares to enter the automatic continuous water absorption measurement state and the water absorption area image acquisition state; when the bottom of the porous material 3 can contact the water surface within 2-4 seconds, the first person sends an instruction, and the second person operates an electronic computer to start the automatic water absorption capacity measurement and the image acquisition function of the water absorption area; at this time, the weight measuring device 7, i.e. the precision analytical balance, transmits a signal to the electronic computer through the data line, and real-time data of the weight and corresponding time are stored in an Excel table of the electronic computer. Meanwhile, the CCD camera 14 performs image acquisition at regular intervals at a frequency set by the electronic computer, and stores the acquired images in a designated folder of the electronic computer. The first person continues to adjust the experiment clamping device 29 to slowly descend the porous material 3 to be immersed in the water until the bottom of the material extends to about 2mm below the water surface; then, the water is influenced by the capillary force of the material and vertically migrates upwards, and the dynamic image and the water absorption weight change data of the water migration process are automatically and synchronously recorded by the electronic computer; the operator only needs to observe the electronic computer and the experimental device at the moment, so that accidents are prevented, and the electronic computer can automatically stop collecting the image and weight data after the preset time is reached.
Thirdly, a data processing stage:
the average water absorption height treatment method comprises the following steps: deleting the image which is not contacted with the water surface in the collected image, and regarding the image which is just contacted with the water surface as a first water absorption image; carrying out uniform and standard automatic batch cutting processing on the material water absorption pictures through image processing software, taking care that all water absorption areas are contained in a cutting frame, carrying out automatic batch dyeing processing on all the water absorption pictures through the image processing software to obtain the water absorption area corresponding to each picture, and dividing the water absorption area by the width of the porous material 3 to obtain the average water absorption height corresponding to each picture; because each picture is collected at a fixed frequency, if the time corresponding to the first picture is taken as the initial time, the relation between the water absorption height of the porous material 3 and the corresponding time can be obtained.
The treatment method of the water absorption weight comprises the following steps: collecting weight data of the precision analytical balance according to a certain frequency, recording the weight data in an Excel table, processing the weight data by utilizing an Excel function, keeping one data per second, and taking the time corresponding to the first group of data as initial time to obtain the relation between the water absorption weight of the porous material 3 and the corresponding time; because the image acquisition and the weight acquisition of the precision analytical balance are synchronously carried out, the water absorption height and the time corresponding to the water absorption weight data can be ensured to be synchronous.
Determination of porosity and permeability: from the linear relation of the water absorption weight (m) and the water absorption height (h), the porosity (Φ) of the porous material 3 can be obtained:
m＝WBφρh(1)
wherein, W and B are the width and thickness of the material respectively, rho is the density of water, and the time-by-time data of the water absorption height and weight change can be obtained through the experimental test; fitting the water absorption height and water absorption weight data by adopting a least square method, and substituting the data into the formula to obtain the porosity of the porous material 3;
the permeability of the material can be obtained from the following Washburn and Lukas-Soukupova equations (considering the effect of gravity):
wherein the content of the first and second substances,
fitting the above equation with the experimental data of water absorption height changing with time to calculate a and b in the equation, and reusing
The permeability K of the porous material 3 can be obtained.
The equation of the water migration rate is obtained by a Hagen-Poiseulle equation and a fractal theory and is as follows:
wherein the content of the first and second substances,
starting from this equation, if the material is a bundle of parallel capillaries D T1, then can be simplified to get:
when dh/dt is 0, the water absorption height reaches a maximum value, which is set to hmaxThen there is
From the above formula, it can be solved:
the maximum water absorption height h of the porous material 3 can be determined in the experimentmax(the experimental time is long enough), the porosity phi and permeability K of the porous material 3 have been obtained from the above steps, the physical property parameters of water (density rho, viscosity coefficient mu, surface tension sigma) are obtained by measuring the water temperature and looking up the table, the solid-liquid contact angle (theta) and the surface evaporation rate (m)e) Are known. Substituting the known into the above formula, the equivalent maximum pore size of the porous material 3 can be obtained.
Example 1:
when the room air temperature was measured to be 26.2 deg.C, the relative humidity was 60.4%, and the water temperature in the beaker was measured to be 27.7 deg.C, the course and behavior of the water absorption height and water absorption weight of the porous material with time are shown in FIG. 3.
The porosity phi of the material is 80 percent and the permeability K is 1.051 multiplied by 10 percent calculated by the experimental data and the formula in FIG. 3-12Maximum water absorption height hmax175.5mm, the evaporation rate m of water on the surface of the material measured under the experimental conditionse＝3.6×10-4kg/(m2·s)
Substituting the parameters into the formula (5) to obtain the maximum pore diameter λ max of the porous material of 1.795 × 10-5m。
According to the traditional microscopic technical means for acquiring the microstructure of the porous material, such as a Transmission Electron Microscope (TEM), a Scanning Electron Microscope (SEM) and the like, only some local microstructures of a sample to be detected can be obtained, macroscopic parameters reflecting the overall microstructure of the material cannot be rapidly and directly obtained, and the physical water absorption process concerned by people cannot be intuitively observed. Secondly, the traditional Cramer absorbency tester for measuring the water absorption height of the porous fiber material cannot realize accurate, rapid and continuous measurement (especially in the initial stage of the experiment, the measurement error of manually observing the height and reading is large, rapid change of the water absorption height cannot be accurately obtained), and parameters such as microstructure of the material porosity, permeability, pore diameter and the like cannot be obtained. The invention utilizes a system combining real-time dynamic image acquisition and weight acquisition to quickly, continuously, automatically and synchronously observe the water absorption process of the material and obtain the porosity and permeability of the material. And establishing a relation between the macroscopic water absorption characteristic (water absorption height/weight) of the material and the microstructure parameters of the material by virtue of a fractal theory so as to obtain the microstructure characteristics of the material.
In addition, the traditional method for researching the water absorption height and the fractal theory of the porous material does not consider the influence of the water on the surface of the material on the natural evaporation of the ambient environment. Under different ambient air temperature, humidity and water temperature conditions, the evaporation rate of the water on the surface of the material is different, and the water absorption height/performance of the material is directly influenced. In conventional methods, these factors are uncontrollable, resulting in less accurate experimental and theoretical methods.
The system (dynamic image acquisition and weight acquisition technology) and the method (fractal model) adopted by the invention take the influence of the evaporation rate of the water on the surface of the material into consideration. In the experiment, by using the constant temperature and humidity air conditioning system, the temperature, the humidity and the water temperature of the surrounding environment of the sample to be tested can be controlled, and the experiment accuracy is improved. In addition, the surface evaporation rate obtained by an experiment is introduced into the fractal model, so that the prediction precision of the model is improved.
Therefore, the temperature of the molten metal is controlled,
1. the invention relates to a method for obtaining a microstructure macro parameter of a porous material by means of a physical phenomenon experiment and a fractal theory.
2. The electronic computer is connected with and controls a CMOS (CCD) image acquisition system and a precision analytical balance, and the water absorption height and the water absorption weight of the porous material are quickly, continuously, synchronously and accurately acquired by a dynamic image acquisition and weighing method.
3. And automatically processing the collected images in batches by utilizing the internal programming function of the image processing software to obtain the average water absorption height of the material at different moments.
4. The method comprises the steps of obtaining data of water absorption capacity and water absorption height dynamically changing along with time by means of the experiment method, obtaining parameters of porosity and permeability of the porous material by adopting least square fitting, and establishing a relation between microstructure parameters (material equivalent maximum pore diameter, porosity and permeability) and macroscopic water absorption characteristics of the solid porous material by combining a fractal theory model.
5. The fractal model established based on the Hagen-Poiseulle equation not only couples the microstructure parameters obtained by the experimental method, but also considers the influence of the water evaporation rate on the surface of the material, and can more quickly and accurately predict the equivalent maximum aperture of the material.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A fiber material equivalent maximum aperture acquisition system based on measurement comprises a measuring room, an experiment clamping device, an air processing system, an image control system and a central processing system, wherein the air processing system is connected with the measuring room through a ventilation pipeline, and the image control system and the central processing system are respectively electrically connected with the measuring room; the image acquisition unit is respectively and electrically connected with the image control system and the central processing system, and the measurement unit is respectively and electrically connected with the image control system and the central processing system; wherein:
the experimental clamping device clamps the porous material to be tested on the vertical slide rail, extends the liquid temperature testing probe into the middle lower part of the liquid containing device, and puts the liquid on the weight measuring device after the liquid containing device is filled with liquid;
the air treatment system is adjusted to be used for treating fresh air and indoor return air and then sending the treated fresh air and the treated indoor return air into the measuring room;
the experiment clamping device is adjusted to be used for enabling the porous material to slowly descend, and when the bottom of the porous material is about to contact with the water surface, the central processing system starts the automatic water absorption capacity measurement and the image acquisition function of a water absorption area; and as the porous material slowly descends and is immersed in the water, the image acquisition unit acquires time-by-time dynamic images of the water absorption height of the porous material at regular intervals and automatically stores the images; meanwhile, the weight measuring device transmits signals to the central processing system, and real-time data of the weight and corresponding time are automatically stored; the central processing system automatically and synchronously records dynamic images and water absorption weight change data of the water migration process;
the central processing system is also used for processing the pictures acquired by the image acquisition unit in batches to obtain the water absorption areas of the porous materials at different moments, and the average water absorption height of the porous materials is the ratio of the water absorption area to the width of the porous materials;
the weight measuring device is used for measuring the mass change of the liquid containing device, the measurement of the water absorption weight and the water absorption height is synchronously carried out with the data acquisition, the weight reduced by the liquid containing device is the sum of the water absorption capacity and the surface evaporation capacity of the porous material, and the weight measuring device is connected with the central processing system, acquires the data through the central processing system and automatically stores the data;
the weight measuring device is also used for measuring the surface evaporation rate of the porous material in a water absorption saturation state;
and the porosity and permeability of the porous material are obtained through experimental data of water absorption weight and water absorption height, and by utilizing a fractal model,establishing a maximum water absorption height h in the porous materialmaxEquivalent maximum pore diameter lambda of porous materialmaxPorosity phi, permeability K, density rho of the immersion liquid, viscosity coefficient mu, surface tension sigma, solid-liquid contact angle theta and surface evaporation rate meThe relationship between; and substituting the parameters obtained by the experiment into the relation based on the obtained maximum water absorption height of the porous material so as to obtain the equivalent maximum aperture of the porous material.
2. The system for obtaining equivalent maximum pore diameter of fiber material based on measurement according to claim 1, wherein the measurement unit comprises a protective cover, a vertical slide rail, a weight measuring device, a liquid containing device, an experimental material clamping device, a liquid temperature testing probe, and an ambient temperature and humidity sensor, wherein the protective cover is disposed at the periphery of the measurement unit, the vertical slide rail is disposed on the horizontal slide rail, the weight measuring device is disposed at the bottom of the measurement unit, the liquid containing device is disposed above the weight measuring device, the fixed end of the experimental material clamping device is disposed on the vertical slide rail, the material clamping end is suspended above the liquid containing device, the material clamping end can be adjusted by the vertical slide rail to extend the porous material into or out of the liquid containing device, and the liquid temperature testing probe is disposed in the liquid containing device, and the environment temperature and humidity sensor is arranged at the top of the inner side of the protective cover and is electrically connected with the central processing system.
3. The system for obtaining equivalent maximum pore size of fiber material based on measurement according to claim 2, wherein the measuring unit further comprises a temperature adjusting device.
4. The system for obtaining the equivalent maximum pore size of the fiber material based on the measurement according to claim 3, wherein the measurement unit further comprises a temperature controller connected to the temperature adjusting device.
5. The system for obtaining the equivalent maximum pore diameter of the fiber material based on the measurement according to claim 3, wherein the air processing system comprises an air supply unit, a high-efficiency filtering unit, a fan unit, a humidifying unit, a heating unit, a cooling unit, a coarse-effect filtering unit and an air mixing unit, which are sequentially connected, wherein the air supply unit is connected with an air supply outlet at the top end of the measurement chamber through the ventilation pipeline, and the air mixing unit is connected with an air return outlet at the bottom end of the measurement chamber through the ventilation pipeline.
6. The system for obtaining the equivalent maximum aperture of the fiber material based on the measurement according to claim 3, wherein the image capturing unit comprises an image capturing bracket and an image capturing device arranged on the image capturing bracket, and the image capturing bracket is arranged on the horizontal sliding rail and can slide back and forth relative to the background plate.
7. A method for obtaining the equivalent maximum pore diameter of a fiber material based on measurement is characterized by comprising the following steps:
clamping a porous material to be tested on a vertical slide rail through an experiment clamping device, extending a liquid temperature testing probe into the middle lower part of a liquid containing device, and placing the liquid temperature testing probe on a weight measuring device after the liquid containing device is filled with liquid;
adjusting the water temperature in the liquid containing device to enable the water temperature to reach a set value and keeping the water temperature constant; the air conditioning processing system is used for processing fresh air and indoor return air and then sending the processed fresh air and indoor return air into the measuring room;
adjusting the experiment clamping device to enable the porous material to slowly descend, and starting the automatic water absorption capacity measurement and image acquisition functions of a water absorption area by the central processing system when the bottom of the porous material is about to contact the water surface; along with the slow descending and immersion of the porous material in water, the image acquisition unit acquires time-by-time dynamic images of the water absorption height of the porous material at regular intervals and automatically stores the images; meanwhile, the weight measuring device transmits signals to the central processing system, and real-time data of the weight and corresponding time are automatically stored; the central processing system automatically and synchronously records dynamic images and water absorption weight change data of the water migration process;
step four, processing the pictures acquired by the image acquisition unit in batches through a central processing system to obtain the water absorption areas of the porous material at different moments, wherein the average water absorption height of the porous material is the ratio of the water absorption area to the width of the porous material;
measuring the water absorption weight and the water absorption height synchronously with data acquisition, measuring the mass change of the liquid containing device through a weight measuring device, wherein the weight reduced by the liquid containing device is the sum of the water absorption capacity and the surface evaporation capacity of the porous material, and the weight measuring device is connected with a central processing system, and acquires and automatically stores data through the central processing system;
measuring the surface evaporation rate of the porous material in a water absorption saturation state through a weight measuring device;
obtaining the porosity and permeability of the porous material through experimental data of water absorption weight and water absorption height, and establishing a relation between the maximum water absorption height hmax in the porous material and the equivalent maximum pore diameter lambda max, the porosity phi, the permeability K, the density rho of the immersed liquid, the viscosity coefficient mu, the surface tension sigma, the solid-liquid contact angle theta and the surface evaporation rate me of the porous material by using a fractal model;
and step eight, obtaining the maximum water absorption height of the porous material through an experiment, and substituting the parameters obtained through the experiment into the relation to further obtain the equivalent maximum pore diameter of the porous material.
8. The method for obtaining the equivalent maximum pore diameter of the fiber material based on the measurement according to claim 7, wherein the fractal model in the seventh step is a formula (3) for obtaining the water migration rate according to Hagen-Poiseulle equation and fractal theory:
wherein the content of the first and second substances,
wherein h is the average water absorption height; t is water absorption time; beta is the ratio of the minimum aperture to the maximum aperture of the fiber material, and is generally 0.01; lambda [ alpha ]maxRepresents the equivalent maximum pore size of the fibrous material; ρ represents the immersion liquid density; μ represents the viscosity coefficient of the immersion liquid; σ is the surface tension of the immersed liquid; theta is the solid-liquid contact angle; b is the thickness of the fiber material; k represents the permeability of the fibrous material; phi denotes the porosity of the fibrous material; m iseRepresents the evaporation rate of the fiber material in the environment; g is the acceleration of weight, DfFractal dimension of pore volume, DTFractal dimension of tortuosity.
9. The method for obtaining equivalent maximum pore size of fiber material based on measurement as claimed in claim 8, wherein D is the value whenTWhen 1, the formula (3) can be simplified to formula (4):
10. the method for obtaining equivalent maximum pore size of fiber material based on measurement as claimed in claim 9, wherein the water absorption height reaches a maximum value when dh/dt is 0, and the maximum value is hmaxFrom said formula (4), formula (5) can be solved:
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| CN111595427A (en) * | 2020-06-29 | 2020-08-28 | 安徽理工大学 | Humidity experiment environment box capable of continuously weighing |
| CN112288719A (en) * | 2020-10-29 | 2021-01-29 | 中国水产科学研究院渔业机械仪器研究所 | Kelp water content diagnosis method |
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