CN110174434B - Method for measuring heterogeneous content and distribution in porous material - Google Patents
Method for measuring heterogeneous content and distribution in porous material Download PDFInfo
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- CN110174434B CN110174434B CN201910442695.1A CN201910442695A CN110174434B CN 110174434 B CN110174434 B CN 110174434B CN 201910442695 A CN201910442695 A CN 201910442695A CN 110174434 B CN110174434 B CN 110174434B
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Abstract
The invention discloses a method for measuring heterogeneous content and distribution in a porous material, which measures temperature rise and heat flow distribution on two sides of a flaky plane heat source through an arrangement method of tightly attaching a first heat flow meter sensor, the flaky plane heat source and a second heat flow meter sensor, can effectively identify heterogeneous uneven distribution in the measured material, and simultaneously realizes one-time measurement to obtain heterogeneous content on two sides of the flaky plane heat source. On the basis of the method, according to the limited propagation thickness of the temperature disturbance, the testing positions of the sensors are reasonably arranged to avoid measuring blind areas in the material, a function of the content of the heterogeneous substance in the material changing along with the position is obtained through data interpolation and fitting, and finally one-dimensional, planar or three-dimensional distribution of the content of the heterogeneous substance in the material is obtained.
Description
Technical Field
The invention belongs to the technical field of material testing and analysis, and relates to a method for measuring heterogeneous content and distribution in a porous material by using a transient plane heat source method based on a heat flow meter.
Background
When heterogeneous materials invade into the porous material, the physical property parameters and the service performance of the material are changed. For example, porous heat-insulating materials widely used in the field of building energy conservation have moisture absorption characteristics, and the invasion of moisture in the use process causes the reduction of heat-insulating and sound-insulating effects, the breeding and the mildew, the reduction of the service life of the materials and the increase of the building energy consumption. Therefore, the accurate measurement of the heterogeneous content and the distribution of the heterogeneous content of the material is greatly helpful for improving the service performance of the material.
At present, the content of heterogeneous components in the porous material is detected by an electrical method, a thermal method, a ray method and the like. Among them, the thermal method has a wide application range because of its simple and inexpensive measurement. The thermal method is characterized in that a heat source is arranged in a material to be detected, the transient temperature rise of a certain point in the material with a fixed distance from the heat source is monitored, the thermophysical parameters of the material to be detected, such as volume heat capacity, and the variation before and after intrusion of a foreign body are solved, and finally the content of the foreign body in the material to be detected is obtained. The current thermal method for measuring the heterogeneous content of the material has the following defects:
(1) because the heating body and the temperature measuring point are separately arranged, the premise that the temperature measuring point monitors effective temperature rise is that the heating body has larger heat productivity, and the large heat productivity induces natural convection and radiation heat transfer in the porous material, so that the testing precision is reduced;
(2) in actual measurement, the distance between the heating element and the temperature measuring point is not fixed due to the possible material deformation caused by the arrangement of the heating element and the temperature measuring point, so that the accuracy of heterogeneous content measurement is influenced;
(3) the distribution of the heterogeneous substances when the heterogeneous substances invade the material to be detected is possibly not uniform, so that the heat flows generated by the heating body in different directions in the material are possibly not uniform, and the traditional thermal method is only suitable for the situation that the heterogeneous contents in the material are uniformly distributed;
(4) the heterogeneous content value or the value range of the measured material obtained by the existing measuring method is mostly measured by a single measuring point, and the spatial distribution of the heterogeneous content in the material can not be effectively presumed.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for measuring the content and distribution of heterogeneous materials in a porous material, and solves the problem of measurement errors caused by the separated arrangement of a heat source and a measuring point in the prior art.
The technical scheme of the invention comprises the following operation steps:
(1) arranging a first heat flow meter sensor, a sheet-shaped plane heat source and a second heat flow meter sensor in sequence, enabling the first heat flow meter sensor, the sheet-shaped plane heat source and the second heat flow meter sensor to be mutually and tightly attached, and arranging the first heat flow meter sensor, the sheet-shaped plane heat source and the second heat flow meter sensor in the material in parallel with the surface of the material to be detected;
(2) recording the temperature of the measured material which is stable and uniformly distributed as the initial temperature T0；
(3) The heating circuit is switched on, and the total heat flow generated by the sheet-shaped plane heat source with the area of A and the constant heating power of Q in the material is recorded as
Satisfy the relationship
(4) The temperature and heat flow of one side of the sheet-shaped plane heat source are measured by a first heat flow meter sensor and are recorded as T1And
the temperature and the heat flow on the other side of the sheet-shaped plane heat source are measured by a second heat flow meter sensor and are recorded as T2And
(5) subtracting the initial temperature from the temperature measurement data of the first heat flow meter sensor to obtain the corresponding temperature rise value delta T of the measurement point of the heat flow meter sensor at one side of the sheet plane heat source1E(t); subtracting the initial temperature from the temperature measurement data of the second heat flow meter sensor to obtain the corresponding temperature rise value delta T of the measurement point of the heat flow meter sensor on the other side of the flaky plane heat source2E(t)；
(6) Determining the heat flows at two sides of the sheet-shaped plane heat source according to the step (4)
And
determining total heat flow
Distribution coefficient f along both sides of a planar heat source in the form of a sheetiI.e. by
Combining a one-dimensional heat transfer process heat conduction differential equation, boundary conditions and initial conditions of the transient plane heat source to obtain a temperature rise analytic solution delta T of materials on two sides of the sheet plane heat source in the time T of the position of the heat flow meter sensor1(T) and Δ T2(t)；
Temperature rise analytic solution delta T of materials on two sides of sheet-shaped plane heat source at position of heat flow meter sensor1(T) and Δ T2(t) the thermal conductivity differential equation, the boundary conditions, and the initial conditions satisfy:
t＝0，Ti＝T0 (4)
the partial differential equation set is solved by referring to the method in H.S. Carlslaw, J.C. Jaeger.connection of Heat in solids.2nd edition.Oxford Clarendon Press,1986:89-112, and the measured material x ═ l is obtainediThe temperature rise of the boundary is resolved into:
the foot mark i distinguishes two sides of the sheet-shaped plane heat source, and when i is 1, the foot mark i is a measuring point on one side of the sheet-shaped plane heat source, and when i is 2, the foot mark i is a measuring point on the other side of the sheet-shaped plane heat source; t isiIs the temperature of the material to be measured, K; t is0Is the initial temperature of the material to be measured, K; lambda is the thermal conductivity of the material to be tested, Wm-1K-1(ii) a Rho is the density of the measured material, kgm-3(ii) a c is the specific heat capacity of the material to be tested, Jkg-1K-1(ii) a ρ c is the volumetric heat capacity (Jm) of the material to be measured-3K-1)；fiFor total heat flow determined by heat flow meter sensors
The distribution coefficient along both sides of the planar heat source in the form of sheets, i.e.
Is total heat flow of the sheet-shaped plane heat source, W/m2；liThe parallel distance m from a sheet-shaped plane heat source measuring point to the surface of the measured material; n is 1, 2, 3, …, alpha is thermal diffusivity of the tested material, m2/s。
(7) Comparing the temperature rise value delta T of the two sides of the sheet-shaped plane heat source measured in the step (5)1E(t)、ΔT2E(T) and temperature rise analytic solution delta T of measuring point at corresponding position in step (6)1(t)、ΔT2(t) transforming thermophysical parameters in the temperature rise analytical solution to ensure that the temperature rise difference value of the temperature rise measured in the experiment and the temperature rise analytical solution is minimum or within an acceptable threshold value, and obtaining the numerical values of the heat conductivity coefficient lambda, the volumetric heat capacity rho c and the thermal diffusivity alpha at two sides of the flaky plane heat source at the moment;
(8) calculating the heterogeneous contents of the materials at two sides of the flaky plane heat source according to the one-to-one correspondence relationship between the volume heat capacity rho c of the measured material and the heterogeneous contents of the measured material;
(9) since each test datum can only represent the heterogeneous content in the transient heat transfer limited transfer thickness, the first heat flow sensor or the second heat flow sensor is spaced from the plane heat source by the distance diAnd (3) arranging measuring points, repeating the steps (1) to (8) to measure heterogeneous content of different measuring points, carrying out data processing on measured data through data processing software according to the positions of the measuring points and corresponding heterogeneous content, and obtaining heterogeneous content distribution of a certain dimension in the material according to specific measurement requirements.
Whether the heterogeneous content distribution on two sides of the flaky plane heat source is uniform or not can be judged through the step (4): when in use
When the method is used, the heterogeneous content at the material measuring points on the left side and the right side of the flaky plane heat source is uniformly distributed; when in use
When the method is used, heterogeneous content at material measuring points on the left side and the right side of the flaky plane heat source is not uniformly distributed.
When the measuring point arrangement scheme is designed in the step (9), the penetration thickness of temperature disturbance in the material in the heat transfer science is defined, the temperature disturbance at the sheet-shaped plane heat source can only transmit limited thickness in the measured material within a certain period of time, and the material area beyond the thickness is kept in an initial state, so that when measuring points are arranged in the measured material, the measuring points are ensured to be arrangedAt least one measuring point is arranged in the penetration thickness, so that a measuring blind area and the arrangement distance d of the measuring points in the measured material are avoidediIt should satisfy:
wherein: diThe spacing distance, m, between the first heat flow sensor or the second heat flow sensor and the plane heat source; tau is the time length of heating of a single measurement heat source, s; alpha is the thermal diffusivity calculated by the minimum temperature rise difference value of the temperature rise measured by the experiment and the temperature rise analytic solution or within the acceptance threshold value, and m is2/s。
When the measuring point arrangement scheme is designed in the step (9), multi-dimensional measuring point arrangement can be carried out in the measured material according to the specific requirements of heterogeneous distribution measurement, and measuring point position parameters are recorded, so that one-dimensional, planar or three-dimensional distribution of the heterogeneous in the measured material is correspondingly obtained.
The data processing in the step (9) is to perform interpolation processing on the measured multiple groups of heterogeneous content and corresponding position parameters, the data is input in data processing software and corresponding interpolation processing programs are compiled, so that the one-dimensional, planar or three-dimensional distribution condition of the heterogeneous content in the measured material can be obtained, and a fitting function X of the heterogeneous content in the measured material changing along with the position of the measured point can be obtained by fitting according to the interpolation resultwAnd the distribution thereof:
Xw＝(x，y，z，xw) (7)
wherein, x, y and z are coordinates marked by a measuring point in the measured material by taking a certain position as an origin, and m; x is the number ofwThe heterogeneous content corresponds to the position parameter of the measuring point. And obtaining the heterogeneous content at any position in the material by substituting the position parameters according to the fitting function.
The invention has the beneficial effects that: according to the invention, the sheet-type heat flow meter sensors are arranged on both sides of the sheet-shaped plane heat source, the heat flow meter sensors can simultaneously measure heat flow and temperature, heterogeneous uneven distribution is effectively identified through temperature rise and heat flow distribution of materials on both sides of the sheet-shaped plane heat source, and meanwhile, compared with the conventional measuring method, the heterogeneous content of the materials on both sides of the heat source is obtained through one-time measurement. The transient heat transfer limited thickness can also be used for arranging test positions at intervals to obtain the spatial distribution of one-dimensional, planar or three-dimensional heterogeneous content in the tested material. In addition, because the sheet heat source and the heat flow meter are arranged in a fitting manner, the measurement error caused by the separated arrangement of the heat source and the measuring point in the traditional thermal method is avoided, and the heat source heat productivity required by effectively detecting the temperature rise is reduced. The distribution of the heterogeneous content in the space is measured by changing the measuring positions of the heat source and the heat flow meter sensor and taking the limited propagation thickness of the temperature disturbance as the space interval. The method solves the problem of measuring the content and the distribution of the heterogeneous substances in the porous material.
Drawings
FIG. 1 is a schematic view of a measuring probe for measuring the heterogeneous content and distribution thereof in a porous material according to the present invention; in the figure: 1 is a sheet-shaped plane heat source; 2 a first heat flow meter sensor; 3 a second heat flow meter sensor; 4, the material to be detected; l1And l2Respectively the parallel distance m between the flaky plane heat source and the left and right surfaces of the material to be detected; u is the voltage supplied to the heating element, V;
FIG. 2 is a schematic diagram of measuring point arrangement of the method for measuring heterogeneous content and distribution in porous material provided by the present invention, diThe spacing distance, m, between the first heat flow sensor or the second heat flow sensor and the plane heat source; τ is the test time, s; alpha is alpha1、α2The thermal diffusivity m obtained by the minimum temperature rise difference value of the temperature rise and the temperature rise analytic solution of the experiments at two sides of the heat source or within the acceptable threshold value2/s；f1、f2Distributing coefficients for heat flows on two sides of a heat source;
is total heat flow of the sheet-shaped plane heat source, W/m2(ii) a N is 1, 2, 3, N, which is the number of test points;
FIG. 3 is a flowchart illustrating the operation of a method for measuring the heterogeneous content and distribution thereof in the porous material according to the present invention; in the figure: t is1、
And T1、
The temperature and heat flow generated by the sheet-shaped plane heat source on the left side and the right side of the heat source are changed; f. ofiFor total heat flow determined by heat flow meter sensors
Distribution coefficients along both sides of the planar heat source in sheet form, and1+f2＝1；
is total heat flow of the sheet-shaped plane heat source, W/m2；ΔT1E(T) and Δ T2E(t) is the temperature rise of the materials at the two sides of the sheet-shaped plane heat source; delta T1(T) and Δ T2(t) temperature rise analytic solution of materials on two sides of the sheet-shaped plane heat source in t time; d is the difference value between the temperature rise measured by the sensor and the analytic solution approximate temperature rise; dacceptIs an acceptable difference value threshold; tau is the heating time length of a single measurement heat source, s; alpha is the thermal diffusivity calculated by the minimum temperature rise difference value of the temperature rise measured by the experiment and the temperature rise analytic solution or within the acceptable threshold value, and m is2/s。
Detailed Description
The following specifically describes the embodiments of the present invention by taking the measurement of the moisture content of the moisture-absorbing and heat-insulating material as an example.
A method for measuring heterogeneous content and distribution in a porous material comprises the following steps:
(1) arranging a moisture absorption and heat insulation material 4 in a weak heat exchange environment, arranging and tightly attaching a first heat flow meter sensor 2, a sheet-shaped plane heat source 1 and a second heat flow meter sensor 3 according to the sequence of figure 1, arranging the sensors in the material in parallel with the surface of a measured material 4, wherein the parallel distances between the sheet-shaped plane heat source and the left and right surfaces of the measured material are respectively l1And l2. It is suggested to use a sheet-type sheet plane heat source and a sheet-type heat flow meter sensor, and the area size of the sheet-type heat flow meter sensor is far smaller than that of the sheet-type planeThe size of the area of the heat source.
(2) After the temperature distribution of the moisture absorption and heat insulation material is uniform and stable, recording the initial temperature T at the initial measurement moment0；
(3) The heating circuit is switched on, and the total heat flow generated by the sheet-shaped plane heat source with the area of A and the constant heating power of Q in the material is recorded as
Satisfy the relationship
(4) The temperature and heat flow of one side of the sheet-shaped plane heat source are measured by a first heat flow meter sensor and are recorded as T1And
the temperature and the heat flow on the other side of the sheet-shaped plane heat source are measured by a second heat flow meter sensor and are recorded as T2And
(5) subtracting the initial temperature from the temperature measurement data of the first heat flow meter sensor to obtain the corresponding temperature rise value delta T of the measurement point of the heat flow meter sensor at one side of the sheet plane heat source1E(t); subtracting the initial temperature from the temperature measurement data of the second heat flow meter sensor to obtain the corresponding temperature rise value delta T of the measurement point of the heat flow meter sensor on the other side of the flaky plane heat source2E(t)；
(6) Determining the heat flows at two sides of the sheet-shaped plane heat source according to the step (4)
And
determining total heat flow
Distribution coefficient f along both sides of a planar heat source in the form of a sheetiOne dimension combined with transient plane heat sourceObtaining temperature rise analytic solution delta T of two sides of the sheet plane heat source in the time T of the position of the heat flow meter sensor in the heat transfer process by using a heat conduction differential equation, boundary conditions and initial conditions in the heat transfer process1(T) and Δ T2(t)；
Temperature rise analytic solution delta T of materials on two sides of sheet-shaped plane heat source at position of heat flow meter sensor1(T) and Δ T2(t) the thermal conductivity differential equation, the boundary conditions, and the initial conditions satisfy:
t＝0，Ti＝T0 (4)
the partial differential equation set is solved by referring to the method in H.S. Carlslaw, J.C. Jaeger.connection of Heat in solids.2nd edition.Oxford Clarendon Press,1986:89-112, and the measured material x ═ l is obtainediThe temperature rise of the boundary is resolved into:
the foot mark i distinguishes two sides of the sheet-shaped plane heat source, and when i is 1, the foot mark i is a measuring point on one side of the sheet-shaped plane heat source, and when i is 2, the foot mark i is a measuring point on the other side of the sheet-shaped plane heat source; t isiIs the temperature of the material to be measured, K; t is0Is the initial temperature of the material to be measured, K; lambda is the thermal conductivity of the material to be tested, Wm-1K-1(ii) a Rho is the density of the measured material, kgm-3(ii) a c is the specific heat capacity of the material to be tested, Jkg-1K-1(ii) a ρ c is the volumetric heat capacity (Jm) of the material to be measured-3K-1)；fiTo be sensed by heat flow metersTotal heat flow determined by the device
The distribution coefficient along both sides of the planar heat source in the form of sheets, i.e.
Is total heat flow of the sheet-shaped plane heat source, W/m2；liThe parallel distance m from a sheet-shaped plane heat source measuring point to the surface of the measured material; n is 1, 2, 3, …, alpha is thermal diffusivity of the tested material, m2/s；
(7) Calculating the difference value between the actually measured temperature rise obtained in the step (5) and the temperature rise analytical solution obtained in the step (6) by using a formula (8),
wherein D is the root mean square difference value (DEG C) of the calculated temperature rise and the actually measured temperature rise, and delta TM,tIs the temperature rise value (DEG C) at the time T, which is calculated by a formulaE,tIs the temperature rise value (DEG C) at the time t measured by the experiment, and n is the number of the temperature data measured by the experiment. In the invention, one-time measurement comprises two groups of temperature rise data which respectively correspond to the temperature rises of the left side and the right side of the flaky plane heat source, so that the corresponding D values of the left side and the right side of the flaky plane heat source are calculated.
(8) Carrying out optimization solution by using a Matlab optimization tool box, and setting an acceptable deviation D by reasonably matching the heat conductivity coefficient lambda, the volume heat capacity rho c and the thermal diffusivity alpha of the moisture absorption and heat insulation materialacceptSo that the difference value relationship between the temperature rise measured by the sensor and the analytic solution approximate temperature rise satisfies that D is less than or equal to Daccept(ii) a If the porous material absorbs water for example, the upper limit of the parameter matching is the thermal conductivity coefficient lambda and the volume heat capacity rho c of liquid water, and the lower limit of the parameter matching is the thermal conductivity coefficient lambda and the volume heat capacity rho c of the dry heat-insulating material.
(9) Determining values of the thermal conductivity coefficient lambda and the volume heat capacity rho c of the porous material after absorbing the heterogeneous material according to the optimal matching result obtained in the step (8), and obtaining the heterogeneous content of the porous material after absorbing the heterogeneous material, such as the water content in the heat-insulating material, according to the one-to-one correspondence relationship between the volume heat capacity and the heterogeneous content:
wherein x iswIs the volume fraction of water, ρdryDensity of dry insulation material (kgm)-3)，cdryFor drying the specific heat capacity (Jkg) of the heat-insulating material-1K-1)，ρdrycdryFor the volumetric heat capacity (Jm) of dry insulating materials-3·K-1)，cwSpecific heat capacity as moisture (Jkg)-1K-1) ρ c is the bulk heat capacity (Jm) obtained by the optimal matching-3·K-1)。
(10) One-dimensional or planar or three-dimensional measuring point arrangement is carried out in the material and position parameters are recorded, a measuring point arrangement schematic diagram is shown in figure 2, the penetration thickness of temperature disturbance in the material in heat transfer science is defined, the temperature disturbance at a sheet-shaped planar heat source can only transmit limited thickness in the measured material within a certain time, and a material area beyond the thickness keeps an initial state, so that when measuring points are arranged in the measured material, at least one measuring point in the penetration thickness is ensured, a measuring blind area is avoided in the measured material, and the arrangement distance d of the measuring points is arrangediIt should satisfy:
wherein: diThe spacing distance, m, between the first heat flow sensor or the second heat flow sensor and the plane heat source; tau is the heating time length of a single measurement heat source, s; alpha is the thermal diffusivity calculated by the minimum temperature rise difference value of the temperature rise measured by the experiment and the temperature rise analytic solution or within the acceptance threshold value, and m is2/s；
(11) And (4) repeating the steps (1) to (9), obtaining the moisture content at two sides of each measuring point through multiple measurements, and obtaining the moisture content distribution of a certain dimension in the material through interpolation processing of the obtained data.
The program used for the numerical interpolation processing by Matlab is as follows:
uiopen ('data File Path', 1)
[X,Y,Z Xw]＝griddata(x,y,z,xwLinspace (0,900,100) ', linspace (0.4,5, 100)', 'line')% range
pcolor(X,Y,Z,Xw) (ii) a shading inter p% pseudo-colour picture
hold on
scatter(x,y,z'r')
text(x,y,z,arrayfun(@(xw)[”num2str(xw)],xw'UniformOutput', 0))% of marked measuring point positions and heterogeneous content
h is gca; % pointer to obtain current drawing coordinates
set (h, 'FontSize', 16); % set character size
(12) Obtaining a fitting function X of heterogeneous content changing along with the position of a measuring point according to data fittingwAnd the distribution thereof:
Xw＝(x，y，z，xw) (7)
wherein, x, y and z are coordinates marked by a measuring point in the measured material by taking a certain position as an origin, and m; x is the number ofwThe heterogeneous content corresponds to the position of the measuring point. And obtaining the heterogeneous content at any position in the material by substituting the position parameters according to the fitting function.
While the present invention has been described with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments, which are illustrative only and not restrictive, and various modifications which do not depart from the spirit of the present invention and which are intended to be covered by the claims of the present invention may be made by those skilled in the art.
Claims (5)
1. A method for measuring heterogeneous content and distribution in a porous material is characterized by comprising the following steps:
(1) arranging a first heat flow meter sensor, a sheet-shaped plane heat source and a second heat flow meter sensor in sequence, enabling the first heat flow meter sensor, the sheet-shaped plane heat source and the second heat flow meter sensor to be mutually and tightly attached, and arranging the first heat flow meter sensor, the sheet-shaped plane heat source and the second heat flow meter sensor in the material in parallel with the surface of the material to be detected;
(2) recording the temperature of the measured material which is stable and uniformly distributed as the initial temperature T0；
(3) The heating circuit is switched on, and the total heat flow generated by the sheet-shaped plane heat source with the area of A and the constant heating power of Q in the material is recorded as
Satisfy the relationship
(4) The temperature and heat flow of one side of the sheet-shaped plane heat source are measured by a first heat flow meter sensor and are recorded as T1And
the temperature and the heat flow on the other side of the sheet-shaped plane heat source are measured by a second heat flow meter sensor and are recorded as T2And
(5) subtracting the initial temperature from the temperature measurement data of the first heat flow meter sensor to obtain the corresponding temperature rise value delta T of the measurement point of the heat flow meter sensor at one side of the sheet plane heat source1E(t); subtracting the initial temperature from the temperature measurement data of the second heat flow meter sensor to obtain the corresponding temperature rise value delta T of the measurement point of the heat flow meter sensor on the other side of the flaky plane heat source2E(t)；
(6) Determining the heat flows at two sides of the sheet-shaped plane heat source according to the step (4)
And
determining total heat flow
Distribution coefficient f along both sides of a planar heat source in the form of a sheetiI.e. by
Combining a one-dimensional heat transfer process heat conduction differential equation, boundary conditions and initial conditions of the transient plane heat source to obtain a temperature rise analytic solution delta T of materials on two sides of the sheet plane heat source in the time T of the position of the heat flow meter sensor1(T) and Δ T2(t)；
Temperature rise analytic solution delta T of materials on two sides of sheet-shaped plane heat source at position of heat flow meter sensor1(T) and Δ T2(t) the thermal conductivity differential equation, the boundary conditions, and the initial conditions satisfy:
t＝0，Ti＝T0 (4)
solving partial differential equation set to obtain the measured material x ═ liThe temperature rise of the boundary is resolved into:
the foot mark i distinguishes two sides of the sheet-shaped plane heat source, and when i is 1, the foot mark i is a measuring point on one side of the sheet-shaped plane heat source, and when i is 2, the foot mark i is a measuring point on the other side of the sheet-shaped plane heat source; t isiIs the temperature of the material to be measured, K；T0Is the initial temperature of the material to be measured, K; lambda is the thermal conductivity of the material to be tested, Wm-1K-1(ii) a Rho is the density of the measured material, kgm-3(ii) a c is the specific heat capacity of the material to be tested, Jkg-1K-1(ii) a ρ c is the volumetric heat capacity (Jm) of the material to be measured-3K-1)；fiFor total heat flow determined by heat flow meter sensors
The distribution coefficient along both sides of the planar heat source in the form of sheets, i.e.
Is total heat flow of the sheet-shaped plane heat source, W/m2；liThe parallel distance m from a sheet-shaped plane heat source measuring point to the surface of the measured material; n is 1, 2, 3, …, alpha is thermal diffusivity of the tested material, m2/s；
(7) Comparing the temperature rise value delta T of the two sides of the sheet-shaped plane heat source measured in the step (5)1E(t)、ΔT2E(T) and temperature rise analytic solution delta T of measuring point at corresponding position in step (6)1(t)、ΔT2(t) transforming thermophysical parameters in the temperature rise analytical solution to ensure that the temperature rise difference value of the temperature rise measured in the experiment and the temperature rise analytical solution is minimum or within an acceptable threshold value, and obtaining the numerical values of the heat conductivity coefficient lambda, the volumetric heat capacity rho c and the thermal diffusivity alpha at two sides of the flaky plane heat source at the moment;
(8) calculating the heterogeneous contents of the materials at two sides of the flaky plane heat source according to the one-to-one correspondence relationship between the volume heat capacity rho c of the measured material and the heterogeneous contents of the measured material;
(9) since each test datum can only represent the heterogeneous content in the transient heat transfer limited transfer thickness, the first heat flow sensor or the second heat flow sensor is spaced from the plane heat source by the distance diArranging measuring points, repeating the steps (1) to (8) to measure the heterogeneous content of different measuring points, and passing through a data place according to the positions of the measuring points and the corresponding heterogeneous contentAnd processing the measured data by the processing software, and obtaining the non-uniform heterogeneous content distribution of a certain dimension in the material according to the specific measurement requirement.
2. The method for measuring the heterogeneous content and the distribution thereof in the porous material according to claim 1, wherein the step (4) can be used for judging whether the heterogeneous content distribution on both sides of the sheet-shaped plane heat source is uniform or not: when in use
When the method is used, the heterogeneous content at the material measuring points on the left side and the right side of the flaky plane heat source is uniformly distributed; when in use
When the method is used, heterogeneous content at material measuring points on the left side and the right side of the flaky plane heat source is not uniformly distributed.
3. The method for measuring heterogeneous content and distribution in porous material according to claim 1, wherein when designing the measuring point arrangement scheme in step (9), the temperature perturbation at the sheet-like plane heat source can only transmit limited thickness in the measured material within a certain period of time, and the material region beyond the thickness keeps the initial state, so that when arranging measuring points in the measured material, at least one measuring point in the penetrating thickness is ensured, the existence of a measuring blind area in the measured material is avoided, and the arrangement distance d between the measuring points is defined by the penetrating thickness of the temperature perturbation in the material in the heat transfer scienceiIt should satisfy:
wherein: diThe spacing distance, m, between the first heat flow sensor or the second heat flow sensor and the plane heat source; tau is the time length of heating of a single measurement heat source, s; alpha is the thermal diffusivity calculated by the minimum temperature rise difference value of the temperature rise measured by the experiment and the temperature rise analytic solution or within the acceptance threshold value, and m is2/s。
4. The method for measuring the content and distribution of the heterogeneity in the porous material according to claim 1, wherein when the measuring point arrangement scheme is designed in step (9), the measuring point arrangement can be performed in multiple dimensions in the measured material according to the specific requirements of heterogeneous distribution measurement, and the position parameters of the measuring points are recorded, so as to correspondingly obtain the one-dimensional, planar or three-dimensional distribution of the heterogeneity in the measured material.
5. The method for measuring the contents and distribution of heterogeneous substances in porous materials as claimed in claim 1, wherein the data processing in step (9) is interpolation processing of the measured contents of multiple heterogeneous substances and corresponding position parameters, one-dimensional, planar or three-dimensional distribution of the contents of heterogeneous substances in the material to be measured can be obtained by inputting data into data processing software and writing corresponding interpolation processing programs, and a fitting function X of the contents of heterogeneous substances in the material to be measured changing with the positions of the measuring points can be obtained by fitting according to the interpolation resultwAnd the distribution thereof:
Xw＝(x，y，z，xw) (7)
wherein, x, y and z are coordinates marked by a measuring point in the measured material by taking a certain position as an origin, and m; x is the number ofwCorresponding heterogeneous content for the position parameters of the measuring points; and obtaining the heterogeneous content at any position in the material by substituting the position parameters according to the fitting function.
Priority Applications (1)
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