CN103630569A - Method for measuring heterogeneous medium content of material based on volume thermal mass - Google Patents

Abstract

The invention relates to a method for measuring the heterogeneous medium content of a material based on volume thermal mass. A temperature sensor and a heat source are arranged in an object to be measured; after the heat source realizes heating, a data acquirer acquires temperature data. An effective heat conduction coefficient and effective thermal diffusivity are calculated according to experiment data, and then the volume thermal mass is calculated; therefore, the content of heterogeneous medium components is calculated according to a formula disclosed by the invention. The method disclosed by the invention is simple and feasible; real-time monitoring can be realized without implementation of sampling. According to the method, a wet multipore material is used as a mixture containing the heterogeneous medium components, and a transient hot-wire theory is used as a method for measuring the effective heat conduction coefficient and the effective thermal diffusivity, so that a complete process of measuring the heterogeneous medium content is stated in detail. However, the method is not limited to water content detection and can be also applied to detection of gas components doped in multiphase fluid pipelines.

Description

A kind of method of measuring heterogeneous content in material based on volume caloic

Technical field

The invention belongs to material tests analysis field, relate to a kind of method of measuring heterogeneous content in material based on volume caloic.

Background technology

In potpourri, the content of heterogeneous composition has a great impact the characteristic of material itself, and for example the water capacity size of porosint has determined the intensity of material, heat insulating ability, electric conductivity, fresh keeping time etc.This explanation will be take moisture detection as example, but the present patent application is not limited only to water cut, detect, and as mixed the detection of heterogeneous gas content in closed conduit, also belong to range of application of the present invention.

Along with scientific and technical progress, water content detection has been listed in one of elementary item of all kinds of material physico-chemical analysis, covers the various fields such as foodstuff preservation, architecture science, environmental science, geoscience.

Conventional moisture measuring method has: oven drying method, electric-resistivity method, capacitance method etc.Oven drying method needs sampling, and the time is longer, cannot realize, and cannot realize Real-Time Monitoring moisture under a lot of situations.Electric-resistivity method, capacitance method are to utilize the dielectric property of material indirectly to measure, and speed is fast, but bad adaptability, and accuracy is low.

Summary of the invention

The object of the invention is to for the deficiency in existing method, a kind of low cost, simple quick heterogeneous component content detection method are provided, and can Real-Time Monitoring.

A method of measuring heterogeneous content in material based on volume caloic, the method comprises the following steps:

A, in object to be measured, arrange temperature sensor and thermal source; Because the method for heat conducting coefficient measuring, thermal diffusivity has a lot, so the layout of sensor and heat resource form also have a lot, in embodiment below, will take thermal transient collimation method as example explanation.

After b, thermal source heating, the temperature data of pick-up transducers;

C, according to temperature data, solve effective thermal conductivity, effective thermal diffusivity, then solve volume caloic (or claiming average caloic density) according to effective thermal conductivity, effective thermal diffusivity; Because volume caloic changes after mixing heterogeneous composition, according to the change amount of volume caloic, obtain the content of heterogeneous composition.

Except detecting the situation that heterogeneous composition is water, detection method, the step of other heterogeneous component contents are identical.

Method of testing of the present invention fast, accurately, need not sample.For example, the moisture of Real-Time Monitoring construction wall, only need in advance temperature sensor, thermal source to be embedded in body of wall, after heating, record temperature value, heating power, then just can obtain according to formula the water cut of material.Prior pre-buried good device in fluid line, the ratio of equally can Real-Time Monitoring mixing heterogeneous composition in pipeline herein.

Accompanying drawing explanation

Accompanying drawing is to monitor the step schematic diagram that the water cut of insulation material in aircraft body of wall is example.

Embodiment

Below take thermal transient collimation method as example, elaborate above-mentioned several step, but the present invention is not limited only to obtain effective thermal conductivity and effective thermal diffusivity by thermal transient collimation method.When pre-buried hot line and temperature sensor, make probe orientation parallel with pre-buried hot line; Pre-buried hot line adopts stabilized voltage supply power supply; Before test, make the temperature field of trying body inside be tending towards uniformity.

Utilize Hot Wire Technique for Measuring coefficient of heat conductivity and thermal diffusivity, the time is short, have a narrow range of temperature, and can reduce the water translocation of measurand inside in test process as far as possible, thereby obtain data more accurately.Hot line surface guarantees electrical isolation as far as possible, and while selecting hot line type, the resistivity of assurance hot line varies with temperature less, can use nickel filament.

In the equally distributed infinite medium of initial temperature, hot line generates heat with firm power, and the analytic solution of environment temperature are:

$\mathrm{\ΔT}(r,\mathrm{\τ})=-\frac{q}{4\mathrm{\πk}}\mathrm{Ei}\left(\frac{-r^2}{4\mathrm{a\τ}}\right)---\left(1\right)$

Wherein, q is unit length thermal power (W/m), and a is thermal diffusivity (㎡/s), k is coefficient of heat conductivity (Wm ^-1k ^-1), τ is time (s), r is the distance (m) of probe to hot line.The expression formula of function-Ei (x) is

$-\mathrm{Ei}(-x)=E_1\left(x\right)=-\mathrm{\β}-\ln x+\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}\frac{{(-1)}^{k+1}{x}^k}{\mathrm{kk}!}---\left(2\right)$

β=0.57772 is Euler's constant.

When x is very little, second of (2) formula item below be high-order infinitesimal, can ignore.

So when τ long enough, the analytic solution of temperature rise around can be reduced to

$\mathrm{\ΔT}\≈\frac{q}{4\mathrm{\πk}}[-\mathrm{\β}-\ln \left(\frac{r^2}{4\mathrm{a\τ}}\right)]=\frac{q}{4\mathrm{\πk}}[\ln \mathrm{\τ}+\ln \left(\frac{4a}{r^2{C}_E}\right)]---\left(3\right)$

Wherein, C _e=exp (β)

From (3) formula, the logarithm of temperature rise and time is linear relationship.The logarithm of temperature rise and time is fitted to straight line

AT=Alnτ+B （4）

:

$k=\frac{q}{4\mathrm{\πA}}---\left(5\right)$

$a={0.25r}^2{C}_E\exp \left(\frac{B}{A}\right)---\left(6\right)$

Wherein, C _e=1.7810.

According to (5) (6), can obtain effective thermal conductivity, the effective thermal diffusivity of material.

Take and wet porosint as example, in step c, according to effective thermal conductivity, effective thermal diffusivity, solve heterogeneous content (water cut), detailed step is:

1. the average density of material is the volume fraction weighting according to each component;

2. the mean specific heat of material is the massfraction weighting according to each component;

Porous body for dry, has:

ρ _dry=ρ ₁x ₁ (7)

c _dry≈c ₁ (8)

For containing wet porosint, have:

ρ _eff=ρ ₁x ₁+ρ ₂x ₂ (9)

$\begin{array}{c}{c}_{\mathrm{eff}}\≈c_1{y}_1+c_2{y}_2\\ =c_1\frac{{\mathrm{\ρ}}_1{x}_1}{{\mathrm{\ρ}}_1{x}_1+{\mathrm{\ρ}}_2{x}_2}+c_2\frac{{\mathrm{\ρ}}_2{x}_2}{{\mathrm{\ρ}}_1{x}_1+{\mathrm{\ρ}}_2{x}_2}\end{array}---\left(10\right)$

Again because

$c_{\mathrm{dry}}=\frac{k_{\mathrm{dry}}}{a_{\mathrm{dry}}{\mathrm{\ρ}}_{\mathrm{dry}}}---\left(11\right)$

${\mathrm{\ρ}}_{\mathrm{eff}}{c}_{\mathrm{eff}}=\frac{k_{\mathrm{eff}}}{a_{\mathrm{eff}}}---\left(12\right)$

(7) (8) (9) (10) are updated in (12):

$\frac{k_{\mathrm{dry}}}{a_{\mathrm{dry}}}+c_2{\mathrm{\ρ}}_2{x}_2=\frac{k_{\mathrm{eff}}}{a_{\mathrm{eff}}}---\left(13\right)$

Wherein, ρ: density c: specific heat ρ c: volume caloic x: volume fraction

Y: massfraction eff: the actual parameter 1 that contains wet stock: solid phase 2: liquid phase

K: coefficient of heat conductivity a: thermal diffusivity dry: dry

Formula (13) is exactly the expression formula that finally solves water cut.The effective thermal conductivity, the effective thermal diffusivity that according to the experimental data gathering, solve wet stock, solve volume caloic, then the physical parameter when dry, solves x ₂, i.e. the volume fraction of moisture, the massfraction of moisture also can be tried to achieve subsequently.

Hot line adopts stabilized voltage supply power supply, and hot line can not be too thick, as far as possible the thermal capacitance of minimizing itself.When measuring wet stock, if necessary can be to hot line wrap insulate material processed.Temperature data can be remembered automatically with registering instrument, or manual record, and during manual record, the time interval in early stage is short, and the time interval in later stage can be longer.Subsequently the logarithm of temperature, time is drawn in coordinate system, fit to straight line, obtain slope A and intercept B in formula (4).Utilize subsequently the formula providing to try to achieve wet stock effective thermal conductivity, effective thermal diffusivity herein, then obtain the change of volume caloic.The coefficient of heat conductivity of drying material, thermal diffusivity can be looked into related data, or also by this method of testing, measure, and finally try to achieve the water cut of wet stock.

Claims (3)

1. based on volume caloic, measure a method for heterogeneous content in material, it is characterized in that, in object to be measured, arrange temperature sensor and thermal source; After thermal source heating, the temperature data of pick-up transducers; From temperature data, obtain effective thermal conductivity, effective thermal diffusivity; According to effective thermal conductivity, effective thermal diffusivity, first solve volume caloic; According to the change amount of volume caloic, obtain again the content of heterogeneous composition.

2. method according to claim 1, is characterized in that, the layout of sensor and heat resource form adopt thermal transient collimation method; When pre-buried hot line and temperature sensor, need make probe orientation parallel with pre-buried hot line; Pre-buried hot line adopts stabilized voltage supply power supply; Before test, make the temperature field of trying body inside be tending towards uniformity.

3. method according to claim 1 and 2, is characterized in that, hot line is the constant nickel filament of resistance.

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