CN101464423B - Thermal conductivity coefficient measurement instrument for solid material - Google Patents

Abstract

The invention provides a device for measuring the coefficient of heat conductivity of a solid material. The device comprises a heating plate, wherein, the heating plate comprises a first hot band, a second hot band and a third hot band which are distributed side by side; the first hot band includes a rectangular groove, and the third hot band includes a rectangular groove; the second hot band includes two rectangular grooves; all the rectangular grooves are made of nickel and are electrically connected with each other in the form of wheatstone bridge; and the measuring device further includesa power supply for providing two opposite nodes of the heating plate with constant energy, and a data acquisition system which is connected with the heating plate and used for collecting information about changes in voltage and temperature of other two opposite nodes in the heating plate, thereby obtaining the heat conductivity coefficient and the thermal diffusion coefficient of the material to be tested. The measuring instrument is capable of measuring the coefficient of heat conductivity from a heat insulating material to a metal material in a very short period of time, with the range of the obtained heat conductivity coefficient being 0.01-300Wm<-1>K<-1> and the uncertainty of the heat conductivity coefficient obtained within 5%.

Description

A kind of measurement mechanism of coefficient of heat conductivity of solid material

Technical field

The present invention relates to relate to the material thermal conductivity technical field of measurement and test, relate in particular to a kind of heat conductivity measuring device of solid material.

Background technology

The physical parameter of evaluating material heat-insulating property is exactly the temperature conductivity of material itself, and its inverse has determined the thermal resistance of material, and this is a thermal physical property parameter, and this parameter has decisive role for the heat-insulating property of evaluating material; Coefficient of heat conductivity has important purposes as the important physical parameter of material in fields such as chemical industry, material, the energy, power and Refrigeration Engineerings, is requisite basic data in many industrial flows and the product design.Along with fast development of modern industry, the thermal conductivity measurement of solid material is subject to people's attention day by day.

Methods such as the measurement by experiment of the coefficient of heat conductivity of material, theoretical calculate or computer simulation obtain, but at present still based on experiment measuring.According to the experiment measuring principle of coefficient of heat conductivity, its measuring method roughly can be divided into steady state method and unstable state method.

Steady state method be meant when the Temperature Distribution on the sample reach stable after, promptly the Temperature Distribution in the sample is time-independent stable temperature field, flows through the method that parameters such as the heat of sample and thermograde are determined the coefficient of heat conductivity of sample by mensuration.The characteristics of steady state method are that experimental principle is simple, yet this steady state method needs one dimension hot-fluid accurately, need set up thermal compensation device usually; Need simultaneously to arrange that a plurality of temperature points obtain even temperature and distribute; Therefore the electrical control of experimental provision and adjusting circuit more complicated; The needed measurement operating mode of this external preparation and experimentizing, all more consuming time and relatively harsher to environmental requirement, steady state method mainly includes guarded-plate method, heat flow meter method, pipe method etc.The unstable state method is meant that specimen temperature changes in time in the experiment measuring process, by temperature variations and other correlation parameters of some point in the measurement sample, thus the method for the coefficient of heat conductivity of definite sample; This method Measuring Time is short, accuracy is higher, and is low to environmental requirement, but also owing to be subjected to the restriction of measuring method itself, be used for the material that heat conducting coefficient measuring is tending towards constant more, mainly contain thermal transient collimation method, tropical method, normal power heat resource method, laser scintigraphy etc.

The measuring principle of transient state torrid zone method and thermal transient collimation method is very similar, get two measure-alike testing samples, sandwich a very thin sheet metal between the two, be the torrid zone, on the torrid zone, apply constant heating power, as constant thermal source, the temperature variation in the torrid zone can obtain by measuring the tropical changes in resistance that goes up, and also can directly record with thermopair.Further can obtain the variation relation that temperature and time is gone up in the torrid zone, just can obtain temperature conductivity according to its principle relational expression.This method can well contact the torrid zone with detected materials, simultaneously, and compares the temperature conductivity that can better measure solid material than heat-pole method, and heat-pole method is mainly used in measurement gas or there is bigger advantage fluent material temperature conductivity aspect.

Method heat conducting coefficient measuring used tropical cross sectional dimensions in the torrid zone is 4 * 0.008mm ², the resistivity of the metal material that it is selected is 5 * 10 ^-3, detected materials is of a size of 80 * 50 * 15mm ³In order to make good thermo-contact is arranged between the detected materials and the torrid zone, need add the lower oil of some viscosity ratio at they surface of contact, in addition, the transient state heat bridge method that on tropical method basis, occurs, promptly constitute the form distribution of Wheatstone bridge with eight resistance, the temperature and time of original tropical method relation is converted into voltage and the time relation that is easy to measure, utilizes constant current source to come entire circuit is heated.But this method adopts the constant prerequisite of supposing the system general power in measuring process, and theoretical system that obtains and corresponding constant current measurement scheme all are wrong.

In a word, at present those skilled in the art press for develop a kind of can be simple to operate and can select for use different modes accurately to measure the instrument of the coefficient of heat conductivity of solid material.

Summary of the invention

The purpose of this invention is to provide a kind of simple to operate, and can adopt different mode accurately measure the coefficient of heat conductivity of solid material and thermal diffusion coefficient measurement mechanism.

For achieving the above object, the invention discloses a kind of measurement mechanism of coefficient of heat conductivity of solid material, comprise, heating plate, this heating plate comprises: and first torrid zone of column distribution, second torrid zone, the 3rd torrid zone; This first torrid zone and the 3rd torrid zone comprise a rectangular channel respectively, this second torrid zone comprises two rectangular channels, described each rectangular channel is the nickel material preparation, and the form with Wheatstone bridge is electrically connected, described four rectangular channel equivalences are four resistance, and respectively as four arms of described Wheatstone bridge;

Power supply is used to that two opposite nodes provides constant energy in this heating plate;

Data acquisition system (DAS) is connected in described heating plate, and is used for gathering the voltage and the temperature variation of other two relative nodes of described heating plate, and the coefficient of heat conductivity that obtains this detected materials.

Further, the spacing of two rectangular channel outer walls comprising of described second torrid zone is 0.2 ± 0.1mm.

Further, the length of described rectangular channel is that 100 ± 10mm, inwall spacing are that 0.2 ± 0.1mm, the degree of depth are that the thickness of 20 ± 10 μ m, inwall and contiguous outer wall is 0.4 ± 0.2mm.

Further, described power supply is the power supply of constant current, constant voltage or permanent power.

Further, the equivalent resistance of described first rectangular channel is R=3 Ω.

Further, described detected materials length more than or equal to 130mm, width more than or equal to 70mm.

Further, described device also comprises and is used to condiment that detected materials and heating plate are contacted closely.

For achieving the above object, the invention also discloses a kind of thermal conductivity measurement method of solid-state material, comprising: comprising:

Above-mentioned heating plate is positioned in the middle of two detected materials;

Select relative measurement pattern or absolute measurement pattern;

The humidity and the temperature of record detected materials kind and environment;

On described heating plate, load constant current source, constant pressure source or constant power source;

Gather the output voltage at Wheatstone bridge two ends and this output voltage over time and handle institute's image data, obtain the coefficient of heat conductivity of this detected materials;

Wherein, described heating plate comprises: and first torrid zone of column distribution, second torrid zone, the 3rd torrid zone; This first torrid zone and the 3rd torrid zone comprise a rectangular channel respectively, this second torrid zone comprises two rectangular channels, described each rectangular channel is the nickel material preparation, and the form with Wheatstone bridge is electrically connected, described four rectangular channel equivalences are four resistance, and respectively as four arms of described Wheatstone bridge.

Further, also comprise before the step of described selection measurement pattern, load the condiment that a described detected materials and described heating plate contact closely.

Further, the length of described detected materials more than or equal to 130mm, width more than or equal to 70mm.

Compared with prior art, the present invention has the following advantages:

At first, measurement mechanism of the present invention can be measured the coefficient of heat conductivity of various different materials in a short period of time, and the scope of the coefficient of heat conductivity of its measurement is 0.01～300Wm ^-1K ^-1, and the uncertainty of measured coefficient of heat conductivity is in 5%, and can be good at measuring thermal diffusion coefficient;

Secondly, it is the heating plate of arranging by the form with Wheatstone bridge that the heater strip that uses the nickel material preparation is formed that the present invention utilizes the principle of constant pressure source heat conducting coefficient measuring, when two detected materials compress this heating plate, the voltage and the temperature variation of two the relative nodes in centre by measuring this Wheatstone bridge draw the coefficient of heat conductivity and the thermal diffusion coefficient of detected materials according to measuring principle of the present invention; This method is simple, and is easy to operate, and within the scope-30 of the temperature variation when measuring ℃-100 ℃;

Moreover, on the method basis, the transient state torrid zone of prior art, develop and symmetrical transient state torrid zone method, convert measurement voltage signal to measuring temperature signal in the tropical method, and the tropical device of the constant current source transient state that obtains thus symmetry, the constant pressure source transient state tropical device of symmetry and the tropical device of constant power source transient state symmetry, this device can be very fast and the coefficient of heat conductivity of high-precision measurement solid material, and greatly reduce cost of manufacture.

Description of drawings

The structure vertical view of the heating plate that Fig. 1 comprises for measurement mechanism of the present invention;

Fig. 2 is the enlarged diagram of the local A among Fig. 1 of the present invention;

Fig. 3 is the enlarged diagram of the local B among Fig. 1 of the present invention;

Fig. 4 is the schematic equivalent circuit of heating plate of the present invention;

Fig. 5 is the decomposing schematic representation of the measurement mechanism of measurement mechanism of the present invention under the absolute measurement pattern;

Fig. 6 is the schematic equivalent circuit that heating plate of the present invention loads steady current;

Fig. 7 is the measurement mechanism combination synoptic diagram of measurement mechanism of the present invention under the absolute measurement pattern;

Fig. 8 is the schematic equivalent circuit that heating plate of the present invention loads steady current;

Fig. 9 is the schematic equivalent circuit that heating plate of the present invention loads constant voltage;

Figure 10 is the measurement mechanism combination synoptic diagram of measurement mechanism of the present invention under the relative measurement pattern;

Figure 11 is the measurement curve map of the embodiment of measurement mechanism heat conducting coefficient measuring of the present invention.

Embodiment

Below in conjunction with drawings and Examples solid material heat conductivity measuring device of the present invention is further specified.

Coefficient of heat conductivity is one of important thermophysical property of material, and the temperature conductivity of material is the important parameter that characterizes the energy-saving building materials rerum natura, and it is accurately measured very important theory and engineering using value.Because coefficient of heat conductivity is more with the composition and the structural change of material, determine that with experimental technique material thermal conductivity almost becomes the unique channel of research material coefficient of heat conductivity.

Coefficient of heat conductivity is the physical quantity of reflection material capacity of heat transmission size, is also referred to as temperature conductivity, and unit is Wm ^-1K ^-1

Core idea of the present invention is to utilize the measurement mechanism of the measurement solid material coefficient of heat conductivity that tropical method sets up, promptly use thermal transient bridge method, in conjunction with constant current source, constant pressure source or constant power source detected materials is measured, adopt heating plate of the present invention, set up the measuring method of new solid material coefficient of heat conductivity, this method can be measured the coefficient of heat conductivity from the thermal insulation material to the metal material in a short period of time, and the scope of its heat conducting coefficient measuring is 0.01～300Wm ^-1K ^-1, and Measurement Uncertainty is in 5%.

Embodiment 1

Structure vertical view with reference to heating plate of the present invention shown in Figure 1, Fig. 2 and Fig. 3 have provided regional area A and the structure for amplifying synoptic diagram of local area B and the size of having demarcated heater strip in the drawings among Fig. 1, unit is mm among the figure, and the selected material of heating plate is the thick pure nickel sheets of 20 μ m.

As can be seen from Figure 1, a kind of solid material heat conductivity measuring device of the present invention comprises: heating plate 101, and this heating plate 101 comprises: and first torrid zone 102, second torrid zone 103, the 3rd torrid zone 105 of column distribution; These first heat, 102 bands and the 3rd torrid zone 105 comprise the rectangular channel of a nickel material preparation respectively, this second torrid zone 103 comprises that two spacings are the rectangular channel of 0.2 ± 0.1mm (as shown in Figure 3), and described rectangular channel is that the length of nickel material preparation is that 100 ± 10mm, inwall spacing are that 0.2 ± 0.1mm, the degree of depth are that the thickness of 20 ± 10 μ m, inwall and contiguous outer wall is 0.4 ± 0.2mm; Described rectangular channel is electrically connected with the form of Wheatstone bridge, and the rectangular channel described in the present embodiment interconnects by lead 104, and connects power supply and data acquisition system (DAS) by lead 104;

Power supply is used to the two opposite nodes of this heating plate that constant energy is provided; Wherein, this power supply can be constant current source, constant pressure source or constant power source;

Data acquisition system (DAS), the upper surface that is used to gather described heating plate and lower surface additional phase with detected materials after the voltage and the temperature variation of other two relative nodes, obtain the coefficient of heat conductivity of detected materials.

In concrete implementation procedure, preferably the thickness of the outer wall of the inwall of each rectangular channel and vicinity is 0.4mm, and the inwall spacing is 0.2mm, and in the present embodiment, setting each rectangular channel equivalence is a resistance.System deviation during such design can reduce to measure, the influence that brings is less than 0.01%.Thereby, this heating plate can equivalence be the circuit connection diagram that is made of Wheatstone bridge four resistance in center, the fringe region of described heating plate is equivalent to lead and connects described rectangular channel as shown in Figure 4, the resistance R 1 of each rectangular channel equivalence, resistance R 2, resistance R 3 and resistance R 4 are equivalent to four arms of electric bridge, and the dash area resistance among Fig. 4 is called internal resistance, and all the other two resistance are called non-essential resistance.In addition, each resistance among Fig. 4 is approximately equal all, and its difference is less than per mille.

Embodiment 2

Measuring principle and the corresponding measurement mechanism of constant current source being measured device below in conjunction with accompanying drawing are elaborated:

With reference to heating plate structural representation of the present invention shown in Figure 1, present embodiment adopts the mode of steady current to come to provide energy to heating plate, promptly between the A of Wheatstone bridge shown in Figure 4 and D point, load steady current, the measurement mechanism structure of the coefficient of heat conductivity of loading constant current source is included as the constant current source 005 that heating plate 101 provides energy as shown in Figure 5, on the heating plate 101, lower surface connects identical detected materials 004 and detected materials 002 (detected materials 004 is identical with detected materials 002 in the present embodiment) respectively, be used to gather the B of heating plate 101, voltage that C is 2 and the data acquisition system (DAS) of temperature variation 006, and be used to condiment 001 that detected materials and heating plate are contacted closely; This data acquisition system (DAS) can also comprise the temperature measuring equipment of electric logging equipment, measurement and the record temperature variation of measuring also record current variation in addition.

When using constant current source measurement device to measure, the first step, the heating plate that the outside is covered the nickel material preparation of layer protecting film be placed on two block lengths more than or equal to 130mm, width more than or equal in 70mm, the detected materials of the same race of height more than or equal to 25mm;

Second step loaded constant current source on the heating plate two opposite nodes, the built-in third gear of constant current source that present embodiment uses, i.e. and 0.15A, 0.3A, 0.6A, and error that should crossing current source output current is 5/10000ths;

In the 3rd step, gather the output voltage of B and C point (as shown in Figure 4), automatic processes and displays coefficient of heat conductivity of this data acquisition system (DAS) and thermal diffusion coefficient by data acquisition system (DAS).

Load the equivalent circuit diagram of exporting behind the constant current source with reference to heating plate of the present invention shown in Figure 6, when adding a stable electric current at this heating plate, this heating plate is to the certain heat of detected materials transmission, by corresponding B that measures this heating plate and electric current and the temperature variation that C is ordered, export corresponding signal; Select relative measurement pattern or absolute measurement pattern, and then gather this signal by data acquisition system (DAS), and handle automatically, measurement result and coefficient of heat conductivity finally are presented on the program interface, obtain the coefficient of heat conductivity of detected materials;

The measuring principle that the absolute measurement pattern of this constant current source measurement device is used such as the following derivation of equation:

Load constant current at A and D point, then B and the C voltage of ordering is:

$U_{\mathrm{BC}}=\frac{I}{2}(R_3-R_4)---\left(1\right)$

In the formula: R ₀₃And R ₀₄Be respectively arm R ₃With arm R ₄Resistance.

Each resistance can be expressed from the next with the variation of temperature relation:

R(T)＝R(0℃)(1+αT)(2)

In the formula: the resistance of R (0 ℃) when being 0 ℃, α is the temperature-coefficient of electrical resistance of nickel, T is a temperature.Wushu (2) is brought formula (1) into, and arrangement obtains:

In the formula: subscript I and O represent internal resistance and non-essential resistance respectively.

To the torrid zone of each resistance correspondence, its medial temperature is:

$\stackrel{\&OverBar;}{T}\left(t\right)=\frac{\mathrm{\&Phi;}}{4\mathrm{\&pi;L\&lambda;}}[3-\mathrm{\&gamma;}+2\ln \mathrm{\&tau;}+O\left(\frac{1}{{\mathrm{\&tau;}}^2}\right)]---\left(4\right)$

In the formula: Φ is a heating power, and L is the length in the torrid zone of each resistance correspondence, and λ is a coefficient of heat conductivity, and γ=0.5772156649...... is an Euler's constant, $\mathrm{\&tau;}=\frac{\sqrt{4\mathrm{at}}}{D}$ Be time constant, a is a thermal diffusion coefficient, and D is the width in the torrid zone of each resistance correspondence, and t is the time.

When τ＞4, formula (4) block influence meeting less than per mille, thereby the Measuring Time that needs satisfies following formula (5):

$\mathrm{\&tau;}=\frac{\sqrt{4\mathrm{at}}}{D}>4\&DoubleRightArrow;t>\frac{4D^2}{a}---\left(5\right)$

The power of considering the corresponding torrid zone of internal resistance is 2 times of the corresponding tropical power of non-essential resistance, and the equivalent width of internal resistance is 2.2 times of outside tropical equivalent width, can obtain the temperature difference between the corresponding torrid zone of internal resistance and the corresponding torrid zone of non-essential resistance:

$\mathrm{\&Delta;}\stackrel{\&OverBar;}{T}=T^I-T^O=\frac{2\mathrm{\&Phi;}}{4\mathrm{\&pi;L\&lambda;}}[3-\mathrm{\&gamma;}+2\mathrm{<figure-callout\; id="4"\; label="ln"\; filenames="H2009100764264E00061.png"\; state="\{\{state\}\}">ln</figure-callout>}\frac{\sqrt{4\mathrm{at}}}{2.2D}]-\frac{\mathrm{\&Phi;}}{4\mathrm{\&pi;L\&lambda;}}[3-\mathrm{\&gamma;}+2\mathrm{<figure-callout\; id="4"\; label="ln"\; filenames="H2009100764264E00061.png"\; state="\{\{state\}\}">ln</figure-callout>}\frac{\sqrt{4\mathrm{at}}}{D}]---\left(6\right)$

$=\frac{\mathrm{\&Phi;}}{4\mathrm{\&pi;L\&lambda;}}(\ln \frac{\exp (3-\mathrm{\&gamma;})a}{5.86{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="H2009100764264E00061.png"\; state="\{\{state\}\}">D</figure-callout>}}^2}+\ln t)$

Substitution formula (3) can obtain:

$U_{\mathrm{BC}}=\frac{\mathrm{\&alpha;}{I}_B\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="H2009100764264E00061.png"\; state="\{\{state\}\}">R</figure-callout>}}_0\mathrm{\&Phi;}}{8\mathrm{\&pi;L\&lambda;}}(\ln \frac{\exp (3-\mathrm{\&gamma;})a}{5.86{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="H2009100764264E00061.png"\; state="\{\{state\}\}">D</figure-callout>}}^2}+\ln t)---\left(7\right)$

In actual measurement, can record the time dependent curve of voltage at BC two ends, it is as follows further can to fit to linear relation to the experimental data of τ＞4:

$U_{\mathrm{BC}}=m(\frac{n}{m}+\ln t)---\left(8\right)$

In the formula: m is a slope, and n is an intercept.

The coefficient of contrast formula (7) and (8) can obtain the equation of heat conducting coefficient measuring and thermal diffusion coefficient:

$a=4{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="H2009100764264E00061.png"\; state="\{\{state\}\}">D</figure-callout>}}^2\exp (\frac{n}{m}-3+\mathrm{\&gamma;})---\left(10\right)$

In measuring process, the variation of used constant power source is less than 5/1000ths, thereby heating power is expressed as:

At last, the equation of heat conducting coefficient measuring is

Formula (12) is the formula that constant current source is measured the measurement material thermal conductivity of device use.Tropical length L in this formula (12), temperature coefficient α, resistance resistance R (0 ℃) in the time of 0 degree centigrade can determine before experiment that temperature T can be obtained by thermometer or other temperature measuring equipment measurement when measuring beginning, and wherein, slope m is by voltage U _BCChange curve match in time obtains, and measures electric current I by known measuring resistance R ₀With the top voltage U that records ₀Determine.

All theoretical algorithms all are integrated in the control program of data acquisition system (DAS), each resistance of equivalence is about R=3 Ω in the heating plate of Shi Yonging in the present embodiment, in order in measurement, to obtain stable and signal accurately, make the variable power of whole heating plate less as far as possible, the wherein most preferred selection of I=0.3A present embodiment.

Embodiment 3

Be elaborated below in conjunction with the measuring principle and the corresponding measurement mechanism of accompanying drawing to the constant pressure source measurement mechanism:

Adopt stable voltage to come to provide energy in the present embodiment, thereby obtain the another kind of experimental provision and the corresponding measuring principle of heat conducting coefficient measuring to heating plate.The structure of heating plate as shown in Figure 1, loading constant pressure source of the present invention as shown in Figure 7 and the measurement mechanism under absolute measurement pattern combination synoptic diagram, this device is identical with above-mentioned constant current source measurement device; When this constant current source loads described heating plate, analyze with equivalent circuit diagram as shown in Figure 8;

When adopting the constant pressure source measurement mechanism to measure to detected materials, the measuring process of the same constant current source: the first step, the outside cover heating plate that the heater strip of layer protecting film forms be placed on two block lengths more than or equal to 130mm, width more than or equal between 70mm, the detected materials of the same race of height more than or equal to 25mm;

Second step loaded constant pressure source on the heating plate two opposite nodes, constant pressure source is electrically connected with heating plate, and the built-in third gear of the constant pressure source of present embodiment use is exported, 0.4V, 0.8V, 1.6V, and the output current precision is ten thousand/.

In the 3rd step, by data acquisition system (DAS) collection B and the C output voltage and the temperature of ordering as shown in Figure 8, this data acquisition system (DAS) is handled automatically and is shown and can obtain thermal diffusion coefficient simultaneously in addition by coefficient of heat conductivity.

When loading constant pressure source on heating plate, the equivalent circuit diagram of this constant pressure source measurement mechanism as shown in Figure 8.A and D two ends at heating plate during experiment measuring add constant voltage, and the output voltage of measurement B and C end obtains coefficient of heat conductivity and thermal diffusion coefficient that measurement slope of a curve and intercept obtain needs over time.

Below in conjunction with Fig. 8 the computing formula derivation of the coefficient of heat conductivity under the absolute measurement pattern of present embodiment constant pressure source is elaborated:

As shown in Figure 4, at the A and the D point loading constant voltage U of heating plate, the voltage that B and C are ordered can be expressed as:

$U_{\mathrm{BC}}=\frac{R_{03}-R_{04}}{R_{03}+R_{04}}U---\left(13\right)$

Following formula is split into internal resistance and non-essential resistance (in four arms of the Wheatstone bridge shown in Fig. 4, the resistance of dash area is that internal resistance, other resistance are called non-essential resistance) is:

$U_{\mathrm{BC}}=\frac{R^I-R^O}{R^I+R^O}U---\left(14\right)$

In the formula: subscript I and O represent internal resistance and non-essential resistance respectively.

Each resistance can be expressed from the next with the variation of temperature relation in the prior art:

R(T)＝R(0℃)(1+αT)(15)

In the formula: the resistance of R (0 ℃) when being 0 ℃, α is the temperature-coefficient of electrical resistance of nickel.Wushu (15) substitution formula (14) arrangement obtains:

$U_{\mathrm{BC}}=\frac{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="H2009100764264E00061.png"\; state="\{\{state\}\}">U</figure-callout>}}{2}\frac{\mathrm{\&alpha;}(T^I-T^O)}{1+\mathrm{\&alpha;}\left(\frac{T^I+T^O}{2}\right)}---\left(16\right)$

To the torrid zone of each resistance correspondence, its medial temperature is:

$\stackrel{\&OverBar;}{T}\left(t\right)=\frac{\mathrm{\&Phi;}}{4\mathrm{\&pi;L\&lambda;}}[3-\mathrm{\&gamma;}+2\ln \mathrm{\&tau;}+O\left(\frac{1}{{\mathrm{\&tau;}}^2}\right)]---\left(17\right)$

In the formula: Φ is a heating power, and L is this tropical length, and λ is a coefficient of heat conductivity, and γ=0.5772156649...... is an Euler's constant, $\mathrm{\&tau;}=\frac{\sqrt{4\mathrm{at}}}{D}$ Be time constant, a is a thermal diffusion coefficient, and D is the width in the torrid zone, and t is the time.

When τ＞4, formula (4) block influence meeting less than per mille, thereby Measuring Time need satisfy:

$\mathrm{\&tau;}=\frac{\sqrt{4\mathrm{at}}}{D}>4,$ Obtain: $t>\frac{4D^2}{a}---\left(18\right)$

The power of considering the corresponding torrid zone of internal resistance is 2 times of the corresponding tropical power of non-essential resistance, and the equivalent width of internal resistance is 2.2 times of outside tropical equivalent width, can obtain the temperature difference between the corresponding torrid zone of internal resistance and the corresponding torrid zone of non-essential resistance:

$\mathrm{\&Delta;}\stackrel{\&OverBar;}{T}=T^I-T^O=\frac{2\mathrm{\&Phi;}}{4\mathrm{\&pi;L\&lambda;}}[3-\mathrm{\&gamma;}+2\mathrm{<figure-callout\; id="4"\; label="ln"\; filenames="H2009100764264E00061.png"\; state="\{\{state\}\}">ln</figure-callout>}\frac{\sqrt{4\mathrm{at}}}{2.2D}]-\frac{\mathrm{\&Phi;}}{4\mathrm{\&pi;L\&lambda;}}[3-\mathrm{\&gamma;}+2\mathrm{<figure-callout\; id="4"\; label="ln"\; filenames="H2009100764264E00061.png"\; state="\{\{state\}\}">ln</figure-callout>}\frac{\sqrt{4\mathrm{at}}}{D}]---\left(19\right)$

$=\frac{\mathrm{\&Phi;}}{4\mathrm{\&pi;L\&lambda;}}(\ln \frac{\exp (3-\mathrm{\&gamma;})a}{5.86{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="H2009100764264E00061.png"\; state="\{\{state\}\}">D</figure-callout>}}^2}+\ln t)$

Substitution formula (16) can obtain:

$U_{\mathrm{BC}}=\frac{\mathrm{U\&alpha;\&Phi;}}{8\mathrm{\&pi;L\&lambda;}}\frac{1}{1+\mathrm{\&alpha;}\left(\frac{T^I+T^O}{2}\right)}(\ln \frac{\exp (3-\mathrm{\&gamma;})a}{5.86{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="H2009100764264E00061.png"\; state="\{\{state\}\}">D</figure-callout>}}^2}+\ln t)---\left(20\right)$

In actual measurement, can record the time dependent curve of voltage at B, C two ends, and then can fit to following linear relation to the experimental data of τ＞4 o'clock:

$U_{\mathrm{BC}}=m(\frac{n}{m}+\ln t)---\left(21\right)$

In the formula: m is a slope, and n is an intercept.

The coefficient of contrast formula (20) and (21) can obtain:

$\mathrm{\&lambda;}=\frac{\mathrm{U\&alpha;\&Phi;}}{8\mathrm{\&pi;Lm}}\frac{1}{1+\mathrm{\&alpha;}\left(\frac{T^I+T^O}{2}\right)}---\left(22\right)$

$a=4{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="H2009100764264E00061.png"\; state="\{\{state\}\}">D</figure-callout>}}^2\exp (\frac{n}{m}-3+\mathrm{\&gamma;})---\left(23\right)$

In measuring process, the variation of heating power is less than 5/1000ths, and heating power is expressed as:

Can obtain at last:

Before the measurement, to tropical length L, temperature coefficient α, long resistance resistance R 0 degree centigrade the time _L(0 ℃) and short resistance resistance R in the time of 0 degree centigrade _S(0 ℃) can preestablish, and temperature T can be obtained by thermometer measure when measuring beginning, and slope m and intercept n are by voltage U _BCChange curve match in time obtains, and measuring voltage U is by voltage table U ₀Measure.The measurement control program that all numerical value that obtain are transferred to the LabVIEW establishment at last calculates automatically, draw the coefficient of heat conductivity and the thermal diffusion coefficient of detected materials according to formula (25) and (23), present embodiment loads constant voltage U=0.8V between A and D be optimum selection.

Embodiment 4

Be elaborated below in conjunction with the measuring principle and the corresponding measurement mechanism of accompanying drawing to the constant power source measurement mechanism:

Adopt stable constant power source to come to provide energy in the present embodiment, thereby obtain the third experimental provision and the corresponding measuring principle of heat conducting coefficient measuring to heating plate.The structure of heating plate such as the same shown in Figure 1, the structural representation of entire measuring device can with reference to the decomposing schematic representation of the combination synoptic diagram of Fig. 7 or Fig. 5; This constant power source is different for being internal circuit configuration with the difference of constant pressure source, constant current source, the equivalent circuit diagram during with reference to loading constant power source shown in Figure 9; And analyze in conjunction with the equivalent circuit diagram of Fig. 4 heating plate.

When selecting the constant power source measurement mechanism to treat the side material to measure, the first step, the outside cover heating plate that the heater strip of the nickel material preparation of layer protecting film forms be placed on two block lengths more than or equal to 130mm, width more than or equal in 70mm, the detected materials of the same race of height more than or equal to 25mm;

Second step on the heating plate two opposite nodes, loaded constant power source, the built-in third gear power output that present embodiment uses, and 0.06W, 0.24W, 0.96W, output accuracy are per mille.

In the 3rd step, by data acquisition system (DAS) collection B and the C output voltage of ordering as shown in Figure 4, this data system carries out automatic processes and displays coefficient of heat conductivity and thermal diffusion coefficient.

When loading constant power source on heating plate, the equivalent circuit diagram of this constant power source measurement mechanism as shown in Figure 9.A and D two ends at heating plate during experiment measuring add constant power, the output voltage of measuring B and C end over time, slope of a curve and intercept obtain the coefficient of heat conductivity and the thermal diffusion coefficient that need then.

Below in conjunction with Fig. 9 the computing formula derivation of the coefficient of heat conductivity under the absolute measurement pattern of present embodiment constant power source is elaborated:

Load firm power Φ at A and D point, measured coefficient of heat conductivity can be determined by formula (12) and (25):

$a=4{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="H2009100764264E00061.png"\; state="\{\{state\}\}">D</figure-callout>}}^2\exp (\frac{n}{m}-3+\mathrm{\&gamma;})---\left(27\right)$

Equally, before measurement, need be to tropical length L, temperature coefficient α, long resistance resistance R 0 degree centigrade the time _L(0 ℃) and short resistance resistance R in the time of 0 degree centigrade _S(0 ℃) preestablishes, and temperature T can be obtained by thermometer measure when measuring beginning, and slope m and intercept n are by voltage U _BCChange curve match in time obtains, and measuring voltage U is by voltage table U ₀Measure.The measurement control program that all numerical value that obtain are transferred to the LabVIEW establishment at last calculates, and draws the coefficient of heat conductivity of the detected materials that loads constant power source under the absolute measurement pattern and the measure equation of thermal diffusion coefficient according to formula (26) and (27).

Embodiment 5

In specific implementation, have only a detected materials usually, so the present invention can also select the relative measurement pattern of constant current source, constant pressure source, constant power source measurement mechanism to measure.Below the relative measurement principle of constant current source, constant pressure source, constant power source is described in detail.

The formula of its constant current source, constant pressure source, constant power source relative measurement is all identical, in conjunction with shown in Figure 10, is the device decomposing schematic representation of coefficient of heat conductivity relative measurement of the present invention; The apparatus structure of the relative measurement pattern of its constant power source, constant current source and constant pressure source is identical, when selecting relative measurement in data acquisition system (DAS), with a block of material M ₁As the standard material 010 (this material is commonly known in the art) of the standard material SRM1450c of U.S. measurement standard Institute for Research and Technology, measure its coefficient of heat conductivity λ with absolute mode before the experiment ₀, or obtain the coefficient of heat conductivity of known this standard material 010 each temperature correspondence by tabling look-up.

When selecting firm power/constant/constant current, the Temperature Distribution on the heating plate of the present invention will be subjected to the constraint of these two kinds of materials simultaneously, and it is λ that described formula (12), (25), (26) are comprehensive coefficient of heat conductivity _AllThat is to say the coefficient of heat conductivity sum that this comprehensive coefficient of heat conductivity is detected materials and standard material.

The pushing over formula and can know of absolute measurement principle by above-mentioned firm power/constant/constant current, thereby the coefficient of heat conductivity λ of the detected materials of described relative measurement pattern satisfies following relational expression:

λ＝2λ _all-λ ₀(29)

In the apparatus structure of constant power source, constant current source and constant pressure source, select the relative measurement pattern, in primary control program (PCP), increase formula (29), can in data acquisition system (DAS), obtain the coefficient of heat conductivity of the relative measurement of detected materials.

Embodiment 6

Below the measurement/method of operating of described measurement mechanism is elaborated:

The key step of the coefficient of heat conductivity of use constant current source measurement device, constant pressure source measurement mechanism or constant power source measurement mechanism measurement detected materials and the measuring method of thermal diffusion coefficient comprises:

Step S01: heating plate is positioned in the middle of two detected materials, the condition length that described detected materials need satisfy more than or equal to 130mm, width more than or equal to 70mm or height more than or equal to 25mm;

Step S02: select absolute measurement pattern or relative measurement pattern;

Step S03: the humidity and the temperature of record detected materials kind and environment;

Step S04: load constant current source, constant pressure source or constant power source;

Step S05: gather and deal with data, obtain the coefficient of heat conductivity of this detected materials.

Preferred embodiment, before step S02, press the condiment of this device configuration, as Fig. 5 or apparatus structure synoptic diagram shown in Figure 7; And then select to measure the absolute measurement pattern, secondly, can adopt in the present embodiment to take multiple measurements: whether need promptly to select continuous coverage repeatedly (at interval 30 minutes once); Coefficient of heat conductivity and the thermal diffusion coefficient measured will be shown on the interface respectively, and are stored in the specified file.

Certainly, in this experimental implementation method, can also select the relative measurement pattern, be placed on standard material the upper surface of heating plate, detected materials be placed on the lower surface of heating plate this moment, select the relative measurement pattern, the same other operation steps, and then can obtain the coefficient of heat conductivity and the thermal diffusion coefficient of detected materials.

Embodiment 7

Below in conjunction with concrete empirical curve constant pressure source measurement mechanism of the present invention is elaborated: experiment can be carried out at-30 ℃～100 ℃, when using absolute measurement, (metal material is two of the detected materials of 130mm * 70mm * 25mm) to need 130mm * 70mm * 10mm, when using absolute measurement, (metal material is one of the detected materials of 130mm * 70mm * 25mm), need note the humidity in room during measurement only to need 130mm * 70mm * 10mm.After setting sample, on operation interface, select relative measurement pattern or absolute measurement pattern, press initiating key, wait for certain hour, described data acquisition system (DAS) demonstrates the accurate measurement result of coefficient of heat conductivity.

Figure 11 is that example has provided the empirical curve of at room temperature measuring the standard material SRM1450c of U.S. measurement standard Institute for Research and Technology with absolute method with the constant pressure source, and point discrete among the figure is an experimental data, and horizontal ordinate is the natural logarithm of time, and ordinate is an output voltage.Learn by formula (18), get $t>\frac{4D^2}{a}$ Point carry out match, it is as follows to obtain linear formula:

U＝-1.175534+1.622887ln(t) (30)

Thereby obtain:

m＝1.622887；n＝-1.175534 (31)

Substitution formula (25) and formula (23) obtain

λ＝0.039W·m ^-1·K ^-1 (32)

a＝0.12mm ²·s ^-1 (33)

The nominal value of NIST under this temperature and corresponding density is λ=0.038Wm ^-1K ^-1, difference of them is less than 5%.

Utilize measurement mechanism of the present invention, select absolute measurement pattern and relative measurement pattern that the coefficient of heat conductivity of following material is measured, the results are shown in table 1, wherein λ _aBe the thermal conductivity value that absolute method is measured, λ _rBe relative method measured value.

The thermal conductivity value of table 1 different materials

In the above-described embodiments, the description of each embodiment is all emphasized particularly on different fields, do not have the part that describes in detail among certain embodiment, can get final product referring to the associated description of other embodiment.

At last, also need to prove, in this article, relational terms such as first and second grades only is used for an entity or operation are made a distinction with another entity or operation, and not necessarily requires or hint and have the relation of any this reality or in proper order between these entities or the operation.And, term " comprises ", " comprising " or its any other variant are intended to contain comprising of nonexcludability, thereby make and comprise that process, method, article or the equipment of a series of key elements not only comprise those key elements, but also comprise other key elements of clearly not listing, or also be included as this process, method, article or equipment intrinsic key element.Do not having under the situation of more restrictions, the key element that limits by statement " comprising ... ", and be not precluded within process, method, article or the equipment that comprises described key element and also have other identical element.

More than the constant current source of a kind of solid material coefficient of heat conductivity provided by the present invention is measured device, constant pressure source measurement mechanism, constant power source measurement mechanism and solid material coefficient of heat conductivity measuring method be described in detail, used specific case herein principle of the present invention and embodiment are set forth, the explanation of above embodiment just is used for helping to understand method of the present invention and core concept thereof; Simultaneously; for one of ordinary skill in the art; according to thought of the present invention; the part that all can change in specific embodiments and applications, in sum, this description should not be construed as limitation of the present invention; under the situation that does not break away from the spirit and scope of the present invention; can also make various variations and modification, so all technical schemes that are equal to also belong to category of the present invention, scope of patent protection of the present invention should be defined by the claims.

Claims (10)

1. the measurement mechanism of the coefficient of heat conductivity of a solid material is characterized in that, comprise,

Heating plate, this heating plate comprises: and first torrid zone of column distribution, second torrid zone, the 3rd torrid zone; This first torrid zone and the 3rd torrid zone comprise a rectangular channel respectively, this second torrid zone comprises two rectangular channels, described each rectangular channel is the nickel material preparation, and the form with Wheatstone bridge is electrically connected, described four rectangular channel equivalences are four resistance, and respectively as four arms of described Wheatstone bridge;

Power supply is used to that two opposite nodes provides constant energy in this heating plate;

Data acquisition system (DAS) is connected in described heating plate, and is used for gathering the voltage and the temperature variation of other two relative nodes of described heating plate, and the coefficient of heat conductivity that obtains this detected materials.

2. measurement mechanism as claimed in claim 1 is characterized in that, the spacing of two rectangular channel outer walls that described second torrid zone comprises is 0.2 ± 0.1mm.

3. measurement mechanism as claimed in claim 1 is characterized in that, the length of described rectangular channel is that 100 ± 10mm, inwall spacing are that 0.2 ± 0.1mm, the degree of depth are that the thickness of 20 ± 10 μ m, inwall and contiguous outer wall is 0.4 ± 0.2mm.

4. measurement mechanism as claimed in claim 1 is characterized in that, described power supply is the power supply of constant current, constant voltage or permanent power.

5. measurement mechanism as claimed in claim 1 is characterized in that, the equivalent resistance of described first rectangular channel is R=3 Ω.

6. measurement mechanism as claimed in claim 1 is characterized in that, described detected materials length more than or equal to 130mm, width more than or equal to 70mm.

7. measurement mechanism as claimed in claim 1 is characterized in that, also comprises being used to condiment that detected materials and heating plate are contacted closely.

8. a method of using the described measurement mechanism of claim 1 to measure the solid-state material coefficient of heat conductivity is characterized in that, comprising:

Heating plate is positioned in the middle of two detected materials;

Select relative measurement pattern or absolute measurement pattern;

The humidity and the temperature of record detected materials kind and environment;

On described heating plate, load constant current source, constant pressure source or constant power source;

Gather the output voltage at Wheatstone bridge two ends and this output voltage over time and handle institute's image data, obtain the coefficient of heat conductivity of this detected materials;

Wherein, described heating plate comprises: and first torrid zone of column distribution, second torrid zone, the 3rd torrid zone; This first torrid zone and the 3rd torrid zone comprise a rectangular channel respectively, this second torrid zone comprises two rectangular channels, described each rectangular channel is the nickel material preparation, and the form with Wheatstone bridge is electrically connected, described four rectangular channel equivalences are four resistance, and respectively as four arms of described Wheatstone bridge.

9. method as claimed in claim 8 is characterized in that, also comprises before the step of described selection measurement pattern, loads the condiment that a described detected materials and described heating plate contact closely.

10. method as claimed in claim 8 is characterized in that, the length of described detected materials more than or equal to 130mm, width more than or equal to 70mm.

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