CN103364434B - The hemisphere of large difference sample is to the measuring method of total emissivity - Google Patents

Abstract

The invention specifically discloses a method for measuring the hemispherical total emissivity of a sample with a large temperature difference. The steps include: selecting a strip-shaped conductor material sample, heating the sample in a vacuum environment, and using a radiation temperature field measuring device to obtain the hemispherical total emissivity in a stable heating state. The temperature field distribution on the surface of the sample; the sample is divided into multiple micro-element control bodies along its axial direction, and the steady-state energy balance equation of the micro-element control body is established; based on the surface temperature field distribution of the sample and the voltage and current at both ends of the sample , calculate the numerical distribution of the hemispherical emissivity of the sample with temperature in the heating steady state. This method of the present invention is suitable for measuring the hemispherical total emissivity of a conductor material sample with a large temperature gradient distribution, overcomes the technical limitations of the existing steady-state calorimetry method for the sample to have a uniform temperature test area, and greatly reduces the The restriction on sample size and specifications is small, and it is simple and feasible.

Description

Measurement method of hemispherical total emissivity of samples with large temperature difference

technical field

The invention relates to the field of measuring the hemispherical total emissivity of conductor materials, in particular to a method for measuring the hemispherical total emissivity of a conductor material sample with a large temperature difference.

Background technique

Hemispherical total emissivity is one of the important thermophysical parameters of materials, which characterizes the surface thermal radiation ability of materials, and is an important basic physical property data for the study of radiation measurement, radiation heat transfer and thermal efficiency analysis. With the wide application of new materials in high-tech fields such as energy power and aerospace, more urgent needs have been put forward for the measurement of hemispherical total emissivity. Compared with other thermal physical parameters, the hemispherical total emissivity measurement method The technical research is still insufficient, and the data of the hemispherical full emissivity of different materials is still lacking. It is necessary to obtain the hemispherical full emissivity of the object through precise experimental measurement.

At present, the methods for measuring the hemispherical total emissivity of materials mainly include radiation spectroscopy and calorimetry. Calorimetry is widely used because of its simple equipment structure, convenient operation, and high accuracy. It can be divided into transient calorimetry and steady-state calorimetry. The experimental principle of steady-state calorimetry is to calculate the hemispherical total emissivity of the material surface by measuring the heat transfer and surface temperature of the sample in thermal equilibrium. Researchers at home and abroad have adopted different sample specifications and heating methods to form A variety of steady-state calorimetry application modes have been developed. For example:

a. Use the heating plate to heat the bottom surface of the material in the vacuum chamber, and calculate the full-wavelength emissivity of the material by measuring the current, voltage and temperature of the upper surface of the material;

b. Stick two sample sheets on both sides of the heating sheet, hang them in the vacuum chamber with the wire of the heating sheet, heat them with current, and solve the hemispherical total emissivity by measuring the electric power and the surface temperature of the material;

c. Select the slender strip sample and heat it under vacuum environment (called hot wire method), and regard the area where the central temperature of the strip sample is relatively uniform as the test analysis area, thereby ensuring the temperature and temperature of the sample test analysis area. Accuracy of energy measurements.

At present, most of the existing hemispherical total emissivity measurement methods and systems based on steady-state calorimetry are suitable for testing samples with approximately uniform temperature distribution in the test area, although the hot wire method can be used to select longer strip samples The technical requirement of approximately uniform temperature in the test area of the heated sample can be achieved, but the preparation of a long hot wire sample is extremely difficult for the experiment, and even for a specific test sample, the technical requirement cannot be met at all. Therefore, it is very meaningful to develop a method for measuring the hemispherical total emissivity of conductive material samples with a large temperature gradient distribution in response to the application requirements of high-temperature radiation thermal physical property measurement of actual conductive materials.

Contents of the invention

(1) Technical problems to be solved

The purpose of the present invention is to provide a method for measuring the hemispherical total emissivity of samples with large temperature difference, so as to overcome that the prior art is only applicable to conductor material samples with approximately uniform temperature distribution test area, and cannot be used for samples with large temperature difference. problem of measurement.

(2) Technical solution

In order to solve the above technical problems, the present invention provides a method for measuring the hemispherical total emissivity of a sample with a large temperature difference, characterized in that the steps of the method include:

S1. Select a strip-shaped conductor material sample, heat the sample in a vacuum environment, and use a radiation temperature field measuring device to obtain a temperature field distribution on the surface of the sample in a stable heating state;

S2. Divide the sample into multiple microelement control volumes along its axial direction, and establish a steady-state energy balance equation for the microelement control volumes;

S3. Based on the surface temperature field distribution of the sample and the voltage and current at both ends of the sample, calculate the numerical distribution of the hemispherical emissivity of the sample with temperature in the heating steady state.

Wherein, in the step S2, the sample is equally divided into N microelement control bodies along its axial direction, and the temperature in each microelement control body is consistent, and the steady-state energy balance equation of the microelement control body is:

Q _j -ε _j ·S _j ·σ·(T _j ⁴ -T _e ⁴ )+A _j ·λ _j ·(T _j+1 +T _j-1 -2T _j )/l _j ＝0

Among them, j is the number of the micro-element control body, j=2,...,N-1, j=1 and j=N respectively represent the boundary micro-element control body of the sample; Q _j is the heating electric power of the sample micro-element control body j , obtained by calculating the voltage and current at both ends of the sample; (T ₁ ,T ₂ ,…T _N ) is the temperature of each micro-element control body, obtained by measuring the radiation temperature field measurement equipment, and is a known quantity; T _e is The temperature of the vacuum water wall is a known quantity; ε _j is the hemispherical total emissivity of the sample element control body j, which means the hemispherical total emissivity when the temperature is T _j , which is an unknown quantity; σ is Stephen- Boltzmann's constant is a known quantity; λ _j is the thermal conductivity of the sample microelement control body j, which means the thermal conductivity when the temperature is T _j , which is a known quantity; the length of the sample is L, width w, thickness d. The length l _j =L/N of the micro-element control body j of the sample, the cross-sectional area A _j =w d of the micro-element control body j, and the surface area S _j =2l _j ·(w+d ), are measured known quantities.

Among them, since the resistivity of the sample changes linearly with the temperature, the heating electric power Q _j of the micro-element control body j is:

Q _j ＝I ² ·R _j,0 (1+ρT _j )

In the formula, j=1,...,N; I is the current flowing through the sample, which can be measured, which is a known quantity; ρ is the temperature coefficient of the sample resistivity, which is a known quantity; R _j,0 is at 0°C The resistance of the micro-element control body whose length is l _j , because the lengths of the N micro-element control bodies are all equal, the resistances R _j,0 of the micro-element control body are also equal, both are R ₀ ;

The voltage U across the sample is:

$\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&rho;T</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span>$

The resistance R ₀ of the micro-element control body is calculated according to the voltage U, current I, temperature T _j of the micro-element control body and the temperature coefficient of sample resistivity ρ, and Q _j = I ² ·R _j,0 (1+ρT _j ) Substituting the steady-state energy balance equation and simultaneously solving the energy balance equations of the micro-element control body, the numerical distribution of the hemispherical total emissivity of the sample with temperature under the steady heating state is obtained.

Wherein, the radiation temperature field measurement equipment is calibrated and calibrated before use.

Wherein, the content of calibration and calibration of the radiation temperature field measurement equipment includes: before using the radiation temperature field measurement equipment, setting the distance between the sample and the radiation temperature field measurement equipment, and adjusting the measurement optical path of the radiation temperature field measurement equipment to be perpendicular to the sample surface; The spectral transmittance value of the optical window in the test path, the radiation temperature field measuring equipment can observe the sample surface through the optical window on the wall of the vacuum chamber; the spectral emissivity value of the test sample, the spectral range should be the same as the measurement spectrum of the radiation temperature field measuring equipment Corresponding.

Wherein, the radiation temperature field measurement device is a thermal imager.

Wherein, in the step S1, the two ends of the strip conductor sample are fixed on the sample holder, placed in a vacuum chamber with a water-cooled inner wall, and the two ends of the strip conductor sample are energized and heated to a stable temperature state.

Wherein, the temperature test range of the sample is 300°C to 2000°C.

(3) Beneficial effects

The method for measuring the hemispherical total emissivity of the large temperature difference material of the present invention uses radiation temperature field measuring equipment to obtain the temperature field distribution on the surface of the sample in a stable heating state, and then divides the sample into multiple microelement control bodies along its axial direction, Establish the steady-state energy balance equation of the micro-element control body, and finally calculate the numerical distribution of the hemispherical emissivity of the sample with temperature under the heating steady state based on the surface temperature field distribution of the sample and the voltage and current at both ends of the sample. It is suitable for measuring the hemispherical total emissivity of conductor materials with a large temperature gradient distribution, overcomes the technical limitations of the existing steady-state calorimetry method for samples with uniform temperature test areas, and greatly reduces the constraints on sample size specifications At the same time, by using the radiation temperature field measurement equipment to obtain the temperature field distribution information on the surface of the heated sample, this test method is superior to the contact thermocouple point temperature measurement method, avoiding the complicated operation of installing thermocouples, thermoelectric Technical defects such as the influence of heat conduction loss of the pair wire and the limited point measurement can only be realized.

detailed description

Embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but should not be used to limit the scope of the present invention.

The method for measuring the hemispherical total emissivity of materials with a large temperature difference in this embodiment is suitable for measuring the hemispherical total emissivity of conductor materials with a large temperature gradient distribution, and the specific steps of the method include:

S1. Select a strip conductor material sample, fix both ends of the strip conductor sample on the sample holder, place it in a vacuum chamber with a water-cooled inner wall, evacuate the vacuum chamber to 1.0×10 ^-3 Pa, and place the strip conductor sample in two The terminal is energized and heated to a stable temperature state, and the temperature range is preferably 300°C to 2000°C.

The temperature distribution uniformity of strip conductor material samples is related to the sample length and size. The longer the sample length, the more uniform the temperature distribution. The realization of sample temperature uniformity is a relatively strict technical requirement, which makes sample preparation more difficult. In order to be easy to process, this embodiment selects a strip-shaped conductor material sample (length is 100mm, width is 10mm, and thickness is 0.1mm), but, due to the cooling effect at both ends of the sample holder, in this shorter sample axial direction There will be a large temperature gradient in the direction, that is, the axial temperature distribution of the strip conductor material sample is not uniform.

In order to overcome the above problems, in the heating steady state, this embodiment uses a non-contact radiation temperature field measurement device to measure the temperature of the strip conductor material sample. After the radiation temperature field measurement device is calibrated, it can measure and obtain the surface of the heated sample. The temperature field distribution information and the measurement of the sample temperature field distribution information provide an important data source for the subsequent calculation of the hemispherical total emissivity. This temperature measurement method is superior to the contact thermocouple point temperature measurement method, and avoids technical defects such as the complicated operation of installing the thermocouple, the influence of the heat conduction loss of the thermocouple wire, and the limited point measurement.

The radiation temperature field measuring equipment of this embodiment selects a thermal imager, and the content of its calibration and calibration includes: a) Before using the thermal imager, set the distance between the sample and the thermal imager, and adjust the measurement optical path of the thermal imager to be perpendicular to the surface of the sample ; b) knowing the spectral transmittance value of the optical window in the test path, the thermal imager can observe the sample surface through the optical window on the wall of the vacuum chamber; c) knowing the spectral emissivity value of the test sample, the spectral range should be the same as that of the thermal imager corresponding to the measured spectrum.

S2. In a stable heating state, the axial temperature distribution of the strip-shaped conductor material sample is uneven, with a large temperature gradient, and the length of the sample is greater than its width and thickness. The sample can be regarded as along the length direction (that is, the axial direction) For the one-dimensional steady-state heat conduction problem, since the temperature distribution of the sample along the axial direction is not uniform, it cannot be treated as an isothermal surface. Therefore, the sample is divided into N micro-element control bodies along the axial direction, and the temperature in each micro-element control body is consistent. , the steady-state energy balance equation of the micro-element control volume is:

Q _j -ε _j ·S _j ·σ·(T _j ⁴ -T _e ⁴ )+A _j ·λ _j ·(T _j+1 +T _j-1 -2T _j )/l _j ＝0

Among them, j is the number of the micro-element control body, j=2,...,N-1, j=1 and j=N respectively represent the boundary micro-element control body of the sample; Q _j is the heating electric power of the sample micro-element control body j , obtained by calculating the voltage and current at both ends of the sample; (T ₁ ,T ₂ ,…T _N ) is the temperature of each micro-element control body, obtained by measuring the radiation temperature field measurement equipment, and is a known quantity; T _e is The temperature of the vacuum water wall is a known quantity; ε _j is the hemispherical total emissivity of the sample element control body j, which means the hemispherical total emissivity when the temperature is T _j , which is an unknown quantity; σ is Stephen- Boltzmann's constant is a known quantity; λ _j is the thermal conductivity of the sample microelement control body j, which means the thermal conductivity when the temperature is T _j , which is a known quantity; the length of the sample is L, width w, thickness d. The length l _j =L/N of the micro-element control body j of the sample, the cross-sectional area A _j =w d of the micro-element control body j, and the surface area S _j =2l _j ·(w+d ), are measured known quantities.

In this embodiment, the 100mm-long sample is divided into 100 micro-element control bodies along the axial direction, that is, N=100, the steady-state energy balance equations of the micro-element control volume:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; \&sigma;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ <span\; class="notranslate">\; .</span>\\ <span\; class="notranslate">\; .</span>\\ <span\; class="notranslate">\; .</span>\\ {\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 99</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; \&sigma;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 99</span>}}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 99</span>}}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 100</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 98</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 99</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 99</span>}}\end{array}\right.$

S3. Since the resistivity of the sample changes linearly with the temperature, the heating electric power Q _j of the micro-element control body j is:

Q _j ＝I ² ·R _j,0 (1+ρT _j )

Among them, j=1,...,N; I is the current flowing through the sample, which can be measured, which is a known quantity; ρ is the temperature coefficient of the sample resistivity, which is a known quantity; R _j,0 is the value at 0°C The resistance of the micro-element control body whose length is l _j , because the lengths of N micro-element control bodies are all equal, the resistances R _j,0 of the micro-element control body are also equal, all of which are R ₀ .

The voltage U across the sample is:

$\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&rho;T</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span>$

Calculate the resistance R ₀ of the micro-element control body according to the voltage U, current I, temperature T _j of the micro-element control body and the temperature coefficient of sample resistivity ρ, and then obtain the heating electric power Q _j with respect to the temperature T _{j of the micro-element control body j} The expression Q _j ＝I ² ·R _j,0 (1+ρT _j ), put the expression into the steady-state energy balance equation, and get the hemispherical total emissivity ε _j of the micro-element control body j with respect to the micro-element control The steady-state energy balance equation of the temperature T _j of the body j, and the simultaneous solution of the energy balance equations of the micro-element control body can obtain the hemispherical total emissivity values of the sample at different temperatures.

Considering each micro-element control body as a temperature point, then this steady-state energy balance equation can also reflect the numerical distribution of the hemispherical total emissivity of the sample with temperature in a stable heating state.

The embodiments of the present invention have been presented for purposes of illustration and description, but are not intended to be exhaustive or to limit the invention to the form disclosed. Many modifications and changes will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to better explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention and design various embodiments with various modifications as are suited to the particular use.

Claims (6)

1. the hemisphere of large difference sample is to a measuring method for total emissivity, it is characterized in that, the step of described method comprises:

S1. tape conductor material sample is chosen, described sample two ends are fixed on sample clamp, be positioned in the vacuum chamber with water-cooled inwall, and by described sample two ends electrified regulation to equilibrium temperature state, obtain the described sample surface temperature field distribution under thermal-stable state with radiant temperature field measuring equipment;

S2. described sample is axially divided into multiple infinitesimal control volume along it, sets up the steady state energy balance equation of infinitesimal control volume;

S3. based on the surface temperature field distribution of described sample and the voltage and current at sample two ends, the hemisphere calculating described sample under thermal-stable state is to the numeric distribution of emissivity with temperature;

In described step S2, sample is axially divided into N number of infinitesimal control volume along it, the temperature in each infinitesimal control volume is consistent, and the steady state energy balance equation of infinitesimal control volume is:

Q _j-ε _j·S _j·σ·(T _j ⁴-T _e ⁴)+A _j·λ _j·(T _j+1+T _j-1-2T _j)/l _j＝0

In formula, j is the numbering of infinitesimal control volume, j=2 ..., N-1, j=1 and j=N represent the border infinitesimal control volume of sample respectively; Q _jfor the heating electric power of sample infinitesimal control volume j, calculated by the voltage and current at sample two ends and obtain; (T ₁, T ₂... T _n) be the temperature of each infinitesimal control volume, being measured by radiant temperature field measuring equipment and obtain, is measure known quantity; T _ethe temperature of the water-cooled inwall of described vacuum chamber, for measuring known quantity; ε _jbe the hemisphere of sample infinitesimal control volume j to total emissivity, namely represent temperature be T _jtime hemisphere to total emissivity, be unknown quantity; σ is Shi Difen-Boltzmann constant, is known quantity; λ _jbe the coefficient of heat conductivity of sample infinitesimal control volume j, namely represent that temperature is T _jtime coefficient of heat conductivity, be known quantity; The length of sample is the length l of L, width w, thickness d, sample infinitesimal control volume j _jthe cross-sectional area A of=L/N, infinitesimal control volume j _jthe surface area S of=wd, infinitesimal control volume j _j=2l _j(w+d) measurement known quantity, is.

2. the hemisphere of large difference sample according to claim 1 is to the measuring method of total emissivity, it is characterized in that, because the resistivity of sample makes linear change with temperature, then and the heating electric power Q of infinitesimal control volume j _jfor:

Q _j＝I ²·R _j,0(1+ρT _j)

Wherein, j=1 ..., N; I is the electric current flowing through sample, can record, for measuring known quantity; ρ is sample resistivity temperature coefficient, is known quantity; R _{j, 0}length when being 0 DEG C is l _jthe resistance of infinitesimal control volume because the identical length etc. of N number of infinitesimal control volume, the resistance R of infinitesimal control volume _{j, 0}also all equal, be R ₀;

The voltage U at sample two ends is:

$U=I\&CenterDot;R_0\&CenterDot;\underset{j=1}{\overset{N}{\&Sigma;}}(1+{\mathrm{\&rho;T}}_j)$

According to the temperature T of voltage U, electric current I, infinitesimal control volume _jand sample resistivity temperature coefficient ρ calculates the resistance R of infinitesimal control volume ₀, by Q _j=I ²r _{j, 0}(1+ ρ T _j) substitute into steady state energy balance equation, the energy equation of simultaneous solution infinitesimal control volume, just obtain sample hemisphere under stable heated condition to the numeric distribution of total emissivity with temperature.

3. the hemisphere of large difference sample according to claim 1 is to the measuring method of total emissivity, it is characterized in that, described radiant temperature field measuring equipment carries out demarcation calibration before use.

4. the hemisphere of large difference sample according to claim 3 is to the measuring method of total emissivity, it is characterized in that, the content that calibration demarcated by described radiant temperature field measuring equipment comprises: before radiant temperature field measuring equipment uses, distance between sample and radiant temperature field measuring equipment is set, and the optical path adjusting radiant temperature field measuring equipment is perpendicular to sample surfaces; The spectral transmission rate score of the optical window in test path, radiant temperature field measuring equipment can observe sample surfaces by the optical window of vacuum chamber wall; The spectral emissions rate score of test sample, spectral range is corresponding with the measure spectrum of radiant temperature field measuring equipment.

5. the hemisphere of large difference sample according to claim 1 is to the measuring method of total emissivity, it is characterized in that, described radiant temperature field measuring equipment is thermal imaging system.

6. according to the hemisphere of the large difference sample in claim 1-5 described in any one to the measuring method of total emissivity, it is characterized in that, the Range of measuring temp of described sample is 300 DEG C ~ 2000 DEG C.