CN109613054A - A kind of direct-electrifying longitudinal direction Determination of conductive coefficients method - Google Patents

A kind of direct-electrifying longitudinal direction Determination of conductive coefficients method Download PDF

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CN109613054A
CN109613054A CN201811533289.8A CN201811533289A CN109613054A CN 109613054 A CN109613054 A CN 109613054A CN 201811533289 A CN201811533289 A CN 201811533289A CN 109613054 A CN109613054 A CN 109613054A
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temperature
coefficient
section
direct
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CN109613054B (en
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杨决宽
孔龙
陈云飞
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Southeast University
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Southeast University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N25/00—Investigating or analyzing materials by the use of thermal means
    • G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity

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Abstract

The invention discloses a kind of direct-electrifying longitudinal direction Determination of conductive coefficients methods, it is intracavitary that sample is placed in vacuum constant temperature, and it is connected in measuring circuit with four electrode approach, vacuum constant temperature chamber temperature is controlled to stablize in given value, direct current and alternating current are applied simultaneously to sample section, obtain the resistance R of sample section at a given temperature0With slope b；The temperature for changing vacuum chamber obtains the resistance R under different temperatures0With slope b, to obtain the temperature-coefficient of electrical resistance α and thermal coefficient λ-side coefficient of heat transfer h curve at each temperature of sample section；At a temperature of each measurement, the test twice of different sample sections gives two not parallel λ-h curves, seeks the intersection point (h of this two λ-h curvesc, λc), obtain the true side coefficient of heat transfer h of sample at this temperaturecWith thermal coefficient λc.The side heat exchange of influence this invention removes to(for) longitudinal Determination of conductive coefficients, can be used for wire rod, micrometer fibers and one-dimensional nano structure longitudinal direction Determination of conductive coefficients.

Description

A kind of direct-electrifying longitudinal direction Determination of conductive coefficients method
Technical field
The invention belongs to thermal physical property of solid material parameter testing technical fields, and in particular to a kind of direct-electrifying is longitudinally thermally conductive Coefficient testing method.
Background technique
Direct-electrifying method is one of main test method of conductive material thermal coefficient.It leads the longitudinal direction that can be used to measure wire rod Hot coefficient can also be used to the thermally conductive system in longitudinal direction for measuring single micrometer fibers, one-dimensional nano structure such as GB/T 3651-2008 Number.During the test, electric current is applied to sample, generates Joule heat to heat sample.Part Joule heat is along sample Longitudinal direction reaches substrate, and another part Joule heat is lost by the heat convection and radiation heat transfer of sample side.Accurately It determines the sample side coefficient of heat transfer, determines the measuring accuracy of direct-electrifying method longitudinal direction thermal coefficient.
For characteristic size in the sample of millimeter magnitude, GB/T 3651-2008 when not being powered, uses thermoelectricity first The temperature difference between the temperature difference and environment and sample of even measurement sample itself, so as to find out sample side and The coefficient of heat transfer of environment.Then in energization, the temperature of sample and environment is measured, the axial direction for finding out sample is led Hot coefficient.Method in GB/T 3651-2008 has modified the influence that side exchanges heat for measurement result.But it exchanges heat in side and is When number is larger, the method in GB/T 3651-2008 cannot obtain satisfied as a result, especially to the lower material of thermal conductivity, problem More prominent (Hu Peng, publishing house, Chen Zeshao Measure Technology of Heat & Thermophysics (second edition) China Science & Technology University, 2009, 120-122)。
Particularly, it when measuring micrometer fibers or one-dimensional nano structure, is surveyed since external temperature sensor can not be used The temperature of sample is measured, therefore the testing process in GB/T 3651-2008 is no longer applicable in.Due to accurately measuring single micron The side coefficient of heat transfer of fiber or one-dimensional nano structure is extremely difficult, therefore micrometer fibers or one-dimensional nano structure thermal coefficient are surveyed In examination, usually ignore the influence of side heat exchange, or estimate the side coefficient of heat transfer using posture material radiant emissivity, causes There are large errors for test result.
Summary of the invention
Goal of the invention: the invention proposes a kind of direct-electrifying longitudinal direction Determination of conductive coefficients methods, can simultaneously obtain tested The longitudinal thermal coefficient and the side coefficient of heat transfer of sample, to eliminate the influence that side exchanges heat for longitudinal Determination of conductive coefficients.
A kind of technical solution: direct-electrifying longitudinal direction Determination of conductive coefficients method of the present invention, comprising the following steps:
(1) that sample is placed in vacuum constant temperature is intracavitary, and is connected in measuring circuit with four electrode approach, wherein internal Sample segments between two electrodes are sample section；
(2) control vacuum constant temperature chamber temperature is stablized in given value, sample section is applied simultaneously DC current with exchange Electric current obtains the resistance R of sample section at such a temperature0With slope b；
(3) temperature for successively changing vacuum chamber repeats step (2), obtains the resistance R under different temperatures0With slope b, obtain The temperature-coefficient of electrical resistance α of sample section and thermal coefficient λ-side coefficient of heat transfer h curve at each temperature；
(4) the distance between (1) described internal electrode is changed the step, step (2)-(3) are repeated；
(5) at a temperature of each measurement, it is bent that the test twice of different sample sections gives two not parallel λ-h Line finds out the intersection point (h of this two λ-h curvesc, λc), hcThe as true side coefficient of heat transfer of sample at this temperature, λc As longitudinal thermal coefficient of sample at this temperature.
The sample segment length is 20 times or more of sample diameter or thickness.
The sample is connected in measuring circuit with four electrode approach, wherein two electrodes of outside are current feed, Internal two electrodes are used for voltage lead.
The step (2) the following steps are included:
(21) DC current is used to detect the resistance of sample section for heating sample section, alternating current；
(22) AC voltage drop in sample section is measured, the resistance R of sample segments is calculated；It measures on sample Direct current pressure drop calculates the Joule heat UI generated in sample section, and carries out linear fit to R and UI:
R=R0+b×UI (1)
Obtain the resistance R of sample section at a given temperature0With slope b.
The step (3) the following steps are included:
(31) using the R under different temperatures0Calculate the temperature-coefficient of electrical resistance α of sample section:
(32) at a temperature of each measurement, it is assumed that a side coefficient of heat transfer h obtains one by following formula and corresponding leads Hot coefficient lambdah:
Wherein, AsFor the lateralarea of sample section, L is sample segment length, and P is sample section cross section Perimeter, AcFor the cross-sectional area of sample section.
The utility model has the advantages that compared with prior art, the invention has the benefit that by carrying out different length twice to sample Measurement, while obtaining longitudinal thermal coefficient of the sample side coefficient of heat transfer and sample, side heat exchange can be eliminated and led for longitudinal The influence of hot coefficient test, and operating procedure is simple, measurement result is accurate.
Detailed description of the invention
Fig. 1 is test method schematic diagram of the present invention；
Fig. 2 is λ-h curve graph under different temperatures.
Specific embodiment
The present invention is described in further details with embodiment with reference to the accompanying drawing.
By taking the carbon fiber test that diameter is 8 μm as an example, direct-electrifying longitudinal direction Determination of conductive coefficients method of the invention, including Following steps:
(1) referring to Fig. 1, sample 1 is placed on four intracavitary electrodes 2 of vacuum constant temperature, to realize sample 1 with four electricity Pole mode is connected in measuring circuit.Electrode 2 is fixed in substrate 3.Sample segments between internal two electrodes are sample section, In the present embodiment, sample segment length is 7.25mm.
(2) control constant temperature chamber temperature stablize 300K, using current source 4 in sample 1 simultaneously apply direct current with exchange Electric current, wherein DC current is used to detect the resistance of sample section for heating sample section, alternating current.
Measure the AC voltage drop v in sample sectionac, calculate the resistance R=v of sample segmentsac/iac, measure detected sample Direct current pressure drop U in product section, calculates the Joule heat UI generated in sample section.Linear fit is carried out to R and UI:
R=R0+b×UI (1)
Obtain the resistance R of sample section at a given temperature0With slope b.
(3) temperature for successively changing vacuum chamber is 290-250K, and repeats step (2) at each temperature, obtains difference At a temperature of R0And b.
According to the definition of temperature-coefficient of electrical resistance
Use the R under different temperatures0Calculate the temperature-coefficient of electrical resistance α of sample section.
Basic theories according to steady state heat transfer is available, in above-mentioned heating process, the average temperature rising of sample section For
A in formulasFor the lateralarea of sample section, h is the side coefficient of heat transfer, and h is sample segment length, and P is quilt The perimeter of sample section cross section, AcFor the cross-sectional area of sample section, λ is the thermal coefficient of sample.According to electricity Temperature coefficient definition is hindered, is in average temperature risingWhen, the resistance of sample can be expressed as
It is available by formula (1), (3), (5)
At a temperature of each measurement, by assuming that a series of possible side coefficient of heat transfer h, obtain a system by formula (6) Arrange corresponding thermal coefficient λ.In this way at a temperature of each measurement, a λ-h curve is obtained, as shown in Figure 2.
(4) change the distance between electrode 2, to change the length of sample section, in this embodiment, sample segments Length becomes 5.62mm, repeats step (2)-(3).
(5) at a temperature of each measurement, above-mentioned test twice gives two not parallel λ-h curves.What Fig. 2 was provided is Two λ-h curves when 300K.Seek the intersection point (h of this two λ-h curvesc, λc), hcThe as true side of sample at this temperature The coefficient of heat transfer, λcThe as true longitudinal thermal coefficient of sample 1 at this temperature.In the present embodiment, it is found out by Fig. 2 Coefficient of heat transfer h in side when 300Kc=3.04W/m2- K, sample longitudinal direction thermal coefficient λc=9.34W/m-K.

Claims (5)

1. a kind of direct-electrifying longitudinal direction Determination of conductive coefficients method, which comprises the following steps:
(1) that sample is placed in vacuum constant temperature is intracavitary, and is connected in measuring circuit with four electrode approach, wherein internal two electricity Sample segments between pole are sample section；
(2) control vacuum constant temperature chamber temperature is stablized in given value, applies DC current and alternating current simultaneously to sample section, Obtain the resistance R of sample section at such a temperature0With slope b；
(3) temperature for successively changing vacuum chamber repeats step (2), obtains the resistance R under different temperatures0With slope b, it is tested The temperature-coefficient of electrical resistance α of sample segments and thermal coefficient λ-side coefficient of heat transfer h curve at each temperature；
(4) the distance between (1) described internal electrode is changed the step, step (2)-(3) are repeated；
(5) at a temperature of each measurement, the test twice of different sample sections gives two not parallel λ-h curves, asks Intersection point (the h of this two λ-h curves outc, λc), hcThe as true side coefficient of heat transfer of sample at this temperature, λcAs should At a temperature of sample longitudinal thermal coefficient.
2. a kind of direct-electrifying longitudinal direction Determination of conductive coefficients method according to claim 1, which is characterized in that described tested Sample segment length is 20 times or more of sample diameter or thickness.
3. a kind of direct-electrifying longitudinal direction Determination of conductive coefficients method according to claim 1, which is characterized in that step (1) The sample is connected in measuring circuit with four electrode approach, wherein two electrodes of outside are current feed, two electricity of inside Pole is used for voltage lead.
4. a kind of direct-electrifying longitudinal direction Determination of conductive coefficients method according to claim 1, which is characterized in that the step (2) the following steps are included:
(21) DC current is used to detect the resistance of sample section for heating sample section, alternating current；
(22) AC voltage drop in sample section is measured, the resistance R of sample segments is calculated；Measure the direct current on sample Voltage drop calculates the Joule heat UI generated in sample section, and carries out linear fit to R and UI:
R=R0+b×UI (1)
Obtain the resistance R of sample section at a given temperature0With slope b.
5. a kind of direct-electrifying longitudinal direction Determination of conductive coefficients method according to claim 1, which is characterized in that the step (3) the following steps are included:
(31) using the R under different temperatures0Calculate the temperature-coefficient of electrical resistance α of sample section:
(32) at a temperature of each measurement, it is assumed that a side coefficient of heat transfer h obtains a corresponding thermally conductive system by following formula Number λ:
Wherein, AsFor the lateralarea of sample section, L is sample segment length, and P is the perimeter of sample section cross section, AcFor the cross-sectional area of sample section.
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111323453A (en) * 2020-03-25 2020-06-23 武汉大学 Method and device for measuring convective heat transfer coefficients of different surface roughness under microscale
CN111537560A (en) * 2020-06-12 2020-08-14 上海上大瑞沪微系统集成技术有限公司 Method and equipment for testing heat conductivity coefficient by using joule self-heating method

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CN102279204A (en) * 2010-06-09 2011-12-14 中国科学院工程热物理研究所 Detection method for thermal conductivity and thermal diffusivity of anisotropic material
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CN101881741A (en) * 2009-05-08 2010-11-10 清华大学 One-dimensional material thermal conductivity measurement system and measurement method thereof
CN101782541B (en) * 2009-12-09 2011-10-05 中国科学院工程热物理研究所 Method and device for testing thermal physical property of solid material with independent probe by using harmonic method
CN102279204A (en) * 2010-06-09 2011-12-14 中国科学院工程热物理研究所 Detection method for thermal conductivity and thermal diffusivity of anisotropic material
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111323453A (en) * 2020-03-25 2020-06-23 武汉大学 Method and device for measuring convective heat transfer coefficients of different surface roughness under microscale
CN111537560A (en) * 2020-06-12 2020-08-14 上海上大瑞沪微系统集成技术有限公司 Method and equipment for testing heat conductivity coefficient by using joule self-heating method

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