CN114264692B - Method for simultaneously measuring thermal conductivity and emissivity of micro-nano material - Google Patents
Method for simultaneously measuring thermal conductivity and emissivity of micro-nano material Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 38
- 239000002086 nanomaterial Substances 0.000 title claims abstract description 16
- 238000010438 heat treatment Methods 0.000 claims abstract description 107
- JUWSSMXCCAMYGX-UHFFFAOYSA-N gold platinum Chemical compound [Pt].[Au] JUWSSMXCCAMYGX-UHFFFAOYSA-N 0.000 claims abstract description 14
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 31
- 238000005259 measurement Methods 0.000 claims description 22
- 229910052697 platinum Inorganic materials 0.000 claims description 5
- 238000003466 welding Methods 0.000 claims description 3
- 238000013178 mathematical model Methods 0.000 claims description 2
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 5
- 229910052802 copper Inorganic materials 0.000 description 5
- 239000010949 copper Substances 0.000 description 5
- 238000012360 testing method Methods 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- 239000002041 carbon nanotube Substances 0.000 description 3
- 229910021393 carbon nanotube Inorganic materials 0.000 description 3
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- 239000000463 material Substances 0.000 description 3
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- 230000000704 physical effect Effects 0.000 description 2
- 229910052582 BN Inorganic materials 0.000 description 1
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 1
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
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Abstract
The invention discloses a method for simultaneously measuring thermal conductivity and emissivity of a micro-nano material. The measuring method mainly comprises the following steps: (1) And simultaneously measuring the heat conductivity and the emissivity of the polymer composite fiber by using a double-hot wire structure. (2) And respectively bonding two ends of a to-be-tested sample to the central positions of two parallel platinum gold wires (double hot wires), comparing the average temperature rise change of the hot wires before and after lapping the to-be-tested sample to obtain the heat conducted by the hot wire at the heating end to the to-be-tested wire and the heat obtained by the hot wire at the receiving end, and determining the heat conductivity and emissivity of the to-be-tested wire. (3) The measured thermal conductivity (lambda=71.7w.m ‑1·K‑1) and emissivity (epsilon=0.14) of the single platinum gold wire are consistent with the reference value; meanwhile, the thermal conductivity and the emissivity of the high polymer composite material fiber are respectively 1.67 W.m ‑1·K‑1 and 0.45. The measuring principle disclosed by the invention has no special requirements on the property of the to-be-measured line, and has the advantages of high measuring precision, wide application range and the like.
Description
Technical Field
The invention belongs to the technical field of measuring thermal conductivity and emissivity of micro-nano materials, and particularly relates to a method for simultaneously measuring the thermal conductivity and emissivity of the micro-nano materials.
Background
With the progress of micro-nano technology, novel materials such as fibers, carbon nanotubes, semiconductor quantum dots, nanoparticles and the like are increasingly applied to the fields of aerospace, energy conversion, thermal management and the like. The performance of micro devices is highly dependent on the internal heat transfer capability, so the research on the thermal properties of micro-nano materials is very important. Because of the large difference between the thermophysical properties of the micro-nano material and the macro-scale material, the analytical test method for representing the macro-scale thermal field distribution is not applicable under the micro-nano scale, so that the micro-nano scale thermophysical property measurement becomes one of the key technologies. Thermal conductivity measurement experiments based on steady state methods tend to be difficult to ignore the effects of radiation, such as the steady state T-type method disclosed in literature ：Fujii M,Zhang X,Xie H,et al.Measuring the thermal conductivity of a single carbon nanotube.Phys Rev Lett,2005,95:065502: wang Zhaoliang, tang Dawei, zheng Xinghua, et al, 3 omega methods for measuring the thermal conductivity and heat capacity of individual carbon fibers, engineering thermophysical journal 2007,28 (3): 3 omega methods disclosed by 490-492, literature: yi W, lu L, zhang D L.linear SPECIFIC HEAT of carbon nanotubes Physics Rev B,1999,59 (14): microdevice method disclosed by R9015-R9018. The measuring method is modified on the basis of a T-type steady-state method, and the thermal conductivity and the emissivity of the wire to be measured are obtained simultaneously by measuring the temperature rise change condition of the other end of the wire to be measured under the vacuum condition.
Disclosure of Invention
The invention aims to provide a novel method for simultaneously measuring the thermal conductivity and the emissivity of a micro-nano material.
The technical solution for realizing the purpose of the invention is as follows:
the method for simultaneously measuring the thermal conductivity and the emissivity of the micro-nano material obtains the thermal conductivity and the emissivity of the micro-nano material by the following formula:
Thermal conductivity:
Emissivity:
Wherein the method comprises the steps of
Wherein Re h represents heating-end heat resistance, re s represents receiving-end heat resistance
L h、ls represents the heating-end heat ray and receiving-end heat ray lengths, respectively, lambda h represents the heat ray thermal conductivity, and a h represents the heat ray cross-sectional area; l f denotes the length of the wire to be measured, A f denotes the cross-sectional area of the wire to be measured, I 1、U1 denotes the heating-end heating-wire current and voltage respectively,Represents the average temperature rise of the heating end heating wire,/>The average temperature rise of the hot wire at the receiving end is represented, P f represents the transverse perimeter of the wire to be measured, T 0 represents the set ambient temperature, and sigma represents the Stefan-Boltzmann constant.
Compared with the prior art, the invention has the remarkable advantages that:
(1) The measurement experiment is carried out in a vacuum environment, so that the influence of convection heat transfer on a measurement result can be avoided; the receiving end heating wire is arranged, so that the temperature rise change of the other end of the wire to be measured can be effectively measured, and the temperature rise of the two ends of the wire to be measured can be obtained; the experiment belongs to a steady state method, but can avoid the influence of radiation and heat dissipation through the established heat transfer model, and can calculate the emissivity of the corresponding to-be-measured line;
(2) The temperature rise at two ends of the to-be-measured line is obtained by utilizing the temperature resistance characteristic of the platinum gold wire, so that the system error caused by the radiation neglected by a general steady-state method is solved from the source, and the measurement accuracy is improved.
Drawings
FIG. 1 is a flow chart of the method for measuring emissivity and thermal conductivity according to the present invention.
Fig. 2 is a schematic diagram of an experimental apparatus.
FIG. 3 is a sample base physical diagram connected to a temperature control column.
Fig. 4 is a physical model of a measurement experiment.
Fig. 5 is a diagram showing the temperature rise change of the hot wire at both ends and the wire to be measured.
Fig. 6 is a power-resistance curve of the receiving-side hot wire of example 1.
Fig. 7 is a graph showing the power-resistance curve of the heating tip of example 1.
Fig. 8 is a power-resistance curve of the receiving end of example 2.
Fig. 9 is a heating end heat ray power-resistance curve of example 2.
Detailed Description
The invention is further described with reference to the drawings and specific embodiments.
Referring to fig. 2, the method for simultaneously measuring the thermal conductivity and the emissivity of the micro-nano material according to the invention comprises the following steps:
step 1, manufacturing a measuring base 1 by using a high heat conduction pure copper material, using 8 copper columns (2, 3,4,5,6,7,8, 9) with the width of about 1cm as heat sinks, and fixing the copper columns on the base 1 by using ceramic glue. One platinum wire is welded on four heat sinks (2, 3,4, 5), the section of platinum wire is denoted as a heating end heat wire, the other platinum wire is welded on the remaining 4 heat sinks (6, 7,8, 9), the section of platinum wire is denoted as a receiving end heat wire, and the two platinum wires are kept parallel.
And 2, respectively adhering two ends of the wire to be tested to the middle points of the two parallel platinum gold wires in the step1 by using heat-conducting silica gel, representing the intersection point of the wire to be tested and the heating end hot wire as an upper node, and representing the intersection point of the wire to be tested and the receiving end hot wire as a lower node.
And 3, fixing the sample base on the temperature control column through screws, placing the sample base in a constant temperature cavity, opening a mechanical pump and a molecular pump, and reducing the pressure in the vacuum cavity to below 1X 10 -3 Pa, so that the influence of heat convection can be eliminated.
And 4, introducing constant direct current I s to a receiving end hot wire between the heat sinks 6 and 9 through a high-precision power supply, measuring receiving end hot wire voltage U s between the heat sinks 7 and 8, obtaining the change rule of the resistance of the receiving end hot wire along with heating power under different current conditions, collecting receiving end hot wire resistance values R s corresponding to 5 different heating powers P s, drawing a P s-Rs curve, and finishing fitting, wherein the intercept is the initial resistance R s0 of the receiving end hot wire.
And 5, introducing constant current I h to a heating end hot wire between the heat sinks 2 and 5 through a high-precision power supply, measuring the heating end hot wire voltage U h between the heat sinks 3 and 4, obtaining the change rule of the heating end hot wire resistance along with heating power under different currents, collecting heating end hot wire resistance values R h corresponding to 5 different heating powers P h, drawing a P h-Rh curve, and finishing fitting, wherein the intercept is the initial resistance R h0 of the heating end hot wire.
And 6, introducing constant current I 1 to a heating end hot wire between the heat sinks 2 and 5 through a high-precision power supply, measuring heating end hot wire voltage U 1 between the heat sinks 3 and 4, and simultaneously, introducing micro current I 2 (the temperature rise caused by the micro current I 2 is negligible) to a receiving end hot wire between the heat sinks 6 and 9 through the high-precision power supply, and measuring receiving end hot wire voltage U 2 between the heat sinks 7 and 8.
Similar to the steady-state T-type method, the invention also utilizes the temperature resistance characteristic of the platinum resistor to obtain corresponding temperature change according to the change of the resistor. The experiment used a platinum wire (Pt) as the hot wire, and the relation of platinum wire resistance to temperature can be expressed as:
RT＝R0[1+βT(T-273.15)]
Wherein R T is the platinum wire resistance at the set temperature T, beta T is the temperature resistance coefficient of the platinum gold wire at the set temperature, and R 0 is the platinum wire resistance at the set temperature 273.15K. In the whole experimental process, the temperature rise of the heating wire is small, so that the temperature resistance coefficient can be considered to be unchanged.
In the step, the platinum wire resistance under the power is obtained by collecting the current and the voltage, and the average temperature rise of the platinum wire can be calculated according to the temperature resistance characteristic of the platinum wire:
r is the measured and calculated platinum wire resistance, R 0 is the initial resistance of the platinum wire at normal temperature, β is the temperature coefficient of the platinum wire at normal temperature, and β= 0.003746/K.
Then, combining the step 5, the average temperature rise of the heating end heating wire can be obtained:
Wherein R 1 is heating end heat ray resistance, calculated from measurement data
Combining the step 4, the average temperature rise of the hot wire of the receiving end can be obtained:
Wherein R 2 is the hot-wire resistance of the receiving end, calculated by the measurement data
The heating end heating wire is electrified, at the moment, the temperature rise distribution on the heating end heating wire is changed into a saddle shape from a parabolic shape when the to-be-tested wire is not connected, and at the same time, heat is transferred to the receiving end heating wire through the to-be-tested wire, so that the temperature rise of the receiving end heating wire is caused, and the temperature rise distribution is in a triangular shape, as shown in figure 5. Establishing a physical model as shown in fig. 4, setting the intersection point of the heating end heating wire and the heat sink 4 as a coordinate origin, and setting the direction of the platinum wire along the heat sink 3 as the x-axis direction, so as to obtain a one-dimensional steady-state heat conduction differential equation of the heating end heating wire:
Wherein ΔT h(x)＝Th(x)-T0 represents the temperature of the heating wire rising after passing current, T h (x) is the temperature of the heating wire at the position of the heating wire from the origin x along the coordinate direction after passing current, T 0 is the initial temperature (namely the set ambient temperature), I 1 is the current passing through the heating wire, U 1 is the measured heating wire voltage between the heat sinks 3 and 4, λ h is the platinum wire heat conductivity coefficient (measured by the direct current method), l h is the heating wire length between the heat sinks 3 and 4, and A h is the heating wire cross-sectional area measured by vernier calipers.
Boundary conditions of the heating hot wire temperature rise control equation between the origin of coordinates and the upper node are as follows:
wherein DeltaT j is the temperature rise of the upper node, and solving the above formula to obtain the temperature rise of the heating end heating wire along the x-axis direction is as follows:
wherein Re h is the heating end hot wire thermal resistance between heat sinks 3, 4:
Average temperature rise on heating end heat line:
deducing an upper node temperature rise expression:
finally, the temperature rise distribution expression of the heating end heating wire along the x-axis direction can be obtained:
For the receiving-end heating wire, a small current (a small current relative to the heating end can only cause a small temperature rise change of the heating wire and can be ignored), so that the receiving-end heating wire can be regarded as a one-dimensional heat conduction condition without an internal heat source. At this time, the intersection point of the receiving-end hot wire and the heat sink 7 is taken as the origin of coordinates, and the direction of the platinum wire along the heat sink 8 is taken as the x axis, so that the one-dimensional heat conduction differential equation of the receiving-end hot wire is that:
The Δt s(x)＝Ts(x)-T0 represents the temperature of the receiving end hot wire raised after receiving the heat flow from the wire under test, T s (x) is the temperature of the receiving end hot wire at the position x from the origin along the coordinate direction, and T 0 is the initial temperature (i.e. the set ambient temperature).
The boundary conditions of the temperature rise control equation from the origin of coordinates to the lower node part of the hot line at the receiving end are as follows:
Wherein, Δt k is the lower node temperature rise, l s is the receiving end hot wire length between heat sinks 7, 8, and the temperature rise expression formula along the x-axis direction of the receiving end hot wire can be obtained by solving the formula through vernier caliper measurement:
Then the average temperature rise over the receive-side hot line:
the following node temperature rise expression can be obtained:
finally, the temperature rise distribution (represented by average temperature rise) of the receiving end hot wire along the x-axis direction can be obtained:
And 7, establishing a mathematical model through the temperature rise of the upper node and the lower node, solving and calculating to finally obtain the emissivity and the thermal conductivity value of the to-be-tested line.
The wire to be measured is perpendicular to the two parallel hot wires, and two ends of the wire to be measured are respectively stuck to the middle positions of the hot wires to form a double-hot wire structure. For the to-be-measured line, heat is transmitted from the upper node to the lower node, and in the process, only heat conduction and radiation exist (convection is negligible under a vacuum environment), so that the one-dimensional steady-state heat conduction process without an internal heat source and considering radiation can be considered, wherein the upper node is set as an origin of coordinates, the x-axis direction is along the to-be-measured line direction, and then the one-dimensional steady-state heat conduction differential equation is as follows:
Wherein Δt f(x)＝Tf(x)-T0 represents the temperature of the line under test rising after receiving the heat flow, T f (x) is the temperature of the line under test at the position x from the origin along the coordinate direction, and T 0 is the initial temperature (i.e., the set ambient temperature). d is a function derivative symbol, A f and P f respectively represent the cross-sectional area and the cross-sectional perimeter of the to-be-measured line, lambda f is the heat conductivity of the to-be-measured line, h f is the radiation heat exchange coefficient of the to-be-measured line, and in the actual measurement process, the rising temperature of the to-be-measured line is small, so that the radiation heat exchange coefficient can be calculated by the following formula:
Epsilon is the emissivity of the line to be measured, sigma = 5.67 x 10 -8W·m-2·K-4, is the stefin-boltzmann constant.
This differential equation is solved:
τ 1、τ2 is a parameter to be determined, and the boundary conditions of two ends of the line to be measured are as follows:
l f is the length of the line to be measured, which can be measured by a vernier caliper.
The line under test is temperature-rising along the x-axis:
According to conservation of heat, the heat flow led out from the heating end hot wire at the upper node is equal to the heat flow received by the node on the wire to be tested, and the upper node is the midpoint of the heating end hot wire between the heat sinks 4 and 3, so that the temperature symmetrical distribution of the left side and the right side of the heating end hot wire separated by the wire to be tested can be considered, and therefore, only the temperature distribution on half the length of the heating end hot wire needs to be considered:
The above formula is combined:
equation (1) can be finally obtained:
Wherein τ 1、τ2 is a set parameter, and expressions are respectively:
According to the law of conservation of energy, the difference between the heat flows of the upper node and the lower node of the line to be measured is equal to the heat flow radiated to the environment by the line to be measured, namely:
By combining the above formulas, it is possible to obtain:
equation (2) can be finally obtained:
Solving equations (1) and (2), and finally obtaining an expression of the heat conductivity and the emissivity of the wire to be measured:
Wherein the method comprises the steps of
Example 1
The description process of the above measurement method does not specify any specific object, that is to say, the method is applicable to measurement of thermal conductivity and emissivity of any micro-nano material. In order to further detail the operation flow and measurement result of the application of the method, the application of the present invention will be described in detail by taking a 100 μm platinum gold wire with known thermophysical parameters as a wire to be measured as an example. Fig. 2 shows a sample holder which has been lapped. The measurement operation is performed in the following steps, and this measurement example is performed at normal temperature.
And step1, fixing 8 heat sinks on a high-heat-conductivity pure copper base, and using a precise electric welding machine to weld two 50 mu m platinum wires serving as temperature sensing elements on the heat sinks in parallel.
And 2, taking a 100-mu m platinum wire as a wire to be tested, and respectively overlapping two ends of the wire to be tested on the middle points of a heating end hot wire between the heat sinks 7 and 8 and a receiving end hot wire between the heat sinks 3 and 4 by using heat-conducting silica gel.
And 3, fixing the sample base which is well overlapped with the to-be-measured line on a temperature control column through a screw, placing the sample base in a constant temperature cavity, opening a mechanical pump and a molecular pump, and reducing the pressure in the vacuum cavity to be below 1 multiplied by 10 -3 Pa.
And 4, introducing constant direct current I s to a receiving end hot wire between the heat sinks 6 and 9 through a high-precision power supply, measuring receiving end hot wire voltage U s between the heat sinks 7 and 8, obtaining a change rule of the resistance of the receiving end hot wire along with heating power under different currents, collecting receiving end hot wire resistance values R s corresponding to 5 different heating powers P s, drawing a P s-Rs curve, and finishing fitting, wherein the intercept is the initial resistance R s0 of the receiving end hot wire.
As shown in fig. 6, in the fitted curve, the intercept is 1.0406 Ω, which represents that the initial resistance of the hot line at the receiving end is 1.0406 Ω.
And 5, introducing constant current I h to a heating end hot wire between the heat sinks 2 and 5 through a high-precision power supply, measuring the heating end hot wire voltage U h between the heat sinks 3 and 4, obtaining the change rule of the heating end hot wire resistance along with heating power under different currents, collecting heating end hot wire resistance values R h corresponding to 5 different heating powers P h, drawing a P h-Rh curve, and finishing fitting, wherein the intercept is the initial resistance R h0 of the heating end hot wire.
As shown in fig. 7, the intercept of the fitted curve is 1.3065 Ω, which represents that the initial resistance of the heating terminal heat line is 1.3065 Ω.
And 6, passing a constant current I 1 to a heating end hot wire between the heat sinks 2 and 5 through a high-precision power supply, measuring a heating end hot wire voltage U 1 between the heat sinks 3 and 4, and simultaneously, passing a micro current I 2 (the temperature rise caused by the micro current I 2 is negligible) to a receiving end hot wire between the heat sinks 6 and 9, and measuring a receiving end hot wire voltage U 2 between the heat sinks 7 and 8.
In this step, I 1 =35 mA is set, and U 1 =90.72 mV is measured, so that the heating-end heat-wire resistance R 1＝U1/I1 =1.512 Ω between the heat sinks 2, 5 at this time can be obtained, and the average temperature rise of the heating-end heat wire at this time can be obtained according to step 5).
Meanwhile, the receiving-end hot wire is led with micro current I 2 =1 mA, and U 2 = 1.0871mV is measured, so that receiving-end hot wire resistance R 2＝U2/I2 = 1.0871 Ω between heat sinks 7, 8 at this time can be obtained, and the average temperature rise of the receiving-end hot wire at this time can be obtained according to step 4:
and 7, combining the thermophysical parameters of the platinum gold wires, calculating the corresponding heat conductivity and emissivity value of the wire to be measured according to a formula, and completing a measurement experiment.
And measuring the length of the heating end heat wire between the heat sinks 3 and 4 by using a vernier caliper to obtain l h =18.64 mm, and measuring the length of the receiving end heat wire between the heat sinks 7 and 8 to obtain l s =14.64 mm, wherein the heating end heat wire and the receiving end heat wire both adopt platinum gold wires with the purity of 99.95% and the diameter of 50 μm, so that A h＝1.96×10-9m2,Ph＝1.57×10-4 m, and according to the theoretical thermophysical parameter values of the platinum gold wires, the thermal conductivities of the heating end heat wire and the receiving end heat wire are lambda h＝71.6W·m-1·K-1, and the thermal resistances of the heating end heat wire and the receiving end heat wire are Re h＝1.327×105K/W,Res＝1.042×105 K/W respectively.
The length of the wire to be measured (i.e. the distance from the upper node to the lower node) was measured using a vernier caliper to give l f = 17mm, which uses a platinum wire with a diameter of 100 μm with a purity of 99.95%, thus a f＝7.85×10-9m2,Pf＝3.14×10-4 m.
According to the formula:
Wherein the method comprises the steps of
Substituting the data calculation yields the final thermal conductivity λ f＝71.7W·m-1·K-1, emissivity epsilon f =0.14. The standard value of the thermal conductivity of the platinum wire is 71.6W.m -1·K-1, and the standard value of the emissivity is 0.1-0.3.
Example 2
The measurement is performed using the composite material as an object to be measured. The composite material is prepared by doping 30wt% of hexagonal boron nitride and 3wt% of multiwall carbon nanotubes with polyvinylidene fluoride, adopting an electrostatic spinning process, performing hot pressing to obtain a composite film, then cutting to obtain a composite material to-be-tested line, wherein the length dimension of the to-be-tested line is measured by a vernier caliper, and the width parameter and the thickness parameter are measured by a microscope. The measurement operation was performed in the following steps, and this measurement example was performed at normal temperature (T 0 =300K).
And step1, fixing 8 heat sinks on a high-heat-conductivity pure copper base, and using a precise electric welding machine to weld two 50 mu m platinum wires serving as temperature sensing elements on the heat sinks in parallel.
And 2, cutting a to-be-measured line with the length of 3mm, and respectively overlapping two ends of the to-be-measured line on the middle points of a heating end hot line between the heat sinks 7 and 8 and a receiving end hot line between the heat sinks 3 and 4 by using heat-conducting silica gel.
And 3, fixing the sample base which is well overlapped with the to-be-measured line on a temperature control column through a screw, placing the sample base in a constant temperature cavity, opening a mechanical pump and a molecular pump, and reducing the pressure in the vacuum cavity to be below 1 multiplied by 10 -3 Pa.
And 4, introducing constant direct current I s to a receiving end hot wire between the heat sinks 6 and 9 through a high-precision power supply, measuring receiving end hot wire voltage U s between the heat sinks 7 and 8, obtaining a change rule of the resistance of the receiving end hot wire along with heating power under different currents, collecting receiving end hot wire resistance values R s corresponding to 5 different heating powers P s, drawing a P s-Rs curve, and finishing fitting, wherein the intercept is the initial resistance R s0 of the receiving end hot wire.
As shown in fig. 8, in the fitted curve, the intercept is 0.8952 Ω, which represents that the initial resistance of the hot line at the receiving end is 0.8952 Ω.
And 5, introducing constant current I h to a heating end hot wire between the heat sinks 2 and 5 through a high-precision power supply, measuring the heating end hot wire voltage U h between the heat sinks 3 and 4, obtaining the change rule of the heating end hot wire resistance along with heating power under different currents, collecting heating end hot wire resistance values R h corresponding to 5 different heating powers P h, drawing a P h-Rh curve, and finishing fitting, wherein the intercept is the initial resistance R h0 of the heating end hot wire.
As shown in fig. 9, the intercept of the fitted curve is 1.1229 Ω, which represents that the initial resistance of the heating terminal heat line is 1.1229 Ω.
And 6, passing a constant current I 1 to a heating end hot wire between the heat sinks 2 and 5 through a high-precision power supply, measuring a heating end hot wire voltage U 1 between the heat sinks 3 and 4, and simultaneously, passing a micro current I 2 (the temperature rise caused by the micro current I 2 is negligible) to a receiving end hot wire between the heat sinks 6 and 9, and measuring a receiving end hot wire voltage U 2 between the heat sinks 7 and 8.
In this step, I 1 =35 mA is set, and U 1 = 41.1668mV is measured, so that the heating-end heat-wire resistance R 1＝U1/I1 = 1.1762 Ω between the heat sinks 2, 5 at this time can be obtained, and the average temperature rise of the heating-end heat wire at this time can be obtained according to step 5:
Meanwhile, the receiving-end hot wire is led with micro current I 2 =4ma, and U 2 = 3.597mV is measured, so that receiving-end hot wire resistance R 2＝U2/I2 = 0.8993 Ω between heat sinks 7,8 at this time can be obtained, and the average temperature rise of the receiving-end hot wire at this time can be obtained according to step 4:
And 7, combining the thermophysical parameters of the platinum gold wires, calculating the corresponding heat conductivity and emissivity value of the wire to be measured according to a formula, and completing the measurement process.
And measuring the length of the heating end heat wire between the heat sinks 3 and 4 by using a vernier caliper to obtain l h =17.46 mm, and simultaneously measuring the length of the receiving end heat wire between the heat sinks 7 and 8 to obtain l h =13.6 mm, wherein the heating end heat wire and the receiving end heat wire both adopt platinum gold wires with the purity of 99.95% and the diameter of 50 mu m, so that A h＝1.96×10-9m2,Ph＝1.57×10-4 m, and according to the theoretical thermophysical parameter values of the platinum gold wires, the thermal conductivities of the heating end heat wire and the receiving end heat wire are lambda h＝71.6W·m-1·K-1, and the thermal resistances of the heating end heat wire and the receiving end heat wire are Re h＝1.2426×105K/W,Res＝9.6787×104 K/W respectively.
The length of the line to be measured (i.e. the distance from the upper node to the lower node) is measured by a vernier caliper to obtain l f =3.0 mm, the line to be measured is cut out by a composite material self-made by a laboratory, the width of the line to be measured is 211.25 μm by a microscope, and the thickness of the line to be measured is 64.40 μm, so that the line to be measured is A f＝1.36×10-8m2,Pf＝5.51×10-4 m.
According to the formula:
Wherein the method comprises the steps of
Substituting the data calculation yields a thermal conductivity λ f＝1.67W·m-1·K-1, emissivity epsilon f =0.45.
The method for simultaneously measuring the thermal conductivity and the emissivity of the micro-nano material has wide application range, and can be applied to the thermal physical property measurement of the platinum gold wire in the example 1 and the composite material in the example 2, and also can be applied to the thermal physical property measurement of various micro-nano materials. The foregoing embodiments and description have been provided to illustrate the principles and technical effects of the present invention and to provide various changes and modifications without departing from the basic method of the invention, which changes and modifications fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (1)
1. The method for simultaneously measuring the thermal conductivity and the emissivity of the micro-nano material is characterized by comprising the following steps of:
Step 1, fixing 8 heat sinks on a base, welding two platinum wires on the heat sinks in parallel, overlapping wires to be measured to form a double-heat-wire measuring platform, placing the double-heat-wire measuring platform into a constant temperature cavity, and vacuumizing;
Step 2, a direct current I s is conducted to a heating wire of a receiving end, a voltage value U s of the two ends is collected, a heating power-resistance curve is drawn and fitted, an initial resistance R s0 of the heating wire of the receiving end is obtained, the same operation is conducted on the heating wire of the receiving end, and an initial resistance R h0 of the heating wire of the heating end is obtained; the initial resistances of the obtained two ends of the heating wire are the intercept of the fitted power-resistance curve;
Step 3, introducing a constant current I 1 to the heating end hot wire, measuring the voltage U 1 of the heating end hot wire, simultaneously introducing a micro current I 2 to the receiving end hot wire, measuring the voltage U 2 of the receiving end hot wire, and calculating according to the data in the step 2 to obtain the average temperature rise of the heating end hot wire and the receiving end hot wire; obtaining the average temperature rise of the heating end heating wire and the receiving end heating wire, wherein the average temperature rise of the heating end heating wire is as follows:
Beta is the temperature resistance coefficient of the platinum gold wire at normal temperature, R 1 is the heating end hot wire resistance, and
The average temperature rise of the hot wire at the receiving end is as follows:
Wherein R 2 is the hot-wire resistance of the receiving end, and is obtained from the measurement data
Step 4, utilizing temperature rise data to obtain the emissivity and the heat conductivity of the to-be-measured line by establishing a mathematical model and solving;
the thermal conductivity and the emissivity of the micro-nano material are obtained by the following formula:
Thermal conductivity:
Emissivity:
Wherein the method comprises the steps of
Wherein Re h represents heating-end heat resistance, re s represents receiving-end heat resistance
L h、ls represents the heating-end heat ray and receiving-end heat ray lengths, respectively, lambda h represents the heat ray thermal conductivity, and a h represents the heat ray cross-sectional area; l f denotes the length of the wire to be measured, A f denotes the cross-sectional area of the wire to be measured, I 1、U1 denotes the heating-end heating-wire current and voltage respectively,Represents the average temperature rise of the heating end heating wire,/>The average temperature rise of the hot wire at the receiving end is represented, P f represents the transverse perimeter of the wire to be measured, T 0 represents the set ambient temperature, and sigma represents the Stefan-Boltzmann constant.
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| CN104880482A (en) * | 2015-04-13 | 2015-09-02 | 中国科学院物理研究所 | Method and device for measuring heat conductivity of quasi-one-dimensional conductive material |
| CN106018377A (en) * | 2016-05-06 | 2016-10-12 | 清华大学 | System Raman spectrum method for comprehensively measuring heat conduction and optical characteristics of nanometer materials with supports and suspensions |
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| CN107290381A (en) * | 2017-07-27 | 2017-10-24 | 东南大学 | A kind of measurement apparatus and method of the nano wire thermal conductivity based on T-shaped structure |
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| CN104880482A (en) * | 2015-04-13 | 2015-09-02 | 中国科学院物理研究所 | Method and device for measuring heat conductivity of quasi-one-dimensional conductive material |
| CN106018377A (en) * | 2016-05-06 | 2016-10-12 | 清华大学 | System Raman spectrum method for comprehensively measuring heat conduction and optical characteristics of nanometer materials with supports and suspensions |
| CN107085007A (en) * | 2017-03-09 | 2017-08-22 | 清华大学 | Detect the device and method of one-dimensional micro-nanometer conducting material thermoelectricity performance parameter |
| CN107290381A (en) * | 2017-07-27 | 2017-10-24 | 东南大学 | A kind of measurement apparatus and method of the nano wire thermal conductivity based on T-shaped structure |
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