CN110907490B - A thermal conductivity testing device and method for high thermal conductivity materials - Google Patents
A thermal conductivity testing device and method for high thermal conductivity materials Download PDFInfo
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Abstract
本申请公开了一种高导热材料的热导率测试装置及方法，属于热导率测试技术领域，解决了现有技术中加热组件的热流密度较低，热导率测量结果不准确的问题。装置包括加热组件、热量汇聚组件、冷板和信号采集处理单元，加热组件放置于热量汇聚组件的上方，热量汇聚组件用于增大加热组件的热流密度φ至(8～9)φ，加热试样上表面，冷板用于冷却试样下表面。测试方法如下：将试样置于热量汇聚组件与热流计之间，热流计下方设置冷板；启动加热组件，使试样上表面温度升至待测温度，恒温；启动加热组件后，启动冷却循环水机，使试样下表面温度至待测温度，恒温；整个系统达到平衡后，采集数据，计算热导率。本申请可用于高导热材料的热导率测试。
The present application discloses a thermal conductivity testing device and method for high thermal conductivity materials, belonging to the technical field of thermal conductivity testing, which solves the problems of low heat flux density of heating components and inaccurate thermal conductivity measurement results in the prior art. The device includes a heating component, a heat gathering component, a cold plate and a signal acquisition and processing unit. The heating component is placed above the heat gathering component. The upper surface of the sample, and the cold plate is used to cool the lower surface of the sample. The test method is as follows: place the sample between the heat gathering component and the heat flow meter, and set a cold plate under the heat flow meter; start the heating component, make the upper surface temperature of the sample rise to the temperature to be measured, and keep a constant temperature; after starting the heating component, start cooling Circulating water machine, make the temperature of the lower surface of the sample to the temperature to be measured, constant temperature; after the whole system reaches equilibrium, collect data and calculate the thermal conductivity. This application can be used for thermal conductivity testing of high thermal conductivity materials.
Description
Technical Field
The application relates to the technical field of thermal conductivity testing equipment, in particular to a thermal conductivity testing device and method for high-thermal conductivity materials.
Background
The thermal conductivity testing technology is based on a one-dimensional steady-state Fourier heat transfer law as a theoretical basis, a sample with a certain width-thickness ratio is placed between a heating unit and a cooling device, when the temperatures of a hot surface and a cold surface of the sample are uniformly constant under a certain temperature difference, a quasi-one-dimensional longitudinal steady-state heat flow can be established in the sample (particularly in a central area) under an ideal state, and the effective thermal conductivity of the sample can be obtained according to the heat flow density, the temperature of the hot surface of the sample, the temperature of the cold surface of the sample and the thickness of the sample.
At present, no mature test method exists for testing the thermal conductivity of high thermal conductivity materials with the thermal conductivity of more than or equal to 150W/(m.K), such as porous high thermal conductivity carbon foam. In the existing research, a transient laser pulse method heat conduction instrument and a steady-state protective heat flow meter method heat conduction instrument are respectively selected to carry out a heat conductivity test on the material, and the fact that the thickness of a sample greatly affects a measurement result when the laser pulse method is used for testing is found, and the maximum value of the heat conductivity among the heat conductivity values measured when the thicknesses of the same batch of samples are different can exceed 50%, so that a reliable heat conductivity value cannot be obtained; the measurement range of the existing heat conduction instrument by a protective heat flow meter method is 0.1W/(m.K) -15W/(m.K), when high-heat-conduction carbon foam is measured, the temperature difference applied to the upper surface and the lower surface of a sample can only reach about 1.5 ℃, the requirement of the temperature difference of 15-25 ℃ cannot be met, the signal-to-noise ratio of a temperature difference signal is poor, and great influence is caused on the measurement result.
Disclosure of Invention
In view of the above analysis, the present application aims to provide a thermal conductivity testing apparatus and method for a high thermal conductivity material, so as to solve the problems in the prior art that the temperature difference between the upper surface and the lower surface of a sample is low, the measurement result of the thermal conductivity is inaccurate, and the consistency is poor due to the low heat flow density of a common heating assembly.
The purpose of the application is mainly realized by the following technical scheme:
the application provides a heat conductivity testing arrangement of high heat conduction material, assemble subassembly, cold plate and signal acquisition processing unit including heating element, heat, and heating element places in the top that the heat assembles the subassembly, and the heat assembles the subassembly and is used for increasing heating element's heat flux density phi to (8 ~ 9) phi, and then heats the sample upper surface, and the cold drawing is used for cooling off the sample lower surface.
In one possible design, an in-situ thickness measuring unit is further included.
In one possible design, the heating assembly is a rectangular parallelepiped.
In one possible design, the heat sink assembly includes an upper section, a middle section and a lower section from top to bottom, the upper section is a cuboid, the middle section is a quadrangular frustum, and the lower section is a cuboid.
In one possible design, the upper surface of the upper section conforms to the lower surface of the heating assembly, and the upper surface of the upper section is the same size as the lower surface of the heating assembly.
In one possible design, the upper surface of the middle section is the same size as the lower surface of the upper section; area S of lower surface of middle section2Less than the upper surface of the middle section1(ii) a The upper surface of the lower section is the same size as the lower surface of the middle section.
In one possible design, the height H of the upper section1Height H of the middle section2And height H of the lower section3The proportion of (A) is as follows: h1:H2:H3＝1：(20～30)：(10～15)。
In one possible design, the heating assembly comprises a uniform temperature plate, a heating plate and a heat insulating layer which are sequentially stacked, wherein the heating plate comprises a heating wire or a plurality of heating strips, and the heating temperature of the heating plate gradually increases along the direction gradually far away from the center of the heating plate.
In one possible design, the heating assembly, the heat converging assembly and the cold plate are all wrapped with a layer of heat insulating material.
The application also provides a thermal conductivity testing method of the high thermal conductivity material, which comprises the following steps:
step 1: placing a sample between the heat convergence assembly and the cold plate, and arranging a heat flow meter between the lower surface of the sample and the cold plate;
step 2: starting the heating assembly to raise the temperature of the upper surface of the sample to a temperature to be measured, and keeping the temperature constant;
and step 3: after the heating assembly is started in the step 2, starting the cooling circulating water machine to enable the temperature of the lower surface of the sample to reach the temperature to be measured, and keeping the temperature constant;
and 4, step 4: after the whole system reaches the balance state, the signal acquisition and processing unit acquires the surface temperature data T of the sample3Temperature data T of the lower surface of the sample4And calculating the heat conductivity of the sample according to the heat flow density phi of the sample and the thickness d of the sample.
Compared with the prior art, the application can realize at least one of the following beneficial effects:
a) the application provides a heat conductivity testing arrangement of high heat conduction material assembles the subassembly through setting up the heat to assemble the size of each part of subassembly through the accurate control heat, make the heat current on the lower surface of hypomere perpendicular downwards as far as possible, and can enlarge heating element's heat flux density phi to (8 ~ 9) phi, and then guarantee that the difference in temperature of sample upper surface and sample lower surface reaches 15 ~ 25 ℃, realize the accurate measurement of sample heat conductivity.
b) The utility model provides a heating element is for dividing the body structure, and the continuous platelike structure of nonblock, the hot plate includes heater strip or many heating laths, and along the direction of keeping away from the center of hot plate gradually, the heating temperature of hot plate risees gradually, the heat dissipation problem of heating element edge has fully been considered, through the temperature of the hot plate that improves marginal area, make marginal area's hot plate temperature be higher than central area's heating plate temperature, thereby compensate the heat dissipation of heating element edge, improve the holistic temperature uniformity of hot plate, make it tend to one-dimensional steady state thermal current more, improve the accuracy of thermal conductivity test.
c) The application of the testing device adopts the in-situ thickness measuring unit, the thickness of the sample can be measured in real time, the thickness of the sample is measured before lofting in the prior art, and the accuracy of thermal conductivity testing can be further improved by adopting the in-situ thickness measuring unit.
Additional features and advantages of the application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the application. The objectives and other advantages of the application may be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the application, wherein like reference numerals are used to designate like parts throughout.
Fig. 1 is a schematic structural diagram of a thermal conductivity testing apparatus for high thermal conductivity materials according to the present application;
FIG. 2 is a schematic structural view of a heating element according to embodiment 4 of the present application;
FIG. 3 is a pictorial view of a first configuration of a heating plate in the heating assembly of the present application;
FIG. 4 is a schematic structural view of a second configuration of a heating plate in the heating assembly of the present application;
FIG. 5 is a schematic view of a third configuration of a heating plate in the heating assembly of the present application;
FIG. 6 is a graph of heating temperature versus time for the heating plate provided in example 4 of the present application;
fig. 7 is a temperature distribution diagram of the lower surface of the vapor chamber in the heating assembly according to embodiment 5 of the present application.
Reference numerals:
1-a heating assembly; 11-a temperature-equalizing plate; 12-a heating plate; 13-a thermally insulating layer; 2-a heat sink assembly; 21-upper section; 22-middle section; 23-lower section; 3-a cold plate; 4-a signal acquisition processing unit; 5-sample; 61-a first thermocouple; 62-a second thermocouple; 63-a third thermocouple; 64-a fourth thermocouple; 7-heating power supply assembly; 8-heat flow meter; 9-cooling the circulating water machine; 10-heat insulating material.
Detailed Description
The preferred embodiments of the present application will now be described in detail with reference to the accompanying drawings, which form a part hereof, and which together with the embodiments of the application serve to explain the principles of the application.
In a thermal conductivity test, the current common heating assembly has low heat flow density, when a high thermal conductivity material is measured, for example, a material with a thermal conductivity of more than or equal to 150W/(m.K), the temperature difference applied to the upper surface and the lower surface of a sample can only reach about 1.5 ℃, the requirement of the temperature difference of 15 ℃ to 25 ℃ can not be met, and the signal-to-noise ratio of a temperature difference signal is poor, so that the measurement result of the thermal conductivity is inaccurate and poor in consistency, and the measurement result is greatly influenced.
Example 1
The embodiment provides a thermal conductivity testing device of a high thermal conductive material, which is shown in fig. 1-5 and comprises a heating component 1, a heat gathering component 2, a cold plate 3 and a signal acquisition and processing unit 4, wherein the heating component 1 is placed above the heat gathering component 2, the heat gathering component 2 is used for increasing the heat flux phi of the heating component 1 to (8-9) phi, so as to heat the upper surface of a sample 5, and the cold plate 3 is used for cooling the lower surface of the sample 5.
Compared with the prior art, the heat conductivity testing device of high heat conduction material that this application provided can increase heating element 1's heat flux density through setting up heat and assemble subassembly 2, and then guarantees that the difference in temperature of sample upper surface and sample lower surface reaches 15 ~ 25 ℃, realizes the accurate measurement of sample heat conductivity.
In addition, the testing device further comprises an in-situ thickness measuring unit (for example, a laser displacement measurer), and the in-situ thickness measuring unit can be arranged on the upper surface of the sample, because, in the testing process of the thermal conductivity, the thickness of the sample 5 can change along with the change of the lower surface temperature and the upper surface temperature, and the thickness of the sample 5 can be measured in real time by using the in-situ thickness measuring unit, so that compared with the prior art that the thickness of the sample 5 is measured before lofting, the accuracy of the thermal conductivity test of the high thermal conductivity material can be further improved by using the in-situ thickness measuring unit.
It should be noted that the heat collecting assembly 2 includes, from top to bottom, an upper section 21, a middle section 22 and a lower section 23, where the upper section 21 is a rectangular parallelepiped, the middle section 22 is a quadrangular frustum, and the lower section 23 is a rectangular parallelepiped.
In order to improve the tightness of the heat converging component 2 and prevent heat dissipation, the heat converging component 2 is of an integrally formed structure.
Specifically, the heating element 1 has a rectangular parallelepiped structure.
In particular, the dimensions of the heating assembly 1 may be: length l1200-400 mm, width w1200-400 mm, height h110-20 mm; illustratively, the dimensions of the heating assembly 1 are: 300 mm. times.300 mm. times.20 mm (l)1×w1×h1)。
In order to utilize the heat of the heating component 1 to the maximum extent and reduce the heat loss of the heating component 1, the upper surface of the upper section 21 is attached to the lower surface of the heating component 1, and the upper surface of the upper section 21 has the same size as the lower surface of the heating component 1; the dimensions of the upper surface of the upper section 21 are therefore: length l2200-400 mm, width w2200-400 mm; illustratively, the dimensions of the upper surface of the upper section 21 are: 300 mm. times.300 mm (l)2×w2)。
The size of the upper surface of the middle section 22 is the same as the size of the lower surface of the upper section 21; area S of the lower surface of the middle section 222Less than the area S of the upper surface of the middle section 221And S is2＝(0.08～0.3)S1The dimensions of the lower surface of the middle section 22 are: length l350 to 150mm in width w350-150 mm; illustratively, the lower surface of the middle section 22 has dimensions of: 100mm X100 mm (l)3×w3)。
The upper surface of the lower section 23 is the same size as the lower surface of the middle section 22.
Due to the requirement of the one-dimensional heat transfer model, after the downward one-dimensional planar heat flow of the heating assembly 1 is subjected to the collecting action of the heat collecting assembly 2, when the downward one-dimensional planar heat flow is conducted to the sample 5 through the lower surface of the lower section 23, the one-dimensional planar heat flow still needs to be maintained. Thus, the height H of the upper section 211Height H of the middle section 222And height H of lower section 233A reasonable matching relationship needs to be selected to achieve this goal. The application evaluates H through a heat transfer simulation method1、H2And H3The influence degree of the matching relation of the three on the one-dimensional heat flow on the lower surface of the lower section 23, and then the reasonable selection range of the three obtained by multiple iterative optimization is as follows: h1：H2：H31 (20-30) and (10-15). When a reasonable height is chosen, the non-uniformity of the heat flow density across the central metering region of the lower surface of the lower section 23 is better than 5%. Exemplary, H1Is 2mm, H2Is 60mm, H3Is 20 mm.
The sizes of all parts of the heat converging assembly 2 are accurately controlled, so that the heat flow on the lower surface of the lower section 23 is downward vertical as much as possible, the heat flow density phi of the heating assembly 1 can be enlarged to (8-9) phi, namely, the heat flow density is enlarged to 8-9 times of the original heat flow density phi, the temperature difference between the upper surface of the sample and the lower surface of the sample is further guaranteed to reach 15-25 ℃, and the accurate measurement of the heat conductivity of the sample is realized.
In order to measure the temperature distribution of the heat converging component 2 and the sample 5 in real time, a first hole groove is arranged at the geometric center of a plane of the middle section 22, which is 2mm away from the upper surface of the middle section 22, and the first hole groove horizontally extends out of the lateral edge from the geometric center of the plane where the first hole groove is located; a second hole groove is arranged at the geometric center of a plane of the lower section 23, which is 2mm away from the lower surface of the lower section 23, and the second hole groove horizontally extends out of the side edge from the geometric center of the plane where the second hole groove is located; a third hole groove is arranged at the geometric center of a plane of the sample 5, which is 2mm away from the upper surface of the sample 5, and the third hole groove horizontally extends out of the side edge from the geometric center of the plane where the third hole groove is located; and a fourth hole groove is arranged at the geometric center of a plane of the sample 5, which is 2mm away from the lower surface of the sample 5, and the fourth hole groove horizontally extends out of the side edge from the geometric center of the plane of the fourth hole groove.
The first hole groove to the fourth hole groove are used for placing thermocouples; specifically, first hole groove is used for placing first thermocouple 61, the second hole groove is used for placing second thermocouple 62, the third hole groove is used for placing third thermocouple 63, the fourth hole groove is used for placing fourth thermocouple 64, the thermocouple adopts above-mentioned thermocouple arrangement mode, can measure the temperature distribution condition of the different positions department that the heat assembles subassembly 2 and sample 5 more accurately, simultaneously, arrange above-mentioned first hole groove to fourth hole groove and can release the heat better and assemble the thermal stress that subassembly 2 and sample 5 produced at the temperature rising and lowering in-process in above-mentioned position, avoid expend with heat and contract with cold and warp.
Above-mentioned diameter of first hole groove to fourth hole groove is too little, and the thermocouple is not well placed, and the diameter is too big, can influence the heat and assemble subassembly 2 and sample 5's heat distribution, therefore the diameter of first hole groove to fourth hole groove is 1 ~ 1.5 mm.
In order to be able to measure the heat flux density through the sample 5 in real time, a heat flow meter 8 is provided below the lower surface of the sample 5.
Specifically, the heat flow meter 8 can be a surface type thin film heat flow meter (with a thickness of 3.5mm), and the heat flow density measurement range is 0-3.14 MW/m2。
The in-situ thickness measuring unit, the heat flow meter 8, the third thermocouple 63 and the fourth thermocouple 64 are all connected with the signal acquisition and processing unit 4, and the signal acquisition and processing unit 4 is used for acquiring temperature measurement values of the third thermocouple 63 and the fourth thermocouple 64, heat flow density measurement values of the heat flow meter 8 and the thickness of the sample 5 and calculating to obtain the thermal conductivity.
In addition, above-mentioned testing arrangement still includes heating power supply module 7, and heating power supply module 7 includes the temperature controller, and first thermocouple 61 and second thermocouple 62 all link to each other with heating power supply module 7, and first thermocouple 61 and second thermocouple 62 transmit the data that record to the temperature controller, and the temperature controller sends signal to heating power supply module 7 behind the analysis data, and then control heating power supply module 7 and adjust output voltage in order to realize the accurate control of temperature.
The below of heat-flow meter 8 is located to cold drawing 3, and cold drawing 3 refrigerates through outside cooling circulation water machine 9, in time takes away the heat of sample 5 below to realize the stability of sample 5 below temperature.
The cold plate 3 may be a copper plate in view of the requirement of the cold plate 3 to conduct heat away quickly, and therefore the cold plate 3 has a good thermal conductivity, and the cost is reduced.
Specifically, considering that the sample 5 is a rectangular parallelepiped structure, in order to minimize the heat loss and save the cost as much as possible, the cold plate 3 and the heat flow meter 8 are both configured as a rectangular parallelepiped structure, and the upper surface sizes of the cold plate 3 and the heat flow meter 8 are the same as the upper surface size of the sample 5.
In view of reducing heat loss, the heat collecting component 2 should be made of an alloy with high thermal conductivity (copper, aluminum alloy, or the like), preferably, the heat collecting component 2 is made of an aluminum alloy, the thermal conductivity of the heat collecting component 2 is 230 to 250W/(m.k), and exemplarily, the thermal conductivity of the heat collecting component 2 is 240W/(m.k).
In order to effectively control the heat dissipation loss of the testing device to the periphery and ensure the realization of the one-dimensional heat flow condition of the sample 5 in the thickness direction, a layer of heat insulating material 10 is wrapped around the outside of a unit consisting of the whole heating assembly 1, the heat converging assembly 2, the sample 5, the cold plate 3 and the heat flow meter 8.
Specifically, in order to minimize the effect of the thermal insulation material 10 on the thermal conductivity test process, the thermal insulation material 10 may be a fiber reinforced silica aerogel thermal insulation material with a low thermal conductivity, and illustratively, the fiber reinforced silica aerogel thermal insulation material has a room temperature thermal conductivity of 0.03W/(m.k).
Considering that the thickness of the heat insulating material 10 is too small, the heat insulating effect is not good enough, the thickness is too large, the increase of the heat insulating effect is not significant, and the cost is wasted, the thickness of the heat insulating material 10 is controlled to be 25-35 mm, and preferably, the thickness of the heat insulating material 10 is 30 mm.
In order to reduce the production cost, the heating element 1 is a copper plate resistance heater.
As shown in fig. 2, in consideration of heat dissipation at the edge of the heating module 1, the heating module 1 includes a uniform temperature plate 11, a heating plate 12 and a heat insulating layer 13 which are sequentially stacked, wherein the heating plate 12 includes a heating wire or a plurality of heating strips, and the heating temperature of the heating plate 12 gradually increases in a direction gradually away from the center of the heating plate 12; establish heating element 1 into components of a whole that can function independently structure, but not massive continuous platelike structure, and along keeping away from the central zone of hot plate 12 gradually, the heating temperature of hot plate 12 risees gradually, the heat dissipation problem in 1 edge of heating element has fully been considered, through the temperature of the hot plate 12 that improves edge zone, make edge zone's hot plate 12 temperature be higher than central zone's hot plate 12 temperature, thereby compensate the heat dissipation of 1 edge of heating element, improve the holistic temperature uniformity of hot plate 12, make it more tend to one-dimensional steady state heat flow, improve the accuracy of thermal conductivity test.
As for the configuration of the heating plate 12, there are three types, specifically, the first type, which may be a square surrounding type configuration, see fig. 3, including a serpentine line that surrounds along a longitudinal symmetry axis of the heating plate 12 in a mirror image manner, from the center to the edge direction of the heating plate 12, the shape of the heating wire is a C shape (here, the C shape refers to a C shape in a broad sense, and can be understood as a surrounding shape with an opening portion, such as a straight line surrounding with a folded edge, a curved line surrounding, and the like), and the distance between two adjacent loops of the heating wire gradually decreases along a direction gradually departing from the center of the heating plate 12, that is, from the center to the edge direction of the heating plate 12, the heating wire includes a plurality of C-shaped wires that are connected end to end, and the plurality of C-shaped wires are sequentially sleeved end to form the serpentine line surrounded by C-shaped wires. Through the structure, the purpose that the heating temperature of the central heating plate 12 gradually far away from the heating plate 12 is gradually increased can be achieved, so that the overall temperature uniformity of the heating plate 12 is improved, the heating plate more tends to one-dimensional steady-state heat flow, and the accuracy of heat conductivity test is improved.
As shown in fig. 3, the heating plate 12 may be a heating plate with a square shape formed by surrounding a heating wire, the heating wire of the heating plate is in a bilateral symmetry structure with a longitudinal symmetry axis of the upper surface of the square heating plate as a reference, the surrounding manner of the left heating wire is that a point on the longitudinal symmetry axis is used as a starting point, the heating wire is surrounded upwards along the C shape, the heating wire is surrounded downwards and leftwards along the C shape after reaching the upper end point of the C shape, the heating wire is surrounded upwards and leftwards along the C shape after reaching the lower end point of the C shape, and the heating wire is sequentially surrounded to form a plurality of C-shaped serpentine lines which are connected end to end from the center to the edge of the heating plate, the C-shaped openings are sequentially enlarged; the surrounding mode of the right side part heating wire is that, the point on the longitudinal symmetry axis is used as a starting point, the upward surrounding is carried out along the C type to the C type upper end point, then the downward surrounding is carried out along the C type right, the downward surrounding is carried out along the C type right again to the C type lower end point, the upward surrounding is carried out along the C type right again, the surrounding is carried out in sequence, the serpentine line which is formed from the center to the edge direction of the heating plate, and the C type opening is sequentially increased and is connected end to end by a plurality of C types is formed. The starting point of the left part heating wire is the same as that of the right part heating wire, and the left part heating wire and the right part heating wire form a square surrounding type configuration which is mirror-symmetrical about the longitudinal symmetry axis.
In a second configuration of the heating plate 12, the shape of the heating plate 12 can be smoothly curved, see fig. 4, i.e. the heating wires in the heating plate 12 are not angled. This is because, the heater strip can produce obvious thermal stress that leads to by expend with heat and contract with cold phenomenon when rising temperature or cooling, and when there is the dog-ear, heater strip component very easily takes place to damage or even fracture in dog-ear, sets up the shape of heater strip component into smooth curve, does not have the dog-ear, can avoid the production of above-mentioned thermal stress to reduce the heater strip component and damage and the emergence of the fracture condition.
The heating plate 12 is shaped as a spiral line, for example, because the corner damage and fracture caused by thermal stress can be avoided, and because the spiral shape is symmetrical with an approximately circular structure, the heating uniformity of the temperature-uniformed high-temperature heating element can be further improved. Along the direction of keeping away from the center of hot plate 12 gradually, the distance between two adjacent circles of helices reduces gradually, that is to say, above-mentioned hot plate 12 adopts interior sparse outer close symmetrical configuration to realize that the heating temperature of hot plate 1 risees gradually, can offset the heat loss at heating element 1 edge like this to further improve heating element 1's heating homogeneity.
Considering from the angle of installation, above-mentioned helix can be the fermat helix, and it is required to explain that the fermat helix is the helix of interior sparse close symmetrical configuration outward, and above-mentioned heating element 1's heating homogeneity can be guaranteed effectively to this kind of structure, in addition, because the both ends of fermat helix all are located the outer lane of spiral to be convenient for with other power supply unit's connection.
In a third configuration of the heating panel 12, the heating panel 12 may comprise a plurality of parallel strips, the width of which gradually decreases away from the center of the heating panel 12, see fig. 5, i.e. the heating panel 12 achieves a gradual increase in the heating temperature of the heating panel 1 by adjusting the width of the strips. Specifically, since the currents applied to both ends of the plurality of strips are the same, the width of the strip near the center of the heating plate 12 is large, the resistance is small, and the amount of heat generation is small, so that the heating temperature of the heating plate 12 in the direction gradually away from the center of the heating plate 12 can be gradually increased. For example, the width of the slats can be controlled to be 20 mm-50 mm, the gap between two adjacent slats can be controlled to be 5 mm-14 mm, and the number of slats can be controlled to be 6-9.
Compared with the prior art, the heat conductivity testing device of high heat conduction material that this application provided can increase heating element's heat flux density through setting up the heat and assemble the subassembly to assemble the size of each part of subassembly through the accurate control heat, make the heat flux on the lower surface of hypomere perpendicular downwards as far as possible, and can enlarge heating element's heat flux density phi to (8 ~ 9) phi, and then guarantee that the difference in temperature of sample upper surface and sample lower surface reaches 15 ~ 25 ℃, realize the accurate measurement of sample heat conductivity.
The application provides a heating element among high heat conduction material's heat conductivity testing arrangement is for dividing the body structure, but the massive continuous platelike structure of non-, and along the central zone of keeping away from the hot plate gradually, the heating temperature of hot plate risees gradually, the heat dissipation problem of heating element edge has fully been considered, through the temperature of the hot plate that improves marginal zone, make marginal zone's hot plate temperature be higher than central zone's hot plate temperature, thereby compensate the heat dissipation of heating element edge, improve the holistic temperature uniformity of hot plate, make it tend to one-dimensional steady-state heat flow more, improve the accuracy of heat conductivity test.
The application of the testing device adopts the in-situ thickness measuring unit, the thickness of the sample can be measured in real time, the thickness of the sample is measured before lofting in the prior art, and the accuracy of thermal conductivity testing can be further improved by adopting the in-situ thickness measuring unit.
Example 2
The embodiment provides a method for testing thermal conductivity of a high thermal conductivity material, which adopts the thermal conductivity testing apparatus in the embodiment 1, wherein the high thermal conductivity material in the embodiment is a carbonaceous foam sample 5, and the method for testing the thermal conductivity comprises the following steps:
step 1: placing a carbonaceous foam sample 5 between the heat converging component 2 and the cold plate 3, and arranging a heat flow meter 8 between the lower surface of the sample and the cold plate 3;
step 2: starting the heating assembly 1 to raise the temperature of the upper surface of the carbonaceous foam sample 5 to a temperature to be measured, and keeping the temperature constant;
and step 3: after the heating assembly is started in the step 2, the cooling circulating water machine 9 is started, the temperature of circulating water is set, and the circulating water is used for refrigerating the sample, so that the temperature of the lower surface of the carbonaceous foam sample 5 reaches the temperature to be measured and reaches the constant temperature;
and 4, step 4: after the whole system reaches an equilibrium state (the temperature of the upper surface of the carbonaceous foam sample, the temperature of the lower surface of the carbonaceous foam sample, the thickness of the carbonaceous foam sample and the heat flow density of the carbonaceous foam sample reach the equilibrium state), the signal acquisition and processing unit 4 acquires the temperature data T of the upper surface of the carbonaceous foam sample 53(measurement value of third thermocouple in FIG. 1), surface temperature data T of carbonaceous foam sample 54(the fourth thermocouple measurement in fig. 1), the heat flow density phi of the carbonaceous foam sample 5 and the thickness d of the carbonaceous foam sample 5, and the thermal conductivity of the sample is calculated according to a one-dimensional steady-state fourier heat transfer formula.
Specifically, in step 1, because the surface of carbonaceous foam sample 5 is porous, and the heat conduction effect is not good in the porous place, so that it is better to make carbonaceous foam sample 5 contact heat convergence subassembly 2 and heat flow meter 8, and it is necessary to uniformly coat the upper and lower surfaces of carbonaceous foam sample 5 with heat conduction paste, and the thickness of heat conduction paste is 0.5-1 mm.
Specifically, during the test, the in-situ thickness measuring unit can measure the thickness d (i.e. the distance between the third hole groove and the fourth hole groove in fig. 1) of the carbonaceous foam sample 5 in real time during the thermal conductivity test.
Specifically, in step 4, the calculation formula of the thermal conductivity λ is as follows:
example 3
This example provides a heat test of a highly thermally conductive carbonaceous foam sample 5 using the thermal conductivity testing apparatus of example 1 above. Wherein, heating element 1 is copper resistance heater, and copper resistance heater's size is: 300 mm. times.300 mm. times.20 mm (l)1×w1×h1) Upper section ofThe dimensions of the upper surface of 21 are: 300 mm. times.300 mm (l)2×w2) (ii) a The dimensions of the lower surface of the middle section 22 are: 100mm X100 mm (l)3×w3)；H1Is 2mm, H2Is 60mm, H3Is 20 mm. The heating test comprises the following steps:
s1, placing the carbonaceous foam sample 5 between the heat convergence component 2 and the cold plate 3, and arranging a heat flow meter 8 between the lower surface of the carbonaceous foam sample 5 and the cold plate 3;
s2, starting the heating component 1 to raise the temperature of the upper surface of the carbonaceous foam sample 5 to 50 ℃ to be measured, and keeping the temperature constant, wherein the temperature of the heating component 1 is 60.7 ℃ at the moment, and the electric heating power is 849W;
s3: after the heating assembly 1 is started in the step S2, the cooling circulating water machine 9 is started, the temperature of the circulating water is set to be 10 ℃, so that the temperature of the lower surface of the carbonaceous foam sample 5 reaches a stable temperature of 32 ℃, and the temperature of the lower water cooling plate is 12.9 ℃; the thickness d of the on-line measurement sample is 30.11 mm; the measurement value of the heat flow meter 8 was recorded as 80704W/m2The thermal conductivity of the carbonaceous foam sample was calculated to be 135W/m.K.
It can be seen through this embodiment that the temperature difference of surface about the sample that adopts this application heat to assemble the device and can guarantee high heat conduction material, and then guarantee the accurate measurement of heat conductivity.
Example 4
The present embodiment provides a thermal conductivity testing apparatus of high thermal conductivity material, wherein the heating plate adopts a square surrounding type configuration (first configuration) made of NiCr alloy, and the thickness is 2.5mm, see fig. 3.
When the heating plate is adopted, the temperatures of different parts of the lower surface of the temperature-equalizing plate are tested, the test result is shown in fig. 6, and as can be seen from fig. 6, the temperatures of different parts of the lower surface of the temperature-equalizing plate can reach more than 1000 ℃, the temperature uniformity is good, and the temperature-equalizing deviation is +/-5.3%.
Example 5
The present embodiment provides a thermal conductivity testing apparatus of a high thermal conductive material, in which a heating plate adopts a configuration of a plurality of strips made of graphite parallel to each other (third configuration), see fig. 5.
Adopting graphite as a heating plate, carrying out ANSYS simulation analysis on the heating up capacity and the temperature equalizing capacity of the heating assembly, wherein the widths of the strips are 20-30-40-50-40-30-20mm in sequence, and the total number of the strips is 7; the gap width is sequentially 11-12-12-12-12-11mm, 6 in total, and the size of the flat plate array is 300mm multiplied by 300 mm. In the simulation model, the heating plate is made of high-purity graphite, the room-temperature thermal conductivity of the heating plate is 108W/m.K, and a sample is made of a certain heat-insulating tile material.
The temperature distribution of the lower surface of the vapor chamber is shown in fig. 7. As can be seen from fig. 7, since the width of the middle strip of the graphite lath is the largest, the heat flow generated in the unit volume is the smallest, and the heat source intensity of the heating strips at the two sides is gradually increased, so that the temperature of the upper surface of the uniform temperature plate is obviously distributed in a strip shape, and gradually increases from the middle to the two sides. The temperature of the central region of the lower surface was counted, and the average value was 1214.2 ℃ with 5.6% of non-uniformity. The result shows that the heating plate of the embodiment can meet the test of high-temperature heat conductivity of more than 1000 ℃, and has better temperature uniformity.
The above description is only for the preferred embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present application should be covered within the scope of the present application.
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