Device and method for testing heat-conducting property of material

Abstract

The invention relates to the field of material heat conductivity coefficient detection, in particular to a solid material heat-conducting property testing device and a method for testing the heat-conducting property of a solid material by using the solid material heat-conducting property testing device. The invention relates to a device for testing the heat-conducting property of a material. The device comprises a weighing device and a shell frame arranged above the weighing device, a heating element is arranged at the bottom in an accommodating cavity of the shell frame, a thermocouple temperature sensor is arranged above the heating element, and a glass container is arranged above the thermocouple sensor; and the thermocouple sensor and the weighing device are electrically connected with the power supply controller. The invention further provides a corresponding use method.

Description

Technical Field

[0001] The present application relates to the field of material thermal conductivity detection, and particularly designs a solid material thermal conductivity testing device. The present application also designs a method for testing the thermal conductivity of a solid material using the device. Background Art

[0002] Carbon fiber composite material is a high-performance composite material, widely used in aerospace, machinery, automobile, medical and other fields. Carbon fiber composite material has high specific strength and specific modulus. Compared with metals with the same mechanical strength, it is lighter and has advantages in weight reduction. As the application fields of carbon fiber composite materials expand from high-end aerospace to civilian use, carbon fiber has certain thermal conductivity and electrical conductivity. In addition to mechanical properties, it can be used as a functional material. The thermal conductivity of carbon fiber needs to be studied.

[0003] The thermal conductivity test of carbon fiber composite materials is mainly carried out on plate-like materials, which are composed of carbon fiber as reinforcement and resin as matrix. The resin is an isotropic material with the same heat transfer capacity in all directions. Carbon fiber is an anisotropic material. It is stretched during its preparation process to produce a high degree of molecular orientation. Its heat transfer direction is mainly along the fiber direction. It is reported in related reports that the thermal conductivity along the fiber direction is two orders of magnitude of that perpendicular to the fiber direction. Therefore, the fiber direction affects the heat transfer capacity of the material in a specific direction. The thicker the fiber, the higher the heat transfer capacity. The thermal conductivity is highest when the heat transfer direction is along the fiber direction and lowest when it is perpendicular to the fiber direction. In the process of measuring the thermal conductivity of carbon fiber composites, it is necessary to test according to certain requirements and standards to ensure consistency to measure the thermal conductivity of carbon fiber composites. Summary of the invention

[0004] In view of the above problems, the present application uses anisotropic composite materials such as carbon fiber composite materials as the target material for thermal conductivity testing, and designs a testing device and a testing method based on the concept of pursuing fast, efficient, low-cost and high accuracy. The testing device and the testing method are universal for thermal conductivity testing of solid materials. The device includes: a shell frame with an insulating function, a housing cavity is defined in the shell frame, and the solid test material is suitable for being removably placed in the housing cavity; a glass container for containing liquid, the glass container is suitable for contacting the upper surface of the solid test material; a thermocouple temperature sensor, the thermocouple temperature sensor is suitable for contacting the lower surface of the solid test material; a heating element, the heating element is located at the bottom of the shell frame; the bottom is a weighing device; and a device power controller with numerical statistics and analysis functions. The testing method is to assemble the materials according to the settings, add an appropriate amount of liquid to the glass container, turn on the power, record the numerical changes of the thermocouple temperature sensor and the numerical changes of the weighing device, and obtain the thermal conductivity of the material by calculation.

[0005] The present invention solves the above technical problems through the following technical solutions: A material thermal conductivity measuring device is special in that it comprises a weighing device, a shell frame placed above the weighing device, a heating element is installed at the bottom of the accommodating cavity of the shell frame, a thermocouple temperature sensor is installed above the heating element, and a glass container is placed above the thermocouple sensor; the thermocouple sensor and the weighing device are both electrically connected to a power controller.

[0006] On the basis of the above technical solution, this application makes the following improvements and perfections to the above technical solution: Furthermore, the shell frame is groove-shaped, and a heat insulation layer is arranged inside the side wall and the bottom plate of the shell frame.

[0007] Furthermore, a transverse annular groove is provided on the inner wall of the shell frame. The transverse annular groove plays the role of locally reducing heat conduction, so as to minimize the possibility of heat generated by the heating element being transferred outward from the shell frame. In order to better achieve this effect, a groove or a hemispherical protrusion is also provided at the bottom of the shell frame.

[0008] According to the above-mentioned material thermal conductivity measuring device, a corresponding material thermal conductivity measuring method is also provided, which is characterized by: Step 1: Place the solid test material on the upper layer of the thermocouple temperature sensor in the housing frame; Step 2: Place a glass container containing an appropriate amount of liquid on top of the solid test material; Step 3: Turn on the power controller and record the temperature change of the thermocouple temperature sensor and the value change of the weighing device; Step 4: Process the data through the power controller or calculate manually to obtain the thermal conductivity of the material, compare it with the thermal conductivity corresponding to the corresponding material table, and determine the thermal conductivity of the material.

[0009] Furthermore, in the step 1, the size of the solid test material is consistent with the temperature sensor; in the step 2, the size of the glass container is consistent with the solid test material.

[0010] Furthermore, in step three, the temperature change ΔT recorded by the thermocouple temperature sensor can be obtained, and the mass change Δm recorded by the weighing device can be obtained. Substituting the above data into the calculation formula, the thermal conductivity of the sample can be obtained.

[0011] Furthermore, it is necessary to use a standard sample with a known thermal conductivity to calibrate the instrument, and the calibration is performed based on the formula in the above steps.

[0012] Compared with the prior art, the beneficial effects of the present application are as follows: the experimental results obtained by the testing device of the present application can reflect the thermal conductivity of the material in actual use; compared with other thermal conductivity tests, the equipment construction cost is low, the test is convenient, and the results are accurate; the present testing device can perform repeated tests and is universal for solid-state material testing; and the present testing device and testing method also have solutions for thermal conductivity tests in different directions of anisotropic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a structural schematic diagram of a material thermal conductivity measuring device; Figure 2 The figure is a schematic diagram of the structure of a device for measuring the thermal conductivity of a material with a thermal insulation layer.

[0014] The reference numerals are recorded as follows: 1. housing frame, 2. glass container, 3. solid test material, 4. thermocouple temperature sensor, 5. heating element, 6. weighing device, 7. power controller. DETAILED DESCRIPTION

[0015] The following embodiments, in conjunction with the accompanying drawings, are only intended to illustrate the technical solutions described in the claims and are not intended to limit the protection scope of the claims.

[0016] Combination Figure 1 Figure 2 This test device has requirements for the use environment to ensure a constant temperature, constant pressure, and constant humidity environment. In order to evenly distribute the temperature, the material is required to be in a disc shape. According to the requirements for the thickness of different materials, this application gives reference suggestions for material selection: high thermal conductivity materials (such as metal elements, graphite, some high thermal conductivity ceramics, etc.), the recommended thickness is (2~5) mm; medium thermal conductivity materials (such as ceramics, alloys, etc.), the recommended thickness is 1~3mm; low thermal conductivity materials (such as plastics, rubber, glass, ceramics, etc.), the recommended thickness is 0.5~2mm.

[0017] First, place the weighing device 6 (which can be an electronic scale) on a flat experimental table, place a shell frame 1 with an insulating function on the upper surface of the weighing device 6, and the side walls and the bottom plate of the shell frame 1 are provided with a thermal insulation layer 11. Place the heating element 5 and the thermocouple temperature sensor 4 at the bottom of the accommodating cavity defined by the shell frame 1, and electrically connect the weighing device 6, the heating element 5, and the thermocouple temperature sensor 4 to the power controller 7.

[0018] Add two-thirds of water into the glass container 2, place it above the solid test material 3, turn on the power controller, control the temperature to a fixed value between room temperature and 40°C, put the glass container 2 together with the solid test material 3 into the accommodating cavity defined by the shell frame 1, so that the solid test material 3 is close to the glass container 2 above and the thermocouple temperature sensor 4 below.

[0019] After continuous heating for a period of time, the water level drops, the overall mass decreases, and the temperature measured by the thermocouple temperature sensor 4 rises, which is recorded as the temperature change ΔT and the mass change Δm. The following is the calculation process of the thermal conductivity formula: The heat absorption formula of liquid vaporization is: Q1=ΔHvap·Δm (1), Where Q represents the heat absorbed by water evaporation, ΔHvap is the heat of vaporization of water, and Δm is the test data of the weighing device. The heat passing through the solid test material is Q2. There is a loss in heat transfer between the heating element and the water, which needs to be corrected, so the formula is created: Q2=R·Q1 (2), Where R is the influence coefficient, and its specific value needs to be calibrated using a standard sample with a known thermal conductivity to define the R value. The heat Q2 of the solid test sample can be calculated by the formula: Q 2 = λ·A· (3) Where λ is the thermal conductivity of the material, A is the surface area of ​​the solid test material, and the material radius is defined as r. T is the thermocouple temperature heat transfer test data, and L is the thickness of the solid test material.

[0020] Combining formulas (1), (2) and (3), we can obtain the thermal conductivity calculation formula (4): λ = R (4) Except for R which needs to be calibrated, all other values ​​are known or obtained by the test device. The thermal conductivity is calculated manually or by using a program written in the power controller.

[0021] It should be noted that the examples described above are for the purpose of explanation only and should not be considered to limit the present application. Although the present application has been described according to exemplary embodiments, it should be understood that descriptive and illustrative language, rather than restrictive language, is used herein. Within the scope of the present description, the present application may be changed without departing from the scope and spirit of the present application.

Claims

1. A material thermal conductivity measuring device, characterized in that: The invention comprises a weighing device (6), a housing frame (1) placed above the weighing device (6), a heating element (5) installed at the bottom of the accommodating cavity of the housing frame (1), a thermocouple temperature sensor (4) installed above the heating element (5), and a glass container (2) placed above the thermocouple sensor (4); the thermocouple sensor (4) and the weighing device (6) are both electrically connected to a power controller (7).

2. The material thermal conductivity measuring device according to claim 1, characterized in that: The shell frame (1) is groove-shaped, and a heat insulation layer is provided inside the side wall and the bottom plate of the shell frame (1).

3. The material thermal conductivity measuring device according to claim 1, characterized in that: A transverse annular groove is provided on the inner wall of the housing frame (1).

4. A method for testing the material thermal conductivity testing device according to any one of claims 1 to 3, characterized in that: Step 1: placing a solid test material (3) on an upper layer of a thermocouple temperature sensor (4) in a housing frame (1); Step 2: Place a glass container (2) containing an appropriate amount of liquid on top of the solid test material (3); Step 3: Turn on the power controller (7) and record the temperature change of the thermocouple temperature sensor (4) and the value change of the weighing device (6); Step 4: Process the data through the power controller (7) or calculate manually to obtain the thermal conductivity of the material, compare it with the thermal conductivity corresponding to the corresponding material table, and determine the thermal conductivity of the material.

5. The testing method according to claim 4, characterized in that: In the step 1, the size of the solid test material (3) is consistent with the temperature sensor (4); in the step 2, the size of the glass container is consistent with the solid test material.

6. The testing method according to claim 4, characterized in that: In step three, the temperature change ΔT recorded by the thermocouple temperature sensor (4) can be obtained, and the mass change Δm recorded by the weighing device (6) can be obtained. Substituting the above data into the formula for calculation, the thermal conductivity of the sample can be obtained.

7. The testing method according to any one of claims 5 to 6, characterized in that: It is necessary to use a standard sample with a known thermal conductivity to calibrate the instrument, and the calibration is performed based on the formula in claim 6.

Images