Device and method for synchronously testing specific heat capacity and heat conductivity coefficient
The synchronous testing device and method using fine thermocouples and an adiabatic environment enable accurate and efficient simultaneous measurement of thermal conductivity and specific heat capacity, addressing inefficiencies in existing methods.
Patent Information
- Application Number
- JP2025087227
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-05-28
- Filing Date
- 2025-05-26
- Publication Date
- 2025-12-10
- Estimated Expiration
- 2045-05-26
AI Technical Summary
Current methods for testing thermal conductivity and specific heat capacity of materials are inefficient and inaccurate due to separate testing processes and the use of large-diameter thermocouples causing significant heat loss and contact thermal resistance.
A synchronous testing device and method using two parallel measurement assemblies with a central heating film and fine thermocouples to collect temperatures at the center and surface points, allowing simultaneous calculation of specific heat capacity and thermal conductivity, and placing the device in an adiabatic calorimeter for accurate results.
The method achieves accurate and efficient simultaneous measurement of specific heat capacity and thermal conductivity, reducing testing costs and improving safety by minimizing heat loss and ensuring a quasi-steady state, applicable to materials like lithium-ion batteries.
Smart Images
Figure 2025179827000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to the field of testing thermally conductive materials, and more particularly to a synchronous testing apparatus and method for specific heat capacity and thermal conductivity. [Background technology]
[0002] Thermal conductivity and specific heat capacity are two important parameters of thermal conductive materials, so accurate measurement of these parameters is crucial. Currently, thermal conductivity and specific heat capacity are tested separately, and there is no technical solution for simultaneously testing both parameters, resulting in low test efficiency. Furthermore, the traditional quasi-steady-state plate method for testing thermal parameters involves solving transient heat conduction problems for an infinitely large plate under constant heat flow boundary conditions, which falls into the second category of boundary conditions, namely, infinitely large plate heat conduction problems. Testing specific heat capacity using an ARC also falls into this category, but the difficulty lies in the inaccuracy of determining when the thermal conductive material enters the quasi-steady state and the inaccuracy of the temperature difference, further leading to inaccurate test results. Furthermore, in actual working conditions, typical thermocouples (K-type, T-type, or other types) are used to detect the temperature of the heating film. However, their large diameter creates a large gap between the materials, resulting in large contact thermal resistance and significant heat loss, which also leads to inaccurate test results.
[0003] In view of this, the present invention is proposed. Summary of the Invention [Problem to be solved by the invention]
[0004] SUMMARY OF THE INVENTION The object of the present invention is to provide a specific heat capacity and thermal conductivity synchronization testing device and testing method that can solve the problem of synchronization and accurate measurement of the specific heat capacity and thermal conductivity of a heat conducting material. [Means for solving the problem]
[0005] In order to achieve the above object, the present invention employs the following technical means: In a first aspect, the present invention provides a synchronous testing device for specific heat capacity and thermal conductivity, the synchronous testing device for specific heat capacity and thermal conductivity includes two measurement target assemblies arranged in parallel, a heating film disposed between the two measurement target assemblies, the area of the heating film being smaller than the contact area of the two measurement target assemblies, a first thermocouple disposed at a central position of the heating film, the first thermocouple being used to collect the temperature at the central position after current is applied to the heating film, a plurality of circumferences are defined with a plurality of preset radii, with a position on the surface of the measurement target assemblies corresponding to the central position as a center, one sampling point being provided at the center of the circle, a plurality of sampling points being provided on the circumference, and a second thermocouple being provided at the sampling point, the second thermocouple being used to collect the temperature at the sampling point after current is applied to the heating film.
[0006] In a second aspect, the present invention provides a synchronous testing method for specific heat capacity and thermal conductivity, which includes: performing a test using the above-mentioned synchronous testing apparatus for specific heat capacity and thermal conductivity, obtaining test temperatures collected by the assembly to be measured from a first thermocouple and a second thermocouple heated to a quasi-steady state stage; determining a variation relationship of the surface temperature of the assembly to be measured with distance based on the test temperatures of sampling points on the circumference collected by the second thermocouple; determining a calculated temperature of the center of the circle based on the variation relationship; and determining the specific heat capacity and thermal conductivity of the assembly to be measured based on the test temperatures collected by the first thermocouple, the temperatures of the sampling points at the center of the circle, and the calculated temperature of the center of the circle. [Effects of the Invention]
[0007] Compared with the prior art, the present invention has the following advantageous effects: the synchronous testing device for specific heat capacity and thermal conductivity of the present invention comprises two parallel-arranged test assemblies with a heating film between them, which is used to heat the test assemblies; during the heating process, the first and second thermocouples are used to collect temperatures at the center of the heating film and at specific positions on the surface of the test assemblies; the collected temperatures can be further used to calculate the specific heat capacity and thermal conductivity of the test assemblies; the device can synchronously test the specific heat capacity and thermal conductivity of thermal conductive materials, where the specific heat capacity includes the average specific heat capacity and the temperature change specific heat capacity; the testing cost is low; and the thermal conductive material can be a lithium-ion battery or other solid material, which has a wide range of applications.
[0008] Additionally, the present invention uses a specific algorithm to calculate the temperature at the center of the assembly being measured, which is more accurate than directly collected temperatures. Furthermore, during testing, the device is placed in an adiabatic calorimeter to create an adiabatic environment, resulting in more accurate test results, the assembly to be measured being more likely to enter a quasi-steady state, the required heating time being shorter, the efficiency being higher, thermal runaway being avoided, and the safety of the test being improved. [Brief explanation of the drawings]
[0009] [Figure 1] FIG. 2 is a schematic diagram illustrating the configuration of a synchronous test device for specific heat capacity and thermal conductivity according to Example 1. [Figure 2] FIG. 10 is a schematic diagram of a flow chart of a synchronous test method for specific heat capacity and thermal conductivity according to Example 2. DETAILED DESCRIPTION OF THE INVENTION
[0010] Hereinafter, exemplary embodiments of the present application will be described with reference to the drawings for ease of understanding. The following description includes various details of the embodiments of the present application, which should be considered as merely exemplary. Therefore, those skilled in the art should recognize that various changes and modifications can be made to the embodiments described below without departing from the scope and spirit of the present application. Similarly, in the following description, descriptions of known functions and structures will be omitted for clarity and conciseness.
[0011] In order to more clearly describe the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly describe the drawings that need to be used to describe the specific embodiments or the prior art. It is clear that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can further obtain other drawings based on these drawings without any creative efforts.
[0012] As mentioned in the background art, the prior art cannot test specific heat capacity and thermal conductivity simultaneously, resulting in inaccurate testing, low testing efficiency, and high costs. Therefore, the present invention uses a specific testing device and testing method to realize accurate and synchronous testing of the specific heat capacity and thermal conductivity of thermal conductive materials. For anisotropic thermal conductive materials, the thermal conductivity here refers to the thermal conductivity in the perpendicular direction, and the specific heat capacity here refers to the average specific heat capacity and the temperature change specific heat capacity. The present invention will be described in more detail below with reference to examples.
[0013] Example 1 As shown in FIG. 1 , this embodiment provides a synchronous testing device for specific heat capacity and thermal conductivity. The synchronous testing device for specific heat capacity and thermal conductivity includes two measurement target assemblies 1 arranged in parallel. A heating film 2 is provided between the two measurement target assemblies 1. The area of the heating film 2 is smaller than the contact area of the two measurement target assemblies 1. A first thermocouple is disposed at the center position 3 of the heating film. The first thermocouple is used to collect the temperature at the center position after current is applied to the heating film. A position corresponding to the center position of the surface of the measurement target assemblies is defined as the center of a circle, and multiple circumferences are defined with multiple preset radii. One sampling point is provided at the center of the circle, and multiple sampling points are provided on the circumference. A second thermocouple is provided at the sampling point. The second thermocouple is used to collect the temperature at the sampling point after current is applied to the heating film.
[0014] Optionally, the heating film is a polyimide heating film. Preferably, the heating film is rectangular, and the side length of the heating film is greater than six times the thickness of the assembly to be measured and less than the width of the assembly to be measured. As can be understood, a rectangular shape includes a rectangle and a square, and whatever the specific shape, it is preferable that the side length of the heating film is within the above range.
[0015] Optionally, the first thermocouple is an ultra-fine T-type thermocouple (class I accuracy, 0.08 mm wire diameter, i.e., the diameter of a single thermocouple wire in the thermocouple is 0.08 mm). The ultra-fine T-type thermocouple is used to minimize the gap between the batteries and to minimize the influence of contact thermal resistance on the temperature.
[0016] Optionally, the second thermocouple is a common T-type thermocouple (class I accuracy, 0.255 mm wire diameter, i.e., the diameter of a single thermocouple wire within the thermocouple is 0.255 mm), but it may also be an R-type, B-type, S-type, etc. thermocouple.
[0017] Generally, K-type thermocouples are commonly used to detect the temperature of new energy batteries, and as can be seen from the standard EN 60584-2, their Class I accuracy means that the measurement error at low temperatures (e.g., -40°C to 375°C) is ±1.5°C. In this embodiment, T-type thermocouples are used as the first and second thermocouples, and both have Class I accuracy. That is, the measurement error at low temperatures (e.g., -40°C to 375°C) is ±0.5°C, making the test results more accurate.
[0018] The "assembly to be measured" above may be a lithium ion battery or other thermally conductive solid material.
[0019] As can be understood, the "position corresponding to the center position of the surface of the assembly to be measured" refers to the position on the surface of the assembly to be measured that is the shortest distance from the center position (point 4 shown in Figure 1). Generally, this shortest distance is equal to the thickness of the assembly to be measured. The second thermocouples are respectively provided on the upper surface of the assembly to be measured (the upper surface) and the lower surface of the assembly to be measured (the lower surface). The second thermocouples on the upper surface and the lower surface are provided symmetrically with respect to the plane on which the heating film is located. That is, the circumference of the upper surface and its sampling points are provided symmetrically with the circumference of the lower surface and its sampling points. Note that for clarity, only the division of the circumference of the upper surface of the assembly to be measured (the upper surface) and its sampling points are shown in Figure 1, and the points marked on each circumference in the figure are sampling points. The case of the assembly to be measured (the lower surface) is completely the same as the case of the assembly to be measured (the upper surface). It should also be understood that the circumference of the surface of the assembly being measured does not need to be actually placed or displayed on the surface of the assembly being measured, as long as the second thermocouple is located at a corresponding circumferential sampling point, and is shown in the figures in this specification for ease of explanation.
[0020] 1, the plurality of circumferences include a first circumference C1, a second circumference C2, and a third circumference C3 from the inside to the outside, the radius of the first circumference is 10 to 30 mm, the second circumference is located 10 to 30 mm away from the first circumference, and the third circumference is located 10 to 30 mm away from the second circumference. Four second thermocouples are uniformly arranged on each of the first circumference, second circumference, and third circumference.
[0021] The radius and distance are independently 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, 22 mm, 24 mm, 26 mm, 28 mm, or 30 mm. The above spacings were obtained by screening based on the heating time and simulation contour plots. In this example, the above spacings are all 10 mm.
[0022] The synchronous testing device for specific heat capacity and thermal conductivity of this embodiment comprises two parallel test assemblies with a heating film between them, which is used to heat the test assemblies. During the heating process, the first and second thermocouples are used to collect temperatures at the center of the heating film and at specific locations on the surface of the test assemblies. The collected temperatures can then be used to calculate the specific heat capacity and thermal conductivity of the test assemblies. This device can synchronously test the specific heat capacity and thermal conductivity of thermal conductive materials, where the specific heat capacity includes the average specific heat capacity and the temperature change specific heat capacity. The testing cost is low, and the thermal conductive material can be a lithium-ion battery or other solid material, which has a wide range of applications.
[0023] Example 2 As shown in Fig. 2, this embodiment provides a synchronous test method for specific heat capacity and thermal conductivity. The synchronous test method for specific heat capacity and thermal conductivity is performed using the synchronous test device for specific heat capacity and thermal conductivity described in embodiment 1. The method includes the following steps: in S110, the synchronous test device for specific heat capacity and thermal conductivity is placed in an adiabatic calorimeter.
[0024] By placing the device in an adiabatic calorimeter (ARC), the device is in an adiabatic environment, making the test results more accurate. Conventional devices are generally placed in insulating materials, which cannot achieve complete insulation, resulting in too large deviations in the test results.
[0025] In S120, the test temperatures collected by the measurement target assembly from the first and second thermocouples heated in the quasi-steady state stage are obtained.
[0026] In an alternative embodiment, the quasi-steady state is determined as follows: after energizing the heating film, if the temperatures of the two circle centers (i.e., positions on the surfaces of the two assemblies to be measured corresponding to the central positions of the heating film) are both a first fixed value or within a set deviation of the first fixed value, or if the temperature difference between the two circle centers and the central position of the heating film is both a second fixed value and is maintained for a set time, or if the temperature difference is a second fixed value or within a set deviation of the second fixed value, then it is determined that the quasi-steady state has been entered.
[0027] After the heating film is energized, the temperature of the center gradually increases over time until it reaches a stable value (which may fluctuate around that value). At this point, the assembly under test has entered a quasi-steady state, and this stable value is the "first fixed value" mentioned above. As can be seen, this first fixed value is not a preset value. Naturally, this determination can also be made by comparing the temperature difference between the two centers and the center of the heating film. If both temperature differences are equal to a second fixed value and maintained for a set time, or if both temperature differences are equal to or within a set deviation of the second fixed value, then the quasi-steady state is determined to have been entered. This second fixed value is similar to the first fixed value and is not a preset value.
[0028] As can be appreciated, the test temperatures collected by the first and second thermocouples are related to the time of collection, and what is actually obtained is data corresponding to temperature and time.
[0029] During the entire test process, if the test temperature collected by the second thermocouple exceeds the safety temperature of the assembly being measured (which is provided by the manufacturer of the assembly being measured; for lithium-ion batteries, if not provided by the manufacturer, it may be set to 55°C), the test must be forcibly terminated to prevent any danger from occurring.
[0030] In S130, the relationship of change in the surface temperature of the assembly to be measured with respect to distance is determined based on the test temperatures of the sampling points on the circumference measured by the second thermocouple.
[0031] In an alternative embodiment, determining the relationship of change in the surface temperature of the assembly to be measured with respect to distance based on the test temperatures of the circumferential sampling points collected by the second thermocouple includes calculating an average temperature of all the circumferential sampling points corresponding to the two assemblies to be measured, and setting the average temperature as a characteristic temperature of the circumference, and determining the relationship of change in the surface temperature of the assembly to be measured with respect to distance based on the characteristic temperature and the circumferential radius.
[0032] In this embodiment, the average temperature of the sampling points on the circumference of the two assemblies to be measured at corresponding positions is used as the characteristic temperature of the circumference, and is combined with the circumference radius to determine the change relationship of the surface temperature of the assembly to be measured with distance. The change relationship can be a function obtained by fitting, and by using this function, the temperature when the distance is 0 (i.e., the center of the circle), i.e., the calculated temperature of the center of the circle, can be obtained.
[0033] In S140, the calculated temperature of the center of the circle is determined based on the above-mentioned change relationship.
[0034] As described in S130, by performing a back calculation based on the change relationship, the calculated temperature of the circle center can be obtained.
[0035] In S150, the specific heat capacity and thermal conductivity of the assembly to be measured are determined based on the test temperature collected by the first thermocouple, the temperature of the sampling point at the center of the circle, and the calculated temperature at the center of the circle.
[0036] In an alternative embodiment, determining the specific heat capacity and thermal conductivity of the assembly to be measured based on the test temperature collected by the first thermocouple, the temperature of the sampling point at the center of the circle, and the calculated temperature of the center of the circle includes determining an average specific heat capacity of the assembly to be measured based on the temperature of the sampling point at the center of the circle and the calculated temperature of the center of the circle; determining a temperature change specific heat capacity of the assembly to be measured based on the temperature of the sampling point at the center of the circle; and determining a thermal conductivity of the assembly to be measured based on the test temperature collected by the first thermocouple, the temperature of the sampling point at the center of the circle, and the calculated temperature of the center of the circle.
[0037] Specifically, the average specific heat capacity is calculated using the following formula (1): JPEG2025179827000002.jpg17135 where Cp1 is the average specific heat capacity, P is the heat generation power (i.e., the power used to heat the heating film), m is the weight of the assembly to be measured, ΔT is the temperature difference from heating to reaching a quasi-steady state, and Δt is the time difference from heating to reaching a quasi-steady state. Specifically, ΔT is the average value of the test temperature and calculated temperature at the center of the circle when the quasi-steady state is reached, minus the test temperature at the center of the circle at the initial heating time.
[0038] The temperature change specific heat capacity is calculated using the following formula (2): JPEG2025179827000003.jpg23159Cp2 is the temperature change specific heat capacity, P is the heating power (i.e., the power used to heat the heating film), m is the weight of the assembly being measured, and dT / dt is the rate of change of temperature at different times during the process from heating to reaching a quasi-steady state.
[0039] The thermal conductivity is calculated using the following formula (3): JPEG2025179827000004.jpg20145 where q0 = P / A, q0 is the constant heat flow density in the heating direction, P is the heat generation power (i.e., the power used to heat the heating film), A is the heating area of the assembly to be measured (i.e., the area of the heating film), h is the thickness of the assembly to be measured, and ΔT' is the temperature difference between two points. Specifically, ΔT' is the difference between the test temperature at the center of the heating film when a quasi-steady state is reached and the average value of the test temperature and calculated temperature at the center of the circle.
[0040] The test method of this embodiment uses a specific algorithm to calculate the temperature at the center of the assembly under test, which is more accurate than directly collected temperatures. Furthermore, during testing, the device is placed in an adiabatic calorimeter to create an adiabatic environment, which makes the test results more accurate and allows the assembly under test to enter a quasi-steady state more easily, shortens the required heating time, increases efficiency, and prevents thermal runaway, improving test safety.
[0041] It should be understood that steps can be rearranged, added, or deleted using various types of flows shown above. For example, the steps described in this application may be performed in parallel, sequentially, or in a different order, and are not limited herein as long as the desired results of the technical solutions disclosed in this application can be achieved.
[0042] The above specific embodiments do not limit the scope of protection of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present application should be included within the scope of protection of the present application.
Claims
1. A synchronous test method for specific heat capacity and thermal conductivity, comprising: The synchronous test method for specific heat capacity and thermal conductivity is performed using a synchronous test device for specific heat capacity and thermal conductivity, the testing device includes two measurement target assemblies arranged in parallel, a heating film is provided between the two measurement target assemblies, and the area of the heating film is smaller than the contact area of the two measurement target assemblies; A first thermocouple is disposed at a central position of the heating film, and the first thermocouple is used to collect the temperature at the central position after the heating film is energized; a position corresponding to the central position on the surface of the assembly to be measured is defined as a center of a circle, a plurality of circumferences are defined with a plurality of preset radii, one sampling point is provided at the center of the circle, a plurality of sampling points are provided on the circumference, and a second thermocouple is provided at the sampling point, and the second thermocouple is used to collect temperatures at the sampling point after current is passed through the heating film; The method comprises: obtaining test temperatures collected by the measurement target assembly from a first thermocouple and a second thermocouple heated to a quasi-steady state stage; determining a relationship of change in surface temperature of the assembly to be measured with distance based on test temperatures at circumferential sampling points collected by the second thermocouple; determining a calculated temperature of the center of the circle based on the change relationship; An average specific heat capacity of the assembly to be measured is determined based on the temperature of the sampling point at the center of the circle and the calculated temperature of the center of the circle, and the average specific heat capacity Cp1 is calculated using the following formula (1); A temperature change specific heat capacity of the assembly to be measured is determined based on the temperature of the sampling point at the center of the circle, and the temperature change specific heat capacity Cp2 is calculated using the following formula (2); determining a thermal conductivity of the assembly to be measured based on the test temperature collected by the first thermocouple, the temperature of the sampling point at the center of the circle, and the calculated temperature at the center of the circle, wherein the thermal conductivity λ is calculated using the following equation (3): where P is the heat generation power, m is the weight of the assembly to be measured, ΔT is the temperature difference from heating to reaching the quasi-steady state, Δt is the time difference from heating to reaching the quasi-steady state, dT / dt is the rate of change of temperature at different times in the process from heating to reaching the quasi-steady state, and q ０ = P / A, where A is the heating area of the assembly to be measured, h is the thickness of the assembly to be measured, and ΔT' is the difference between the test temperature at the center of the heating film and the average value of the test temperature and calculated temperature at the center of the circle when a quasi-steady state is reached.
2. and before acquiring the test temperatures collected by the measurement target assembly from the first and second thermocouples heated to the quasi-steady state stage, further 2. The method for synchronously testing specific heat capacity and thermal conductivity according to claim 1, wherein the device is placed in an adiabatic calorimeter.
3. 2. The synchronous test method for specific heat capacity and thermal conductivity according to claim 1, wherein after the current is applied to the heating film, if the temperatures of the two circle centers are both a first fixed value or are within a set deviation of the first fixed value, or the temperature difference between the two circle centers and the central position of the heating film is both a second fixed value and is maintained for a set time, or the temperature difference is both a second fixed value or is within a set deviation of the second fixed value, it is determined that the quasi-steady state has been entered.
4. determining a relationship of change in surface temperature of the assembly to be measured with respect to distance based on test temperatures at circumferential sampling points collected by the second thermocouple; Calculating an average temperature of all sampling points on the circumference corresponding to the two assemblies to be measured, and setting the average temperature as a characteristic temperature of the circumference; 2. The method for synchronously testing specific heat capacity and thermal conductivity according to claim 1, further comprising determining a relationship of change in the surface temperature of the assembly to be measured with respect to distance based on the characteristic temperature and the circumferential radius.
5. the plurality of circumferences includes, from inside to outside, a first circumference, a second circumference, and a third circumference; The radius of the first circumference is 10 to 30 mm, the second circumference is located at a distance of 10 to 30 mm outside the first circumference, and the third circumference is located at a distance of 10 to 30 mm outside the second circumference; 2. The synchronous testing method for specific heat capacity and thermal conductivity according to claim 1, wherein four second thermocouples are uniformly provided on each of the first circumference, the second circumference, and the third circumference.
6. 2. The method for synchronously testing specific heat capacity and thermal conductivity according to claim 1, wherein the heating film is rectangular, and the side length of the heating film is greater than six times the thickness of the assembly to be measured and less than the width of the assembly to be measured.