Contact thermal resistance and thermal rectification coefficient testing method

Abstract

The invention discloses a contact thermal resistance and thermal rectification coefficient testing method, and belongs to the technical field of testing, and the testing method comprises the steps: testing the forward heat transfer contact thermal resistance and the forward heat transfer average heat flow of a first test sample and a second test sample which are stacked under the working conditions of set pressure and temperature; exchanging the positions of the first test sample and the second test sample, and testing the reverse heat transfer contact thermal resistance and the reverse heat transfer average heat flow under the set pressure and temperature working conditions; and calculating a thermal rectification coefficient according to the forward heat transfer average heat flow and the reverse heat transfer average heat flow. According to the invention, high-precision direct testing of contact thermal resistance and thermal rectification coefficient in different pressure and temperature ranges can be realized, and the device has the advantages of no need of installing a temperature sensor on a sample, simple and rapid operation and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of contact thermal resistance testing, and in particular relates to a contact thermal resistance and thermal rectification coefficient testing method. Background Art

[0002] Thermal contact resistance is a physical quantity that measures the heat transfer resistance between two contact interfaces. It plays a key role in various engineering applications with high requirements for efficient heat transfer. Thermal contact resistance is particularly important in the thermal management systems of electronic equipment, engine cooling systems and other heat-sensitive devices, and its impact extends to the heat dissipation performance, overall efficiency, life and reliability of the equipment. The thermal rectification effect is a phenomenon caused by the asymmetric transmission of positive and negative heat flows in a non-uniform temperature field due to the nonlinear characteristics of materials, structures or interfaces. The thermal rectification effect is of great significance to the development of thermal rectification devices such as thermal diodes, triodes and other thermal elements, as well as the directional and quantitative management of heat flow in micro-nanoscale heat dissipation, the improvement of thermoelectric performance, and the design of thermal switches and transistors. The existing contact thermal resistance test methods include steady-state method and transient method. Although the transient test method is easy to test, its test stability is poor and the calculation process is complicated. The steady-state method is widely used in various tests due to its high efficiency and high precision. However, most of the existing steady-state contact thermal resistance test methods require drilling holes on the sample to install thermocouple sensors, which has certain requirements on the material and shape of the sample during the actual processing, and will cause problems such as cumbersome actual testing process and large workload. There is no method to obtain contact thermal resistance directly through an equivalent method without processing the sample. Summary of the invention

[0003] The present invention aims to provide a contact thermal resistance and thermal rectification coefficient testing method in view of the shortcomings of the existing contact thermal resistance and thermal rectification coefficient testing methods, which have complicated procedures and large workloads. The present invention eliminates the existence of other thermal resistances irrelevant to the contact thermal resistance, eliminates the need to use contact and non-contact methods to test the contact interface temperature, uses an indirect equivalent method to test the contact thermal resistance, and based on high-precision results of heat flow in forward and reverse heat transfer processes, realizes efficient and quick testing of the thermal rectification coefficient.

[0004] To achieve the purpose of the present invention, the technical solution adopted is:

[0005] A method for testing contact thermal resistance and thermal rectification coefficient comprises the following steps:

[0006] Testing the forward heat transfer contact thermal resistance and the forward heat transfer average heat flux of the first test sample and the second test sample stacked under set pressure and temperature conditions;

[0007] Swap the positions of the first test sample and the second test sample to test the reverse heat transfer contact thermal resistance and the reverse heat transfer average heat flux under set pressure and temperature conditions;

[0008] The thermal rectification coefficient is calculated based on the average heat flux of forward heat transfer and the average heat flux of reverse heat transfer.

[0009] Further, testing the forward heat transfer contact thermal resistance and the forward heat transfer average heat flux of the first test sample and the second test sample under set pressure and temperature conditions includes the following steps:

[0010] The first test sample is arranged on the second test sample, a first heat flow meter is arranged on the top surface of the first test sample, a second heat flow meter is arranged on the ground surface of the second test sample, and a plurality of temperature sensors are arranged on the first heat flow meter and the second heat flow meter respectively;

[0011] Applying a load to a set pressure to the first test sample, and heating the first test sample to a set temperature;

[0012] The temperature of the temperature sensor and the position coordinates of the temperature sensor are collected, and the heat flow through the first test sample, the heat flow through the second test sample, and the average heat flow of the forward heat transfer process are calculated.

[0013] Furthermore, thermal conductive silicone grease is evenly applied on the contact surfaces of the first heat flow meter and the second heat flow meter with the first test sample and the second test sample.

[0014] Furthermore, the average heat flow in the forward heat transfer direction is Q f The calculation formula is:

[0015]

[0016] Among them, T 1 —The first temperature sensor measures the temperature, T 3 —The third temperature sensor measures the temperature, T 4 —The fourth temperature sensor measures the temperature, T 6 —The sixth temperature sensor measures the temperature, Z 1 —First sensor position coordinate, Z 3 —Third sensor position coordinate, Z 4 —Fourth sensor position coordinate, Z 6 —The sixth sensor position coordinate, A—The contact surface area of ​​the test sample, k 1 —Thermal conductivity of the first heat flow meter, k 4 —Thermal conductivity of the second heat flow meter, Q 1 —Heat flow of the first test sample, Q 2 - Heat flow through the second test sample.

[0017] Further, testing the forward heat transfer contact thermal resistance and the forward heat transfer average heat flux of the first test sample and the second test sample under set pressure and temperature conditions includes the following steps:

[0018] The first test sample is arranged on the second test sample, a first heat flow meter is arranged on the top surface of the first test sample, a second heat flow meter is arranged on the ground surface of the second test sample, and a plurality of temperature sensors are arranged on the first heat flow meter and the second heat flow meter respectively;

[0019] Collect the test results of the temperature sensor and the position of the temperature sensor, and calculate the upper surface temperature and the lower surface temperature of the sample combination contacted by the heat flow meter;

[0020] Applying a load to a set pressure to the first test sample, and heating the first test sample to a set temperature;

[0021] The forward heat transfer contact thermal resistance is calculated according to the total thermal resistance of the first test sample and the second test sample, the twice thermal resistance of the first test sample, and the twice thermal resistance of the second test sample.

[0022] Furthermore, the forward heat transfer contact thermal resistance TCR f Calculated by the following formula:

[0023] TCR f =TCR 0 =TTR 0 -BTR 1 -BTR 2 ≈TTR 0 -TTR 1 -TTR 2 (2)

[0024] Among them, TTR 0 is the total thermal resistance of the forward heat transfer process, TTR 0 is the overall thermal resistance of the first test sample and the second test sample, BTR 1 is the body thermal resistance of the first test sample, BTR 2 is the thermal resistance of the second test sample, TTR 1 is the total thermal resistance of the first test sample, TTR 2 is the total thermal resistance of the second test sample 4.

[0025] Furthermore, the total thermal resistance TTR of the first test sample 1 and the total thermal resistance TTR of the second test sample 2 Calculated by the following formula:

[0026] TTR 1 =TCR u1 +TCR d1 +BTR 1 ≈BTR 1 (3)

[0027] TTR 2 =TCR u2 +TCR d2+BTR 2 ≈BTR 2 (4)

[0028] Among them, TCR u1 、TCR d1 are the contact thermal resistance between the first heat flow meter and the second heat flow meter and the first test sample when the first test sample is tested alone, TCR u2 、TCR d2 are the contact thermal resistances between the first heat flow meter and the second heat flow meter and the second test sample when the second test sample is tested alone.

[0029] Furthermore, the total thermal resistance TTR of the forward heat transfer process 0 Calculated by the following formula:

[0030]

[0031] TTR 0 =TCR u +TCR 0 +TCR d +BTR 1 +BTR 2 ≈TCR 0 +BTR 1 +BTR 2

[0032] Among them, T H —Surface temperature of the sample assembly in contact with the heat flow meter, T C —The temperature of the lower surface of the sample assembly in contact with the heat flow meter, A—the surface area of ​​the test sample contact surface.

[0033] Furthermore, the surface temperature T of the sample assembly contacted by the heat flow meter is H The temperature of the lower surface T C Calculated by the following formula:

[0034]

[0035] Among them, T 1 —The first temperature sensor measures the temperature, T 2 —The second temperature sensor measures the temperature, T 3 —The third temperature sensor measures the temperature, T 4 —The fourth temperature sensor measures the temperature, T 5 —The fifth temperature sensor measures the temperature, T 6 —The sixth temperature sensor measures the temperature, Z 1 —First sensor position coordinate, Z 3 —Third sensor position coordinate, Z 4 —Fourth sensor position coordinate, Z6 —The sixth sensor position coordinate, Z H —Surface coordinates of the sample assembly, Z C —Lower surface coordinates.

[0036] Further, according to the average heat flow of the forward heat transfer and the average heat flow of the reverse heat transfer, the thermal rectification coefficient TRC is calculated, including the following steps:

[0037]

[0038] Among them, q f ,q r are the heat flux in forward heat transfer and the heat flux in reverse heat transfer, Q f is the average heat flow in the forward direction, Q r is the average heat flux in reverse heat transfer.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The test method described in the present invention starts from the drawbacks of the existing contact thermal resistance test method. It is not necessary to test the contact interface temperature by contact and non-contact methods, and it is not necessary to process the test sample surface before the temperature test. Based on the steady-state heat flow method, the thermal resistance composition is analyzed during the sample test process, and the existence of other contact thermal resistances that affect the contact thermal resistance test results between the test samples is eliminated. The contact thermal resistance between the test samples can be directly obtained in an indirect equivalent manner, which further reduces the complexity of the contact thermal resistance test and effectively improves the test efficiency. The existing contact thermal resistance test device has not yet considered directly testing the thermal rectification coefficient caused by asymmetry such as material properties. However, the calculation method of the contact thermal resistance and the thermal rectification coefficient is in the same vein. Therefore, the forward and reverse asymmetric heat flow can be tested by testing the contact thermal resistance, and then the thermal rectification coefficient caused by the asymmetric contact thermal resistance can be calculated. The present invention can efficiently and accurately test the contact thermal resistance and the thermal rectification coefficient, especially can realize the contact thermal resistance test of samples that cannot be tested by contact temperature test, and can lay a test technology foundation for the study of the thermal rectification effect caused by the asymmetric contact thermal resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is the test principle diagram based on the steady-state heat flow method;

[0042] Figure 2 This is a schematic diagram of the indirect equivalent test of contact thermal resistance;

[0043] Figure 3 This is a schematic diagram of thermal rectification coefficient testing;

[0044] In the figure, 1 is a first heat flow meter, 2 is a second heat flow meter, 3 is a first test sample, 4 is a second test sample, 5 is a heating unit, 6 is a loading unit, and 7 is a cooling unit. DETAILED DESCRIPTION

[0045] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly and comprehensively understood.

[0046] In addition, when an element in the present invention is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only embodiment.

[0047] The existing thermal rectification coefficient test has not yet considered the direct use of a quick and efficient test method that coexists with the contact thermal resistance test system. Starting from the drawbacks of the existing contact thermal resistance test method, it is only necessary to eliminate the existence of the remaining thermal resistances that are irrelevant to the contact thermal resistance, and the contact thermal resistance can be calculated in an indirect equivalent manner, without the need to use contact and non-contact methods to test the contact interface temperature. In addition, the contact thermal resistance and thermal rectification coefficient calculation methods are of the same origin, so the present invention can test the forward and reverse asymmetric heat flow by testing the contact thermal resistance while testing the asymmetric contact thermal resistance, and then calculate the thermal rectification coefficient caused by the asymmetric contact thermal resistance.

[0048] The present invention is based on the steady-state heat flow method. By testing the thermal resistance of the sample combination and the individual samples, the contact thermal resistance is indirectly tested. By testing the forward and reverse heat flow values, the thermal rectification coefficient is tested. It can achieve efficient and accurate testing of the contact thermal resistance and the thermal rectification coefficient under different pressure and temperature conditions.

[0049] A method for testing contact thermal resistance and thermal rectification coefficient of the present invention comprises the following specific steps:

[0050] 1) First, a forward heat transfer test is conducted: two first test samples 3 and second test samples 4 of the same size are stacked vertically and concentrically on a cooling unit 7, with the first test sample 3 on top and the second test sample 4 on the bottom. The first test sample 3 and the second test sample 4 are components in the thermal management system of electronic equipment, engine cooling systems, and other heat-sensitive devices.

[0051] The entire test system comprises, from top to bottom, a loading unit 6, a heating unit 5, a first heat flow meter 1, a second heat flow meter 2, a cooling unit 7, and a data acquisition and processing unit. The first test sample 3 and the second test sample 4 are stacked and placed between the first heat flow meter 1 and the second heat flow meter 2 (such as Figure 1 As shown). The first heat flux meter 1 and the second heat flux meter 2 are made of copper material with strong thermal conductivity. Three temperature sensors are installed vertically and equidistantly on the two heat flux meters to calculate the transferred heat flux based on the one-dimensional steady-state Fourier conduction law. At the same time, in order to eliminate the influence of the contact thermal resistance between the first heat flux meter 1 and the second heat flux meter 2 and the first test sample 3 and the second test sample 4 on the test results during the test, a sufficient amount of thermal conductive silicone grease is evenly applied on the contact surface between the first heat flux meter 1 and the second heat flux meter 2 and the first test sample 3 and the second test sample 4.

[0052] 2) Setting the test pressure load size. According to the set pressure size and the surface-mounted pressure sensor, the mobile loading unit 6 drives the heating unit 5 to rotate and move downward, and contacts the upper surface of the first test sample 3 until the test pressure load is reached and the pressure sensor test result displayed in the data acquisition and processing unit remains stable.

[0053] 3) Set the temperature values ​​of the high temperature end of the heating unit 5 in contact with the upper surface of the first test sample 3 and the low temperature end of the cooling unit 7 in contact with the lower surface of the second test sample 4, and wait for a period of time until the temperatures of the high and low temperature ends of the test sample combination reach the set temperature values ​​and remain stable.

[0054] 4) After the above pressure and temperature conditions are stable, the formal test phase begins. First, the temperature results of the thermocouple sensors on the first heat flow meter 1 and the second heat flow meter 2 during the forward temperature transfer process are tested, that is, the temperature measured by the first temperature sensor T 1 , the third temperature sensor measures the temperature T 3 , the fourth temperature sensor measures the temperature T 4 , the sixth temperature sensor measures the temperature T 6 After the above temperature sensor test results are stable, the final results are extracted. Based on the one-dimensional steady-state Fourier transfer law, combined with the vertical position coordinates of the thermocouple sensor, that is, the first sensor position coordinates Z 1 , the third sensor position coordinate Z 3 , the fourth sensor position coordinate Z 4 , the sixth sensor position coordinate Z 6 and the thermal conductivity of the first heat flow meter 1 and the second heat flow meter 2, that is, the first thermal conductivity k 1 , the fourth thermal conductivity k 4 , calculate the heat flow Q through the first test sample 3 in the forward heat transfer process 1 and the heat flow Q through the second test sample 42 , and their average value, namely the average heat flow Q f (like Figure 1 ). Forward heat transfer average heat flow Q f The mathematical formula for calculation is:

[0055]

[0056] Among them, T 1 —The first temperature sensor measures the temperature, T 3 —The third temperature sensor measures the temperature, T 4 —The fourth temperature sensor measures the temperature, T 6 —The sixth temperature sensor measures the temperature, Z 1 —First sensor position coordinate, Z 2 —Second sensor position coordinate, Z 3 —Third sensor position coordinate, Z 4 —Fourth sensor position coordinate, Z 5 —Fifth sensor position coordinate, Z 6 —The sixth sensor position coordinate, A—the surface area of ​​the test sample contact surface.

[0057] 5) Based on the temperature test results of the thermocouple sensors on the first heat flow meter 1 and the second heat flow meter 2 collected by the data acquisition and processing unit, that is, the temperature T measured by the first temperature sensor 1 , the second temperature sensor measures the temperature T 2 , the third temperature sensor measures the temperature T 3 , the fourth temperature sensor measures the temperature T 4 , the fifth temperature sensor measures the temperature T 5 , the sixth temperature sensor measures the temperature T 6 , combined with the thermocouple sensor position, i.e. the first sensor position coordinate Z 1 , the third sensor position coordinate Z 3 , the fourth sensor position coordinate Z 4 , the sixth sensor position coordinate Z 6 , and the Z coordinate Z of the surface of the sample assembly H and the Z coordinate of the lower surface C , based on the one-dimensional steady-state Fourier conduction law, calculate the surface temperature T of the sample assembly in contact with the heat flow meter H The temperature of the lower surface T C (like Figure 1 The surface temperature T of the sample assembly in contact with the heat flow meter is H The temperature of the lower surface T C The mathematical formula for calculation is:

[0058]

[0059] 6) According to the heat flow Q through the first test sample 3 1 and the heat flow Q through the second test sample 4 2 The surface temperature T of the sample combined with the heat flow meter H The temperature of the lower surface T C , calculate the total thermal resistance TTR of the forward heat transfer process 0 . And the total thermal resistance TTR 0 It is composed of the body thermal resistance of the first test sample 3 and the second test sample 4, the contact thermal resistance between the heat flow meter and the test sample, and the contact thermal resistance between the test samples (such as Figure 2 ), the mathematical formula for calculation is:

[0060]

[0061] TTR 0 =TCR u +TCR 0 +TCR d +BTR 1 +BTR 2 ≈TCR 0 +BTR 1 +BTR 2

[0062] Among them, TCR u 、TCR d 、TCR 0 , BTR 1 , BTR 2 They are the contact thermal resistance between the first heat flow meter 1 and the first test sample 3, the contact thermal resistance between the second heat flow meter 2 and the second test sample 4, the contact thermal resistance between the first test sample 3 and the second test sample 4, the body thermal resistance of the first test sample 3, and the body thermal resistance of the second test sample 4 during the sample combination test. It should be noted that the contact thermal resistance TCR between the first heat flow meter 1 and the first test sample 3 has been basically eliminated due to the application of the thermal conductive silicone grease. u , the contact thermal resistance TCR between the second heat flow meter 2 and the second test sample 4 d , so the influence of this contact thermal resistance on the contact thermal resistance value of the test sample can be ignored.

[0063] 7) The above is the process of testing the combined heat flow and total thermal resistance of the samples during the forward heat transfer process. The testing method proposed in the present invention is to first test the overall thermal resistance TTR of the first test sample 3 and the second test sample 4. 0 Then the thermal resistance TTR of the first test sample 3 and the second test sample 4 is 1 、TTR 2Finally, the overall thermal resistance of the test sample combination minus the thermal resistance of the individual test sample is the contact thermal resistance value to be tested (such as Figure 2 shown).

[0064] Therefore, the same test process as the above steps 1) to 6) is adopted. The steps of the first test sample 3 and the second test sample 4 as well as the pressure and temperature setting conditions are completely consistent with the sample combination test process. Then, only the total thermal resistance TTR of the first test sample 3 and the second test sample 4 is measured separately. 1 、TTR 2 , and then calculate the forward heat transfer contact thermal resistance TCR based on the above calculation principle f Among them, the total thermal resistance TTR of the first test sample 3 and the second test sample 4 is 1 、TTR 2 The mathematical formula for calculation is:

[0065] TTR 1 =TCR u1 +TCR d1 +BTR 1 ≈BTR 1 (4)

[0066] TTR 2 =TCR u2 +TCR d2 +BTR 2 ≈BTR 2 (5)

[0067] Among them, TCR u1 、TCR d1 are the contact thermal resistance between the first heat flow meter 1 and the second heat flow meter 2 and the first test sample 3 when the first test sample 3 is tested alone, TCR u2 、TCR d2 They are the contact thermal resistances between the first heat flow meter 1 and the second heat flow meter 2 and the second test sample 4 when the second test sample 4 is tested alone. Since the thermal conductive silicone grease has been applied, the TCR has been eliminated. u1 、TCR d1 、TCR u2 、TCR d2 , the mathematical formula holds true.

[0068] In order to ensure that the influence of other thermal resistances that affect the contact thermal resistance of the test target has been basically completely eliminated during each test, the thermal impedance of individual samples of different thicknesses is first tested to determine that when thermal grease is applied to the surface of the test sample, the useless contact thermal resistance of the surface can be effectively eliminated, thereby ensuring the effectiveness of the indirect equivalent method.

[0069] Therefore, based on the above test principles, the forward heat transfer contact thermal resistance TCR can be solved directly based on the combined test and the individual test thermal resistance results using an indirect equivalent method. f , and its mathematical formula is:

[0070] TCR f =TCR 0 =TTR 0 -BTR 1 -BTR 2 ≈TTR 0 -TTR 1 -TTR 2 (6)

[0071] 8) The thermal rectification test principle proposed in the present invention is to first test the heat flow value of the forward heat transfer process under a certain pressure and temperature condition, then swap the positions of the first test sample 3 and the second test sample 4, test the heat flow value of the reverse heat transfer process, and finally calculate the thermal rectification coefficient. Since the heat flow value has been tested synchronously when testing the forward and reverse heat transfer contact thermal resistance, the thermal rectification coefficient test can be completed based on the above-mentioned test unit. The forward and reverse heat transfer process is achieved by directly replacing the positions of the upper and lower first test samples 3 and the second test sample 4. Considering the equivalence of the actual applied pressure transfer, the forward and reverse heat transfer process can be achieved without changing the relative positions of the high temperature and low temperature ends.

[0072] In order to test the reverse heat transfer heat flow value required for calculating the thermal rectification coefficient, adjust the upper and lower positions of the second test sample 3 and the second test sample 4, set the same pressure, high temperature end and low temperature end temperature as the above forward heat transfer process, and follow the same test process as steps 2) to 7) above. Reverse heat transfer contact thermal resistance TTR r and the average heat flow Q of reverse heat transfer r The calculation formula and process are the same as those of the forward heat transfer process. The test results are different only due to the asymmetric distribution of temperature and heat flux in the forward and reverse heat transfer processes. The reverse heat transfer contact thermal resistance TTR is calculated. r and the average heat flow Q of reverse heat transfer r .

[0073] 9) According to the average heat flow of forward heat transfer and the average heat flow of reverse heat transfer, calculate the thermal rectification coefficient TRC, and the mathematical formula is:

[0074]

[0075] Among them, q f ,q r Q is the heat flux in forward and reverse heat transfer. f is the average heat flow in the forward direction, Q r is the average heat flux in reverse heat transfer.

[0076] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0077] Example 1

[0078] The present invention takes 718 nickel alloy and silicon carbide material as an example to test the contact thermal resistance and thermal rectification coefficient between samples. The specific steps are as follows:

[0079] 1) First, a forward heat transfer test is carried out, and the 718 nickel alloy and silicon carbide that have been processed with completely identical shapes and sizes are defined as the first test sample 3 and the second test sample 4. Two first test samples 3 and 2 of the same size are concentrically stacked and placed on the cooling unit 7, with the first test sample 3 on the top and the second test sample 4 on the bottom. At the same time, in order to eliminate the influence of the contact thermal resistance between the first heat flux meter 1 and the second heat flux meter 2 and the first test sample 3 and the second test sample 4 on the test results during the test, a sufficient amount of thermal conductive silicone grease is evenly applied on the contact surface between the first heat flux meter 1 and the second heat flux meter 2 and the first test sample 3 and the second test sample 4.

[0080] 2) The test pressure load is set to 1.0 MPa. According to the set pressure and the surface-mounted pressure sensor, the loading unit 6 drives the heating unit 5 to rotate and move downward to contact the upper surface of the first test sample 3 until the test pressure load is reached, and the pressure sensor test result displayed in the data acquisition and processing unit remains stable.

[0081] 3) Set the high temperature end temperature of the heating unit 5 in contact with the upper surface of the sample 1 to 100°C, and the low temperature end temperature of the cooling unit 7 in contact with the lower surface of the second test sample 4 to 20°C. Wait for a while until the high and low temperature end temperatures of the test sample combination reach the set temperature values ​​and remain stable.

[0082] 4) After the above pressure and temperature conditions are stable, the formal test phase begins. First, the temperature results T of the thermocouple sensors on the first heat flow meter 1 and the second heat flow meter 2 during the forward temperature transfer process are tested. 1 , T 3 , T 4 , T 6 After the above temperature sensor test results are stable, the final results are extracted. Based on the one-dimensional steady-state Fourier transfer law, combined with the vertical position coordinate Z of the thermocouple sensor 1 , Z 3 , Z 4 , Z 6 and the thermal conductivity k of the first heat flow meter 1 and the second heat flow meter 2 1 , k 4 , calculate the heat flow Q of the forward heat transfer process through the first test sample 3 and the second test sample 41 , Q 2 , and their average value, namely the average heat flow Q f (like Figure 1 Forward heat transfer average heat flow Q f The result is calculated as:

[0083]

[0084] Among them, T 1 , T 2 , T 3 , T 4 , T 5 , T 6 —Temperature test results of the thermocouple sensors on the first heat flow meter 1 and the second heat flow meter 2, Z 1 , Z 2 , Z 3 , Z 4 , Z 5 , Z 6 —Z coordinates of the thermocouple sensors on the first heat flow meter 1 and the second heat flow meter 2, A—surface area of ​​the contact surface of the test sample.

[0085] 5) Based on the temperature test results T of the thermocouple sensors on the first heat flow meter 1 and the second heat flow meter 2 collected by the data acquisition and processing unit 1 , T 2 , T 3 , T 4 , T 5 , T 6 , combined with the thermocouple sensor position Z 1 , Z 2 , Z 3 , Z 4 , Z 5 , Z 6 , and the Z coordinates Z of the upper and lower surfaces of the sample combination H , Z C Based on the one-dimensional steady-state Fourier conduction law, the temperature T of the upper and lower surfaces of the sample combination in contact with the heat flow meter is calculated. H , T C (like Figure 1 ). The temperature of the upper and lower surfaces is T H , T C The mathematical formula for calculation is:

[0086]

[0087] 6) According to the heat flow Q 1 , Q 2 and temperature T H , T CCalculate the total thermal resistance TTR of the forward heat transfer process 0 . And the total thermal resistance TTR 0 It is composed of the body thermal resistance of the first test sample 3 and the second test sample 4, the contact thermal resistance between the heat flow meter and the test sample, and the contact thermal resistance between the test samples (such as Figure 2 The mathematical formula for calculation is:

[0088]

[0089] TTR 0 =TCR u +TCR 0 +TCR d +BTR 1 +BTR 2 ≈TCR 0 +BTR 1 +BTR 2

[0090] Among them, TCR u 、TCR d 、TCR 0 , BTR 1 , BTR 2 They are the contact thermal resistance between the first heat flow meter 1 and the first test sample 3, the contact thermal resistance between the second heat flow meter 2 and the second test sample 4, the contact thermal resistance between the first test sample 3 and the second test sample 4, the body thermal resistance of the first test sample 3, and the body thermal resistance of the second test sample 4. It should be noted that the above-mentioned application of thermal conductive silicone grease has basically eliminated TCR u 、TCR d , so the influence of this contact thermal resistance on the contact thermal resistance value of the test sample can be ignored.

[0091] 7) The above is the process of testing the heat flow and total thermal resistance of the sample combination during the forward heat transfer process. The testing method proposed in the present invention is to first test the overall thermal resistance TTR of sample combination 1 and 2. 0 Then the thermal resistance TTR of the first test sample 3 and the second test sample 4 is 1 、TTR 2 Finally, the overall thermal resistance of the test sample combination minus the thermal resistance of the individual test sample is the contact thermal resistance value to be tested (such as Figure 2 shown).

[0092] Therefore, the same test process as the above steps 1) to 6) is adopted, and then only the total thermal resistance TTR of the first test sample 3 and the second test sample 4 is measured separately. 1 、TTR 2 , and then calculate the forward heat transfer contact thermal resistance TCR based on the above calculation principle fAmong them, the total thermal resistance TTR of the first test sample 3 and the second test sample 4 is 1 、TTR 2 The mathematical formula for calculation is:

[0093] TTR 1 =TCR u1 +TCR d1 +BTR 1 ≈BTR 1 (4)

[0094] TTR 2 =TCR u2 +TCR d2 +BTR 2 ≈BTR 2 (5)

[0095] Among them, TCR u1 、TCR d1 are the contact thermal resistance between the first heat flow meter 1 and the second heat flow meter 2 and the first test sample 3 when the first test sample 3 is tested alone, TCR u2 、TCR d2 They are the contact thermal resistances between the first heat flow meter 1 and the second heat flow meter 2 and the second test sample 4 when the second test sample 4 is tested alone. Since the thermal conductive silicone grease has been applied, the TCR has been eliminated. u1 、TCR d1 、TCR u2 、TCR d2 , the mathematical formula holds true.

[0096] Therefore, based on the above test principles, the forward heat transfer contact thermal resistance TCR can be solved directly based on the combined test and the individual test thermal resistance results using an indirect equivalent method. f , the result is calculated as:

[0097] TCR f =TCR 0 =TTR 0 -BTR 1 -BTR 2 ≈TTR 0 -TTR 1 -TTR 2 =0.248×10 -3 K.W -1 ·m 2 (6)

[0098] 8) The thermal rectification test principle proposed in the present invention is to first test the heat flow value of the forward heat transfer process under a certain pressure and temperature condition, then swap the positions of the first test sample 3 and the second test sample 4, test the heat flow value of the reverse heat transfer process, and finally calculate the thermal rectification coefficient. Since the heat flow value has been tested synchronously when testing the forward and reverse heat transfer contact thermal resistance, the thermal rectification coefficient test can be completed based on the above-mentioned test unit. The forward and reverse heat transfer process is achieved by directly replacing the positions of the upper and lower first test samples 3 and the second test sample 4. Considering the equivalence of the actual applied pressure transfer, the forward and reverse heat transfer process can be achieved without changing the relative positions of the high temperature and low temperature ends.

[0099] In order to test the reverse heat transfer heat flow value required for calculating the thermal rectification coefficient, adjust the upper and lower positions of the first test sample 3 and the second test sample 4, set the same pressure, high temperature end and low temperature end temperature as the above forward heat transfer process, and follow the same test process as steps 2) to 7) above. Reverse heat transfer contact thermal resistance TTR r and Q r The calculation formula and process are the same as those for the forward heat transfer process. The test results are different only due to the asymmetric distribution of temperature and heat flux in the forward and reverse heat transfer processes. Calculate the reverse heat transfer contact thermal resistance TTR r and Q r According to the same calculation formula as above, the reverse heat transfer contact thermal resistance TTR can be obtained: r and Q r The result is calculated as:

[0100] TCR r =TCR 0 ≈TTR 0 -TTR 1 -TTR 2 =0.222×10 -3 K.W -1 ·m 2 (7)

[0101] Q r =(Q 1 +Q 2 ) / 2=71.276mW·mm -2 (8)

[0102] 9) Calculate the thermal rectification coefficient TRC in forward and reverse heat transfer according to the thermal rectification coefficient calculation formula. The result is calculated as follows:

[0103]

[0104] The beneficial effects of the present invention are further illustrated by taking 718 nickel alloy and silicon carbide materials as examples. By adopting the test method proposed by the present invention, the normal test of this material can be completed, and the test results are compared with the theoretical analysis results to illustrate that the test method has an extremely high accuracy rate, and its error is less than 13%. Therefore, the test method described in the present invention starts with the drawbacks of the existing contact thermal resistance test method, and does not need to use contact and non-contact methods to test the contact interface temperature, and does not need to process the surface of the test sample before the temperature test, and can directly obtain the contact thermal resistance between the test samples in an indirect equivalent manner, further reducing the complexity of the contact thermal resistance test and effectively improving the test efficiency. In addition, by using the same experimental test platform, by testing the forward and reverse asymmetric heat flow, the thermal rectification coefficient caused by the asymmetric contact thermal resistance can be accurately calculated. The present invention can efficiently and accurately test the contact thermal resistance and the thermal rectification coefficient, especially can realize the contact thermal resistance test of samples that cannot be tested by contact temperature test, and can lay a test technology foundation for the research on the thermal rectification effect caused by the asymmetric contact thermal resistance.

[0105] The present invention adopts a test system composed of a loading unit 6, a heating unit 5, a cooling unit 7, a heat flow and temperature test unit, and a data processing unit. By testing the thermal resistance of two individual samples and the combined overall thermal resistance, direct contact thermal resistance testing of multiple materials under different pressure and temperature conditions is achieved, and the test of thermal rectification coefficient under different pressure and temperature conditions is achieved by adjusting the heat flow transfer direction of two different material samples. The test method provided by the present invention can achieve high-precision direct testing of contact thermal resistance and thermal rectification coefficient within different pressure and temperature ranges by adjusting the working range of the loading unit 6, the heating unit 5, and the cooling unit 7, and has the advantages of no need to install a temperature sensor on the sample, simple and quick operation, etc.

[0106] The above is a detailed description and drawings of the preferred embodiments of the present invention, and is not intended to limit the present invention. The entire scope of the present invention shall be subject to the scope of protection required by the patent right. All embodiments and similar structures that are consistent with the design concept of the present invention and similar variations thereof shall be included in the patent protection scope of the present invention.

Claims

1. A method for testing contact thermal resistance and thermal rectification coefficient, characterized in that: The following steps are involved: Testing the forward heat transfer contact thermal resistance and the forward heat transfer average heat flux of the first test sample and the second test sample stacked under set pressure and temperature conditions; Swap the positions of the first test sample and the second test sample to test the reverse heat transfer contact thermal resistance and the reverse heat transfer average heat flux under set pressure and temperature conditions; The thermal rectification coefficient is calculated based on the average heat flux of forward heat transfer and the average heat flux of reverse heat transfer.

2. The contact thermal resistance and thermal rectification coefficient testing method according to claim 1, characterized in that: Testing the forward heat transfer contact thermal resistance and the forward heat transfer average heat flow of the first test sample and the second test sample under set pressure and temperature conditions includes the following steps: The first test sample is arranged on the second test sample, a first heat flow meter is arranged on the top surface of the first test sample, a second heat flow meter is arranged on the ground surface of the second test sample, and a plurality of temperature sensors are arranged on the first heat flow meter and the second heat flow meter respectively; Applying a load to a set pressure to the first test sample, and heating the first test sample to a set temperature; The temperature of the temperature sensor and the position coordinates of the temperature sensor are collected, and the heat flow through the first test sample, the heat flow through the second test sample, and the average heat flow of the forward heat transfer process are calculated.

3. The contact thermal resistance and thermal rectification coefficient testing method according to claim 2, characterized in that: Thermal conductive silicone grease is evenly applied on the contact surfaces of the first heat flow meter and the second heat flow meter with the first test sample and the second test sample.

4. The contact thermal resistance and thermal rectification coefficient testing method according to claim 2, characterized in that: Forward heat transfer average heat flow Q f The calculation formula is: Among them, T1 is the temperature measured by the first temperature sensor, T3 is the temperature measured by the third temperature sensor, T4 is the temperature measured by the fourth temperature sensor, T6 is the temperature measured by the sixth temperature sensor, Z1 is the position coordinate of the first sensor, Z3 is the position coordinate of the third sensor, Z4 is the position coordinate of the fourth sensor, Z6 is the position coordinate of the sixth sensor, A is the contact surface area of ​​the test sample, k1 is the thermal conductivity of the first heat flow meter, k4 is the thermal conductivity of the second heat flow meter, Q1 is the heat flow of the first test sample, and Q2 is the heat flow through the second test sample.

5. The contact thermal resistance and thermal rectification coefficient testing method according to claim 1, characterized in that: Testing the forward heat transfer contact thermal resistance and the forward heat transfer average heat flow of the first test sample and the second test sample under set pressure and temperature conditions includes the following steps: The first test sample is arranged on the second test sample, a first heat flow meter is arranged on the top surface of the first test sample, a second heat flow meter is arranged on the ground surface of the second test sample, and a plurality of temperature sensors are arranged on the first heat flow meter and the second heat flow meter respectively; Collect the test results of the temperature sensor and the position of the temperature sensor, and calculate the upper surface temperature and the lower surface temperature of the sample combination contacted by the heat flow meter; Applying a load to a set pressure to the first test sample, and heating the first test sample to a set temperature; The forward heat transfer contact thermal resistance is calculated according to the total thermal resistance of the first test sample and the second test sample, the twice thermal resistance of the first test sample, and the twice thermal resistance of the second test sample.

6. The contact thermal resistance and thermal rectification coefficient testing method according to claim 5, characterized in that: Forward heat transfer contact thermal resistance TCR f Calculated by the following formula: TCR f =TCR0=TTR0-BTR1-BTR2≈TTR0-TTR1-TTR2(2) Among them, TTR0 is the total thermal resistance of the forward heat transfer process, TTR0 is the overall thermal resistance of the first test sample and the second test sample, BTR1 is the body thermal resistance of the first test sample, BTR2 is the body thermal resistance of the second test sample, TTR1 is the total thermal resistance of the first test sample, and TTR2 is the total thermal resistance of the second test sample 4.

7. The contact thermal resistance and thermal rectification coefficient testing method according to claim 6, characterized in that: The total thermal resistance TTR1 of the first test sample and the total thermal resistance TTR2 of the second test sample are calculated by the following formula: TTR1=TCR u1 +TCR d1 +BTR1≈BTR1(3) TTR2=TCR u2 +TCR d2 +BTR2≈BTR2(4) Among them, TCR u1 、TCR d1 are the contact thermal resistance between the first heat flow meter and the second heat flow meter and the first test sample when the first test sample is tested alone, TCR u2 、TCR d2 are the contact thermal resistances between the first heat flow meter and the second heat flow meter and the second test sample when the second test sample is tested alone.

8. The contact thermal resistance and thermal rectification coefficient testing method according to claim 5, characterized in that: The total thermal resistance TTR0 of the forward heat transfer process is calculated by the following formula: Among them, T H —Surface temperature of the sample assembly in contact with the heat flow meter, T C —The temperature of the lower surface of the sample assembly in contact with the heat flow meter, A—the surface area of ​​the test sample contact surface.

9. The contact thermal resistance and thermal rectification coefficient testing method according to claim 8, characterized in that: The surface temperature T of the sample assembly contacted by the heat flow meter H The temperature of the lower surface T C Calculated by the following formula: Wherein, T1 is the temperature measured by the first temperature sensor, T2 is the temperature measured by the second temperature sensor, T3 is the temperature measured by the third temperature sensor, T4 is the temperature measured by the fourth temperature sensor, T5 is the temperature measured by the fifth temperature sensor, T6 is the temperature measured by the sixth temperature sensor, Z1 is the position coordinate of the first sensor, Z3 is the position coordinate of the third sensor, Z4 is the position coordinate of the fourth sensor, Z6 is the position coordinate of the sixth sensor, and Z H —Surface coordinates of the sample assembly, Z C —Lower surface coordinates.

10. The contact thermal resistance and thermal rectification coefficient testing method according to claim 1, characterized in that: The thermal rectification coefficient TRC is calculated according to the average heat flow of forward heat transfer and the average heat flow of reverse heat transfer, including the following steps: Among them, q f ,q r are the heat flux in forward heat transfer and the heat flux in reverse heat transfer, Q f is the average heat flow in the forward direction, Q r is the average heat flux in reverse heat transfer.

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