Thermal adaptation coefficient measuring device, thermal adaptation coefficient measuring and calculating method and thermal resistance calculating method

Abstract

The invention discloses a thermal adaptation coefficient measuring device, a measuring and calculating method and a thermal resistance calculating method. The device comprises an upper heat flow meter, a lower heat flow meter, a contact type displacement sensor, a heating assembly, a cold end circulation assembly, a supporting system, a pipeline assembly interface and a control system, wherein the upper heat flow meter and the lower heat flow meter are arranged in a vacuum cover; the control system is arranged outside the vacuum cover; the heating assembly and the cold end circulation assembly are respectively connected with a heat flow meter which is symmetrically arranged, and the end part of each heat flow meter is provided with a measurement test piece; the heat flow meter and the measurement test piece are connected with thermocouples; the contact type displacement sensor is arranged at the peripheries of the heat flow meter, the measurement test piece and the thermocouple; an external control system is connected to the interior of the vacuum cover through the pipeline assembly connector. The temperatures on the upper and lower heat flow meters and the test piece are accurately measured, the heat flow passing through the test piece and the heat flow meters is determined, the intermediate quantity is calculated through the temperatures on the test piece and the heat flow meters, and finally the thermal adaptation coefficient and the contact thermal resistance of the accurate calculation result are obtained.

Description

Technical Field

[0001] The invention belongs to the field of thermodynamic testing, and specifically relates to a thermal adaptation coefficient measuring device, a thermal adaptation coefficient measuring method and a calculation method, and a thermal resistance calculation and measurement method. Background Art

[0002] The thermal adaptability coefficient is a physical parameter that represents the energy exchange between gas and solid. It is used to describe the energy exchange efficiency when gas molecules collide with solid surfaces. The factors affecting the thermal adaptability coefficient include the chemical composition, internal structure and heat treatment process of the material, which determine the behavior and performance of the material in a high temperature environment. Contact thermal resistance refers to the phenomenon that the heat transfer efficiency of two objects is low due to factors such as surface roughness, irregular shape, and microscopic gaps on the contact surface. Contact thermal resistance is affected by factors such as contact surface roughness, contact pressure, material properties and temperature. In heat transfer research, thermal adaptability coefficient and contact thermal resistance are very important concepts because they significantly affect heat transfer performance, especially in practical applications. In the field of aerospace, thermal adaptability coefficient is crucial to the calculation of orbital parameters and prediction of space operation life of spacecraft. The management of contact thermal resistance is directly related to the thermal performance of the aircraft and the reliability of the system. In the field of electronics, with the development of microelectronics technology, the requirements for the stability and reliability of materials at high temperatures are getting higher and higher. The accurate measurement of thermal adaptability coefficient and contact thermal resistance helps to select suitable materials, thereby ensuring that electronic equipment maintains stability and reliability in high temperature environments.

[0003] The acquisition of thermal adaptation coefficient and contact thermal resistance is a complex process, and both are also affected by many factors. Therefore, the acquisition in practical applications is a relatively complex process. At present, the thermal adaptation coefficient is mostly obtained by consulting existing literature or obtaining the thermal adaptation coefficient through experience, but this method of obtaining values ​​is not credible, the analysis results are inaccurate, and it will increase uncertainty in practical applications. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a thermal adaptation coefficient and contact thermal resistance measuring device, a thermal adaptation coefficient and contact thermal resistance measuring method and a calculation method, which solves the problem of difficulty in obtaining the thermal adaptation coefficient in the prior art.

[0005] The present invention adopts the following technical solutions to solve the above technical problems:

[0006] The device for measuring thermal adaptability coefficient and contact thermal resistance comprises upper and lower heat flux meters, contact displacement sensors, heating components, cold end circulation components, support systems, pipeline component interfaces, and a control system arranged outside the vacuum hood; wherein the pipeline component is arranged at the lowest end, the support system is arranged in the test area, and is used to fix the heating component and the cold end circulation component, and the heating component is located above the cold end circulation component; the heating component and the cold end circulation component are each connected to a symmetrically arranged heat flux meter, and a measuring specimen is respectively arranged at the end of the heat flux meter; thermocouples are connected to the heat flux meter and the measuring specimen; the contact displacement sensor is arranged on the periphery of the heat flux meter, the measuring specimen, and the thermocouple; and the external control system is connected to the inside of the vacuum hood through the pipeline component interface.

[0007] The support system includes upper and lower support plates, a top plate and a support rod; the support rod and the top plate are fixedly connected to form a support frame, the upper support plate is fixedly connected to the upper end of the support rod, and the lower support plate is movably connected to the lower end of the support rod; the lower support plate is fixed on the electric cylinder and moves up and down along the support rod through the control of the electric cylinder.

[0008] A pressure sensor is arranged below the lower supporting plate.

[0009] The contact type displacement sensor is arranged on the cold end circulation component, and a contact type displacement sensor stopper is correspondingly arranged on the heating component.

[0010] The method for measuring the thermal adaptation coefficient of the gap interface comprises the following steps:

[0011] Step 1: Install the upper and lower test pieces at corresponding positions and adjust them, lower the vacuum cover to the target position, and set several test temperature target values;

[0012] Step 2: Open the vacuum valve and the vacuum pump to evacuate the inside of the vacuum cover to reduce the vacuum degree in the vacuum cover to below 10Pa;

[0013] Step 3, turn on the heating device, wait for a while until the temperature of the test piece reaches a stable state, and fill the vacuum cover with the gas to be measured;

[0014] Step 4: When the pressure of the pressure sensor is adjusted to zero, several contact displacement sensors are reset to zero. On the basis of zeroing, the contact displacement sensors are adjusted to make the target gap between the upper and lower test pieces. After the gas enters the vacuum cover and the gap adjustment is completed, wait for the temperature to approach the target temperature.

[0015] Step 5: After the temperature is stabilized, the heat flow meter and the test piece temperature collected by several thermocouples are fed back to the external control system through the data acquisition device for processing and display, and the interface temperature of the upper and lower test pieces is calculated using the fed-back test piece temperature;

[0016] Step 6: Adjust the heating power to make the surface of the specimen reach the test temperature, and repeat steps 4 to 5 to perform the test until the temperature difference between the upper and lower interfaces of the specimen is less than 10°C, and calculate the thermal adaptation coefficient.

[0017] In step 1, the specific process of installing the upper and lower test pieces at the corresponding positions and adjusting them is as follows:

[0018] Step 1.1, respectively install the upper and lower material specimens to be measured on the upper and lower heat flow meters, and control the upper and lower material specimens to be initially aligned and contacted;

[0019] Step 1.2, firmly fix the aligned material specimens and the upper and lower heat flow meters, install three temperature measuring thermocouples with the same spacing on the upper and lower specimens and the heat flow meter, and after firmly fixing the temperature measuring thermocouples, connect the other end to the cold end circulation assembly;

[0020] Step 1.3, install a heat shield on the support frame of the test area; evenly install several contact displacement sensors on the cold end circulation assembly outside the shield in a circumferential direction, and install a stopper at the position corresponding to the contact displacement sensor on the heating assembly.

[0021] The method for calculating the thermal adaptation coefficient is as follows: first, establish a heat transfer equation between the test pieces; second, use the method of claim 5 to adjust the upper and lower interface temperatures of the test piece to a temperature difference of less than 10°C; then, solve the thermal adaptation coefficient when the temperature difference is less than 10°C according to the heat transfer equation; finally, reversely calculate the thermal adaptation coefficient at each temperature.

[0022] The relationship between the thermal adaptation coefficients of the upper and lower specimen surfaces is expressed by the following formula:

[0023]

[0024] Among them, T u and T d is the surface temperature in the gap between the upper and lower specimens, α1 and α2 are the thermal adaptation coefficients of the upper and lower specimens, k g is the thermal conductivity of the gas in the gap between the upper and lower specimens, q n =q m -q r ,q m is the average value of the heat flux density of the upper and lower heat flux meters, q r is the thermal radiation coefficient between interfaces, P is the gas pressure, γ is the ratio of gas specific heat, R g is the gas constant, and T is the gas temperature in the gap between the specimens.

[0025] T u and T d Calculated by the following formula:

[0026]

[0027] i=7,8,9 are the three thermocouples from top to bottom of the upper specimen, i=10,11,12 are the three thermocouples from top to bottom of the lower specimen, N is the number of thermocouples on the specimen, x i It is the distance from the thermocouple socket on the corresponding specimen to the upper surface of the specimen.

[0028] The contact thermal resistance measurement method is characterized by comprising the following steps:

[0029] Step 1: Install the upper and lower test pieces at corresponding positions and adjust them, install and fix several thermocouples on the heat flow meter and the test piece, and lower the vacuum cover to the target position;

[0030] Step 2: If the test is required under vacuum, open the vacuum valve and vacuum pump, and evacuate the inside of the vacuum cover to reduce the vacuum degree in the vacuum cover to below 10Pa, and then proceed to step 3; if the test is not required under vacuum, directly proceed to step 3;

[0031] Step 3, turn on the heating device. If it is necessary to measure the contact thermal resistance under different gas environments, fill the vacuum cover with the gas to be measured;

[0032] Step 4, adjust the pressure sensor to the pressure value of the test object, adjust the gas pressure to the gas pressure of the test object, adjust the heating power to make the surface of the test object reach the test temperature, and wait for a period of time until the temperature of the test object reaches stability;

[0033] Step 5: After the temperature stabilizes, the heat flow meter and specimen temperatures collected by several thermocouples are fed back to the external control system through the data acquisition device for processing and display. The interface temperature of the upper and lower specimens is inferred using the fed-back specimen temperature to calculate the contact thermal resistance.

[0034] The contact thermal resistance calculation method calculates the interface contact thermal resistance based on the heat transfer equation. The specific calculation formula is as follows:

[0035]

[0036] Where, ΔT c is the interface temperature difference, q m is the average value of the heat flux density of the upper and lower heat flux meters

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. Accurately measure the temperature on the upper and lower heat flow meters and the test piece, determine the heat flow through the test piece and the heat flow meter, calculate the intermediate quantity through the temperature on the test piece and the heat flow meter, and finally obtain the accurate calculation result of the thermal adaptation coefficient.

[0039] 2. The equipment of the present invention can meet the requirements of testing the thermal adaptability coefficient between gas and solid under different pressures, powers, gaps, and gas pressures.

[0040] 3. The device provided by the present invention has vacuum gas control: first, the vacuum cover is evacuated to a vacuum, and then different types of gases or gases of different gas pressures can be filled in. The vacuum suction port on the sealed table is connected to a multi-stage vacuum suction system of a mechanical pump and a diffusion pump with a suction rate of 6L / Min. An electromagnetic high vacuum stop valve is installed on the vacuum pipeline, which is connected to the air compressor and the control cabinet panel to control the opening and closing of the electromagnetic high vacuum stop valve. When the cavity is evacuated, the cavity pressure is first reduced to 0.1Pa by a mechanical pump, and then the pressure of the test cavity is maintained at about 10-4Pa by a diffusion pump. The low vacuum and high vacuum degrees in the cavity are measured and recorded respectively by a resistance gauge and an ionization gauge.

[0041] 4. The thermal adaptation coefficient calculation method of the present invention first controls the surface temperature to be similar through multi-stage temperature control, calculates the thermal adaptation coefficient at the temperature when the surface temperature is similar (the upper and lower thermal adaptation coefficients are equal), and then back-substitutes the thermal adaptation coefficient at the previous temperature based on the thermal adaptation coefficient under similar surface temperature, so that the calculated thermal adaptation coefficient is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The present invention provides a schematic structural diagram of a preferred embodiment of a device and method for measuring the thermal adaptability coefficient of a gap interface.

[0043] Figure 2 This is a schematic diagram of a partial three-dimensional structure of the first angle of the present invention.

[0044] Figure 3 It is a partial enlarged view of part A of the present invention.

[0045] Figure 4 It is a schematic diagram of the main structure of the present invention.

[0046] Figure 5 This is a schematic diagram of a partial three-dimensional structure at a second angle of the present invention.

[0047] Figure 6 It is a schematic diagram of the three-dimensional structure of the reflective ring and the bracket connected to the present invention.

[0048] Figure 7 This is a schematic diagram of the precise control and adjustment of sample spacing in the present invention.

[0049] Figure 8 This is a schematic diagram of the sealing structure of the sapphire observation window of the present invention.

[0050] Fig. 9 It is a schematic diagram of the composition of the vacuum degree adjustment system of the present invention.

[0051] Fig.10 It is a schematic diagram of the specific structure of the heating body of the present invention.

[0052] Among them, the numbers in the figure are: 1, vacuum cover; 2, upper support plate; 3, heating body; 4, guide rod; 5, bearing seat; 6, star-shaped handle; 7, displacement sensor; 8, water-cooled plate; 9, lower support plate; 10, pressure sensor; 11, lower force sensor mounting plate; 12, sealing table; 13, electromagnetic high vacuum stop valve; 14, sealing sleeve; 15, ionization gauge; 16, clamp; 17, movable seat; 18, ball head base; 19, lower heat flux meter; 20, sample; 21, reflection ring; 22, displacement block; 23, R-type wire clamp; 24, fixing plate; 25, wire groove; 26, support pad; 27, sensor fixing block; 28, linear bearing; 29, fastening sleeve; 30, nut; 31, upper heat flux meter; 32, measuring hole; 33, bracket; 34, stepping motor; 35, threading hole; 36, screw. DETAILED DESCRIPTION

[0053] The structure and working process of the present invention will be further described below in conjunction with the accompanying drawings.

[0054] The device for measuring thermal adaptability coefficient and contact thermal resistance comprises upper and lower heat flux meters, contact displacement sensors, heating components, cold end circulation components, support systems, pipeline component interfaces, and a control system arranged outside the vacuum hood; wherein the pipeline component is arranged at the lowest end, the support system is arranged in the test area, and is used to fix the heating component and the cold end circulation component, and the heating component is located above the cold end circulation component; the heating component and the cold end circulation component are each connected to a symmetrically arranged heat flux meter, and a measuring specimen is respectively arranged at the end of the heat flux meter; thermocouples are connected to the heat flux meter and the measuring specimen; the contact displacement sensor is arranged on the periphery of the heat flux meter, the measuring specimen, and the thermocouple; and the external control system is connected to the inside of the vacuum hood through the pipeline component interface.

[0055] Specific embodiment 1, as Figures 1 to 6 As shown,

[0056] A device for measuring thermal adaptability coefficient and contact thermal resistance, comprising an upper heat flux meter 31, a lower heat flux meter 19, a contact displacement sensor 7, a heating component, a cold end circulation component, a support system, a pipeline component interface, and a control system arranged outside the vacuum cover, wherein the heating component comprises a heating body 3; specifically, the device comprises a sealing table plate 12, four movable seats 17 are evenly fixedly installed on the upper surface of the sealing table plate 12, a guide rod 4 is fixedly installed on the top of each movable seat 17, a lower force sensor mounting plate 11 is fixedly installed on the outer sides of the four guide rods 4, a pressure sensor 10 and a ball head base 18 are fixedly installed inside the lower force sensor mounting plate 11, and an upper support plate 2 is fixedly connected to the upper ends of the four guide rods 4. A heating body 3 is fixedly installed at the bottom of the upper support plate 2, an upper heat flux meter 31 is arranged at the bottom of the heating body 3, and three displacement blocks 22 are fixedly installed on the outer side of the heating body 3, a lower support plate 9 is commonly arranged on the outer side of the four guide rods 4, a water cooling plate 8 is fixedly installed on the upper surface of the lower support plate 9, a lower heat flux meter 19 is arranged on the top of the water cooling plate 8, three sensor fixing blocks 27 are fixedly installed on the outer side of the water cooling plate 8, a fastening sleeve 29 is inserted into the interior of each sensor fixing block 27, a displacement sensor 7 is inserted into the interior of the fastening sleeve 29, and a nut 30 is screwed on the outer side of the fastening sleeve 29, a stepping motor 34 is fixedly installed at the bottom of the sealing table board 12, and the stepping motor 34 includes a screw 36 rotatably connected to the lower support plate 9.

[0057] In the implementation, considering the parallelism and surface deformation between the samples 20, three displacement sensors 7 are designed to adjust the spacing, and the parallelism of the two planes is ensured by three points. The lower heat flux meter 19 and the water-cooled plate 8 are installed on the extended screw 36, the top heating body 3 and the upper heat flux meter 31 are fixed, and the bottom screw 36 is controlled and driven by an independent stepper motor 34 to change and adjust the spacing between the tested samples 20. The detection unit is composed of a displacement sensor 7, which is installed on the side of the two heat flux meters. The displacement distance between the tested samples 20 is determined by the contraction state of the top of the displacement sensor 7. When the two tested samples 20 are just in contact, it is considered that the spacing between the samples 20 is exactly 0 at this time, and the displacement sensor 7 is zeroed. The execution unit is composed of a driver, a stepper motor 34 and a screw 36. The driver receives the instructions of the controller and converts them into voltage signals to be transmitted to the stepper motor 34, controls the speed and direction of the stepper motor 34, and controls the movement of the screw 36 through the coupling. The increment of the stepper motor 34 is 0.25 μm. According to the required sample spacing, the distance between the samples 20 is adjusted by adjusting the step length of the stepper motor 34 through the controller in the active mode, taking the spacing between the samples 20 as 0 as the reference.

[0058] The structure in the heating body 3 includes a heating wire made of tungsten wire, which is processed into a mosquito coil disc structure, and the diameter of the heating wire is 1.5mm. The disc heating wire is located in the middle of the heating body, and the upper and lower parts of the heating wire are insulated and protected by boron nitride ceramic plates. There are holes around the boron nitride ceramic plate, which is used to connect with the high thermal conductivity graphite plate at the bottom to facilitate heat transfer to the lower part. Holes and grooves are processed on the graphite plate to fix and install the tungsten heat flux meter. In order to reduce the amount of heat dissipated by the heating wire to the environment, the heating wire, ceramic plate and graphite plate are wrapped in mica insulation material. The mica material has a certain structural strength and low thermal conductivity, and is assembled into a whole by screws. The specific structure is as follows Fig.10 shown.

[0059] like Figure 2 As shown, two linear bearings 28 are sleeved on the outer side of each guide rod 4, the lower support plate 9 and the lower force sensor mounting plate 11 are fixedly connected to the linear bearings 28, and a fixing plate 24 is fixedly mounted on the outer sides of the two corresponding left and right guide rods 4.

[0060] like Figure 1 As shown, a sample 20 is arranged between the lower heat flow meter 19 and the upper heat flow meter 31 , and the sensor fixing block 27 is located directly above the displacement sensor 7 .

[0061] Embodiment 2:

[0062] like Figure 1-6 As shown, on the basis of the first embodiment, the present invention provides a technical solution: the outer side of the guide rod 4 is sleeved with a bearing seat 5, the outer sides of the two bearing seats 5 on the same side are commonly fixedly installed with a support pad 26, the opposite surfaces of the two support pads 26 are fixedly installed with a bracket 33, and the outer side of the bracket 33 is evenly fixedly installed with a plurality of reflection rings 21, and the outer side of each reflection ring 21 is provided with a measuring hole 32, the bearing seat 5 is movably connected to the guide rod 4, and the inside of the bearing seat 5 is screwed with a star handle 6, one end of the star handle 6 is in contact with the guide rod 4, the cross section of the reflection ring 21 is a semi-ring structure, and the reflection ring 21 is located at the lower heat flux meter 19. A sealing sleeve 14 is provided on the outside of the sample 20 and the upper heat flow meter 31, and the outside of the stepper motor 34. The sealing sleeve 14 is made of rubber material, and the sealing sleeve 14 is fixedly connected to the sealing table 12. A vacuum cover 1 and two wire grooves 25 are fixedly installed on the upper surface of the sealing table 12. Each wire groove 25 is located inside the vacuum cover 1. An electromagnetic high vacuum stop valve 13 and an ionization gauge 15 are fixedly installed on the bottom of the sealing table 12. A clamp 16 is provided on the outside of the ionization gauge 15. A threading hole 35 is opened at the bottom of the sealing table 12, and a plurality of R-type wire clamps 23 are fixedly installed on the upper surface of the upper support plate 2.

[0063] During implementation, by setting a six-layer reflection ring 21 with an anti-radiation structure on the outside of the sample 20, it can achieve a better effect of preventing temperature diffusion and maintaining temperature stability. The vacuum cover 1 is also preset with a through hole corresponding to the measuring hole 32. After being designed as a sapphire window, an infrared camera can be used outside to measure the temperature distribution of the sample inside through the camera.

[0064] Vacuum gas control: first evacuate the vacuum cover 1, then fill it with different types of gases or gases of different gas pressures. The preset vacuum suction port on the sealing table 12 is connected to a multi-stage vacuum suction system of a mechanical pump and a diffusion pump with a suction rate of 6L / Min. An electromagnetic high vacuum stop valve 13 is installed on the vacuum pipeline, which is connected to the air compressor and the control cabinet panel to control the opening and closing of the electromagnetic high vacuum stop valve 13. When evacuating the cavity, first use a mechanical pump to reduce the cavity pressure to 0.1Pa, then use a diffusion pump to keep the test cavity pressure at about 10-4Pa, and use the preset resistance gauge and ionization gauge 15 to measure and record the low vacuum and high vacuum in the cavity respectively.

[0065] Based on the structure of the above device, the following is a detailed introduction to the gap interface thermal adaptation coefficient and contact thermal resistance measurement method, including the following steps:

[0066] Step 1: Install the upper and lower test pieces at the corresponding positions and adjust them, lower the vacuum cover to the target position, and plan several test temperature target values ​​to be measured;

[0067] Step 2: Open the vacuum valve and the vacuum pump to evacuate the inside of the vacuum cover to reduce the vacuum degree in the vacuum cover to below 10Pa;

[0068] Step 3, turn on the heating device, adjust the heating power to make the surface of the test piece reach the test temperature, and fill the vacuum cover with the measured gas. If the environment for contact thermal resistance measurement is a vacuum state, it is not necessary to fill the gas;

[0069] Step 4: When measuring the thermal adaptation coefficient, adjust the pressure of the pressure sensor to zero, return several contact displacement sensors to zero, and adjust the contact displacement sensors on the basis of zeroing to make the target gap between the upper and lower test pieces; after the gas enters the vacuum cover and the gap debugging is completed, wait for the temperature to approach the target temperature;

[0070] Step 5: After the temperature is stabilized, the heat flow meter and the test piece temperature collected by several thermocouples are fed back to the external control system through the data acquisition device for processing and display. The interface temperature of the upper and lower test pieces is calculated using the fed-back test piece temperature to calculate the contact thermal resistance;

[0071] Step 6: Adjust the heating power to make the surface of the specimen reach the test temperature, and repeat steps 4 to 5 to perform the test until the temperature difference between the upper and lower interfaces of the specimen is less than 10°C, and calculate the thermal adaptation coefficient.

[0072] The temperature stability standard described in this embodiment is that the temperature change residual is less than 0.02°C.

[0073] Specifically, in step 1, the detailed process of adjusting the position of the measuring specimen is as follows:

[0074] The lower heat flux meter 19 and the water cooling plate 8 are mounted on a movable screw 36, the top heating body 3 and the heat flux meter are fixed, and the bottom screw 36 is driven by an independent stepping motor 34 to change and adjust the spacing between the test samples 20. In order to achieve stable adjustment of the spacing between the samples 20, a control system consisting of a controller, a detection unit, and an execution unit is designed, such as Figure 7 (a) is shown. The detection unit is composed of a displacement sensor 7, which is installed on the side of the two heat flow meters. The displacement distance between the plates is determined by the contraction state of the sensor top. Before the sample 20 contacts, the pressure sensor 10 is cleaned, and the lower sample 20 and the lower heat flow meter 19 are moved upward. When the two tested samples 20 just contact, the pressure sensor 10 has a certain reading. At this time, the lower sample 20 and the heat flow meter are moved in the opposite direction. When the value of the pressure sensor 10 is 0, it is considered that the spacing between the samples 20 is exactly 0 at this time, and the displacement sensor 7 is zeroed. The execution unit is composed of a driver, a stepper motor 34 and a screw 36. The driver receives the instructions of the controller and converts them into voltage signals to be transmitted to the stepper motor 34, controls the speed and direction of the stepper motor 34, and controls the movement of the screw 36 through the coupling. The increment of the stepper motor 34 is 0.25μm. According to the required spacing of the samples 20, the spacing of the samples 20 is 0 as the reference. In the active mode, the step length of the stepper motor 34 is adjusted by the controller to adjust the distance between the samples 20. There are three displacement sensors 7 in total to ensure the parallelism of the entire plane.

[0075] The detailed structure of the axial motion control system is as follows: Figure 7 As shown in (b), the bottom heat flow meter and the cold water plate 8 are installed on the movable rod, which is fixedly connected to the movable plate and moves on the support rod through the bearing. The movable rod contacts the top of the screw rod 36 and is fixed to the screw rod 36 by the locking pin. The top of the screw rod 36 realizes uniform pressure loading by ball head contact, and the screw rod 36 moves vertically in the fixed bearing on the bottom plate, thereby driving the entire movable plate and the test part to move up and down along the support rod.

[0076] Precise gas pressure regulation

[0077] In order to test the thermal adaptability coefficient and contact thermal resistance under different gas pressures, the test part (heating body 3, heat flux meter, test sample 20, water cooling plate 8, pressure sensor 10, temperature measuring probe, etc.) needs to be placed in a vacuum chamber, and the vacuum chamber is fixed to the stainless steel bottom plate by a sealing ring. In order to obtain the corresponding test data, data lead interfaces such as heating system leads, temperature sensors and pressure sensors 10 are provided on the stainless steel bottom plate. All data transmission interfaces are sealed in the data connector by vacuum sealant and then connected to the corresponding instruments (heating power supply, pressure gauge, data acquisition device, etc.). At the same time, a pressure sealing interface is processed on the stainless steel bottom plate, which is connected to the screw 33 of the stepper motor 34. High vacuum silicone grease is applied to the pressure sealing interface to achieve sealing and lubrication effects. In addition, a sapphire observation window needs to be opened on the vacuum chamber. The sealing scheme of the sapphire observation window is as follows: Figure 8 The sealing structure of the observation window consists of a sealing base, a sealing ring, a sapphire glass, and a sealing cover. The sealing base is welded to the vacuum cover. Grooves are processed on the sealing base and the sealing cover and sealing rings are placed. The sapphire glass is placed between the sealing rings and is tightened and fixed by nuts on the sealing base and the sealing cover. After the sealing is completed, the sapphire observation window forms a complete overall structure.

[0078] In order to achieve stable regulation of vacuum degree, the vacuum degree regulation system is designed as follows Fig. 9 As shown, it consists of a vacuum chamber, an exhaust system, an inflation system, and an automatic control system. A vacuum pipeline interface is opened on the vacuum chamber and connected to the exhaust system. First, the vacuum degree in the chamber is reduced to 0.1Pa through a mechanical pump, and then the vacuum degree of the test chamber is maintained at about 10-4Pa through a diffusion pump. At the same time, the vacuum pipeline is connected to the inflation system to fill the vacuum chamber with the required gas. When the vacuum degree of the vacuum chamber needs to be changed, close the exhaust regulating valve V1, control the opening of the inflation flow valve V2, and realize the automatic adjustment of the vacuum degree of the vacuum chamber. The pressure of the vacuum chamber is measured by a high-precision INFICON capacitive silicon pressure sensor 10 (the measurement accuracy is 0.1% of the full scale). According to the comparison of the set gas pressure and the measured pressure, the controller adjusts the opening of the flow control valve to control the gas flow from the gas cylinder into the vacuum chamber. When the vacuum degree of the vacuum chamber is stable, the vacuum degree fluctuation can be 0.01torr (0~100torr), 0.001torr (0~1torr), and 0.0001torr (0~0.1torr).

[0079] The specific operation process of the device is as follows:

[0080] 1. Sample (i.e. measurement specimen) installation

[0081] Fix the heating body 3 and the upper heat flux meter 31, move the lower heat flux meter 19 to separate them by a certain distance, and stick the two tested samples 20 to the upper heat flux meter 31 and the lower heat flux meter 19 respectively (glue needs to be applied on the pasting surface, and thermal grease or inorganic glue should be selected according to the test temperature requirements), then move the screw 36 upward to make the two samples 20 contact, set a certain contact pressure (for example, 16.4kg, 82kg), and keep the samples 20 in contact for a period of time so that the pasting surfaces are tightly combined.

[0082] 2. Temperature probe installation

[0083] When the sample 20 is in a stable contact state, a temperature measuring probe is installed on the back of the tested sample 20. The sample 20 has three openings in the axial direction. The temperature measuring probes are inserted into the openings in sequence and filled tightly with thermal conductive glue.

[0084] 3. Sample spacing adjustment

[0085] Close the contact pressure automatic clamping, and move the screw rod 36 downward. At this time, the reading on the pressure sensor 10 decreases. When the reading of the pressure sensor 10 is 0, the displacement sensor 7 is cleared (determine the zero point position of the contact interface). Then continue to control the screw rod 36 to move downward, observe the reading of the displacement sensor 7, and stop moving when the required spacing is reached.

[0086] 4. Gas pressure regulation

[0087] Close the vacuum chamber inside the vacuum cover 1 and evacuate the chamber. When the gas pressure is at the order of 1E-3, inflate the chamber with the required test gas (such as nitrogen, helium, etc.). When inflating, open the air inlet valve and set a certain opening (such as 2%, 5%, etc.), then input the required gas pressure (such as 1torr, 45torr, etc.) on the gas pressure controller, set the air extraction valve to automatic adjustment mode, and adjust the air extraction rate through PID to maintain the required gas pressure.

[0088] 5. Heating power adjustment

[0089] Start heating after the gas environment stabilizes. Set the initial heating power (such as 100W, 200W) and the temperature of the water chiller (such as 25°C, 30°C). After the temperature of sample 20 stabilizes, measure the temperature on sample 20, adjust the heating power to make sample 20 reach the required temperature, and record the temperature distributions on the upper heat flux meter 31, the lower heat flux meter 19, and sample 20. At this time, the axial temperature of the sample can be regarded as a linear distribution, and the surface temperature of the sample can be linearly calculated from other temperature points of itself. According to the temperature T2 on the surface of the lower sample 20, reduce the heating power so that the temperature T1 on the surface of the upper sample 20 = T2, and record the temperature distributions of the heat flux meter and sample 20 at this time (T1 on the surface of the upper sample 20, T2 on the surface of the lower sample 20). Continue to reduce the heating power so that the temperature T1 on the surface of the upper sample 20 = T2, and record the temperature distributions of the heat flux meter and sample 20 at this time (T1 on the surface of the upper sample 20, T2 on the surface of the lower sample 20). Gradually reduce the heating power according to this method. When the surface temperatures of the upper and lower samples / 20 are close (the temperature difference is less than 10°C), it can be considered that the upper and lower samples / 20 have the same heat accommodation coefficient, and the test is completed.

[0090] Regarding the above device and test method, the specific calculation methods of the heat accommodation coefficient and the contact thermal resistance are described in detail below.

[0091] For the calculation methods of the heat accommodation coefficient and the contact thermal resistance, first, establish the heat transfer equation between the test pieces; calculate the contact thermal resistance according to the temperatures of the test pieces and the heat flux meters fed back by the data; second, apply the method of claim 5 to adjust the upper and lower interface temperatures of the test pieces to a temperature difference less than 10°C; then, solve the heat accommodation coefficient when the temperature difference is less than 10°C according to the heat transfer equation; finally, calculate the heat accommodation coefficients at various temperatures in reverse.

[0092] Specifically, according to the principle of the parallel plate method, when testing the heat accommodation coefficient, the upper and lower test samples 20 are pasted on the heat flux meters in parallel. The upper heat flux meter 31 and the lower heat flux meter 19 are respectively in contact with the heating body 3 and the water cooling plate 8, and the gap between the different plate temperatures and the sample 20 can be controlled. Measure the temperature distributions on the upper and lower heat flux meters and the temperature distribution on sample 20 through thermocouples respectively. Establish the heat transfer equation between the tested samples 20 in the transitional state, and the heat accommodation coefficient of the rarefied gas can be solved.

[0093] In the continuous gas state (λ << L), the heat transfer between the two samples satisfies Fourier's law of heat conduction:

[0094]

[0095] Considering the influence of the rarefied gas effect, the heat transfer mode depends on the Knudsen number:

[0096]

[0097] Where δ is the characteristic length (gap thickness) and λ is the molecular mean free path:

[0098]

[0099] Where K B is the Boltzmann constant (1.38e-23), T is the gas temperature, P is the gas pressure, d g is the molecular collision diameter (3.798×10-10m), μ is the dynamic viscosity, and m is the molecular mass.

[0100] According to the numerical range of Knudsen number, the heat transfer of interstitial gas can be divided into four regions. The range of measurement of this experimental device is (0.001 <K n <10)

[0101] The heat transfer between the plates is:

[0102]

[0103] Where g1 and g2 are the temperature jump distances of the interstitial gas at the two contact interfaces, K g The temperature jump distance is obtained by considering the thermal conductivity of the gas, the motion expression of the gas viscosity coefficient and the ideal gas state equation:

[0104]

[0105] Where γ is the ratio of gas specific heat, C v is the constant volume specific heat of gas. Substituting the molecular mean free path definition and the ideal gas state equation into the formula, we get the formula for the heat transfer coefficient of the gap gas in the temperature jump zone:

[0106]

[0107] Where R g is the gas constant (R g =R / M, R=8.314J / mol / K, M is the relative molecular mass of the gas).

[0108] In summary, when the rarefied gas is in the temperature jump zone (0.001 <K n <10), the heat transfer coefficient between the plates can be accurately calculated. When the test part reaches a steady state, the heat flow of the heat flow meter is equal to the heat transfer of the gas between the samples, and an equation is established to calculate the thermal adaptation coefficient.

[0109] The heat flow calculation formula of the heat flow meter is:

[0110]

[0111] where km is the thermal conductivity of the heat flow meter, dT / dx1 and dT / dx2 represent the heat flux of the upper and lower heat flow meters:

[0112]

[0113] The heat transfer of rarefied gas between the plates is:

[0114]

[0115] Where α1 and α2 are the thermal adaptation coefficients of the upper and lower sample 20 surfaces, i=1, 2, 3 are the three thermocouples from top to bottom of the upper heat flow meter, i=4, 5, 6 are the three thermocouples from top to bottom of the lower heat flow meter, T u and T d are the temperatures of the upper and lower sample surfaces respectively, and the calculation formula is:

[0116]

[0117] Among them, i=7,8,9 are the three thermocouples from top to bottom of the upper specimen, i=10,11,12 are the three thermocouples from top to bottom of the lower specimen, N is the number of thermocouples on the specimen, x i It is the distance from the thermocouple socket on the corresponding specimen to the upper surface of the specimen.

[0118] Therefore, the relationship between the thermal adaptation coefficients of the upper and lower specimen surfaces can be expressed by the following formula:

[0119]

[0120] Among them, T u and T d is the surface temperature in the gap between the upper and lower specimens, α1 and α2 are the thermal adaptation coefficients of the upper and lower specimens, k g is the thermal conductivity of the gas in the gap between the upper and lower specimens, q n =q m -q r ,q m is the average value of the heat flux density of the upper and lower heat flux meters, q r is the thermal radiation coefficient between interfaces, P is the gas pressure, γ is the ratio of gas specific heat, R g is the gas constant, and T is the gas temperature in the gap between the specimens. When the upper and lower surface temperatures are close (temperature difference is less than 10°C), the thermal adaptation coefficients can be approximately considered equal, and the value of the thermal adaptation coefficient can be directly solved. When the upper and lower surface temperatures are very different, there is a certain difference between α1 and α2. It is necessary to continue to adjust the temperature of the upper surface according to the temperature corresponding to α2 on the lower surface at this time, and repeat this process until the upper and lower surface temperatures are close. Calculate the thermal adaptation coefficient at this temperature, and then back-substitute to solve the thermal adaptation coefficient at the previous temperature. The calculation principle is as follows:

[0121] f(α T1 ,α T2 )=y1

[0122] f(α T2 ,α T3 )=y2

[0123]

[0124] f(α Tn ,α Tn )=y n

[0125] When the surface temperatures of the upper and lower specimens are similar, the thermal adaptation coefficients at the upper and lower specimen surface temperatures are equal, and f(α Tn ,α Tn )=y n Calculate the thermal adaptation coefficient.

[0126] Based on the above method, a method for measuring the contact thermal resistance of a material is also disclosed. The interface contact thermal resistance is calculated according to the heat transfer equation. The specific calculation formula is as follows:

[0127]

[0128] Where, ΔT c is the interface temperature difference, calculated according to the following formula:

[0129] ΔT c =T U -T L

[0130]

[0131] The specific calculation principle is as follows:

[0132] According to the temperature of the thermocouples at a certain distance on the upper and lower heat flow meters and the known thermal conductivity of the heat flow meter material, the heat flux density q1 and q2 of the upper and lower interfaces are calculated using Fourier's law of thermal conductivity, and the heat flux through the sample interface is calculated using the average heat flow method. Since the sample interface temperature difference is calculated by the thermocouple extrapolation temperature, a certain number of thermocouples need to be inserted into the test sample. Before the samples come into contact, the distance from the thermocouples on the two samples to their respective end faces is measured.

[0133] Since the end faces are rough, there is a certain contact thickness during actual contact. Therefore, there is a certain distance between the extrapolated positions of the thermocouples, and the temperature difference extrapolated to each end face can be expressed as the temperature difference of the contact interface.

[0134] In the above method, the temperature gradient precise control method is as follows:

[0135] The test sample 20 is placed between two heat flow meters, and the upper and lower heat flow meters are in contact with the heating body 3 and the cooling system water cooling plate 8 respectively. A radiation shield 21 is installed around the heat flow meter 31 and the test sample 20 to reduce the radial heat loss of the test part and maintain the one-dimensionality of the axial heat flow. A pressure sensor 10 is installed at the bottom of the water cooling plate 8. Set the heating power and water cooling cycle temperature, maintain the temperature for a period of time so that the temperature reaches a one-dimensional steady state, and then use a thermocouple to measure the temperature gradient.

[0136] Contact pressure precise control method

[0137] The upper heating body 3 is connected and fixed to the upper heat flux meter 31, the lower water cooling plate 8 is connected and fixed to the lower heat flux meter 19, and the sample 20 is sandwiched between the upper heat flux meter 31 and the lower heat flux meter 19. The bottom screw 36 is controlled and driven by an independent stepper motor 34 to change and adjust the pressure between the test samples 20. In order to achieve stable pressure regulation between samples 20 and stable loading of small pressure on the interface, a servo follow-up feedback control system based on a programmable controller S7-200 PLC is designed, which includes three modules: a detection unit, an execution unit, and a human-machine interface (HMI). The detection unit is composed of a pressure sensor and a pressure gauge. The pressure gauge can read the value of the pressure sensor and transmit the signal to the PLC controller. The execution unit is composed of a servo driver, a servo motor, and a driving screw. The servo driver receives the PLC command and converts it into a voltage signal to transmit to the servo motor, controls the speed and direction of the servo motor, and controls the movement of the driving screw through the coupling. The servo drive and servo motor models are both Panasonic AC Minas series, which have the characteristics of fast response speed, strong overload capacity and high stability. The servo drive has a 32-bit DSP (digital signal processing) chip inside, which is compatible with the human-machine operation control panel. The human-machine interface (HMI) uses a touch screen, and the main adjustable parameters are: motor speed, servo speed, clamping speed, interface pressure, and pressure deviation. The human-machine interface can be used to monitor the system. The touch screen interface is connected to the programming interface of the S7-200PLC through an adapter, and the communication between the operating unit and the mechanical equipment is carried out in the form of variable setting. The pressure sensor uses two ranges, 0~2kg and 0~2t, respectively. After calibration, the accuracy of the pressure sensor is 0.01kg and 0.1kg respectively. The relevant components of the contact pressure control system are shown in Figure c.

[0138] It should be understood that the present solution is not limited to the above-mentioned specific implementation methods, and the devices and structures not described in detail should be understood to be implemented in a common manner in the art; any technician familiar with the art can use the above-disclosed methods and technical contents to make many possible changes and modifications to the technical solution of the present solution without departing from the scope of the technical solution of the present solution, or modify it into an equivalent embodiment with equivalent changes, which does not affect the essential content of the present solution. Therefore, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present solution without departing from the content of the technical solution of the present solution still falls within the scope of protection of the technical solution of the present solution.

Claims

1. Thermal adaptability coefficient and contact thermal resistance measuring device, characterized in that: It includes upper and lower heat flux meters, contact displacement sensors, heating components, cold end circulation components, support systems, pipeline component interfaces, and a control system arranged outside the vacuum hood; wherein the pipeline component is arranged at the lowest end, and the support system is arranged in the test area for fixing the heating component and the cold end circulation component, and the heating component is located above the cold end circulation component; the heating component and the cold end circulation component are each connected to a symmetrically arranged heat flux meter, and a measuring specimen is respectively arranged at the end of the heat flux meter; thermocouples are connected to the heat flux meter and the measuring specimen; the contact displacement sensor is arranged on the periphery of the heat flux meter, the measuring specimen, and the thermocouple; and the external control system is connected to the inside of the vacuum hood through the pipeline component interface.

2. The thermal adaptability coefficient and contact thermal resistance measuring device according to claim 1, characterized in that: The support system includes upper and lower support plates, a top plate and a support rod; the support rod and the top plate are fixedly connected to form a support frame, the upper support plate is fixedly connected to the upper end of the support rod, and the lower support plate is movably connected to the lower end of the support rod; the lower support plate is fixed on the electric cylinder and moves up and down along the support rod through the control of the electric cylinder.

3. The thermal adaptability coefficient and contact thermal resistance measuring device according to claim 2, characterized in that: A pressure sensor is arranged below the lower supporting plate.

4. The thermal adaptability coefficient and contact thermal resistance measuring device according to claim 1, characterized in that: The contact type displacement sensor is arranged on the cold end circulation component, and a contact type displacement sensor stopper is correspondingly arranged on the heating component.

5. A method for measuring the thermal adaptability coefficient of a gap interface based on the thermal adaptability coefficient and contact thermal resistance measuring device according to any one of claims 1 to 4, characterized in that: The steps include: Step 1: Install the upper and lower test pieces at corresponding positions and adjust them, lower the vacuum cover to the target position, and set several test temperature target values; Step 2: Open the vacuum valve and the vacuum pump to evacuate the inside of the vacuum cover to reduce the vacuum degree in the vacuum cover to below 10Pa; Step 3, turn on the heating device, wait for a while until the temperature of the test piece reaches a stable state, and fill the vacuum cover with the gas to be measured; Step 4: When the pressure of the pressure sensor is adjusted to zero, several contact displacement sensors are reset to zero. On the basis of zeroing, the contact displacement sensors are adjusted to make the target gap between the upper and lower test pieces. After the gas enters the vacuum cover and the gap adjustment is completed, wait for the temperature to approach the target temperature. Step 5: After the temperature is stabilized, the heat flow meter and the test piece temperature collected by several thermocouples are fed back to the external control system through the data acquisition device for processing and display, and the interface temperature of the upper and lower test pieces is calculated using the fed-back test piece temperature; Step 6: Adjust the heating power to make the surface of the specimen reach the test temperature, and repeat steps 4 to 5 to perform the test until the temperature difference between the upper and lower interfaces of the specimen is less than 10°C, and calculate the thermal adaptation coefficient.

6. The method for measuring the thermal adaptability coefficient of a gap interface according to claim 5, characterized in that: In step 1, the specific process of installing the upper and lower test pieces at the corresponding positions and adjusting them is as follows: Step 1.1, respectively install the upper and lower material specimens to be measured on the upper and lower heat flow meters, and control the upper and lower material specimens to be initially aligned and contacted; Step 1.2, firmly fix the aligned material specimens and the upper and lower heat flow meters, install three temperature measuring thermocouples with the same spacing on the upper and lower specimens and the heat flow meter, and after firmly fixing the temperature measuring thermocouples, connect the other end to the cold end circulation assembly; Step 1.3, install a heat shield on the support frame of the test area; evenly install several contact displacement sensors on the cold end circulation assembly outside the shield in a circumferential direction, and install a stopper at the position corresponding to the contact displacement sensor on the heating assembly.

7. A method for calculating the thermal adaptability coefficient based on the method for measuring the thermal adaptability coefficient of the gap interface according to claim 5, characterized in that: First, a heat transfer equation is established between the test pieces; second, the temperature of the upper and lower interfaces of the test pieces is adjusted to a temperature difference of less than 10°C by the method of claim 5; then, the thermal adaptation coefficient when the temperature difference is less than 10°C is solved according to the heat transfer equation; finally, the thermal adaptation coefficient at each temperature is reversely calculated.

8. The method for calculating the thermal adaptation coefficient according to claim 7, characterized in that: The relationship between the thermal adaptation coefficients of the upper and lower specimen surfaces is expressed by the following formula: Among them, T u and T d is the surface temperature in the gap between the upper and lower specimens, α1 and α2 are the thermal adaptation coefficients of the upper and lower specimens, k g is the thermal conductivity of the gas in the gap between the upper and lower specimens, q n =q m -q r ,q m is the average value of the heat flux density of the upper and lower heat flux meters, q r is the thermal radiation coefficient between interfaces, P is the gas pressure, γ is the ratio of gas specific heat, R g is the gas constant, and T is the gas temperature in the gap between the specimens.

9. The method for calculating the thermal adaptation coefficient according to claim 8, characterized in that: T u and T d Calculated by the following formula: i=7,8,9 are the three thermocouples from top to bottom of the upper specimen, i=10,11,12 are the three thermocouples from top to bottom of the lower specimen, N is the number of thermocouples on the specimen, x i It is the distance from the thermocouple socket on the corresponding specimen to the upper surface of the specimen.

10. A method for measuring contact thermal resistance based on the thermal adaptability coefficient and contact thermal resistance measuring device according to any one of claims 1 to 4, characterized in that: The steps include: Step 1: Install the upper and lower test pieces at corresponding positions and adjust them, install and fix several thermocouples on the heat flow meter and the test piece, and lower the vacuum cover to the target position; Step 2: If the test is required under vacuum, open the vacuum valve and vacuum pump, and evacuate the inside of the vacuum cover to reduce the vacuum degree in the vacuum cover to below 10Pa, and then proceed to step 3; if the test is not required under vacuum, directly proceed to step 3; Step 3, turn on the heating device. If it is necessary to measure the contact thermal resistance under different gas environments, fill the vacuum cover with the gas to be measured; Step 4, adjust the pressure sensor to the pressure value of the test object, adjust the gas pressure to the gas pressure of the test object, adjust the heating power to make the surface of the test object reach the test temperature, and wait for a period of time until the temperature of the test object reaches stability; Step 5: After the temperature stabilizes, the heat flow meter and specimen temperatures collected by several thermocouples are fed back to the external control system through the data acquisition device for processing and display. The interface temperature of the upper and lower specimens is inferred using the fed-back specimen temperature to calculate the contact thermal resistance.

11. A method for calculating contact thermal resistance based on the contact thermal resistance measurement method according to claim 10, characterized in that: The interface contact thermal resistance is calculated according to the heat transfer equation. The specific calculation formula is as follows: Where, ΔT c is the interface temperature difference, q m is the average value of the sum of the heat flux densities of the upper and lower heat flux meters.

Images