Device and method for testing heat conductivity coefficient by protecting heat flow meter method

Abstract

The invention discloses a heat conductivity coefficient testing device and testing method by a heat flow meter protection method, the testing device comprises a testing cavity and a control box body, the testing cavity is provided with a servo motor, a pressure bearing rod, a stepping motor, an upper heating furnace, a radial heat protection furnace, a lower heating furnace and a coupler; the upper heating furnace is connected with the pressure-bearing rod through a coupler; the lower heating furnace is fixed at the bottom of the test cavity; the servo motor is fixed at the top of the test cavity, drives the upper heating furnace to move through the pressure-bearing rod and the coupler, and applies a pressure load to a tested sample placed on the surface of the lower heating furnace through the upper heating furnace; the radial heat protection furnace is used for inhibiting the radial heat loss of the tested sample; the stepping motor is vertically fixed on the side wall of the testing cavity, and the radial heat protection furnace can be moved and located at a reasonable position in the testing process. According to the temperature values of the upper heating furnace and the lower heating furnace and the thickness of the tested sample, the heat conductivity coefficient at the current temperature is calculated, and the testing accuracy and efficiency are improved.

Description

TECHNICAL FIELD

[0001] The application relates to a protective heat flow meter method heat conductivity testing device and testing method, in particular to a protective heat flow meter method heat conductivity testing device and testing method with accurate pressurization and real-time thickness measurement functions. BACKGROUND

[0002] Heat insulation materials such as various phenolic resin composites and quartz fiber woven composites have been widely applied to various heat protection sleeves, heat protection cylinders and pad plates of various aerospace vehicles; in the civil field, the heat insulation materials are often used in the heat insulation pads of heating bodies of heating furnaces. The composites can break through the inherent performance of single materials and meet the special use requirements of low heat transfer, low density and high modulus after various impregnation, pressurization and sintering processes, and thus are widely applied in various fields. The heat conductivity is an important parameter for evaluating the heat transfer capacity of the materials, the components and structural forms at different positions in the materials after the composite treatment are greatly different, the heat transfer capacity of the materials cannot be evaluated by using the classical theory, and the heat conductivity of the materials, especially the composites, must be obtained through experiments, so that the performance testing of the heat conductivity of the materials, especially the composites, helps to reasonably select the heat insulation materials according to the actual working conditions of the thermal structure equipment, to achieve the expected design target of the thermal structure products and realize the fine structure, to fully exert the potential of the thermal structure equipment and reduce the development cost, and to have important significance for the development of new materials, product inspection and thermal structure design.

[0003] According to whether the data processing is directly related to time, the heat conductivity testing method can be divided into a steady state method and a non-steady state method, wherein the steady state method is a standard method for testing the heat transfer characteristics of the heat insulation materials, and mainly includes a guarded hot plate method, a heat flow meter method and a guarded heat flow meter method. Since the guarded hot plate method and the heat flow meter method suppress the radial heat loss by increasing the radial size of the sample, the edge length or diameter of the measured homogeneous sample is not less than 200mm, and the edge length or diameter of the measured inhomogeneous sample is not less than 300mm, obviously, the larger sample size brings certain pressure to the material production and mechanical processing departments, and is especially not suitable for the special occasions of sampling testing on the products, thereby limiting the popularization and use of the two methods in product testing. The guarded heat flow meter method determines the heat flow and heat resistance of the tested sample according to the heat flow meter test value, but it adopts a radial heat protection furnace to suppress the radial heat loss of the sample, and only needs to process a sample with a diameter of 50.8x(1-20)mm to meet the testing requirements under the condition of ensuring the same testing accuracy, and is especially suitable for the special testing requirements of sampling on the edge area of the product, so that the heat conductivity testing technology based on the guarded heat flow meter method is increasingly favored by the testers.

[0004] Existing protective heat flow meter thermal conductivity testing devices mostly rely on adding constant weights or cylinder pressurization to apply pressure loads. The raising and lowering of the radial protective furnace and the determination of the test position still depend on human intervention. In addition, requirements such as the inability to obtain data on the axial expansion of the sample during the test and the inability to cool down quickly after the test have not been resolved, which limits the widespread use of protective heat flow meter thermal conductivity testing devices. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a thermal conductivity testing device and method using a protective heat flow meter. This device and method have the functions of improving the accuracy of pressure load control, realizing real-time recording of the axial deformation of the test sample, and improving the repeatability of the radial heat protection furnace position, thereby improving the accuracy and efficiency of the test.

[0006] The technical solution of this invention is:

[0007] A protective heat flux method thermal conductivity testing device includes a testing chamber and a control box;

[0008] The test chamber includes a test chamber body and a servo motor, a pressure rod, a stepper motor, an upper heating furnace, a radial heat protection furnace, a lower heating furnace, and a coupling located within the test chamber body. The upper and lower heating furnaces have identical structures and are installed in mirror image. The upper heating furnace is connected to the pressure rod via a coupling, and the lower heating furnace is fixed to the bottom of the test chamber body. The servo motor is fixed to the top of the test chamber body and drives the upper heating furnace to move via the pressure rod and coupling, applying pressure loads to the upper heating furnace and the test sample placed on the lower heating furnace. The radial heat protection furnace is used to suppress radial heat loss of the test sample. The stepper motor is vertically fixed to the side wall of the test chamber body and is used to drive the radial heat protection furnace to move.

[0009] The control box controls the servo motor to drive the upper heating furnace to rise and fall, and controls the stepper motor to drive the radial heat protection furnace to rise and fall.

[0010] Furthermore, both the upper and lower heating furnaces include a heat sink, a heating plate, a metal heat spreader, and a metal heat transfer plate; wherein, the heat sink provides a constant temperature, and the heat sink in the upper heating furnace is connected to a coupling; the heating plate, the metal heat spreader, and the metal heat transfer plate are connected in sequence, and the outer end face of the metal heat transfer plate is in contact with the surface of the test sample.

[0011] Furthermore, the maximum operating temperature of the metal heat transfer plate is not lower than 340℃, the maximum temperature difference between different positions on the surface of the heating plate does not exceed 0.25℃, and the temperature fluctuation within 10 minutes when thermal equilibrium is reached does not exceed 0.25℃.

[0012] Furthermore, the heat sink, heating plate, metal heat spreader, and metal heat transfer plate are bonded together as a whole by applying high-temperature adhesive to their respective contact surfaces, and then covered with insulation cotton.

[0013] Furthermore, the radial heating furnace shaft includes a barrel-shaped high thermal conductivity alloy and a heater. The inner diameter of the barrel-shaped high thermal conductivity alloy is larger than the outer diameter of the upper heating furnace. The heater is covered with insulation material and a support frame. The support frame is connected to a stepper motor. The barrel-shaped high thermal conductivity alloy is connected to the heater to form an isothermal zone with a height of not less than 30 mm.

[0014] Furthermore, the stepper motor lead screw is vertically fixed on the test chamber, and the sliding end of the lead screw is connected to the radial heat protection furnace; limit switches are installed at both ends of the lead screw. When the stepper motor moves downward to the bottom limit switch position, the radial heat protection furnace is in the test position.

[0015] Furthermore, a fan and a cover plate are also provided. Symmetrical through holes are opened on both sides of the servo motor on the top plate of the test chamber. The fan is fixed on the inside of the top plate, and the cover plate that can be flipped out is installed on the outside. By working with the fan, the air flow in the test chamber is enhanced to improve the heat dissipation efficiency.

[0016] Furthermore, the control box is equipped with a main power switch, stepper motor up and down buttons, upper heating furnace up and down buttons, and a zeroing button;

[0017] The main switching power supply is used to supply power to the servo motor, stepper motor, upper heating furnace, radial heat protection furnace, and lower heating furnace;

[0018] The stepper motor up and down buttons are used to control the stepper motor to rise and fall.

[0019] The upper heating furnace rise and fall buttons are used to control the rotation of the servo motor, thereby driving the upper heating furnace to rise and fall.

[0020] The zeroing button is used to control the stepper motor to drive the radial heat protection furnace to reset to the zero position.

[0021] A method for testing thermal conductivity using a protected heat flux meter, comprising:

[0022] After coating the upper and lower surfaces of the test sample with thermal grease, place it on the upper surface of the lower heating furnace;

[0023] The servo motor is controlled to make the upper heating furnace contact the upper surface of the test sample, and the position of the test sample is adjusted to make the upper heating furnace, the test sample and the lower heating furnace coaxial;

[0024] The stepper motor is controlled to move the radial heat protection furnace downward, so that the horizontal center of the radial heat protection furnace is at the same height as the upper surface of the lower heating furnace;

[0025] Set the temperature values ​​of the upper heating furnace, lower heating furnace, and radial heat protection furnace, and turn on the upper heating furnace, lower heating furnace, and radial heat protection furnace; after the upper heating furnace, lower heating furnace, and radial heat protection furnace have all reached a stable thermal equilibrium state, calculate the thermal conductivity at the current temperature based on the temperature values ​​of the upper heating furnace and lower heating furnace and the thickness of the test sample.

[0026] Furthermore, while the upper heating furnace, lower heating furnace, and radial heat-protecting furnace are turned on, the servo motor applies a pressure load to the upper heating furnace and the test sample through the pressure rod. During the test, the test sample expands due to heat, and the servo motor adjusts the elongation of the pressure rod accordingly to maintain a constant output pressure load. The change in the thickness of the test sample is monitored in real time based on the change in the elongation of the pressure rod.

[0027] The advantages of this invention compared to the prior art are:

[0028] (1) The thermal conductivity testing device using the protected heat flow meter method requires the application of a constant pressure load, which is generally achieved through a weight or cylinder. This results in problems such as low automation, low pressure load control accuracy, and poor repeatability, thus reducing the accuracy of thermal conductivity testing. This invention uses a servo motor to apply the pressure load. By setting the pressure load, the control accuracy and repeatability are improved, and the thickness change of the test sample after heating can be monitored in real time through the status of the servo motor's pressure rod. This improves both the accuracy of thermal conductivity testing and the automation capability of the testing equipment.

[0029] (2) The thermal conductivity testing device using the protected heat flow meter method requires a radial heat-protecting furnace to suppress radial heat loss of the test sample. Existing solutions involve manually locating and fixing the retaining spring of the radial heat-protecting furnace. The retaining spring is prone to deformation under prolonged pressure, thus reducing the radial heat protection effect and the accuracy of the thermal conductivity test. It also suffers from low automation. This invention uses a stepper motor to drive the radial heat-protecting furnace to the predetermined position. In this invention, a high-strength backplate connects the two, preventing deformation even after prolonged use. It offers high repeatability of the working position and good heat protection effect, improving the automation capability of the equipment while ensuring the accuracy of the thermal conductivity test.

[0030] (3) When starting a new thermal conductivity test, it is necessary to first lower the temperature of the upper and lower heating furnaces and the radial heat shield furnace. Existing implementations lack rapid cooling functions, forcing operators to rely on natural ventilation or external fans for cooling, resulting in long cooling times, low efficiency, and unsatisfactory results. This invention enhances the gas flow velocity within the test chamber by controlling two fans at the top, thereby increasing the heat exchange between the three heating furnaces and the flowing gas. Furthermore, by changing the fan direction, the airflow can be directed to selectively dissipate heat from a particular heating furnace, improving cooling efficiency and allowing more time to begin the next round of testing. Attached Figure Description

[0031] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0032] Figure 1 This is a schematic diagram of the structure of the thermal conductivity testing device using the heat flux method of the present invention;

[0033] Figure 2 This is a schematic diagram of the upper heating furnace structure of the present invention;

[0034] Figure 3 This is a schematic diagram of the radial heat-protecting furnace structure of the present invention;

[0035] Figure 4 The figures show the temperature variations over time during the testing process in this embodiment of the invention.

[0036] Figure 5 The curves showing the change in servo motor output pressure and the thickness of the test sample monitored by the pressure rod over time during the testing process of this embodiment of the invention are shown. Detailed Implementation

[0037] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0038] This invention proposes a protective heat flux meter method for testing thermal conductivity, such as... Figure 1 As shown, the device includes a test chamber 1, a control box 2, and a high and low temperature heating and cooling constant temperature bath 3.

[0039] The test chamber 1 includes a test chamber body and an encoder servo motor 11, a fan and cover plate 12, a pressure rod 13, a stepper motor 14, an upper heating furnace 15, a radial heat protection furnace 16, a lower heating furnace 18, a bottom insulating pad 110, a coupling 111, and a temperature controller 112 located inside the test chamber.

[0040] The control box 2 includes a main power switch 21, an emergency fault button 22, a reset button 23, a stepper motor up button 24 and down button 25, an up button 26 and down button 27 that can control the servo motor 11 to drive the upper heating furnace 15, a buzzer alarm 28, a zeroing button 29 that controls the stepper motor 14 to drive the radial heating furnace 16 to reset to the "zero point" position, a running status indicator 210, and a fan running control switch 211. The host computer software is written using LabVIEW.

[0041] The servo motor 11 is fixed at the center of the top of the test chamber, and its output power should be greater than the maximum value of the load required for the test and the weight of the upper heating furnace 15. When the up button 26 or down button 27 is pressed, the servo motor 11 moves the upper heating furnace to the designated position; releasing the button keeps the current position unchanged. The pressure load is set in the host computer software. The servo motor rotates and applies a pressure load to the upper heating furnace 15 and the test sample 17 through the pressure rod 13. When the output pressure load matches the set value, the servo motor is in a constant pressure load output state. If the thickness of the test sample 17 changes after heating, it will change the pressure borne by the test sample 17, causing a deviation between the actual output pressure load of the servo motor 11 and the set value in the host computer software. At this time, the servo motor 11 will adjust the length of the pressure rod 13 according to the deviation until the deviation is zero. The servo motor then returns to a constant pressure load output state, and the length adjustment data of the pressure rod 13 is simultaneously uploaded by the servo motor 11 to the host computer software for acquisition and recording. In this embodiment, the stepping accuracy of the servo motor is not less than 0.01mm, and the change in the length of the pressure rod is not less than 30mm.

[0042] The upper heating furnace 15 and the lower heating furnace 18 have the same structure and are installed in a mirror image configuration. For example... Figure 2 As shown, the upper heating furnace 15 mainly consists of a heat sink 19, a heating plate 113, a high thermal conductivity metal heat spreader 114, a metal heat transfer plate 115, and a temperature sensor 116. These components are bonded together as a single unit by applying high-temperature adhesive to their surfaces and are externally covered with insulation cotton. The upper heating furnace 15 is connected to the pressure rod 13 via a coupling 111, and the lower heating furnace 18 is fixed to the center of the bottom of the test chamber 1 with screws. The servo motor 11 transmits the applied pressure load to the upper heating furnace 15 and the test sample 17 via the pressure rod 13 and the coupling 111, and also feeds back the thickness change of the test sample 17 to the host computer software in real time via the servo motor 11. In this embodiment, the heat sink 19 is connected to the high and low temperature heating and cooling constant temperature bath 3 through a water pipe; the diameter of the metal heat transfer plate of the upper heating furnace 15 and the lower heating furnace 18 is 50.8mm, the maximum working temperature is not lower than 340℃, the maximum temperature difference at different positions on the surface of the metal heating plate does not exceed 0.25℃, and the temperature fluctuation within 10 minutes when thermal equilibrium is reached does not exceed 0.25℃.

[0043] The structure of the radial heat-protecting furnace 16 is as followsFigure 3 As shown, it is made of a barrel-shaped high thermal conductivity alloy 118 and an external heater 119. The inner diameter of the barrel-shaped high thermal conductivity alloy 118 is about 5 mm larger than the outer diameter of the upper / lower heating furnace. The heater 119 is covered with heat-insulating material and a supporting frame, which can establish an isothermal zone with a height of not less than 50 mm. During the test, the horizontal center of the protective furnace 16 is at the same height as the upper surface of the metal heat transfer plate of the lower heating furnace 18, and the isothermal zone temperature is set to the average temperature of the upper and lower surfaces of the test sample to suppress radial heat loss of the test sample.

[0044] The stepper motor 14 is vertically fixed to the rear housing of the test chamber by a lead screw. The sliding end of the lead screw is connected to the radial heat protection furnace 16 by a stainless steel plate. The radial heat protection furnace is moved up and down by the stepper motor's up button 24 and down button 25. Limit switches are installed at both ends of the lead screw: when the reset button 23 or the down button 25 is pressed, the stepper motor 14 will move downward to the bottom limit switch position, at which point the radial heat protection furnace 16 is in the test position; when the up button 24 is pressed, the stepper motor 14 will move upward to the top limit switch position, at which point the radial heat protection furnace 16 and the servo motor 11 maintain a safe distance of 10mm to avoid mechanical collision between them.

[0045] Symmetrical through holes are made on both sides of the servo motor 11 on the top plate of the test chamber 1. A fan 12 is fixed on the inner side of the top plate, and an outward-folding cover is installed on the outer side. During the test, the cooling fan 12 and the cover are turned off to keep the gas in the test chamber relatively still. After the test, the cover is opened and the fan is started by the fan operation control switch 211 to force the heating furnace in the test chamber 1 to dissipate heat and cool down quickly.

[0046] This device not only performs the thermal conductivity test using the protected heat flow meter method, but also exchanges data in real time with the servo motor 11 via the host computer software. It can precisely control and monitor the pressure load applied to the test sample 17, record the thickness change value of the test sample 17 in real time, drive the radial heat protection furnace 16 to the designated position via the stepper motor 14 up button 24 and down button 25, and enhance the gas flow in the test chamber to improve heat dissipation efficiency by using the fan 12 operation control switch.

[0047] The working principle of this device is as follows:

[0048] A disc-shaped test sample 17 is coated with thermal grease on its upper and lower surfaces and placed on the metal heat transfer plate of the lower heating furnace 18. The servo motor 11 is controlled to make the upper heating furnace 15 contact the test sample 17. The position of the test sample 17 is adjusted so that the upper heating furnace 15, the test sample 17 and the lower heating furnace 18 are coaxial. The output pressure load of the servo motor 11 is set through the host computer software.

[0049] Pressing the reset button 23 causes the stepper motor 14 to move the radial heat protection furnace 16 downward. After triggering the bottom limit switch, the stepper motor 14 stops moving. At this time, the horizontal center of the radial heat protection furnace 16 is at the same height as the upper surface of the metal heat transfer plate of the lower heating furnace 18. During the experiment, the radial heat protection furnace 16 will remain in its current position.

[0050] During testing, the main power switch 21 is turned on, and the high and low temperature heating and cooling constant temperature bath 3 is started. The temperature values ​​of the upper heating furnace 15, lower heating furnace 18, and radial heat-protecting furnace 16 are set via the host computer software according to the test requirements, and each furnace begins heating. Since the radial heat-protecting furnace 16 can suppress radial heat loss of the test sample 17, after the upper heating furnace 15, lower heating furnace 18, and radial heat-protecting furnace 16 all reach a stable thermal equilibrium state, a steady-state one-dimensional heat flow will be established in the axial direction of the test sample 17. The thermal conductivity at the current temperature can be calculated based on the measured values ​​of the temperature sensors 116 of the upper heating furnace 15 and lower heating furnace 18 and the thickness of the test sample 17. During the test, the servo motor 11 also adjusts the elongation of the pressure rod 13 according to the thermal expansion of the test sample 17. The host computer software can monitor the change in the thickness of the test sample 17 in real time based on the changes in the elongation of the pressure rod 13 uploaded by the servo motor 11.

[0051] The following embodiments are for further illustration of the present invention, and not for limiting the present invention.

[0052] Example One:

[0053] This embodiment provides a protective heat flow meter method for testing thermal conductivity. The test sample is a carbon / polyimide composite material with dimensions of φ50.8×3mm. The test temperatures are set at 50℃, 100℃, 200℃, and 300℃. Based on the test temperature of the sample, the temperatures of the upper heating furnace, lower heating furnace, and radial protective heating furnace are also set. The thermal conductivity test results at each test temperature are shown in Table 1. The temperature difference between the upper and lower heating furnaces is 30℃. After each heating furnace reaches its set temperature, if the continuous temperature fluctuation within 10 minutes is less than 0.25℃, thermal equilibrium is considered to have been reached, and the thermal conductivity at the current temperature is calculated based on the measured temperature values ​​and the thickness of the test sample.

[0054] Table 1. Test results of carbon / polyimide composite materials at 50–300℃ obtained by this device.

[0055]

[0056]

[0057] Example Two:

[0058] This embodiment provides a protective heat flux meter method for testing thermal conductivity, wherein the servo motor is set to a constant output pressure operating mode. The test sample is made of carbon fiber reinforced epoxy composite material, and the test temperatures are set to 50℃ and 100℃. The thermal conductivity test results at each test temperature are shown in Table 2. Figure 4 The curves showing the change of each measured temperature over time during the test are presented. Figure 5 The curves showing the changes in servo motor output pressure and the thickness of the test sample monitored by the bearing rod over time during the test are presented.

[0059] Table 2. Test results of carbon fiber reinforced epoxy composite materials at 50–300℃ obtained by the testing device of this application.

[0060]

[0061] Example Three:

[0062] This embodiment provides a protective heat flow meter method for testing thermal conductivity. The lead screw of a stepper motor is vertically fixed to the rear housing of the test chamber, and its sliding end is connected to the radial heat-protecting furnace via a back plate. When the test sample needs to be replaced, press and hold the "Up" button. The stepper motor will drive the radial heat-protecting furnace upwards continuously until it reaches the top limit switch, at which point it automatically stops. At the top limit switch position, the radial heat-protecting furnace maintains a 10mm safety distance from the servo motor. After replacing the sample, when the radial heat-protecting furnace needs to be moved down to the working position, press and hold the "Down" button. The stepper motor will drive the radial heat-protecting furnace downwards continuously until it reaches the bottom limit switch, at which point it automatically stops. At this point, the horizontal center of the radial heat-protecting furnace is at the same height as the heating surface of the lower heating furnace. See also... Figure 1 .

[0063] Example Four:

[0064] This embodiment provides a thermal conductivity testing device using a protected heat flux meter method. Two fans are symmetrically arranged on either side of a servo motor, and each fan has a switch cover. After the test, the covers and the front panel of the test chamber are opened, and both fans are set to "inlet" mode to rapidly cool the upper heating furnace and the radial heat-protecting furnace. Then, the front panel of the test chamber is closed, the left fan is set to "inlet" mode, and the right fan is set to "outlet" mode to cool the radial heat-protecting furnace and the lower heating furnace. The time taken for the temperatures of the upper and lower heating furnaces and the radial heat-protecting furnace to drop from 300℃ to 50℃ is shown in Table 3 below.

[0065] Table 3 Cooling Time of Heating Furnace

[0066]

[0067] Comparative Example 1

[0068] Comparative Example 1 uses a servo motor to apply pressure load and a stepper motor to control the raising and lowering of the radial heat protection furnace. The similar product used in Comparative Example 1 uses a cylinder to apply pressure and a manual raising and lowering of the radial heat protection furnace. The test sample, test temperature, test parameters, and thermal balance judgment criteria are the same as in Example 1; the difference is that a servo motor is used to apply pressure load and a stepper motor is used to control the raising and lowering of the radial heat protection furnace.

[0069] Comparative Example 2

[0070] Comparative Example 2 demonstrates how the present invention can monitor the thickness change of the test sample during the testing process using a servo motor. Similar products used in Comparative Example 2 do not possess this function. The test sample, test temperature, test parameters, and thermal equilibrium judgment criteria are the same as in Example 2; the difference lies in the use of a servo motor to apply pressure load and to monitor the thickness change of the test sample during the testing process.

[0071] Comparative Example 3

[0072] This invention uses a stepper motor to control the raising and lowering of the radial heat-protecting furnace, resulting in high repeatability in moving it to the working position. In contrast, the similar product used in Comparative Example 3 required manual adjustment of the radial heat-protecting furnace position, leading to poor position repeatability. The procedure for changing the test sample is the same as in Example 3, except that a stepper motor is used to drive the radial heat-protecting furnace upwards and downwards. The working position of the radial heat-protecting furnace is when the stepper motor descends to the bottom limit switch position. The position repeatability deviation is ≤0.3mm.

[0073] Comparative Example 4

[0074] This invention employs fan cooling, achieving high efficiency in a three-stage process, whereas the similar product used in Comparative Example 4 only allows for natural ventilation. The cooling methods for the upper, lower, and radial heating furnaces are the same; the difference lies in using a fan at the top of the test chamber for cooling, and specifically targeting a particular heating furnace by changing the fan's rotation direction. The maximum time to cool from 300°C to 50°C is 42 minutes.

[0075] This invention, while enabling the application of the protective heat flow meter method to test thermal conductivity, also employs a servo motor to precisely control the pressure load applied to the test sample and record the thickness change value of the test sample in real time during the heating process. It also features automatic control of the radial protective furnace lifting and lowering via a stepper motor and the function of moving the radial heating furnace to the working position during the test experiment. Furthermore, it can accelerate the heat dissipation speed through two fans at the top of the test chamber, laying the foundation for improving test efficiency, shortening the cycle, and starting a new round of testing as soon as possible.

[0076] The embodiments described above are merely preferred embodiments of the present invention. Ordinary variations and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A protective heat flux meter method for testing thermal conductivity, characterized in that, Includes the test chamber and control box; The test chamber includes a test chamber body and a servo motor, a pressure rod, a stepper motor, an upper heating furnace, a radial heat protection furnace, a lower heating furnace, and a coupling located within the test chamber body. The upper and lower heating furnaces have identical structures and are installed in mirror image. The upper heating furnace is connected to the pressure rod via a coupling, and the lower heating furnace is fixed to the bottom of the test chamber body. The servo motor is fixed to the top of the test chamber body and drives the upper heating furnace to move via the pressure rod and coupling, applying pressure loads to the upper heating furnace and the test sample placed on the lower heating furnace. The radial heat protection furnace is used to suppress radial heat loss of the test sample. The stepper motor is vertically fixed to the side wall of the test chamber body and is used to drive the radial heat protection furnace to move. The control box controls the servo motor to drive the upper heating furnace to rise and fall, and controls the stepper motor to drive the radial heat protection furnace to rise and fall.

2. The thermal conductivity testing device using the protected heat flux method according to claim 1, characterized in that, Both the upper and lower heating furnaces include a heat sink, a heating plate, a metal heat spreader, and a metal heat transfer plate; wherein, the heat sink provides a constant temperature, and the heat sink in the upper heating furnace is connected to a coupling; the heating plate, the metal heat spreader, and the metal heat transfer plate are connected in sequence, and the outer end face of the metal heat transfer plate is in contact with the surface of the test sample.

3. The thermal conductivity testing device using the protected heat flux method according to claim 2, characterized in that, The maximum operating temperature of the metal heat transfer plate is not lower than 340℃, the maximum temperature difference between different positions on the surface of the heating plate does not exceed 0.25℃, and the temperature fluctuation within 10 minutes when thermal equilibrium is reached does not exceed 0.25℃.

4. The thermal conductivity testing device using the protected heat flux method according to claim 2, characterized in that, The heat sink, heating plate, metal heat spreader, and metal heat transfer plate are bonded together as a whole by applying high-temperature adhesive to their respective contact surfaces, and the outside is covered with insulation cotton.

5. The thermal conductivity testing device using the protected heat flux method according to claim 1, characterized in that, The radial heating furnace shaft includes a barrel-shaped high thermal conductivity alloy and a heater. The inner diameter of the barrel-shaped high thermal conductivity alloy is larger than the outer diameter of the upper heating furnace. The heater is covered with insulation material and a support frame. The support frame is connected to a stepper motor. The barrel-shaped high thermal conductivity alloy and the heater are connected to form an isothermal zone with a height of not less than 50 mm.

6. The thermal conductivity testing device using the protected heat flux method according to claim 1, characterized in that, The stepper motor lead screw is vertically fixed on the test chamber, and the sliding end of the lead screw is connected to the radial heat protection furnace. Limit switches are installed at both ends of the lead screw. When the stepper motor moves downward to the bottom limit switch position, the radial heat protection furnace is in the test position.

7. The protective heat flux method thermal conductivity testing device according to claim 1, characterized in that, Symmetrical through holes are made on both sides of the servo motor on the top plate of the test chamber. A fan is fixed inside the top plate, and an outward-folding cover is installed on the outside. The operation of the fan enhances the airflow in the test chamber to improve heat dissipation efficiency.

8. The protective heat flux method thermal conductivity testing device according to claim 1, characterized in that, The control box is equipped with a main power switch, stepper motor up and down buttons, upper heating furnace up and down buttons, and a zeroing button; The main switching power supply is used to supply power to the servo motor, stepper motor, upper heating furnace, radial heat protection furnace, and lower heating furnace; The stepper motor up and down buttons are used to control the stepper motor to rise and fall. The upper heating furnace rise and fall buttons are used to control the rotation of the servo motor, thereby driving the upper heating furnace to rise and fall. The zeroing button is used to control the stepper motor to drive the radial heat protection furnace to reset to the zero position.

9. A method for testing thermal conductivity using a protected heat flux meter, employing the thermal conductivity testing device for the protected heat flux meter method as described in claim 1, characterized in that, include: After coating the upper and lower surfaces of the test sample with thermal grease, place it on the upper surface of the lower heating furnace; The servo motor is controlled to make the upper heating furnace contact the upper surface of the test sample, and the position of the test sample is adjusted to make the upper heating furnace, the test sample and the lower heating furnace coaxial; The stepper motor is controlled to move the radial heat protection furnace downward, so that the horizontal center of the radial heat protection furnace is at the same height as the upper surface of the lower heating furnace; Set the temperature values ​​of the upper heating furnace, lower heating furnace, and radial heat protection furnace, and turn on the upper heating furnace, lower heating furnace, and radial heat protection furnace; after the upper heating furnace, lower heating furnace, and radial heat protection furnace have all reached a stable thermal equilibrium state, calculate the thermal conductivity at the current temperature based on the temperature values ​​of the upper heating furnace and lower heating furnace and the thickness of the test sample.

10. The method for testing thermal conductivity using a protected heat flux meter according to claim 9, characterized in that, While the upper heating furnace, lower heating furnace, and radial heat protection furnace are turned on, the servo motor applies a pressure load to the test sample through the pressure rod and the upper heating furnace. During the test, the test sample expands due to heat, and the servo motor adjusts the extension of the pressure rod accordingly to maintain a constant output pressure load. Based on the change in the elongation of the bearing rod, the change in the thickness of the test sample is monitored in real time.

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