A device and method for measuring the thermal conductivity of a non-steady high-temperature gas

Abstract

The application relates to the field of a heat conductivity coefficient measuring device of a gas working medium, in particular to a non-steady-state high-temperature gas working medium heat conductivity coefficient measuring device and a measuring method, which comprises a high-sealing sample cavity, a temperature equalizing block used for heating the sample cavity, a constant-temperature furnace used for heating the temperature equalizing block, a gas conveying device used for inputting or outputting the gas to be measured into or out of the sample cavity, and a vacuum device in communication with the sample cavity and used for vacuumizing the sample cavity; wherein a hot-wire sensor is arranged in the sample cavity, and a supporting rod used for supporting the hot-wire sensor is arranged in the sample cavity; the temperature equalizing block is arranged outside the sample cavity, and a temperature measuring system is arranged in the temperature equalizing block; and the gas conveying device comprises a gas inlet tank, a gas recovery tank and pipelines. The application has the effect of solving a series of problems such as temperature control precision of a temperature control system, high-temperature material selection and heating wire material selection which are faced by high-temperature gas heat conductivity coefficient measurement.

Description

Technical Field

[0001] This application relates to the field of devices for measuring the thermal conductivity of gaseous working fluids, and more particularly to a device and method for measuring the thermal conductivity of unsteady-state high-temperature gaseous working fluids. Background Technology

[0002] Thermal conductivity is one of the important thermophysical properties of fluids and a fundamental parameter for quantifying heat transfer processes. It has wide applications in engineering fields involving heat transfer. The accuracy of thermal conductivity measurements for gaseous refrigerants is crucial in nuclear engineering and related fields, especially for the precise thermal design of reactor cores. Inaccurate thermal conductivity measurements can lead to serious accidents.

[0003] From the perspective of measurement principles, methods for measuring thermal conductivity can be broadly categorized into two types: steady-state methods and unsteady-state methods. The steady-state method has a simple experimental principle; however, to obtain accurate one-dimensional heat flow, it usually requires a thermal compensation device; to obtain accurate temperature distribution, multiple temperature measuring points need to be set up. Therefore, the electrical control and adjustment circuitry of the experimental setup is relatively complex, and preparing the necessary measurement conditions and conducting the experiment itself are both time-consuming. Meanwhile, because fluids generate natural convection under temperature gradients, even under one-dimensional heat flow, it is difficult to achieve purely one-dimensional heat conduction; therefore, it is often used to measure the thermal conductivity of solids.

[0004] The solution equations for unsteady-state methods are theoretically more complex and are constrained by the measurement process and environmental conditions, making it difficult to accurately determine boundary conditions and measure the temperature change of the sample over time. Currently, the technology for measuring the thermal conductivity of gases above 500℃ is not yet mature, and related research both domestically and internationally is limited. It faces a series of challenges, including the temperature control accuracy of the temperature control system, the selection of high-temperature resistant materials, and the selection of heating wire materials, presenting significant technical difficulties. Gas thermal conductivity is greatly affected by temperature, and non-uniform temperature fields can lead to convective heat transfer. Therefore, thermal conductivity measurement devices require extremely high precision in the temperature control system. Current temperature control systems cannot simultaneously meet the requirements of this device in terms of the size of the isothermal zone, temperature field stability, temperature control accuracy, and operating temperature range. Summary of the Invention

[0005] To address a series of challenges in measuring the thermal conductivity of high-temperature gases, such as the temperature control accuracy of the temperature control system, the selection of high-temperature resistant materials, and the selection of heating wire materials, this application provides a device for measuring the thermal conductivity of unsteady-state high-temperature gas working fluids.

[0006] This application provides a device for measuring the thermal conductivity of an unsteady high-temperature gaseous working fluid, which adopts the following technical solution:

[0007] A device for measuring the thermal conductivity of an unsteady high-temperature gaseous working fluid, comprising:

[0008] The sample chamber contains a hot wire sensor and a support rod for supporting the hot wire sensor.

[0009] A temperature control system is provided outside the sample chamber and includes a temperature homogenizing block and a constant temperature furnace. The temperature homogenizing block is provided outside the sample chamber and a temperature measuring system is provided inside the temperature homogenizing block. The constant temperature furnace is arranged outside the temperature homogenizing block and is used to heat the temperature homogenizing block.

[0010] A gas delivery device for inputting or outputting the gas to be tested into the sample chamber, including an inlet tank, a recovery tank, and pipelines;

[0011] A vacuum device, connected to the sample chamber, is used to evacuate the sample chamber.

[0012] By adopting the above technical solution, the temperature homogenizing block can improve the temperature uniformity of the outer wall of the sample chamber through the optimized design of the internal heat conduction path. The constant temperature furnace indirectly heats the sample chamber by heating the temperature homogenizing block, avoiding local overheating caused by direct heating. With the real-time feedback control of the temperature measurement system, and through the matching design of the pipeline diameter and pressure regulating valve, the gas flow rate can be continuously adjusted. It can suppress natural convection through the vacuum device at low speeds, and simulate forced convection environment at high speeds, covering the full flow state measurement from static gas to turbulent gas.

[0013] Preferably, the sample chamber is located at the center of the temperature equalization block, the temperature equalization block is built into the constant temperature furnace, and the constant temperature furnace is equipped with heating wires and thermocouples.

[0014] By adopting the above technical solution, the temperature equalization block acts as a heat conduction medium, transforming the non-uniform heat flow of the constant temperature furnace into a uniform heat flow around the sample cavity. It serves as a heat conduction bridge between the constant temperature furnace and the sample cavity. The heating wires inside the constant temperature furnace are evenly distributed along the outer periphery of the temperature equalization block, reducing the temperature difference of the temperature equalization block and avoiding material aging caused by local overheating. The thermocouple is directly embedded inside the temperature equalization block, which can quickly capture temperature changes and reflect the real ambient temperature of the sample cavity in real time.

[0015] Preferably, a high-temperature resistant needle valve is installed at the inlet and outlet of the sample chamber.

[0016] By adopting the above technical solution, the needle valve can work stably within a large range of pressure difference between the inside and outside of the sample chamber. It can achieve micro-flow gas replenishment in a low-pressure vacuum environment, maintain the matching relationship between the free path of gas molecules and the diameter of the hot wire, and withstand high-speed scouring under high-pressure conditions, avoiding the flow fluctuations caused by valve core vibration in traditional shut-off valves.

[0017] Preferably, the support rod is connected to the sample chamber via a ceramic seal.

[0018] By adopting the above technical solution, the high-temperature resistant and deformation-resistant ceramic sealing material forms a rigid support interface, controls the thermal deformation rate of the support rod at high temperature, and the low thermal expansion coefficient of the ceramic sealing layer is highly matched with the support rod material, which can reduce the thermal stress of the sealing interface and avoid the risk of cracks or falling off due to uneven thermal expansion and contraction. The ceramic sealing process forms a non-porous sealing interface with high sealing reliability in high temperature vacuum environment.

[0019] Preferably, the temperature to be measured in the sample chamber is 500-800℃, and the temperature measurement system includes a high-temperature temperature sensor and a temperature measurement bridge. The temperature measurement system maintains the stability of the temperature under the high-temperature field.

[0020] By adopting the above technical solutions, the temperature measurement system achieves accurate temperature measurement, dynamic compensation, and stable temperature field in the high-temperature range of 500-800℃ through the selection of high-temperature resistant sensors, high-precision bridge design, and closed-loop control algorithm. It not only provides a reliable temperature reference for hot wire sensors, but also controls errors from the underlying data source of the measurement model, solving the problem of insufficient measurement accuracy caused by temperature signal drift and temperature field fluctuation at high temperatures in existing technologies.

[0021] Preferably, the air inlet tank is connected to the sample chamber via a first pipeline, the recovery tank is connected to the sample chamber via a second pipeline, and a first valve and a pressure transmitter are installed between the air inlet tank and the sample chamber.

[0022] By adopting the above technical solution, the gas inlet tank and recovery tank are connected to the sample chamber through pipelines. Combined with the coordinated control of the first valve and the pressure transmitter, the technical problems of unstable gas flow, insufficient pressure control accuracy and working fluid waste in high-temperature gas measurement are systematically solved, providing stable boundary conditions for the sample chamber.

[0023] Preferably, the pressure transmitter is positioned close to the sample chamber, the first valve is positioned close to the air inlet tank, and the vacuum device is installed on the second pipeline.

[0024] By adopting the above technical solution, the pressure transmitter for real-time pressure signal acquisition without delay is placed close to the sample chamber inlet, directly obtaining the true pressure of the gas in the sample chamber, rather than the lag pressure at the far end of the pipeline. This reduces response time and improves the accuracy of pressure fluctuation capture. In transient hot-wire method measurement, the pressure signal and hot-wire temperature response are synchronized, and the influence of gas density on thermal conductivity is corrected in real time, reducing the density calculation error under high-pressure supercritical conditions. The first valve can complete the coarse adjustment of pressure and flow rate before the gas enters the sample chamber, isolating the pressure fluctuation in the gas inlet tank upstream of the sample chamber and improving the pressure stability of the sample chamber side.

[0025] Preferably, the vacuum device includes a vacuum pump and a vacuum valve 82, a second valve is installed between the pressure transmitter and the first valve, the vacuum valve 82 is disposed between the second valve and the vacuum pump, and a third valve is provided on the first pipeline.

[0026] By adopting the above technical solution, after receiving the vacuum command, the vacuum valve 82 opens, working with the vacuum pump to extract the gas from the sample chamber and increase the pressure inside the sample chamber. When the vacuum pump stops, the vacuum valve 82 automatically closes, cutting off the passage between the sample chamber and the pump body, preventing atmospheric or pump oil vapor from flowing back into the sample chamber, and protecting the hot wire sensor from contamination. The vacuum level can be adjusted by changing the opening of the vacuum valve 82 to keep the vacuum level in the sample chamber stable. The pressure zone protection of the second valve is set between the pressure transmitter and the first valve, forming an independent pressure control isolation zone. The sample chamber can be isolated without stopping the system, and the pressure transmitter can be zero-point calibrated, avoiding the time-consuming problem caused by the traditional whole-system depressurization. When a leak occurs on the first valve or the gas inlet tank side, closing the second valve can control the leak at the gas inlet end, and the vacuum device can quickly remove residual gas. The gas inlet passage of the third valve can be flexibly switched to adapt to the working conditions.

[0027] A method for measuring the thermal conductivity of an unsteady-state high-temperature gas working fluid, using an unsteady-state high-temperature gas working fluid thermal conductivity measuring device, includes the following steps:

[0028] The sample chamber is filled with sample;

[0029] Turn on the constant temperature furnace, set the heating temperature, and maintain it stable;

[0030] The pressure of the sample to be tested is controlled to near the target pressure through the first valve, the second valve, the third valve and the air inlet tank, and the measurement begins after stabilization;

[0031] Turn on the power supply to the hot wire, select the appropriate heating power, control the temperature rise, and take at least three measurements with an interval of at least 5 minutes between each measurement.

[0032] Complete the thermal conductivity measurement;

[0033] Repeat the steps to perform multiple measurements until the required experimental conditions are achieved.

[0034] By adopting the above technical solution, the sample chamber is pre-evacuated using a vacuum device and then filled with the gas to be tested, keeping the residual air concentration at a low level to avoid cross-contamination during multi-component gas measurement. The three-stage linkage of the first valve, the second valve, and the pressure transmitter improves the target pressure control accuracy and reduces the gas density calculation error. The isothermal furnace adopts a gradient heating strategy, combined with the thermal buffering effect of the temperature equalization block, to control the axial temperature gradient of the sample chamber. The multiple measurement strategy provides data support for safety verification and avoids engineering accidents caused by misjudgment due to single-point measurement.

[0035] Preferably, the step of filling the sample chamber with the sample specifically includes the following steps:

[0036] Turn on the vacuum pump and vacuum valve 82;

[0037] Close the first and third valves and evacuate the sample chamber.

[0038] Once the vacuum level reaches the target value, turn off the vacuum pump and open the air inlet tank.

[0039] Fill the sample chamber with a small amount of the gas to be tested and keep it for 10-15 minutes.

[0040] The sample chamber was evacuated again;

[0041] Repeat the above steps at least 3 times;

[0042] Calculate the residual impurities, and if the requirements are met, connect the gas to be tested. The gas to be tested will flow into the sample chamber by gravity due to the pressure difference.

[0043] By adopting the above technical solution, through three cycles of vacuuming, micro-filling, and vacuuming again, the residual impurities are diluted and discharged through vacuuming after each filling with the gas to be tested, thereby reducing the concentration of residual impurities in the sample chamber. The pressure difference gravity filling without disturbance utilizes the pressure difference between the gas inlet tank 10 and the sample chamber to allow the gas to be tested to flow in by gravity, avoiding airflow impact and ensuring that the hot wire sensor remains stationary during the filling process, preventing the hot wire position from shifting due to mechanical disturbance.

[0044] In summary, this application includes at least one of the following beneficial technical effects:

[0045] 1. The homogenizing block, through its optimized internal heat conduction path design, can improve the temperature uniformity of the outer wall of the sample chamber. The constant temperature furnace indirectly heats the sample chamber by heating the homogenizing block, avoiding local overheating caused by direct heating. Combined with the real-time feedback control of the temperature measurement system, and through the matching design of the pipeline diameter and pressure regulating valve, the gas flow rate can be continuously adjusted. It can suppress natural convection through the vacuum device at low speeds, and can also simulate forced convection environment at high speeds, covering the full flow state measurement from static gas to turbulent gas.

[0046] 2. After pre-evacuating the sample chamber using a vacuum device, the sample chamber is filled with the gas to be tested, keeping the residual air concentration at a low level to avoid cross-contamination during multi-component gas measurements. The three-stage linkage of the first valve, the second valve, and the pressure transmitter improves the accuracy of target pressure control and reduces gas density calculation errors. The isothermal furnace adopts a gradient heating strategy, combined with the thermal buffering effect of the temperature equalization block, to control the axial temperature gradient of the sample chamber. The multiple measurement strategy provides data support for safety verification and avoids engineering accidents caused by misjudgment due to single-point measurement. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the overall structure of the non-steady-state high-temperature gas working fluid thermal conductivity measuring device in the embodiments of this application.

[0048] Explanation of reference numerals in the attached drawings: 1. Sample chamber; 2. Hot wire sensor; 3. Support rod; 4. Irradiation block; 5. Temperature sensor; 6. Constant temperature furnace; 7. Pressure transmitter; 8. First valve; 81. Second valve; 82. Vacuum valve; 83. Third valve; 9. Vacuum pump; 10. Inlet tank; 11. Recovery tank. Detailed Implementation

[0049] The following is in conjunction with the appendix Figure 1 This application will be described in further detail.

[0050] This application discloses a device and method for measuring the thermal conductivity of an unsteady high-temperature gaseous working fluid. (Refer to...) Figure 1 A device for measuring the thermal conductivity of an unsteady high-temperature gas working fluid includes a highly sealed sample chamber 1, a homogenizing block 4 for heating the sample chamber 1, a constant-temperature furnace 6 for heating the homogenizing block 4, a gas delivery device for inputting or outputting the gas to be measured into or out of the sample chamber 1, and a vacuum device connected to the sample chamber 1 for evacuating the sample chamber 1. A hot-wire sensor 2 is installed inside the sample chamber 1, along with a support rod 3 for supporting the hot-wire sensor 2. The support rod 3 is connected to the sample chamber 1 via a ceramic seal. The high-temperature resistant and deformation-resistant ceramic seal material forms a rigid support interface, controlling the thermal deformation rate of the support rod 3 at high temperatures. The low thermal expansion coefficient of the ceramic seal layer is highly matched with the material of the support rod 3, reducing the thermal stress at the seal interface and avoiding the risk of cracking or detachment due to uneven thermal expansion and contraction. The ceramic seal process ensures sealing reliability under high-temperature vacuum conditions, forming a non-porous sealing interface.

[0051] In an optional embodiment, to ensure the sealing of sample chamber 1 under high-temperature conditions, sample chamber 1 is made of nickel-based alloy 617 and sealed by full welding, and connected to support rod 3 by ceramic sealing. In a preferred embodiment, the hot wire sensor 2 is at the micrometer level. When a constant instantaneous heat flow is applied to the hot wire source, the thermal conductivity of the medium can be calculated based on the relationship between the hot wire temperature and time.

[0052] The sample chamber 1 is located at the center of the temperature homogenizing block 4, which is built into the constant temperature furnace 6. The constant temperature furnace 6 contains heating wires and thermocouples. The temperature homogenizing block 4 acts as a heat conduction medium, converting the non-uniform heat flow of the constant temperature furnace 6 into a uniform heat flow around the sample chamber 1. It serves as a heat conduction bridge between the constant temperature furnace 6 and the sample chamber 1. The heating wires within the constant temperature furnace 6 are evenly distributed along the outer periphery of the temperature homogenizing block 4, reducing the temperature difference and preventing material aging caused by localized overheating. The thermocouples are directly embedded inside the temperature homogenizing block 4, allowing for rapid temperature capture and real-time reflection of the actual ambient temperature of the sample chamber 1. In an optional embodiment, a high-temperature platinum resistance temperature sensor 5 is installed inside the temperature homogenizing block 4. In another optional embodiment, the heating wire is made of high-temperature resistance thermometer alloy SGHYZ, and the temperature homogenizing block 4 is made of nickel-based alloy 617. The combined effect of the constant temperature furnace 6 and the temperature homogenizing block 4 improves temperature control accuracy. A high-temperature resistant needle valve is installed at the inlet and outlet of sample chamber 1. The needle valve can work stably within a large pressure difference range inside and outside sample chamber 1. It can achieve micro-flow gas replenishment in low-pressure vacuum environment to maintain the matching relationship between the free path of gas molecules and the diameter of the hot wire. It can also withstand high-speed scouring under high-pressure conditions, avoiding flow fluctuations caused by valve core vibration in traditional shut-off valves, and reducing gas flow and flow heat transfer inside sample chamber 1.

[0053] The temperature control system is located outside the sample chamber 1 and includes a temperature homogenizing block 4 and a constant temperature furnace 6. The temperature homogenizing block 4 is located outside the sample chamber 1 and contains a temperature measuring system. The constant temperature furnace 6 is located outside the temperature homogenizing block 4 and is used to heat the temperature homogenizing block 4. In an optional embodiment, the temperature to be measured inside the sample chamber 1 is 500-800℃. The temperature measuring system includes a high-temperature sensor 5 and a temperature measuring bridge, and maintains the stability of the temperature under high-temperature conditions. Through the selection of high-temperature resistant sensors, the design of high-precision bridges, and closed-loop control algorithms, the temperature measuring system achieves accurate temperature measurement, dynamic compensation, and temperature field stability in the high-temperature range of 500-800℃. This not only provides a reliable temperature reference for the hot-wire sensor 2 but also controls errors from the underlying data source of the measurement model, solving the problem of insufficient measurement accuracy caused by temperature signal drift and temperature field fluctuations at high temperatures in the prior art.

[0054] A gas delivery device, used to input or output the gas to be measured into or out of the sample chamber 1, includes an inlet tank 10, a recovery tank 11, and pipelines. The recovery tank 11 is connected to the sample chamber 1 via a first pipeline, and the inlet tank 10 is connected to the sample chamber 1 via a second pipeline. A first valve 8 and a pressure transmitter 7 are installed between the inlet tank 10 and the sample chamber 1. The pressure transmitter 7 is positioned close to the sample chamber 1, and the first valve 8 is positioned close to the inlet tank 10. A vacuum device is installed on the second pipeline. The design of connecting the inlet tank 10 and the recovery tank 11 to the sample chamber 1 via pipelines, combined with the coordinated control of the first valve 8 and the pressure transmitter 7, systematically solves the technical problems of unstable gas flow, insufficient pressure control accuracy, and working fluid waste in high-temperature gas measurement, providing stable boundary conditions for the sample chamber 1. The pressure transmitter 7, which acquires real-time pressure signals without delay, is located close to the inlet of the sample chamber 1 to directly obtain the true pressure of the gas inside the sample chamber 1, rather than the lag pressure at the far end of the pipeline. This reduces response time and improves the accuracy of pressure fluctuation capture. In transient hot-wire method measurement, it synchronizes the pressure signal and hot-wire temperature response, corrects the influence of gas density on thermal conductivity in real time, and reduces density calculation errors under high-pressure supercritical conditions. The first valve 8 can complete the coarse adjustment of pressure and flow rate before the gas enters the sample chamber 1, isolating the pressure fluctuations in the gas inlet tank 10 upstream of the sample chamber 1 and improving the pressure stability on the sample chamber 1 side.

[0055] A vacuum device is connected to the sample chamber 1 to evacuate the sample chamber 1. The vacuum device includes a vacuum pump 9 and a vacuum valve 82. A second valve 81 is installed between the pressure transmitter 7 and the first valve 8. The vacuum valve 82 is located between the second valve 81 and the vacuum pump 9. A third valve 83 is provided on the first pipeline. Upon receiving a vacuum command, vacuum valve 82 opens, working with vacuum pump 9 to extract gas from sample chamber 1 and increase the pressure within sample chamber 1. When vacuum pump 9 stops, vacuum valve 82 automatically closes, cutting off the passage between sample chamber 1 and pump body, preventing atmospheric or pump oil vapor from flowing back into sample chamber 1 and protecting hot wire sensor 2 from contamination. The vacuum level can be adjusted by changing the opening of vacuum valve 82 to maintain a stable vacuum level in sample chamber 1. The pressure zone protection of the second valve 81: The second valve 81 is located between pressure transmitter 7 and the first valve 8, forming an independent pressure control isolation zone. Sample chamber 1 can be isolated without stopping the system, allowing zero-point calibration of pressure transmitter 7 and avoiding the time-consuming problem caused by traditional full-system depressurization. When leakage occurs on the first valve 8 or the inlet tank 10 side, closing the second valve 81 can control the leakage at the inlet end, and the vacuum device can quickly remove residual gas.

[0056] A method for measuring the thermal conductivity of an unsteady-state high-temperature gas working fluid, using an unsteady-state high-temperature gas working fluid thermal conductivity measuring device, includes the following steps:

[0057] S1. Fill the sample chamber 1 with the sample.

[0058] The specific steps include:

[0059] S1.1 Turn on vacuum pump 9 and vacuum valve 82;

[0060] S1.2 Close the first valve 8 and the third valve 83, and evacuate the sample chamber 1;

[0061] S1.3 After the vacuum level reaches the target value, turn off the vacuum pump 9 and open the air inlet tank 10;

[0062] S1.4 Fill a small amount of the gas to be tested into sample chamber 1 and keep it for 10-15 minutes;

[0063] S1.5 Vacuum chamber 1 is evacuated again;

[0064] S1.6 Repeat steps S1.1-S1.5 at least 3 times;

[0065] S1.7 Calculate the residual impurities. If the requirements are met, connect the gas to be tested. The gas to be tested flows into the sample chamber 1 by gravity due to the pressure difference.

[0066] S2. Turn on the constant temperature furnace 6, set the heating temperature, and maintain it stable.

[0067] S3. Control the pressure of the sample to be tested to near the target pressure through the first valve 8, the second valve 81, the third valve 83 and the air inlet tank 10, and start the measurement after stabilization.

[0068] S4. Turn on the power supply voltage of the hot wire, select the appropriate heating power, control the temperature rise, and take measurements at least three times, with an interval of at least 5 minutes between each measurement.

[0069] S5. Complete the thermal conductivity measurement.

[0070] S6. Repeat steps S2-S5 multiple times to achieve the required experimental conditions.

[0071] The implementation principle of this application embodiment is as follows: When a constant heat flow is applied to the heat source, the thermal conductivity of the medium can be calculated based on the relationship between the temperature of the heat wire and time. Considering the high temperature resistance problem, the cavity is made of nickel-based alloy 617, and the heat wire and support rod 3 are made of high-purity platinum. The temperature control system consists of a temperature equalization block 4 and a constant temperature furnace 6. Heating wires and thermocouples are arranged in the constant temperature furnace 6. The temperature equalization block 4 is made of nickel-based alloy 617. Under the combined action of the constant temperature furnace 6 and the temperature equalization block 4, the temperature control accuracy is improved. The temperature equalization block 4 uses a high-temperature platinum resistance thermometer and a super temperature measuring bridge to improve the temperature measurement accuracy and realize the measurement of the thermal conductivity of the gas within a large pressure and temperature range, so as to obtain the thermal conductivity of the gas under different temperature and pressure conditions.

[0072] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A device for measuring the thermal conductivity of an unsteady-state high-temperature gaseous working fluid, characterized in that, include: The sample chamber (1) is equipped with a hot wire sensor (2) and a support rod (3) for supporting the hot wire sensor (2). The sample chamber (1) is made of nickel-based alloy 617 and is fully welded and sealed. The support rod (3) is connected to the sample chamber (1) by ceramic sealing. The temperature control system is set outside the sample chamber (1) and includes a temperature equalization block (4) and a constant temperature furnace (6). The sample chamber (1) is arranged at the center of the temperature equalization block (4). The temperature equalization block (4) is equipped with a temperature measuring system. The temperature equalization block (4) is built into the constant temperature furnace (6). The constant temperature furnace (6) is equipped with a heating wire and a thermocouple. The temperature equalization block (4) acts as a heat conduction medium to convert the non-uniform heat flow of the constant temperature furnace (6) into a uniform heat flow around the sample chamber (1). The temperature measuring system maintains the stability of the temperature under high temperature field. The temperature control system also includes a high temperature platinum resistance temperature sensor (5) and a temperature measuring bridge. The temperature to be measured in the sample chamber (1) is 500~800℃. A gas delivery device for inputting or outputting the gas to be tested into or out of the sample chamber (1), including an inlet gas tank, a recovery gas tank and pipelines; A vacuum device is connected to the sample chamber (1) and is used to evacuate the sample chamber (1).

2. The device for measuring the thermal conductivity of unsteady high-temperature gas working fluid according to claim 1, characterized in that, A high-temperature resistant needle valve is installed at the inlet and outlet of the sample chamber (1).

3. The device for measuring the thermal conductivity of unsteady high-temperature gas working fluid according to claim 1, characterized in that, The air inlet tank is connected to the sample chamber (1) through a first pipeline, and the recovery tank (11) is connected to the sample chamber (1) through a second pipeline. A first valve (8) and a pressure transmitter (7) are installed between the air inlet tank and the sample chamber (1).

4. The device for measuring the thermal conductivity of unsteady high-temperature gas working fluid according to claim 3, characterized in that, The pressure transmitter (7) is located near the sample chamber (1), the first valve (8) is located near the air inlet tank, and the vacuum device is installed on the second pipeline.

5. The device for measuring the thermal conductivity of unsteady high-temperature gas working fluid according to claim 4, characterized in that, The vacuum device includes a vacuum pump (9) and a vacuum valve. A second valve (81) is installed between the pressure transmitter (7) and the first valve (8). The vacuum valve is located between the second valve (81) and the vacuum pump (9). A third valve (83) is provided on the first pipeline.

6. A method for measuring the thermal conductivity of an unsteady-state high-temperature gas working fluid, using the unsteady-state high-temperature gas working fluid thermal conductivity measuring device according to any one of claims 1-5, characterized in that, Including the following steps: The sample chamber (1) is filled with sample, including at least 3 vacuum cycles; Turn on the constant temperature furnace (6), set the heating temperature, and maintain it stable; The pressure of the sample to be tested is controlled to be near the target pressure by the first valve (8), the second valve (81), the third valve (83) and the air inlet tank, and the measurement begins after stabilization; Turn on the power supply to the hot wire, select the appropriate heating power, control the temperature rise, and take at least three measurements with an interval of at least 5 minutes between each measurement. Complete the thermal conductivity measurement; Repeat the steps to perform multiple measurements until the required experimental conditions are achieved.

7. The method for measuring the thermal conductivity of an unsteady high-temperature gas working fluid according to claim 6, characterized in that, The process of filling the sample chamber (1) with the sample specifically includes the following steps: Turn on the vacuum pump (9) and vacuum valve (82); Close the first valve (8) and the third valve (83) to evacuate the sample chamber (1); Once the vacuum level reaches the target value, turn off the vacuum pump (9) and open the air inlet tank; A small amount of the gas to be tested is introduced into the sample chamber (1) and kept for 10-15 minutes; The sample chamber (1) was evacuated again; Repeat the above steps at least 3 times; Calculate the residual impurities, and if the requirements are met, connect the gas to be tested. The gas to be tested flows into the sample chamber by gravity due to the pressure difference (1).

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