Device and method for measuring thermal properties of low-temperature vacuum ice-containing lunar regolith simulant

Abstract

The present invention provides a device and method for measuring the thermal properties of cryogenic vacuum ice-containing lunar soil simulants, belonging to the field of thermal measurement. It solves the problem that the existing equipment for measuring thermal properties cannot measure the thermal properties of ice-containing lunar soil simulants in a low-temperature and vacuum environment. It includes an environmental prefabrication module, a measurement module, a heating module, and a temperature data acquisition module. The environmental prefabrication module includes a refrigerator, a sample chamber, and a vacuum pump. The refrigerator is arranged inside the sample chamber, and the vacuum pump is connected to the sample chamber. The measurement module includes a sample rack, heating wires, and heat-sensitive wires. The sample rack is fixed inside the sample chamber and is connected to the refrigerator. The ice-containing lunar soil simulants to be measured are arranged inside the sample rack. The heating wires and the heat-sensitive wires are arranged in parallel inside the sample rack, and temperature sensors are arranged on both the heating wires and the heat-sensitive wires. The heating module is connected to the heating wires, and the temperature data acquisition module is connected to the temperature sensors. It is mainly used for measuring the thermal properties of ice-containing lunar soil simulants.

Description

Technical Field

[0001] The present invention belongs to the field of thermal measurement, and particularly relates to a device and method for measuring the thermal properties of a low-temperature vacuum ice-containing lunar soil simulant. Background Art

[0002] Among the existing devices for laboratory measurement of thermal properties on the market, those using the steady-state method are fewer, and the measurement principles can be roughly divided into the heat flow meter method, the guarded hot plate method, and the double hot plate method; there are more devices using the transient method, and its measurement principles are mostly the transient plane source method and the laser flash method.

[0003] However, the measurement range of the existing thermal property measurement devices is difficult to meet the measurement requirements of the simulated lunar soil, and there is a large gap between the measurement environment and the real environment, and the actual heat transfer form of the lunar soil in a low-temperature and vacuum environment cannot be simulated. Summary of the Invention

[0004] In view of this, the present invention aims to provide a device and method for measuring the thermal properties of a low-temperature vacuum ice-containing lunar soil simulant to solve the problem that the existing devices for measuring thermal properties cannot measure the thermal properties of the ice-containing lunar soil simulant in a low-temperature and vacuum environment.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A device for measuring the thermal properties of a low-temperature vacuum ice-containing lunar soil simulant, which includes an environmental prefabrication module, a measurement module, a heating module, and a temperature data acquisition module. The environmental prefabrication module includes a refrigerator, a sample chamber, and a vacuum pump. The refrigerator is arranged in the sample chamber, and the vacuum pump is connected to the sample chamber. The measurement module includes a sample rack, heating wires, and sensing wires. The sample rack is fixed inside the sample chamber, and the sample rack is connected to the refrigerator. The sample rack is provided with a measured lunar soil simulant. The heating wires and the sensing wires are arranged in parallel in the sample rack, and temperature sensors are arranged on both the heating wires and the sensing wires. The heating module is connected to the heating wires, and the temperature data acquisition module is connected to the temperature sensors.

[0006] Furthermore, the refrigerator is connected to a temperature controller.

[0007] Furthermore, the sample rack is connected to the refrigerator through a sample rack cover, and the sample rack cover is made of brass.

[0008] Furthermore, the heating module is a controllable DC power supply.

[0009] Furthermore, the temperature data acquisition module includes a temperature transmitter and a computer. The temperature transmitter is connected to the temperature sensor for signal transmission, and the temperature transmitter is connected to the computer for communication.

[0010] Further, the temperature sensor is fixed to the heating wire and the heat-sensing wire by means of adhesion.

[0011] Further, the sample holder is made of polytetrafluoroethylene.

[0012] Further, both the heating wire and the heat-sensing wire are made of nickel-chromium alloy wire.

[0013] Further, the temperature sensor is a platinum resistance.

[0014] The present invention also provides a method for measuring the thermal properties of a cryogenic vacuum ice-containing lunar soil simulant, which includes the following steps:

[0015] Step 1: Place the lunar soil simulant to be measured in the sample holder, adjust the environmental prefabrication module to make the temperature and pressure in the sample chamber reach the set range, and wait for the lunar soil simulant to be measured to reach a thermal steady state;

[0016] Step 2: Set the output current and output voltage of the controllable DC power supply to ensure a constant current output, heat the lunar soil simulant to be measured, and observe the temperature rise curve through the temperature data acquisition module;

[0017] Step 3: Stop heating, wait for the heat-sensing wire to reach the maximum temperature rise, and export the experimental data;

[0018] Step 4: Wait for the lunar soil simulant to be measured to return to the initial temperature, repeat Step 2 and Step 3 multiple times, and take the average value of the calculation results.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention can measure the thermal properties of an ice-containing lunar soil simulant under low-temperature and vacuum conditions, with a fast measurement speed, about 5 minutes for the measurement time, good measurement accuracy, and the measurement accuracy can be further improved after calibration. The measurement temperature range is relatively wide, up to -200°C - 100°C, and the measurement vacuum degree is large, and the lowest air pressure can reach 0.75 Pa, which provides a favorable help for the research on the thermal properties of ice-containing lunar soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0021] Figure 1 is a schematic structural diagram of a device for measuring the thermal properties of a cryogenic vacuum ice-containing lunar soil simulant according to the present invention;

[0022] Figure 2 is a schematic structural diagram of the measurement module according to the present invention;

[0023] Figure 3 is a schematic diagram of the working principle of the measurement module according to the present invention;

[0024] Figure 4 System error diagram of thermal conductivity inversion with different thermal conductivities according to the present invention;

[0025] Figure 5 System error diagram of thermal conductivity inversion with different specific heat capacities according to the present invention;

[0026] Figure 6 System error diagram of specific heat capacity inversion with different thermal conductivities according to the present invention.

[0027] 1 - Refrigerator, 2 - Sample chamber, 3 - Sample rack, 4 - Sample rack cover, 5 - Vacuum pump, 6 - Temperature controller, 7 - Controllable DC power supply, 8 - Temperature transmitter, 9 - Computer, 10 - Heating wire, 11 - Heat sensing wire, 12 - Temperature sensor, 13 - Simulated lunar soil sample to be measured. Detailed implementation manner

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0029] See Figures 1-6 Describing this embodiment, a device for measuring the thermal properties of a low - temperature vacuum ice - containing simulated lunar soil includes an environmental pre - treatment module, a measurement module, a heating module, and a temperature data acquisition module. The environmental pre - treatment module includes a refrigerator 1, a sample chamber 2, and a vacuum pump 5. The refrigerator 1 is arranged inside the sample chamber 2, and the vacuum pump 5 is connected to the sample chamber 2. The measurement module includes a sample rack 3, a heating wire 10, and a heat sensing wire 11. The sample rack 3 is fixed inside the sample chamber 2, and the sample rack 3 is connected to the refrigerator 1. A simulated lunar soil sample 13 to be measured is arranged inside the sample rack 3. The heating wire 10 and the heat sensing wire 11 are arranged in parallel inside the sample rack 3, and temperature sensors 12 are arranged on both the heating wire 10 and the heat sensing wire 11. The heating module is connected to the heating wire 10, and the temperature data acquisition module is connected to the temperature sensor 12.

[0030] The environmental prefabrication module in this embodiment is used to provide a low-temperature and vacuum measurement environment. The refrigerator 1 is connected to the temperature controller 6, and the temperature of the refrigerator is controlled through the temperature controller 6. The sample holder 3 is connected to the refrigerator 1 through the sample holder cover 4. The measurement module is fixed in the sample chamber 2 through the sample holder cover 4 by means of threaded connection, while heat exchange is carried out and the measured lunar soil simulant 13 is refrigerated. The temperature sensor 12 is fixed on the heating wire 10 and the sensing wire 11 by means of adhesion. The heating module is a controllable DC power supply 7, which is used to make the heating wire 10 pass through a constant current, so that it heats the measured lunar soil simulant 13 at a constant power. The temperature data acquisition module includes a temperature transmitter 8 and a computer 9. The temperature transmitter 8 is connected to the temperature sensor 12 for signal transmission, and the temperature transmitter 8 is communicatively connected to the computer 9, which is used to monitor and record the temperature data of the temperature sensor 12, and to invert the thermal properties of the measured lunar soil simulant 13 through the interpretation of the temperature data.

[0031] The working principle of the measurement module is as Figure 3 shown. In the environment of the measured lunar soil simulant 13 in a thermal equilibrium state, a constant power is applied to the heating wire 10, and the heating wire 10 and the surrounding measured medium will generate a temperature rise. The single-wire method and the double-wire method in the transient hot-wire method are used to invert the temperature data of the heating wire 10 and the sensing wire 11, so as to obtain the thermal properties of the measured lunar soil simulant 13.

[0032] The environmental prefabrication module adopts an ultra-low temperature lunar soil water ice physical property measurement system, which consists of a temperature control system and a vacuum system. It can be in a sample space of 60mm×60mm×60mm, and the temperature control range is between 10K - 300K, which can cover the temperature range from the lunar polar region to room temperature; the air pressure control range is between 10 -2 Pa - 10 5 Pa. It is fixed on the cold head of the refrigerator 1 through a specific sample holder 3, and physical property parameter measurement experiments such as heat, force, electricity, light, and magnetism can be carried out in this system.

[0033] The measurement module uses a sample holder 3 and a sample holder cover 4 made of brass. The heating wire 10 and the sensing wire 11 are both made of nickel-chromium alloy wire with a diameter of 0.15mm, and the temperature sensor 12 is a Pt100-M213A platinum resistance

[0034] The heating module selects a controllable DC power supply MS-155D to provide a constant current. The output range of its voltage is 0 - 15V, and the output range of its current is 0 - 5A, meeting the requirements of the thermal physical property measurement experiment of the ice-containing lunar soil simulant.

[0035] The temperature data acquisition module uses a THMA paperless recorder to read the temperature data, and then transmits it to the computer 9 for real-time display and monitoring.

[0036] This embodiment is a method for measuring the thermal properties of a low-temperature vacuum ice-containing lunar soil simulant, which includes the following steps:

[0037] Step 1: Place the lunar soil simulant 13 to be measured in the sample holder 3, adjust the environmental prefabrication module to make the temperature and pressure in the sample chamber 2 reach the set range, and wait for the lunar soil simulant 13 to reach a thermal steady state;

[0038] Step 2: Set the output current and output voltage of the controllable DC power supply 7 to ensure a constant current output, heat the lunar soil simulant 13 to be measured, and observe the temperature rise curve through the temperature data acquisition module;

[0039] Step 3: Stop heating, wait for the sensing wire 11 to reach the maximum temperature rise, and export the experimental data;

[0040] Step 4: Wait for the lunar soil simulant 13 to be measured to return to the initial temperature, repeat Step 2 and Step 3 multiple times, and take the average value of the calculation results.

[0041] The key points of the measurement module lie in the material selection and the control of measurement errors. The sample holder 3 is made of polytetrafluoroethylene, the sample holder cover 4 is made of brass, the heating wire 10 and the sensing wire 11 are both made of nickel-chromium alloy wire, and the temperature sensor 12 is a platinum resistance (Pt100). The above material selections are used as simulation inputs to conduct simulation studies on the measured media with different thermal properties.

[0042] First, conduct simulations on the measured media with different thermal conductivities, and calculate the difference in the thermal conductivity inversion system. The thermal conductivity ranges from 0.001 - 1 W / (m·K), the density is 1.6×10 3 kg / m 3 , and the specific heat capacity is 1000 J / (kg·°C). Figure 4 This is the calculation result of the systematic error. It can be analyzed from the image that: 1. When measuring the temperature of the heating wire 10 and the sensing wire 11 and the platinum resistance pasted on the heating wire 10 and the sensing wire 11 respectively, the errors of the inverted thermal conductivity are similar, and the temperature rise of the platinum resistance can be used to replace the temperature rise of the hot wire; 2. The measurement error of the single-wire method is smaller than that of the double-wire method. For the simulated lunar soil samples with lower thermal conductivity and smaller sizes, the heat capacities of the sensing wire 11 and the platinum resistance cannot be ignored, and there is a certain difference between their temperature changes and the temperature changes of the theoretical temperature measurement points, resulting in a larger measurement error for the double-wire method.

[0043] Next, conduct simulations on the measured media with different specific heat capacities, and calculate the systematic error of the thermal conductivity inversion. The specific heat capacity ranges from 300 - 1100 J / (kg·°C), the thermal conductivity is 0.01 W / (m·K), and the density is 1.6×10 3 kg / m 3 . Figure 5This is the calculation result of the systematic error. It can be analyzed from the image that as the specific heat capacity of the measured medium increases, the measurement error increases continuously, and this is more obvious for the double-line method. The reason is still that as the specific heat capacity increases, the thermal diffusivity decreases, resulting in the temperature change of the platinum resistance on the sensing line 11 preceding that of the sensing line 11. Therefore, the difference between the temperature changes of the sensing line 11 and the platinum resistance on it and the temperature change of the theoretical temperature measurement point becomes larger, thus bringing a larger error.

[0044] Finally, simulations are carried out on the measured media with different thermal conductivities to calculate the systematic error of the specific heat capacity inversion. The thermal conductivity ranges from 0.001 to 0.1 W / (m·K), the density is 1.6×10 3 kg / m 3 , and the specific heat capacity is 1000 J / (kg·°C). Figure 6 This is the calculation result of the systematic error. It can be analyzed from the image that for the measurement of the specific heat capacity of the test sample, the accuracy of the double-line method is higher than that of the single-line method. The reason is that a part of the heating power of the heating line 10 is used for the heating of the heating wire itself. The accuracy of the specific heat capacity inversion by the single-line method is greatly affected by the heat capacity of the heating line 10 itself, while the double-line method inversion is related to the entire heating process and is less affected by the heat capacity of the heating wire. Therefore, the error of the specific heat capacity inverted by the single-line method is larger than that of the double-line method.

[0045] In summary, for the transient hot-wire method experimental bench that has been set up, the error of the thermal conductivity inversion by the single-line method is smaller than that of the double-line method, and when the thermal conductivity of the measured medium is about 0.01 W / (m·K), the measurement error is smaller; the error of the specific heat capacity inversion by the double-line method is smaller and the error change is smaller. Therefore, through the simulation study of the measurement error of the measurement module, the inversion strategy of using the single-line method to invert the thermal conductivity and the double-line method to invert the specific heat capacity is determined.

[0046] The measurement accuracy can be further improved through the calibration experiment. The process of the calibration experiment is as follows: Select water (5% agar) and aerogel felt as the calibration materials. The thermal conductivity of the aerogel felt is measured by a Hotdisk thermal conductivity meter, and the specific heat capacity is measured by the DSC sapphire method. Its thermal parameters at 20°C room temperature and 101 kPa are shown in Table 1. The thermal conductivities of the above two calibration materials cover the range of 10 -2 -10 -1 W / (m·K), and there is no convection influence.

[0047] Table 1 Thermal parameters of calibration materials (20°C, 101 kPa)

[0048]

[0049] The calibration experiment sets three heating parameters: the temperature rise of heating wire 10 is 10 K, the temperature rise of the platinum resistor of the heating wire is 10 K, and the temperature rise of the platinum resistor of the heating wire is 5 K. Through simulation, the heating power and heating time of 6 groups of experiments are determined. The calibration experiment is carried out under the conditions of 20 °C and 101 kPa. The average results of the thermal property inversion of 3 groups of calibration experiments for each material are shown in Table 2. The calibration equation set is as follows:

[0050] λ 标 = 0.9152λ 单 - 0.0022

[0051] C 标 = 0.8911C 双 - 0.1106

[0052] Table 2 Calibration experiment results

[0053]

[0054] This embodiment is an experiment for measuring the thermal properties of an ice-containing lunar soil simulant. Two kinds of lunar soil simulants with different ice contents are set: a dry lunar soil simulant and a lunar soil simulant with an ice content of 10%; two extreme measurement environments are set: 80 K, 10 -1 Pa (low temperature and low pressure) and 300 K, 10 5 Pa (normal temperature and normal pressure). When preparing the samples, the density of the ice-containing lunar soil simulant is controlled to be 1.5×10 3 kg / m 3 . The inversion results of the thermal property measurement of the ice-containing lunar soil simulant are shown in Table 3, and the calibrated thermal parameters are shown in Table 4.

[0055] Table 3 Measurement results of the thermal properties of the ice-containing lunar soil simulant

[0056]

[0057] Table 4 Calibration results of the thermal properties of the ice-containing lunar soil simulant

[0058]

[0059] The embodiments of the present invention disclosed above are only used to help explain the present invention. The embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. According to the content of this specification, many modifications and changes can be made. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can understand and utilize the present invention well.

Claims

1. A device for measuring the thermal properties of a low-temperature vacuum ice-containing lunar soil simulant, characterized in that: It includes an environmental prefabrication module, a measurement module, a heating module, and a temperature data acquisition module. The environmental prefabrication module includes a refrigerator (1), a sample chamber (2), and a vacuum pump (5). The refrigerator (1) is arranged inside the sample chamber (2), and the vacuum pump (5) is connected to the sample chamber (2). The measurement module includes a sample rack (3), a heating wire (10), and a heat-sensitive wire (11). The sample rack (3) is fixed inside the sample chamber (2), and the sample rack (3) is connected to the refrigerator (1). The sample rack (3) is provided with a measured lunar soil simulant (13). The heating wire (10) and the heat-sensitive wire (11) are arranged in parallel inside the sample rack (3), and temperature sensors (12) are arranged on both the heating wire (10) and the heat-sensitive wire (11). The temperature sensors (12) are platinum resistors. The heating wire (10) is connected to the heating module, so that the heating wire (10) and the surrounding measured lunar soil simulant (13) will generate a temperature rise, and the heat-sensitive wire (11) will also generate a temperature rise change accordingly. The temperature data acquisition module is connected to the temperature sensors (12).

2. A device for measuring the thermal properties of a low-temperature vacuum ice-containing lunar soil simulant according to claim 1, characterized in that: The refrigerator (1) is connected to a temperature controller (6).

3. A device for measuring the thermal properties of a low-temperature vacuum ice-containing lunar soil simulant according to claim 1, characterized in that: The sample rack (3) is connected to the refrigerator (1) through a sample rack cover (4), and the sample rack cover (4) is made of brass.

4. A device for measuring the thermal properties of a low-temperature vacuum ice-containing lunar soil simulant according to claim 1, characterized in that: The heating module is a controllable DC power supply (7).

5. A device for measuring the thermal properties of a low-temperature vacuum ice-containing lunar soil simulant according to claim 1, characterized in that: The temperature data acquisition module includes a temperature transmitter (8) and a computer (9). The temperature transmitter (8) is connected to the temperature sensors (12) for signal transmission, and the temperature transmitter (8) is communicatively connected to the computer (9).

6. A device for measuring the thermal properties of a low-temperature vacuum ice-containing lunar soil simulant according to claim 1, characterized in that: The temperature sensors (12) are fixed on the heating wire (10) and the heat-sensitive wire (11) by means of adhesion.

7. A device for measuring the thermal properties of a low-temperature vacuum ice-containing lunar soil simulant according to claim 1, characterized in that: The sample rack (3) is made of polytetrafluoroethylene.

8. A device for measuring the thermal properties of a low-temperature vacuum ice-containing lunar soil simulant according to claim 1, characterized in that: Both the heating wire (10) and the heat-sensitive wire (11) are nickel-chromium alloy wires.

9. A measurement method for a device for measuring the thermal properties of a low-temperature vacuum ice-containing lunar soil simulant as claimed in claim 1, characterized in that: It includes the following steps: Step 1: Place the simulated lunar soil sample to be measured (13) in the sample holder (3), arrange the heating wire (10) and the temperature-sensing wire (11) in parallel in the sample holder (3), adjust the environmental prefabrication module to make the temperature and air pressure in the sample chamber (2) reach the set range, and wait for the simulated lunar soil sample to be measured (13) to reach thermal steady state; Step 2: Set the output current and output voltage of the controllable DC power supply (7) to ensure a constant current output to the heating wire (10), heat the simulated lunar soil sample to be measured (13), and observe the temperature rise curve of the platinum resistor on the heating wire (10) through the temperature data acquisition module; Step 3: Stop heating the heating wire (10), wait for the platinum resistor on the temperature-sensing wire (11) to reach the maximum temperature rise, and export the experimental data; Step 4: Wait for the simulated lunar soil sample to be measured (13) to return to the initial temperature, repeat Step 2 and Step 3 multiple times, take the average value of the calculation results, obtain the thermal conductivity of the simulated lunar soil sample to be measured (13) using the single-line method of the transient hot wire method, and obtain the specific heat capacity of the simulated lunar soil sample to be measured (13) using the double-line method of the transient hot wire method.

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