Method for measuring emissivity of high-temperature solid material

Abstract

The invention relates to the technical field of high-temperature solid material emissivity measurement, in particular to a high-temperature solid material emissivity measurement method, which comprises the following steps: S1, preparing a first to-be-measured sample by using a to-be-measured solid material; s2, placing the first to-be-tested sample in the middle of a hearth of the box-type electric furnace; s3, raising the temperature of the hearth and the first to-be-tested sample to T1, and keeping the temperature for a preset time length; s4, measuring the temperature of the first to-be-tested sample by using an infrared thermometer; s5, manufacturing a second to-be-tested sample by using a material used by the hearth; s6, placing a second to-be-tested sample in the middle of the hearth; s7, raising the temperature of the hearth and the second to-be-tested sample to T1, and keeping the temperature for a preset time length; and S8, measuring the temperature of the second to-be-tested sample by using an infrared thermometer. By adopting the measuring method, the internal temperature of the first to-be-measured sample and the internal temperature of the second to-be-measured sample are uniformly distributed, the influence of hearth reflection radiation on a measuring result is eliminated through a given algorithm, and the requirements for test conditions and the test cost are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-temperature solid material emissivity measurement, and in particular to a high-temperature solid material emissivity measurement method. BACKGROUND

[0002] The emissivity of the surface of a high-temperature solid material is an important parameter for measuring its thermal radiation capability, and directly affects the accuracy of heat transfer analysis, energy conversion and temperature measurement. In the fields of aerospace, energy and power, and steel metallurgy, it is crucial to accurately measure the emissivity of high-temperature (greater than 500℃) solid materials.

[0003] There are several existing methods for measuring the emissivity of high-temperature solid materials: first, the sample is heated from the back, and the thermal radiation energy of the front surface of the sample is measured. Since the front surface of the sample is exposed to the air, it dissipates heat to the air, so the temperature of the front surface of the sample is lower than that of the back surface. Especially for non-metallic solid materials such as ceramic materials, the thermal conductivity is poor, and the temperature difference between the front and back surfaces of the sample will be large. Second, the front and back surfaces of the sample are heated, and a test hole is reserved in the middle of the heating device. The temperature in the area where the test hole is located is higher than the air temperature, which dissipates heat to the air, also causing the temperature inside the sample to be uneven. Although the heating device is wrapped with thermal insulation material, the temperature on the side of the thermal insulation material facing the air will be higher than the air temperature, and the thermal radiation generated will be superimposed on the thermal radiation energy emitted by the sample, interfering with the accuracy of the thermal radiation measurement and causing large measurement errors. Moreover, the thermal radiation from the side edges of the test hole will be reflected to the radiometer by the sample, causing measurement errors.

[0004] The existing technical solutions in the above have the following defects: when measuring the emissivity of high-temperature solid materials using the existing high-temperature solid material emissivity measurement methods, the measurement error is large. SUMMARY

[0005] In order to reduce the measurement error, the present application provides a high-temperature solid material emissivity measurement method.

[0006] The present application provides a high-temperature solid material emissivity measurement method, which adopts the following technical solution: A high-temperature solid material emissivity measurement method, comprising: S1. using a to-be-tested solid material to make a first to-be-tested sample; S2. placing the first to-be-tested sample in the middle of the hearth of a box-type electric furnace; S3. raising the temperature of the hearth and the first to-be-tested sample to T1 and maintaining for a preset time; S4. measuring the temperature of the first to-be-tested sample using an infrared temperature measuring instrument; S5. using the material used for the hearth to make a second to-be-tested sample; S6. Placing the second sample to be tested in the middle of the furnace; S7. Raising the temperature of the furnace and the second sample to be tested to T1 and keeping for a preset time length; S8. Measuring the temperature of the second sample to be tested by using the infrared thermometer.

[0007] By using the above technical scheme, by using the above measurement method, the internal temperature distribution of the first sample to be tested and the second sample to be tested is uniform, and the heat loss is reduced, so that the first sample to be tested and the second sample to be tested can be heated to a higher test temperature. By using the given algorithm, the influence of the reflection radiation of the inner wall of the furnace on the measurement result is eliminated, and the influence of the edge thermal radiation of the test hole on the measurement result is eliminated, so that the measured emissivity of the high-temperature solid material to be tested is closer to the true reflectivity, and the measurement error is reduced. At the same time, the operation is relatively simple, the structure of the device used for measuring the emissivity of the high-temperature solid material is simplified, and it is not necessary to additionally install a cold plate or a shielding cover to isolate the furnace, and it is not necessary to additionally set a standard blackbody furnace as a reference, so that the requirements for the test conditions and the test cost are reduced. The reliability of the measurement is higher, and the measurement can be widely applied to the measurement of the emissivity of high-temperature solid materials in the fields of energy power, aerospace and the like.

[0008] The application is further provided that: in step S4, the emissivity of the infrared thermometer is adjusted, so that the brightness temperature T2 displayed on the infrared thermometer is equal to T1, and the apparent emissivity value of the infrared thermometer is recorded as ε1; according to the working principle of the infrared thermometer, it can be known that: wherein, ε S is the emissivity of the solid material to be tested, c1 is the first radiation constant, λ is the wavelength, c2 is the second radiation constant, T1 is the temperature in the furnace, T2 is the brightness temperature displayed on the infrared thermometer, F is the proportion of the inner wall emission radiation of the furnace that can reach the surface of the first sample to be tested, and ε f is the emissivity of the material used for the furnace.

[0009] The application is further provided that: in step S8, the emissivity of the infrared thermometer is adjusted, so that the brightness temperature T2 displayed on the infrared thermometer is equal to T1, and the apparent emissivity value of the infrared thermometer is recorded as ε2; according to the working principle of the infrared thermometer, it can be known that: wherein, c1 is the first radiation constant, λ is the wavelength, c2 is the second radiation constant, T1 is the temperature in the furnace, T2 is the brightness temperature displayed on the infrared thermometer, F ’ is the proportion of the inner wall emission radiation of the furnace that can reach the surface of the second sample to be tested, and ε f is the emissivity of the material used for the furnace.

[0010] This application further specifies that the first and second test samples have the same shape and size, and by derivation, F = F′ = 1 - F 12 Among them, F 12 The shape factor is the area of ​​one side of the first / second test sample relative to the area of ​​the test hole.

[0011] By adopting the above technical solution, F is first calculated, and then the emissivity ε of the material used in the furnace is calculated. f Then the emissivity ε of the solid material under test is calculated. s This is to eliminate measurement errors caused by reflected radiation from the inner wall of the furnace.

[0012] This application is further configured such that: a test hole is provided on the side of the box furnace near the infrared thermometer; In step S4, the lens of the infrared thermometer, the center of the test hole, and the center of the first test sample are aligned on the same straight line. In step S8, the lens of the infrared thermometer, the center of the test hole, and the center of the second test sample are aligned on the same straight line.

[0013] By adopting the above technical solutions, it is beneficial to improve measurement accuracy.

[0014] This application further specifies that: the first test sample, the second test sample, and the test hole are circular; the diameter of the test hole is 20-30 mm; the diameter of the first test sample and the diameter of the second test sample are the same, both being 10%-20% larger than the diameter of the test hole.

[0015] By adopting the above technical solutions, it is beneficial to improve measurement accuracy.

[0016] This application further specifies that: the distance between the surface of the first test sample / second test sample and the test hole is m; the distance between the side of the box furnace with the test hole and the opposite side is n; m / n = 1 / 3 - 1 / 2.

[0017] By adopting the above technical solution, it is beneficial to achieve a uniform internal temperature distribution of the first and second test samples, and also to reduce heat loss, which is conducive to heating the first and second test samples to a higher test temperature.

[0018] This application is further configured such that: in steps S3 and S7, a first preset flow rate of protective gas is continuously introduced into the furnace; In steps S4 and S8, a second preset flow rate of protective gas is continuously introduced into the furnace. The second preset flow rate is less than the first preset flow rate.

[0019] By adopting the above technical scheme, the protective gas can effectively prevent the high-temperature solid material from being oxidized, and the accuracy of the measurement is ensured.

[0020] The application is further configured to: before step S1, install a sample support for supporting and fixing the first test sample / the second test sample in the hearth.

[0021] To sum up, the application has the following beneficial technical effects: 1. By adopting the above measurement method, the internal temperature distribution of the first test sample and the second test sample is uniform, and the heat loss is reduced, so that the first test sample and the second test sample can be heated to a higher test temperature. By using the given algorithm, the influence of the inner wall reflection radiation of the hearth on the measurement result is eliminated, and the influence of the edge thermal radiation of the test hole on the measurement result is also eliminated, so that the measured emissivity of the high-temperature test solid material is closer to the true reflectivity, and the measurement error is reduced. At the same time, the operation is relatively simple, the structure of the device for measuring the emissivity of the high-temperature solid material is simplified, and there is no need to additionally install a cold plate or a shielding cover to isolate the hearth, and there is no need to additionally set a standard blackbody furnace as a reference, thereby reducing the requirements for the test conditions and the test cost.

[0022] 2. The protective gas is introduced, which can effectively prevent the high-temperature solid material from being oxidized, and the accuracy of the measurement is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a schematic view of the internal structure of the device for measuring the emissivity of the high-temperature solid material; Figure 2 is a flowchart of an embodiment of the method for measuring the emissivity of the high-temperature solid material.

[0024] Reference signs: 110, box-type electric furnace; 111, hearth; 112, test hole; 113, thermocouple; 120, infrared temperature measuring instrument; 130, sample support; 200, first test sample. DETAILED DESCRIPTION

[0025] The following will be described in detail with reference to the accompanying drawings Figures 1-2 The application will be further described in detail.

[0026] Reference Figure 1 and Figure 2 , the application discloses a method for measuring the emissivity of a high-temperature solid material, which comprises: S1. A first test sample 200 is made of a test solid material.

[0027] S2. The first test sample 200 is placed on a sample support 130 in the middle of the hearth 111 of the box-type electric furnace 110.

[0028] It should be noted that the whole furnace 111 is made of the same material, and the temperature of the inner wall of the whole furnace 111 is consistent when heated, and the temperature distribution in the furnace 111 is uniform. The first sample 200 is in the middle of the furnace 111, which realizes the purpose of simultaneous heating of the front and back, and is beneficial to the uniform distribution of the internal temperature of the first sample 200. At the same time, the heat loss is reduced, and the upper limit of the temperature of the first sample 200 is improved.

[0029] S3. The temperature of the furnace 111 and the first sample 200 is raised to T1 and maintained for a predetermined time.

[0030] It should be noted that when the temperature of the furnace 111 and the first sample 200 is raised to T1, it is maintained for more than 5 minutes to make the first sample 200 and the furnace 111 in a thermal equilibrium state.

[0031] S4. The temperature of the first sample 200 is measured using an infrared thermometer 120.

[0032] In this step, the emissivity of the infrared thermometer 120 is adjusted so that the brightness temperature T2 displayed on the infrared thermometer 120 is equal to T1, and the apparent emissivity value of the infrared thermometer 120 is recorded as ε1; according to the working principle of the infrared thermometer 120, it can be known that: Wherein, ε S is the emissivity of the solid material to be measured, c1 is the first radiation constant, λ is the wavelength, c2 is the second radiation constant, T1 is the temperature in the furnace 111, T2 is the brightness temperature displayed on the infrared thermometer 120, F is the share of the outcoming radiation of the inner wall of the furnace 111 that can reach the surface of the first sample 200, ε f is the emissivity of the material used in the furnace 111, the first term on the left side of formula (1) represents the thermal radiation energy of the first sample 200 at temperature T1 and wavelength λ, and the second term on the left side represents the thermal radiation energy of the outcoming radiation of the inner wall of the furnace 111 at temperature T1 and wavelength λ that is reflected by the surface of the first sample 200.

[0033] Since T1=T2, formula (1) can be simplified as: ε s +F(1-ε s )ε f =ε1 (2) S5. The second sample is made of the material used in the furnace 111.

[0034] S6. The second sample is placed in the middle of the furnace 111.

[0035] It should be noted that the second sample to be tested is in the middle of the furnace 111, which realizes the purpose of heating the front and back at the same time, and is beneficial to the uniform distribution of the internal temperature of the second sample to be tested. At the same time, the heat loss is reduced, and the upper limit of the temperature of the second sample to be tested is improved.

[0036] S7. The temperature of the furnace 111 and the second sample to be tested is raised to T1, and maintained for a preset time.

[0037] It should be pointed out that when the temperature of the furnace 111 and the second sample to be tested is raised to T1, it is maintained for more than 5 minutes, so that the second sample to be tested and the furnace 111 are in a state of thermal equilibrium.

[0038] S8. The temperature of the second sample to be tested is measured by using the infrared thermometer 120.

[0039] In this step, the emissivity of the infrared thermometer 120 is adjusted, so that the brightness temperature T2 displayed on the infrared thermometer 120 is equal to T1, and the apparent emissivity value of the infrared thermometer 120 is recorded as ε2; according to the working principle of the infrared thermometer 120, it can be known that: Where c1 is the first radiation constant, λ is the wavelength, c2 is the second radiation constant, T1 is the temperature in the furnace 111, T2 is the brightness temperature displayed on the infrared thermometer 120, F ’ is the share of the outcoming radiation of the inner wall of the furnace 111 that can reach the surface of the second sample to be tested, ε f is the emissivity of the material used by the furnace 111. The first term on the left side of formula (2) represents the thermal radiation energy of the second sample to be tested at temperature T1 and wavelength λ, and the second term on the left side represents the thermal radiation energy of the outcoming radiation of the inner wall of the furnace 111 at temperature T1 and wavelength λ, which is reflected by the surface of the second sample to be tested.

[0040] Since T1=T2, formula (2) can be simplified as: ε f +F′(1-ε f )ε f =ε2 (4) The shape and size of the first sample to be tested 200 and the second sample to be tested are the same, and it is deduced that F=F′=1-F 12 (5) Where F 12 is the shape factor of the area of one side of the first sample to be tested 200 / second sample to be tested to the area of the test hole 112.

[0041] Wherein, r1 is the radius of the first sample 200 / the second sample, r2 is the radius of the test hole 112. m is the distance between the surface of the first sample 200 / the second sample and the test hole 112.

[0042] R1 can be calculated by formula (8), R2 can be calculated by formula (9), X can be calculated by formula (7), and F can be calculated by formula (6) 12 , and then F and F can be calculated by formula (5) ’ , and then the emissivity ε of the material of the furnace 111 can be calculated by formula (4) f , and then the emissivity ε of the solid material to be measured can be calculated by formula (2) s .

[0043] By using the above measurement method, the internal temperature distribution of the first sample 200 and the second sample is uniform, and the heat loss is reduced, so that the first sample 200 and the second sample can be heated to a higher test temperature (above 1500℃). By using the given algorithm, the influence of the reflection of the inner wall of the furnace 111 on the measurement result is eliminated, and the influence of the thermal radiation of the edge of the test hole 112 on the measurement result is eliminated, so that the measured emissivity of the high-temperature solid material to be measured is closer to the true reflectivity, and the measurement error is reduced. At the same time, the operation is simple, the structure of the device for measuring the emissivity of the high-temperature solid material is simplified, and there is no need to additionally install a cold plate or a shielding cover to isolate the furnace 111, and there is no need to additionally set a standard blackbody furnace as a reference, so that the requirements for the test conditions and the test cost are reduced. The reliability of the measurement is higher, and the measurement can be widely applied to the measurement of the emissivity of high-temperature solid materials in the fields of energy power, aerospace, etc.

[0044] In one embodiment, as shown in Figure 1 , the box-type electric furnace 110 is provided with a test hole 112 on one side close to the infrared temperature measuring instrument 120. The box-type electric furnace 110 is provided with a thermocouple 113 for observing the temperature in the furnace. The first sample 200, the second sample, and the test hole 112 are circular. The diameter of the test hole 112 is 20mm, 25mm, or 30mm. The diameter of the first sample 200 is the same as that of the second sample, and is 10%-20% larger than the diameter of the test hole 112. In this way, the measurement accuracy is improved. The distance between the surface of the first sample 200 / the second sample and the test hole 112 is m. The distance between the side of the box-type electric furnace 110 provided with the test hole 112 and the opposite side is n. m / n=1 / 3-1 / 2. This is beneficial to the uniformity of the internal temperature distribution of the first sample 200 and the second sample, reduces the heat loss, and is beneficial to the first sample 200 and the second sample being heated to a higher test temperature.

[0045] In one embodiment, the lens of the infrared thermometer 120, the center of the test hole 112 and the center of the first sample to be tested 200 are aligned in step S4. In step S8, the lens of the infrared thermometer 120, the center of the test hole 112 and the center of the second sample to be tested are aligned. In this way, the measurement accuracy is improved. In steps S3 and S7, the first preset flow of protective gas is continuously introduced into the furnace 111. In steps S4 and S8, the second preset flow of protective gas is continuously introduced into the furnace 111. The protective gas can be nitrogen, argon, etc., which can effectively prevent the high-temperature solid material from being oxidized, and ensure the accuracy of the measurement. The second preset flow should be less than the first preset flow, reducing the heat carried away by the flowing protective gas during measurement, and avoiding uneven temperature distribution inside the furnace 111.

[0046] In one embodiment, before step S1, the sample support 130 for supporting and fixing the first sample to be tested 200 / second sample to be tested is installed in the furnace 111, so as to support and fix the first sample to be tested 200 / second sample to be tested.

[0047] The implementation principle of the embodiment is: by using the above measurement method, the internal temperature distribution of the first sample to be tested 200 and the second sample to be tested is uniform, and the heat loss is reduced, so that the first sample to be tested 200 and the second sample to be tested can be heated to a higher test temperature. By using the given algorithm, the influence of the reflected radiation of the furnace 111 on the measurement result is eliminated, and the influence of the edge thermal radiation of the test hole 112 on the measurement result is also eliminated, so that the measured emissivity of the high-temperature solid material to be tested is closer to the true reflectivity, and the measurement error is reduced. At the same time, the operation is relatively simple, the structure of the device used for measuring the emissivity of the high-temperature solid material is simplified, and there is no need to additionally install a cold plate or a shielding cover to isolate the furnace 111, and there is no need to set a standard blackbody furnace as a reference, thereby reducing the requirements for the test conditions and the test cost. The measurement is more reliable, and can be widely applied to the measurement of the emissivity of high-temperature solid materials in the fields of energy power, aerospace, etc.

[0048] The embodiments of the specific implementation are the preferred embodiments of the present application, but do not limit the protection scope of the present application, so that: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method of measuring the emissivity of a high temperature solid material, characterized in that, The method comprises the following steps: S1. preparing a first test sample from the solid material to be tested; S2. placing the first test sample in the middle of the hearth of a box-type electric furnace; S3. raising the temperature of the hearth and the first test sample to T1 and keeping for a preset time; S4. measuring the temperature of the first test sample by using an infrared thermometer; S5. preparing a second test sample from the material used for the hearth; S6. placing the second test sample in the middle of the hearth; S7. raising the temperature of the hearth and the second test sample to T1 and keeping for a preset time; S8. measuring the temperature of the second test sample by using the infrared thermometer.

2. The method of claim 1, wherein In step S4, the emissivity of the infrared thermometer is adjusted so that the brightness temperature T2 displayed on the infrared thermometer is equal to T1, and the apparent emissivity value of the infrared thermometer is recorded as ε1; according to the working principle of the infrared thermometer, it is known that: wherein ε S is the emissivity of the solid material to be measured, c1 is the first radiation constant, λ is the wavelength, c2 is the second radiation constant, T1 is the temperature in the furnace, T2 is the brightness temperature shown on the infrared thermometer, is the fraction of the radiation emitted by the inner wall of the furnace which reaches the surface of the first sample to be tested, and ε f is the emissivity of the material of the furnace.

3. The method for measuring the emissivity of high-temperature solid materials according to claim 2, characterized in that, In step S8, the emissivity of the infrared thermometer is adjusted so that the brightness temperature T2 displayed on the infrared thermometer is equal to T1, and the apparent emissivity value of the infrared thermometer is recorded as ε2; according to the working principle of the infrared thermometer, it is known that: wherein c1 is a first radiation constant, λ is the wavelength, c2 is a second radiation constant, T1 is the temperature inside the furnace, T2 is the brightness temperature shown on the infrared thermometer, F ’ is the fraction of the emitted radiation of the inner wall of the furnace which reaches the surface of the second sample to be tested, ε f is the emissivity of the material used for the furnace.

4. The method for measuring the emissivity of high-temperature solid materials according to claim 3, characterized in that, The first test sample and the second test sample have the same shape and size, and it is deduced that F = F' = 1 - F 12 wherein F 12 is the shape factor of the area of one side of the first sample under test / the second sample under test to the area of the test hole.

5. The method of claim 1, wherein The box-type electric furnace is provided with a test hole on the side close to the infrared thermometer; In step S4, the lens of the infrared thermometer, the center of the test hole, and the center of the first test sample are on the same straight line; In step S8, the lens of the infrared thermometer, the center of the test hole, and the center of the second test sample are on the same straight line.

6. The method for measuring the emissivity of high-temperature solid materials according to claim 5, characterized in that, The first test sample, the second test sample, and the test hole are circular; the diameter of the test hole is 20-30 mm; the diameter of the first test sample is the same as that of the second test sample, and both are 10%-20% larger than the diameter of the test hole.

7. The method for measuring the emissivity of high-temperature solid materials according to claim 5, characterized in that, The distance between the surface where the first / second test sample is located and the test hole is m; the distance between the side of the box-type electric furnace where the test hole is provided and the opposite side is n; m / n = 1 / 3-1 / 2.

8. The method of claim 1, wherein In steps S3 and S7, a first preset flow rate of protective gas is continuously introduced into the hearth; In steps S4 and S8, a second preset flow rate of the protective gas is continuously introduced into the hearth; The second preset flow rate is smaller than the first preset flow rate.

9. The method of claim 1, wherein Before step S1, a test sample support for supporting and fixing the first / second test sample is installed in the hearth.

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