A method for measuring the infrared emissivity of a transparent medium hemisphere

Abstract

The present invention provides a method for measuring the hemispherical infrared emissivity of a transparent medium, and the steps are as follows: establishing a model for measuring the hemispherical infrared emissivity of a transparent material by a radiometer; selecting materials with different infrared emissivities as base materials and measuring the hemispherical infrared emissivity of the base materials; preparing a transparent or translucent material into a sheet sample; using different base materials as bases, respectively, using a radiometer to measure the hemispherical infrared emissivity of different surfaces of the sample, and obtaining a hemispherical infrared emissivity measurement value; substituting the hemispherical infrared emissivity of the base material and the hemispherical infrared emissivity measurement value of the sample surface into the model for measuring the hemispherical infrared emissivity of the transparent material by the radiometer for solving, and obtaining the infrared radiation parameters of the transparent medium sample. The present invention adopts a radiometer as a measuring device, and can realize the measurement of double-sided infrared radiation parameters of transparent or translucent materials under normal temperature conditions, and has the advantages of simple measurement method, low measurement cost, and high measurement accuracy.

Description

Technical Field

[0001] The invention belongs to the field of infrared thermal radiation measurement, and in particular relates to a method for measuring the infrared emissivity of a transparent medium hemisphere. Background Art

[0002] For infrared thermal radiation measurement of transparent or translucent materials, the spectral method is commonly used. The spectrophotometer emits light of different wavelengths, measures the transmittance, reflectivity and other parameters of the material to different spectra, and then integrates them to obtain the infrared radiation parameters of the material. The maximum wavelength of light emitted by the current mainstream spectrophotometer is 25μm. According to Planck's law, the wavelength with the largest spectral radiation power of an object at room temperature is about 10μm, and the infrared radiation power in the range of <25μm accounts for about 83% of the total infrared radiation power. For gray body materials whose spectral radiation parameters are independent of wavelength, the accuracy of this test method is sufficient to meet the needs of engineering applications. If the radiation parameters of the material change significantly with wavelength, 17% of the infrared radiation energy cannot be tested by this test method, so the accuracy of the test results cannot be guaranteed. Summary of the invention

[0003] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art, to provide a method for measuring the hemispherical infrared emissivity of a transparent medium, and to solve the problem of insufficient accuracy in measuring infrared radiation parameters of transparent or semi-transparent materials at room temperature.

[0004] The technical solution of the present invention is:

[0005] A method for measuring the hemispherical infrared emissivity of a transparent medium comprises the following steps:

[0006] 1) Establish a radiometer model to measure the hemispherical infrared emissivity of transparent materials;

[0007] 2) Select three materials with different infrared emissivity as base materials, namely base material A, base material B and base material C;

[0008] 3) Measure the hemispherical infrared emissivity of base material A, base material B, and base material C;

[0009] 4) Prepare a transparent or translucent material into a sheet sample, and mark the upper and lower surfaces of the sample as surface 1 and surface 2 respectively;

[0010] 5) Using substrate material A, substrate material B, and substrate material C as substrates, respectively, a radiometer is used to measure the hemispherical infrared emissivity of sample surface 1 and surface 2 when facing upward, respectively, to obtain the measured value of the hemispherical infrared emissivity of the sample;

[0011] 6) Using the measurement results of step 3) and step 5) in combination with a radiometer to measure the hemispherical infrared emissivity model of transparent materials, the infrared radiation parameters of the sample are obtained.

[0012] Preferably, in step 1), the model of the hemispherical infrared emissivity of the transparent material measured by the radiometer is specifically:

[0013]

[0014] Among them, ε a is the measured value of the hemispherical infrared emissivity of a transparent material measured using a radiometer, ε m1 is the hemispherical infrared emissivity of the transparent material’s upward surface, ε m2 is the hemispherical infrared emissivity of the transparent material’s surface facing downward, τ m1 is the infrared transmittance of light passing through the transparent material from top to bottom, τ m2 is the infrared transmittance of light passing through a transparent material from bottom to top, ε b is the infrared emissivity of the substrate material, k = L(T e ) / L 0 (T), where L 0 (T) is the infrared radiation intensity of the black body at temperature T, in W / (m 2 K), L(T e ) is the temperature T e When the infrared radiation intensity of the radiometer hemispherical absorption cover to the sample is W / (m 2 K).

[0015] Preferably, the infrared radiation parameters of the sample are obtained by combining the measurement results of step 3) and step 5) with a radiometer to measure the hemispherical infrared emissivity model of the transparent material:

[0016] Substituting the measurement results of step 3) and step 5) into the radiometer model for measuring the hemispherical infrared emissivity of transparent materials, the following expression is obtained:

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023] Among them, ε A1is the measured value of hemispherical infrared emissivity with base material A as the base and sample surface 1 facing upward, ε A2 is the measured value of hemispherical infrared emissivity with base material A as the base and sample surface 2 facing upward, ε B1 is the measured value of hemispherical infrared emissivity with base material B as the base and sample surface 1 facing upward, ε B2 is the measured value of hemispherical infrared emissivity with base material B as the base and sample surface 2 facing upward, ε C1 is the measured value of hemispherical infrared emissivity with base material C as the base and sample surface 1 facing upward, ε C2 is the measured value of hemispherical infrared emissivity with base material C as the base and sample surface 2 facing upward, ε s1 is the hemispherical infrared emissivity of the sample surface 1, ε s2 is the hemispherical infrared emissivity of the sample surface 2, τ s1 is the hemispherical infrared transmittance when light enters from sample surface 1 and exits from surface 2, τ s2 is the hemispherical infrared transmittance when light enters from sample surface 2 and exits from surface 1, ε A is the infrared emissivity of the substrate material A, ε B is the infrared emissivity of the base material B, ε C is the infrared emissivity of the base material C;

[0024] Select any five equations from the above expressions and solve them to obtain the infrared radiation parameter ε of the transparent medium sample. s1 , ε s2 , τ s1 , τ s2 .

[0025] Preferably, the infrared emissivity ε of the base material A is A ≤0.1.

[0026] Preferably, the infrared emissivity ε of the base material B is B ≥0.85.

[0027] Preferably, the infrared emissivity of the base material C is 0.3≤ε C ≤0.7.

[0028] Preferably, the thickness of the transparent medium sample is less than or equal to 5 mm.

[0029] Preferably, the ambient temperature for measuring the hemispherical infrared emissivity in step 3) or step 5) is 15°C to 35°C.

[0030] Preferably, the measurement accuracy of the radiometer is better than 0.015.

[0031] Preferably, the hemispherical infrared emissivity of the hemispherical absorption cover of the radiometer is not less than 0.9.

[0032] The advantages of the present invention compared with the prior art are:

[0033] The present invention provides a method for measuring the hemispherical infrared emissivity of a transparent medium. The method analyzes the energy transfer relationship in the cavity of a radiometer when the hemispherical infrared emissivity of a transparent or translucent material is measured by a radiometer at room temperature, considers the influence of the measurement substrate on the energy balance in the cavity of the radiometer, establishes a transparent medium infrared emissivity model, uses a radiometer as a measurement device, introduces materials with different emissivities as substrates into the measurement system for measurement, and brings the measurement results into the model for calculation and solution to obtain infrared thermal radiation parameters, thereby effectively improving the measurement accuracy. Meanwhile, the measurement method is simple and low in cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the testing device of the present invention;

[0035] Figure 2 The figure is a flow chart of the testing method of the present invention. DETAILED DESCRIPTION

[0036] A method for measuring the hemispherical infrared emissivity of a transparent medium comprises the following steps:

[0037] S1: Establish a radiometer model to measure the hemispherical infrared emissivity of transparent materials;

[0038] Specifically, the present invention uses a radiometer as a measuring device. Preferably, the measuring accuracy of the radiometer is better than 0.015. Figure 1 As shown, during the measurement, the sample to be tested is placed on a substrate 4 with a constant temperature, and a hemispherical absorption cover 2 with a black paint sprayed on the inner surface is buckled on the sample to be tested 1. A heater with constant power is installed in the absorption cover to keep the temperature stable during the test. Preferably, the hemispherical infrared emissivity of the hemispherical absorption cover is not less than 0.9. The inner surface of the cover and the surface of the sample to be tested form a closed cavity. Since the material has a certain transmittance to infrared radiation, the infrared radiation of the lower surface of the sample and the substrate of the sample to be tested also passes through the sample and enters the closed cavity formed by the sample and the absorption cover. For transparent or translucent materials with the same infrared emissivity on the upper and lower surfaces, ignoring multiple reflections of energy, the infrared radiation reaching the radiometer probe 3 can be approximately calculated according to the following formula:

[0039] L(T)=X{[ε s +ε s (1-ε b )τ s +ε b τ s ]]L 0 (T)+[(1-τs -ε s )+τ s 2 (1-ε b )]L(T e )}+L1(T e ) (1)

[0040] Where L(T) is the infrared radiation intensity reaching the radiometer probe when the sample temperature is T, and the unit is W / (m 2 K);

[0041] L 0 (T) is the infrared radiation intensity of the black body at temperature T, in W / (m 2 K);

[0042] L(T e ) is the temperature T e When the infrared radiation intensity of the absorption cover to the sample is W / (m 2 K);

[0043] L1(T e ) is the temperature T e When the infrared radiation intensity of the absorption cover to the radiometer probe is W / (m 2 K);

[0044] X is the angular coefficient of the sample to the radiometer probe;

[0045] ε s is the infrared emissivity of the sample;

[0046] τ s is the infrared transmittance of the sample;

[0047] ε b is the infrared emissivity of the substrate.

[0048] where ε s (1-ε b )τ s L 0 (T) is the portion of infrared radiation from the lower surface of the sample that is reflected by the substrate and then passes through the sample into the cavity, ε b τ s L 0 (T) is the portion of the infrared radiation of the substrate that passes through the sample and enters the cavity, τ s 2 (1-ε b )L(T e ) is the part of the infrared radiation of the sample from the absorption cover that passes through the sample, is reflected by the substrate and then enters the cavity.

[0049] According to the infrared radiation measured by the probe, the infrared emissivity of the opaque object corresponding to the same intensity of infrared radiation can be calculated according to the formula: L(T) = X[ε a L 0 (T)+(1-ε a )L(T e )]+L1(T e ), so:

[0050] X[ε a L 0 (T)+(1-ε a )L(T e )]+L1(T e )=X{[ε s +ε s (1-ε b )τ s +ε b τ s ]L 0 (T)+[(1-τ s -ε s )+τ s 2 (1-ε b )]L(T e )}+L1(T e ) (2)

[0051] L(T e ) and L 0 (T) are two fixed values, take L(T e ) / L 0 (T) = k, then the above formula can be converted to:

[0052]

[0053] Formula (3) is the model for measuring the hemispherical infrared emissivity of a transparent material by a radiometer when the infrared emissivity of the two surfaces is the same. The emissivity of the substrate ε is b It can be found that the unknown quantity in the above formula is ε s , τ s There are three parameters in total, namely, emissivity, ρ and k. To obtain the values ​​of these three parameters, a system of equations consisting of three equations is required. Therefore, three materials with different emissivity can be used as substrates, and three equations can be obtained through three measurements.

[0054] Parameter k is an internal parameter of the system related to the state of the test system. If this parameter is known, the infrared radiation parameters of transparent or translucent materials with the same infrared emissivity on the upper and lower surfaces can be measured by using two different substrate materials as substrate materials.

[0055] For transparent or translucent materials with different emissivity and transmittance on both sides, the infrared emissivity of the upper surface (the side facing the absorber) is taken as ε m2 , the infrared emissivity of the lower surface (the side facing the substrate) is, and the corresponding transmittance of light passing through the material from top to bottom is τ m1 , the transmittance when passing through the material from bottom to top is τ m2 , then formula (2) should be expressed as:

[0056] X[ε a L 0 (T)+(1-ε a )L(T e )]+L1(T e )=X{[ε m1 +ε m2 (1-ε b )τ m2 +ε b τ m2 ]L 0 (T)+[(1-τ m1 -ε m1 )+τ m1 τ m2 (1-ε b )]L(T e )}+L1(T e ) (4)

[0057] The above formula can be transformed into:

[0058]

[0059] Formula (5) is the model for measuring the hemispherical infrared emissivity of transparent materials by a radiometer when the emissivity and transmittance of the two surfaces are different. There are 5 unknown quantities in the above formula, and at least 5 equations are required to calculate the values ​​of each unknown quantity. Similarly, three materials with different emissivity can be used as substrates, and each substrate is measured on the front and back sides of the sample. Six equations are obtained through six measurements. Selecting 5 of them can solve all the unknown quantities in the formula.

[0060] S2: Select three materials with different infrared emissivity as base materials, namely base material A, base material B, and base material C.

[0061] Specifically, the infrared emissivity ε of the base material A is A Satisfy ε A ≤0.1; infrared emissivity of base material B ε B Satisfy ε B ≥0.85; infrared emissivity of base material C ε C Satisfy 0.3≤ε C ≤0.7.

[0062] S3: Calibrate the radiometer and measure the hemispherical infrared emissivity of the base material A, the base material B, and the base material C respectively. Preferably, the measurement environment temperature is between 15°C and 35°C.

[0063] S4: Prepare a transparent or translucent material into a sheet sample, and represent the upper and lower surfaces of the sample as surface 1 and surface 2 respectively; specifically, the thickness of the sheet sample is less than or equal to 5 mm.

[0064] S5: Using substrate material A, substrate material B, and substrate material C as substrates, respectively, and using a radiometer to measure the hemispherical infrared emissivity of sample surface 1 and surface 2 when facing upward, respectively, to obtain hemispherical infrared emissivity measurement values; preferably, the measurement environment temperature is between 15°C and 35°C.

[0065] S6: Substitute the measurement results of step 3 and step 5 into the radiometer to measure the hemispherical infrared emissivity model of transparent materials for solution to obtain the infrared radiation parameters of the transparent medium sample.

[0066] Specifically, the following expression is obtained by substituting the measurement results into the radiometer model for measuring the hemispherical infrared emissivity of transparent materials:

[0067]

[0068]

[0069]

[0070]

[0071]

[0072]

[0073] Among them, ε A1 is the measured value of hemispherical infrared emissivity with base material A as the base and sample surface 1 facing upward,

[0074] ε A2 is the measured value of hemispherical infrared emissivity with base material A as the base and sample surface 2 facing upward,

[0075] ε B1 is the measured value of hemispherical infrared emissivity with base material B as the base and sample surface 1 facing upward,

[0076] ε B2 is the measured value of hemispherical infrared emissivity with base material B as the base and sample surface 2 facing upward,

[0077] εC1 is the measured value of hemispherical infrared emissivity with base material C as the base and sample surface 1 facing upward,

[0078] ε C2 is the measured value of hemispherical infrared emissivity with base material C as the base and sample surface 2 facing upward,

[0079] ε s1 is the hemispherical infrared emissivity of the sample surface 1,

[0080] ε s2 is the hemispherical infrared emissivity of sample surface 2,

[0081] τ s1 is the hemispherical infrared transmittance when light enters from sample surface 1 and exits from surface 2,

[0082] τ s2 It is the hemispherical infrared transmittance when light enters from sample surface 2 and exits from surface 1.

[0083] Select any 5 equations from the above expressions and solve them to obtain the infrared radiation parameter ε of the sample. s1 , ε s2 , τ s1 , τ s2 .

[0084] The following is further described in conjunction with specific embodiments. The test process is as follows: Figure 2 As shown:

[0085] In this embodiment, a translucent material with a 4 mm thick single crystal silicon lens coated on both sides is used as a sample. The different coating states on the two surfaces of the sample result in different infrared radiation parameters on the two surfaces.

[0086] Three materials with different emissivity were selected as the measurement substrate, namely double-sided aluminum-coated polyester film, black paint material and single-sided aluminum-coated polyimide film. The measurement equipment used was the AE1 portable radiometer from the American D&S company.

[0087] Step 1: After the radiometer is calibrated, the emissivity of the three substrate materials is measured. The infrared emissivity of opaque materials can be directly measured using the calibrated test equipment. The actual measured emissivity of the aluminum film is 0.03, the emissivity of black paint is 0.95, and the emissivity of single-sided aluminum-coated polyimide is 0.68.

[0088] Step 2: The two surfaces of the test sample are marked as 1 and 2 respectively. The double-sided aluminum-plated polyester film of substrate A is placed on the test bench as the substrate. The sample 1 is placed upward on the substrate. The radiometer is used to measure the emissivity in this state to obtain the measurement result ε A1 =0.26, then place the sample 2 face up on the substrate and re-measure to obtain the measurement result εA2 =0.40.

[0089] Step 3: Replace substrate B (black paint material), measure the emissivity of sample 1 facing upward and the emissivity of sample 2 facing upward, and obtain the measurement result ε B1 =0.40,ε B2 =0.54.

[0090] Step 4: Replace substrate C (single-sided aluminum-plated polyimide film) and measure the emissivity of sample 1 facing upward and 2 facing upward respectively to obtain the measurement result ε C1 =0.38,ε C2 =0.51.

[0091] Step 5: Select 5 of the 6 measurement results obtained and substitute them into formula (5) to form an equation system. In order to verify the correctness of the measurement method, different parameters are selected to form the following two equation systems:

[0092]

[0093]

[0094] Step 6: Solve equations (6) and (7), and the results are shown in Table 1:

[0095] Table 1 Solution results of the equation group

[0096]

[0097] In the two sets of results, the emissivity values ​​are basically the same, and the maximum difference in transmittance values ​​is about 0.07, and the measurement results have good accuracy.

[0098] The above description is only an embodiment of the present invention and is not intended to limit the embodiments of the present invention. Any other equivalent changes or modifications made by a person familiar with the art based on the characteristic scope of the present invention should be included in the scope of the patent application of the present invention.

[0099] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A method for measuring the infrared emissivity of a transparent medium hemisphere, characterized in that Here are the steps: 1) Establish a radiometer model to measure the hemispherical infrared emissivity of transparent materials; 2) Select three materials with different infrared emissivity as base materials, namely base material A, base material B and base material C; 3) Measure the hemispherical infrared emissivity of base material A, base material B, and base material C; 4) Prepare a transparent or translucent material into a sheet sample, and mark the upper and lower surfaces of the sample as surface 1 and surface 2 respectively; 5) Using substrate material A, substrate material B, and substrate material C as substrates, respectively, a radiometer is used to measure the hemispherical infrared emissivity of sample surface 1 and surface 2 when facing upward, respectively, to obtain the measured value of the hemispherical infrared emissivity of the sample; 6) Using the measurement results of step 3) and step 5) in combination with a radiometer to measure a hemispherical infrared emissivity model of a transparent material, the infrared radiation parameters of the sample are obtained; It is characterized in that, in the step 1), the model of the hemispherical infrared emissivity of the transparent material measured by the radiometer is specifically: Among them, ε a is the measured value of the hemispherical infrared emissivity of a transparent material measured using a radiometer, ε m1 is the hemispherical infrared emissivity of the transparent material’s upward surface, ε m2 is the hemispherical infrared emissivity of the transparent material’s surface facing downward, τ m1 is the infrared transmittance of light passing through the transparent material from top to bottom, τ m2 is the infrared transmittance of light passing through a transparent material from bottom to top, ε b is the infrared emissivity of the substrate material, k = L(T e ) / L 0 (T), where L 0 (T) is the infrared radiation intensity of the black body at temperature T, in W / (m 2 K), L(T e ) is the temperature T e When the infrared radiation intensity of the radiometer hemispherical absorption cover to the sample is W / (m 2 K); It is characterized in that, in the step 6), the infrared radiation parameters of the sample are obtained by combining the measurement results of step 3) and step 5) with the radiometer to measure the hemispherical infrared emissivity model of the transparent material: Substituting the measurement results of step 3) and step 5) into the radiometer model for measuring the hemispherical infrared emissivity of transparent materials, the following expression is obtained: Among them, ε A1 is the measured value of hemispherical infrared emissivity with base material A as the base and sample surface 1 facing upward, ε A2 is the measured value of hemispherical infrared emissivity with base material A as the base and sample surface 2 facing upward, ε B1 is the measured value of hemispherical infrared emissivity with base material B as the base and sample surface 1 facing upward, ε B2 is the measured value of hemispherical infrared emissivity with base material B as the base and sample surface 2 facing upward, ε C1 is the measured value of hemispherical infrared emissivity with base material C as the base and sample surface 1 facing upward, ε C2 is the measured value of hemispherical infrared emissivity with base material C as the base and sample surface 2 facing upward, ε s1 is the hemispherical infrared emissivity of the sample surface 1, ε s2 is the hemispherical infrared emissivity of the sample surface 2, τ s1 is the hemispherical infrared transmittance when light enters from sample surface 1 and exits from surface 2, τ s2 is the hemispherical infrared transmittance when light enters from sample surface 2 and exits from surface 1, ε A is the infrared emissivity of the substrate material A, ε B is the infrared emissivity of the base material B, ε C is the infrared emissivity of the base material C; Select any five equations from the above expressions and solve them to obtain the infrared radiation parameter ε of the transparent medium sample. s1 , ε s2 , τ s1 , τ s2 .

2. The method for measuring the hemispherical infrared emissivity of a transparent medium according to claim 1, characterized in that: The infrared emissivity ε of the base material A A ≤0.

1.

3. The method for measuring the hemispherical infrared emissivity of a transparent medium according to claim 2, characterized in that: The infrared emissivity ε of the base material B B ≥0.

85.

4. The method for measuring the hemispherical infrared emissivity of a transparent medium according to claim 3, characterized in that: The infrared emissivity of the base material C is 0.3≤ε C ≤0.

7.

5. A method for measuring hemispherical infrared emissivity of a transparent medium according to any one of claims 1 to 4, characterized in that: The thickness of the transparent medium sample is less than or equal to 5 mm.

6. A method for measuring hemispherical infrared emissivity of a transparent medium according to any one of claims 1 to 4, characterized in that: The ambient temperature for measuring the hemispherical infrared emissivity in step 3) or step 5) is 15° C. to 35° C.

7. A method for measuring hemispherical infrared emissivity of a transparent medium according to any one of claims 1 to 4, characterized in that: The measurement accuracy of the radiometer is better than 0.

015.

8. A method for measuring hemispherical infrared emissivity of a transparent medium according to any one of claims 1 to 4, characterized in that: The hemispherical infrared emissivity of the hemispherical absorption cover of the radiometer is not less than 0.9.

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