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NB/T 10308-2019: (Infrared temperature field distribution test method for electric heating element)
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(Infrared temperature field distribution test method for electric heating element)
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NB/T 10308-2019
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Basic data | Standard ID | NB/T 10308-2019 (NB/T10308-2019) | | Description (Translated English) | (Infrared temperature field distribution test method for electric heating element) | | Sector / Industry | Energy Industry Standard (Recommended) | | Classification of Chinese Standard | K04 | | Classification of International Standard | 17.200.01 | | Word Count Estimation | 19,133 | | Date of Issue | 2019-11-04 | | Date of Implementation | 2020-05-01 | | Issuing agency(ies) | National Energy Administration | NB/T 10308-2019: (Infrared temperature field distribution test method for electric heating element)
---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
Infrared temperature field distribution test method for electric heating element
ICS 17.200.01
K 04
NB
Energy Industry Standards of the People's Republic of China
Infrared temperature field distribution test method for electric heating element
2019-11-04 released
2020-05-01 implementation
Issued by National Energy Administration
Table of contents
Foreword...II
1 Scope...1
2 Normative references...1
3 Terms and definitions...1
4 Test purpose and main physical parameters...2
5 Technical requirements...2
6 Preparation procedures before testing...4
7 Testing and shooting...7
8 Post-processing...8
9 Test report...8
Appendix A (informative appendix) Illustration of the field of view...9
Appendix B (informative appendix) Infrared absorption spectrum of polyethylene material infrared window...10
Appendix C (informative appendix) The emissivity of the outer material of commonly used electric heating elements...11
Appendix D (informative appendix) Common non-metallic materials emissivity...12
Appendix E (informative appendix) Atmospheric transmittance correction parameters...13
Appendix F (Normative Appendix) Calculation Method of Heat Uniformity...14
References...16
Figure 1 Schematic diagram of the plastic paste control method...6
Figure 2 Schematic diagram of radiance...7
Figure A.1 Schematic diagram of field of view...9
Figure A.2 Schematic diagram of instantaneous field of view...9
Figure B.1 Infrared absorption spectrum of polyethylene...10
Figure E.1 Atmospheric transmittance correction parameters (atmospheric window)...13
Figure F.1 Example of dividing sub-areas of electric heating elements...14
Table B.1 Infrared absorption spectrum of polyethylene...9
Table C.1 Common metal materials 8μm～14μm band emissivity...11
Table D.1 Common non-metallic materials 8μm～14μm band emissivity...12
Foreword
This standard was drafted in accordance with the rules given in GB/T 1.1-2009.
This standard was proposed by China Electrical Equipment Industry Association.
This standard is under the jurisdiction of the National Electrical Accessories Standardization Technical Committee (SAC/TC 67).
Drafting organizations of this standard. Wuhu Jiulong Controller Co., Ltd., China Electrical Equipment Research Institute Co., Ltd., Hefei Midea Electric Ice
Box Co., Ltd., Guangdong Midea Refrigeration Equipment Co., Ltd., Xiamen Fulan Home Appliance Technology Co., Ltd., Weikai Testing Technology Co., Ltd., Zhejiang
Hongyan Electric Co., Ltd., Xi'an Xumai Intelligent Home Appliance Technology Co., Ltd., Xi'an Kaiyijin Electronic Technology Co., Ltd., Zhejiang Ouyi Smart Kitchen
Housing Co., Ltd., Dongguan Ruijing Electrical Technology Co., Ltd.
The main drafters of this standard. Zhuang Weiwei, Zhu Zhouyang, Zhou Yang, Zhang Tianyu, Peng Shichang, Kong Ruixun, Wang Fengqin, Chen Feng, Quan Yongde,
Fang Zhiming, Lin Jinli.
Infrared temperature field distribution test method for electric heating element
1 Scope
This standard specifies the use of infrared radiation principle, the use of infrared thermal imagers to measure the infrared temperature field distribution of electric heating elements
Method requirements, including environmental requirements, personnel requirements, equipment requirements, measurement method specifications, image processing, etc.
This standard is applicable to the continuous non-contact surface temperature measurement of electric heating elements or their nearby parts within a period of time.
The degree point can be one, multiple, or even one surface.
2 Normative references
The following documents are indispensable for the application of this document. For dated reference documents, only the dated version applies to this document.
For undated references, the latest version (including all amendments) applies to this document.
GB/T 9445-2015 Non-destructive testing personnel qualification and certification
GB/T 27025-2008 General requirements for the competence of testing and calibration laboratories
3 Terms and definitions
The following terms and definitions apply to this document.
3.1
Electric heating element
A component that generates heat based on the principle of Joule's law.
3.2
Infrared imager
Based on the principle of infrared detection, the infrared radiation energy of the object is converted through infrared optical system, infrared detector and electronic processing system, etc.
It is a device that distributes a visible image of the measured temperature in a two-dimensional coordinate system.
3.3
(Infrared thermal imager) working band
The response wavelength range of the infrared detector of the infrared thermal imager.
3.4
Infrared spectral transmittance
The ratio of the radiant flux of infrared rays passing through an object to the radiant flux incident on the surface of the object.
3.5
Field of view; FOV
The horizontal and vertical angles at which the object is completely imaged in the infrared thermal imager.
Note. The angle of view passes through the horizontal field of view (HFOV, Horizontal Field of View) and the vertical field of view (VFOV, Vertical Field of View)
And display field of view (DFOV, Display Field of View). Refer to Figure A.1 in Appendix A for schematic diagrams of various viewing angles.
3.6
Instantaneous field of view; IFOV
The spatial optical angle corresponding to the single sensitive element of the infrared thermal imager detector after passing through the optical system. Also called spatial resolution.
Note. See Figure A.2.in Appendix A for the schematic diagram of the instantaneous field of view.
3.7
Measuring field of view; MFOV
The infrared thermal imager detector can accurately measure the smallest pixel range of the data.
3.8
Normal emissivity
The emitted radiation intensity of an object at a specific wavelength and temperature is the same as that of an ideal black body at the same wavelength and temperature.
The ratio of degrees.
3.9
Background radiation
All radiation received by the infrared sensor device and emitted by the non-detected surface.
Note. Background radiation includes reflected radiation from external sources.
3.10
Radiance
The off-source radiant flux per unit projected area within unit solid angle.
Note. The unit is watts per sphere square meter [W/(sr·m2)].
4 Test purpose and main physical parameters
4.1 Purpose of infrared temperature field distribution test for heating elements
Compared with the contact-type single-point temperature measurement method, the infrared temperature field distribution test can simultaneously measure the surface temperature of the entire heating source
Quantities, so that users can understand the surface temperature distribution of electric heating elements. At the same time, since the infrared temperature field distribution test is a non-contact measurement method, it is not
Must be in contact with electric heating elements that have high temperatures during work, so that users can safely and quickly obtain temperature field data.
This standard overcomes the problem of greater uncertainty in infrared temperature field measurement by establishing a series of standardized basic test methods, and makes electric heating
The data of the infrared temperature field distribution test of the element is as accurate as possible, and the effective temperature of the heating element under normal or abnormal working conditions is obtained by this
Field data.
4.2 Main physical parameters
The main physical parameters that affect the measurement results.
a) Emissivity, dimensionless;
b) Wavelength, in micrometers (μ m);
c) The angle of view, in radians (rad).
5 Technical requirements
5.1 Environmental requirements
5.1.1 Attention should be paid to the temperature status of the electric heating element under inspection, so that personnel and equipment should be kept a safe distance from it to avoid burns or equipment.
The equipment is damaged.
5.1.2 The test environment should try to avoid errors caused by background radiation. In addition, you should try to avoid including the sun and lighting lamps
The light source causes measurement errors. Generally, the test should be shielded from the sun and turned off the lights, or by building a closed matt non-glossy black paint test corner or no
Wind net box to avoid external radiation interference.
5.1.3 The temperature and humidity of the environment where the infrared thermal imager is located during measurement shall not exceed its design requirements.
For measurement, use a cooling device to protect the infrared thermal imager or test through an infrared window.
5.1.4 The working and storage environment of the infrared thermal imager should avoid the influence of static electricity, arc welding machine and strong electromagnetic field.
5.1.5 The working and storage environment of the infrared thermal imager should also meet the requirements of its technical manual.
5.1.6 It should be noted that if there are high concentrations of dust or smoke in the measurement environment, the measurement results will be inaccurate.
5.2 Personnel requirements
5.2.1 The personnel performing the test shall be qualified and certified according to GB/T 9445-2015 or the system agreed by all parties to the contract, and the employer or
Its agent conducts professional professional training and operation authorization.
5.2.2 The inspector shall abide by the safety requirements of the inspected heating element site, wear protective work clothes and wear protective clothing according to the requirements of the inspection site.
Turn off protective equipment.
5.2.3 Unless they have a licensed electrician, professional engineer or other equivalent qualifications, the person responsible for infrared temperature measurement should not perform
The installation, debugging, and replacement of electric heating elements completed by the staff.
5.2.4 This standard does not fully specify the safety requirements for measurement. All parties using this standard are obliged to establish appropriate safety requirements before measurement.
Quanhe health guidelines.
5.3 Equipment requirements
5.3.1 The infrared thermal imager should have the following functions.
a) It should be able to detect the temperature of the surface of the electric heating element under test and generate infrared thermal imaging images or videos;
b) It should be able to collect infrared information in the measured area, perform measurement and display the surface temperature distribution image in time;
c) It should be able to record and store images, data and text annotations quickly and accurately.
5.3.2 Written procedures or work instructions shall be formulated according to the product instruction manual or technical manual, and the infrared thermal imager shall be periodically maintained.
Protection, calibration, measurement and inspection to ensure that the instrument functions normally.
5.3.3 If necessary, the laboratory should be equipped with a black body radiation source calibration box to calibrate and calibrate the infrared thermal imager before each test.
5.3.4 Regardless of whether the infrared thermal imager is in operation or not, no enhanced energy source (such as laser radiation) should be used to irradiate the infrared thermal imager mirror.
head.
5.3.5 After the infrared thermal imager is used, the opened end cover or other lens protection devices should be closed immediately to prevent the lens from being contaminated or
damage. Once the lens is contaminated by dust or grease, the lens should be cleaned according to the product manual.
5.3.6 All infrared thermal imaging cameras referred to in this standard shall have an over-temperature alarm function.
5.3.7 At least a thermocouple that meets the operating temperature range of the electric heating element under test shall be equipped to measure the surface temperature of the electric heating element.
Calibration should be performed at least once a year or meet the measurement requirements, and the measurement accuracy of the thermocouple should be higher than that of the infrared used in accordance with this standard.
The measurement accuracy of the thermal imager, that is, the measurement uncertainty of the thermocouple should be lower than the measurement uncertainty of the infrared thermal imager used in accordance with this standard
degree.
5.3.8 Since the functions and performance of different infrared thermal imagers are quite different, this standard only covers the general requirements when using infrared thermal imagers for measurement.
Require regulations. This standard does not explain or exclude abnormal situations during the measurement process.
6 Preparation procedures before testing
6.1 General
Since the heating element generally has a higher temperature when it is working, the test should first follow the safety principle, and it should be fully prepared before each test.
Prepare to ensure that no personal injury or equipment damage occurs during the test. Secondly, the acquisition of accurate test data is based on the
Measure the performance and function of electric heating element and infrared thermal imager on the basis of a full understanding. Finally, it should be based on changes in the electric heating element and the environment under test
Make adjustments to the test equipment and test parameters in time.
6.2 Understanding the electric heating element under test
For the electric heating element under test, at least the following information should be obtained before testing.
a) The model, input voltage and current, heating medium, installation method and working mode of the electric heating element under test;
b) The emissivity of the surface material in the response band of the infrared detector;
c) Estimated operating temperature.
6.3 Functions of infrared thermal imager
6.3.1 The temperature measurement range of the infrared thermal imager should match the operating temperature range of the electric heating element under test, and have matching applicable conditions.
Determined by consulting related technical manuals. It is recommended to use an infrared thermal imaging camera with a working band of 8 μ m to 14 μ m, and in the range permitted by conditions
In the enclosure, select an infrared thermal imager with high thermal sensitivity.
6.3.2 In order to determine whether the infrared thermal imager to be used in the test meets the requirements for use, the tester should obtain at least the following information.
a) Response wavelength of infrared detector;
b) Temperature measurement range;
c) Temperature measurement accuracy and temperature resolution;
d) Lens focal length or focusing range;
e) Lens field angle parameters;
f) Spatial resolution.
6.4 Installation of heating elements and test equipment
6.4.1 The installation method of the heating element should facilitate the observation of the inspected part by the infrared thermal imager.
6.4.2 Select the infrared thermal imager corresponding to the working band according to the nature of the measured object.
6.4.3 Before each measurement, the electric heating element and the infrared thermal imager should be fixed by appropriate equipment.
6.4.4 The infrared thermal imager should be installed in the direction of the maximum radiation surface of the electric heating element or the normal direction of the surface to be measured, so that the observation direction is directly opposite to the electric heating
The surface of the component to be tested.
6.4.5 For the part of the electric heating element that cannot be directly observed by the infrared thermal imager, measure the part by an appropriate method, such as
Observe after refracting through a flat mirror.
6.4.6 For electric heating elements that require heat conduction medium to assist in heat dissipation during work, the container of the appliance during normal work should be installed to hold appropriate
Water or other media are used to dissipate heat to prevent electric heating elements from exceeding the designed limit operating temperature.
6.4.7 When the measurement requires the use of infrared windows for protection, you can refer to Appendix B or other related work manuals to make changes to the infrared thermal imager.
Line temperature compensation and infrared spectrum transmittance compensation.
6.4.8 When the surface emissivity of the heating element is low, special attention should be paid to adjusting the position of the infrared thermal imager and the heating element to avoid infrared reflection.
Shoot at a strong angle to avoid the influence of external radiation.
6.5 Adjustment of measuring distance
6.5.1 According to the focal length of the infrared thermal imager lens, the field of view (FOV), the instantaneous field of view (IFOV) and the measured field of view (MFOV) etc.
Adjust the relative distance between the optical lens of the infrared thermal imager and the component under test, so that the infrared thermal imager is as reliable as possible within the allowable range of the safe distance
It is close to the electric heating element under test to improve the resolution ability and temperature measurement accuracy of the infrared thermal imager on the surface details of the electric heating element under test. Adjustment of field of view
See Appendix A for calculations.
6.5.2 When the measured area is large or the structure is slender, the temperature of the measured component should be obtained through multiple local shots at a short distance.
场信息。 Field information.
6.6 Temperature correction
6.6.1 Focus adjustment
Adjust the focus of the image by turning the external lens ring of the infrared thermal imager or using the electronic focusing function to make the image clear.
6.6.2 Emissivity adjustment
6.6.2.1 Material property setting method
When the measurement is only used for preliminary determination and there is no requirement for temperature measurement accuracy, you can check the emissivity of the surface material of the heating element.
Method to quickly set the emissivity.
The emissivity of different materials can be found in Appendix C and Appendix D. The values in the two appendices are only average values, and the actual emissivity of the material also depends on
Due to the following factors.
a) temperature;
b) Surface composition (such as polishing, oxidation, roughness, sandblasting, etc.);
c) Transmittance (such as film).
Note. The measurement angle, the geometry of the material surface, the thickness of the material, the measured spectral range, the surface oxidation of the heating element or other chemical reactions under high temperature conditions
Should and other factors can also affect emissivity under certain conditions.
In general, non-metals have higher emissivity than metals; non-oxidized metals have lower emissivity than oxidized metals; rough surfaces
It has a higher emissivity than a polished surface of the same material.
6.6.2.2 Contact measurement contrast setting method
Arrange a contact thermometer (such as a thermocouple) or a contact sensor on the relatively flat part of the electric heating element under test. Adjust the heating element
When it reaches the temperature heating state, use a thermometer or sensor to read the heating temperature. At the same time, use an infrared thermal imager to measure the temperature near the location
Section emissivity parameters until the displayed temperature is consistent with the temperature measured by the thermometer or sensor. Keep this emissivity parameter as the material emissivity.
The heating temperature of the heating element should be estimated before the measurement, and the thermocouple type with the appropriate measurement range should be selected.
6.6.2.3 Pasting comparison method
As shown in the left picture of Figure 1, before the measurement, the special material plastic sticker is closely attached to the heating surface of the component under test.
When measuring, set the emissivity to the emissivity of the sticker, as shown in the right figure of Figure 1, and record the temperature of the sticker after obtaining the temperature. Then, check
Look at the temperature of the area adjacent to the sticker, and adjust the emissivity so that the measured temperature of the unsticked area is the same as the recorded sticker temperature.
The emissivity is the emissivity of the area of the electric heating element under test.
During the measurement, the heating element should be in a constant temperature state.
This method is suitable for electric heating elements with flat surface and uniform temperature distribution.
Attention should be paid to selecting the appropriate type of sticker to withstand the high temperature when the heating element heats up.
Figure 1 Schematic diagram of the plastic-sticking comparison method
6.6.2.4 Spraying method
Before the measurement, spray acrylic resin paint or other non-conductive powder uniformly on the surface of the electric heating element to be tested, and set the emissivity to the coating.
Firing rate.
This method is suitable for the measurement when the surface of the heating element is polished or has a rust layer and other emissivity inconsistencies.
6.6.3 Transmittance correction
Adjust the atmospheric transmittance parameters according to the test environment temperature, humidity and dust particle concentration.
Generally, the daily indoor living environment can be set to 1, the atmospheric transmittance correction parameters of different bands can be found in Appendix E, and other special environmental conditions can be
Consult relevant technical manuals.
6.6.4 Background radiation temperature correction
The thermal radiation detected by the infrared thermal imager when measuring an opaque object is a combination of the thermal radiation emitted by the object and the background radiation. Should be some kind
Ways to compensate for background radiation or reduce background radiation to obtain accurate test data.
Under normal circumstances, background radiation compensation can be automatically processed by the device's own function.
If the ambient temperature is equal to or higher than the measured electric heating element (such as the electric heating element in a high-temperature furnace), the influence of background radiation is very large.
By establishing a test environment that meets the requirements of 5.1.2, background radiation can be minimized.
6.7 Handling of common special circumstances
6.7.1 When the surface material of the electric heating element under test is uneven, there is a large area of loose rust layer, or the surface emissivity is lower than 0.5, etc.,
The method of 6.6.2.4 should be used as far as possible to avoid external source reflection interference and uniform emissivity.
6.7.2 In the methods of 6.6.2.2 to 6.2.2.4, the measurement uncertainty can be reduced by repeating multiple measurements and averaging.
6.7.3 When the emissivity of the material changes greatly with temperature, the temperature correction coefficient of the emissivity should be increased to ensure the measurement
Quantity accuracy.
6.7.4 Some infrared thermal imagers provide temperature offset tables for calibration. In this case, the user should perform manual calculations to obtain more accurate
Exact temperature.
6.7.5 If the measured process will experience dew point or frost point, the emissivity of the surface of the heating element may change. If the surface is completely
Covered with dew, the surface will have the emissivity of the liquid water formed on the surface. If the surface is completely covered by frost, the emissivity will be frosty
Emissivity.
7 Testing and shooting
7.1 During the test, try to avoid moving, adjusting, and touching electric heating elements under working conditions.
7.2 The heating element works under the tested working condition (such as temperature rise or stable heating condition), and the infrared thermal imager will
Start shooting at the right time, record infrared thermal image photos or record infrared video. The function can be switched before and after shooting, and the part of the electric heating element under test can be photographed
Visible light photo.
7.3 For electric heating elements with a multi-faceted structure, the radiance of different heating surfaces obtained from one direction is different, and the shooting angle should be adjusted to the phase
After shooting in the normal direction, or after conversion by the following method, and record the conversion process and data.
Referring to Figure 2, the radiance of the corresponding angle can be calculated according to formula (1).
7.4 For electric h...
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