GB/T 2680-2021 PDF English

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GB/T 2680-2021: Glass in building - Determination of light transmittance, solar direct transmittance, total solar energy transmittance, ultraviolet transmittance and related glazing factors
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GB/T 2680: Historical versions

Standard ID	USD	BUY PDF	Delivery	Standard Title (Description)	Status
GB/T 2680-2021	559	Add to Cart	5 days	Glass in building - Determination of light transmittance, solar direct transmittance, total solar energy transmittance, ultraviolet transmittance and related glazing factors	Valid
GB/T 2680-1994	479	Add to Cart	3 days	Determination of light transmittance, solar direct transmittance, total solar energy transmittance and ultraviolet transmittance for glass in building and related glazing factors	Obsolete
GB 2680-1981	199	Add to Cart	2 days	Sheet glass-Determination of transmittancy of visible rays	Obsolete

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GB/T 2680-2021: Glass in building - Determination of light transmittance, solar direct transmittance, total solar energy transmittance, ultraviolet transmittance and related glazing factors

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(Architectural glass. Determination of visible light transmittance, direct sunlight transmittance, total solar transmittance, ultraviolet transmittance and related window glass parameters) ICS 81.040 Q30 National Standards of People's Republic of China Replace GB/T 2680-1994 Visible light transmittance of architectural glass, direct sunlight Transmittance, total solar transmittance, ultraviolet transmittance And measurement of related window glass parameters Released on 2021-03-09 2021-10-01 implementation State Administration of Market Supervision and Administration Issued by the National Standardization Management Committee

Table of Contents

Foreword Ⅰ 1 Scope 1 2 Normative references 1 3 Terms and definitions 1 4 Measurement conditions 2 4.1 Sample 2 4.2 Instrument 2 5 Measurement of various parameters 2 5.1 Visible light transmittance 2 5.2 Visible light reflectance 4 5.3 Solar radiant flux 7 5.4 Direct sunlight transmittance 7 5.5 Direct sunlight reflectance 9 5.6 Direct sunlight absorption ratio 10 5.7 Total solar transmittance 10 5.8 Secondary heat transfer coefficient to the indoor side 10 5.9 Shading factor 13 5.10 Light-to-heat ratio 13 5.11 Ultraviolet transmittance 13 5.12 Emissivity 15 5.13 The total transmittance of solar infrared heat energy 16 6 Test report 18 Appendix A (Normative Appendix) Calculation of Thermal Resistance of Glass Components 19 References 26 Preface This standard was drafted in accordance with the rules given in GB/T 1.1-2009. This standard replaces GB/T 2680-1994 "Visible light transmittance of architectural glass, direct solar transmittance, total solar transmittance ﹑Determination of ultraviolet transmittance and related window glass parameters". Compared with GB/T 2680-1994, the main technical changes of this standard are as follows. ---Added 8 terms and definitions (Chapter 3); ---The requirements for samples have been added, and the requirements for instrument parameters have been modified (4.1, 4.2); ---Added two new measurement methods (5.10, 5.13) for the light-to-heat ratio and total solar infrared thermal energy transmittance; ---The test conditions and correction coefficients for emissivity have been added (5.12); ---Appendix A has been added. This standard was proposed by the China Building Materials Federation. This standard is under the jurisdiction of the National Standardization Technical Committee for Building Glass (SAC/TC255). Drafting organizations of this standard. China Building Materials Inspection and Certification Group Qinhuangdao Co., Ltd. (National Glass Quality Supervision and Inspection Center), Beijing Aobo Technology Co., Ltd., China Southern Glass Group Co., Ltd., Wuhan Shengke Technology Development Co., Ltd., PerkinElmer Enterprise Management (Part 1 Hai) Co., Ltd., Shimadzu Enterprise Management (China) Co., Ltd., Shanghai Zichuang Coating Technology Co., Ltd., Taiwan Glass Changjiang Glass Co., Ltd., Yi Energy Saving Glass (Wuhu) Co., Ltd., Bengbu City Product Quality Supervision and Inspection Institute, China Building Materials Inspection and Certification Group Co., Ltd., Shenyang Ziwei Mechanical and Electrical Equipment Co., Ltd., Dongguan Yinjian Glass Engineering Co., Ltd. The main drafters of this standard. Huang Jianbin, Zhang Zhemin, Xu Wuyi, Yuan Jing, Tan Xiaojian, Dai Zhong, Yang Jianjun, Li Xinman, Wu Jie, Yuan Hanhua, Chen Chen, Hou Yanhong, Han Song, Zhao Zidong, Xie Wenming, Gao Yonghui, Li Pan, Han Ying, Jiang Meiqin, Wang Chuan, Cao Yaoqiang. The previous versions of the standard replaced by this standard are as follows. ---GB/T 2680-1994. Visible light transmittance of architectural glass, direct sunlight Transmittance, total solar transmittance, ultraviolet transmittance And measurement of related window glass parameters 1 Scope This standard specifies the visible light transmittance, visible light reflectance, solar radiation flux, direct solar transmittance, and solar transmittance of architectural glass. Direct sunlight reflectance, direct sunlight absorption ratio, total solar transmittance, secondary heat transfer coefficient to the indoor side, shading coefficient, light and heat Measurement methods of ratio, ultraviolet transmittance, emissivity, total solar infrared heat transmittance and related window glass parameters. This standard applies to transparent materials such as single-layer glass and multi-layer window glass. 4 Measurement conditions 4.1 Specimen 4.1.1 Single-layer glass can be directly used as a sample, a sample can be cut out or a slice of glass of the same material can be used. 4.1.2 The samples of multi-layer window glass components can be cut into a single piece or sliced with a single piece of glass of the same material. 4.1.3 The sample should be kept clean during the measurement. 4.2 Apparatus 4.2.1 The measurement wavelength range and wavelength interval of the spectrophotometer, Fourier infrared spectrometer and other instruments used in the measurement shall meet this standard The requirements of the wavelength range and wavelength interval of each parameter in the. 4.2.2 In the measurement process of the instrument used for the measurement, the angle between the optical axis of the illuminating beam and the normal line of the sample surface does not exceed 10°, and the illuminating beam The angle between any light ray and the optical axis does not exceed 5°. 4.2.3 When measuring diffuse samples or samples containing diffuse components, the instrument for measuring transmittance and reflectance should be equipped with an integrating sphere. 4.2.4 To determine the transmittance of the sample, it should include the part of the transmitted light emitted by multiple reflections on each glass surface of the sample. 4.2.5 Determine the reflectance of the sample, which should include the part of the reflected light emitted by multiple reflections on each glass surface of the sample. 4.2.6 The accuracy of the instrument to measure transmittance and reflectance should be within ±1%. 5 Determination of various parameters 5.1 Visible light transmittance 5.1.1 Calculation method of visible light transmittance The visible light transmittance τv is calculated by formula (1). Sλ --- the relative spectral distribution of solar radiation; Δλ ---wavelength interval; SλΔλ---the product of the relative spectral distribution of solar radiation Sλ and the wavelength interval Δλ, the value of SλΔλ is shown in Table 2. 5.5.2 Outdoor side spectral reflectance of single glass or single-layer window glass assembly The outdoor side spectral reflectance ρo(λ) of a single glass or single-layer window glass assembly is the outdoor side spectral reflectance measured by the sample. 5.5.3 Outdoor spectral reflectance of multi-layer window glass components The calculation of the outdoor spectral reflectance ρo(λ) of the multi-layer window glass assembly can be carried out in the same way as described in 5.2.1. 5.6 Direct sunlight absorption ratio The direct sunlight absorption ratio αe is calculated by formula (11). 5.7 Total solar transmittance The total solar transmittance g is calculated by formula (14). g=τe qi (14) Where. g --- Total solar transmittance of the sample; τe --- the direct sunlight transmittance of the sample; qi --- Secondary heat transfer coefficient of the sample to the indoor side. 5.8 Secondary heat transfer coefficient to the indoor side 5.8.1 Boundary conditions In order to calculate the secondary heat transfer coefficient qi of the sample to the indoor side, the heat transfer coefficient he of the outdoor surface of the sample, and the heat transfer coefficient of the indoor surface of the sample hi, the following general boundary conditions are specified. Sample placement. vertical placement; The wind speed on the outdoor side surface is about 4m/s, and the corrected emissivity of the glass surface is 0.837; Indoor side surface. natural convection. If other boundary conditions are used to meet special requirements, they should be stated in the test report. 5.8.2 Heat transfer coefficient of the outdoor surface of the sample According to the conventional boundary conditions specified in 5.8.1, the heat transfer coefficient of the outdoor surface of the sample he=23W/(m2·K). 5.8.3 Surface heat transfer coefficient of the sample chamber According to the conventional boundary conditions specified in 5.8.1, the surface heat transfer coefficient hi of the sample chamber is calculated by formula (15). hi=3.6 4.4εi 0.837 (15) Where. hi---the heat transfer coefficient of the indoor surface of the sample, in watts per square meter Kelvin [W/(m2·K)]; εi ---corrected emissivity of the interior surface of the sample chamber. 5.8.4 The secondary heat transfer coefficient of single glass or single-layer window glass components to the indoor side The secondary heat transfer coefficient qi of the single glass or single-layer window glass component to the indoor side is calculated by formula (16). qi=αe hi he hi (16) Where. qi---the secondary heat transfer coefficient of the sample to the indoor side; αe---The direct sunlight absorption ratio of the sample; hi---the heat transfer coefficient of the indoor surface of the sample, in watts per square meter Kelvin [W/(m2·K)]; he---The heat transfer coefficient of the outdoor surface of the sample, in watts per square meter Kelvin [W/(m2·K)]. 5.8.5 The secondary heat transfer coefficient of the double-glazed window assembly to the indoor side The secondary heat transfer coefficient qi of the double-glazed glass component to the indoor side is calculated by formula (17). qi= (αe1 αe2)/he αe2/Λ[] 1/hi 1/he 1/Λ() (17) Where. qi --- the secondary heat transfer coefficient of the sample to the indoor side; αe1---The direct sunlight absorption ratio of the first (outdoor side) glass in the double-layer window glass assembly; αe2---The direct sunlight absorption ratio of the second (indoor) glass in the double-layer window glass assembly; he---The heat transfer coefficient of the outdoor surface of the sample, in watts per square meter Kelvin [W/(m2·K)]; Λ ---The heat conduction between the outdoor side surface and the indoor side surface of the double glazing unit, in watts per square meter Kelvin [W/(m2·K)]; hi---the heat transfer coefficient of the indoor surface of the sample, in watts per square meter Kelvin [W/(m2·K)]. The direct sunlight absorption ratio αe1 of the first piece of glass (outdoor side) in the double glazing assembly is calculated by formula (18). αe1= 2500nm λ=300nm α1(λ) α'1(λ)τ1(λ)ρ2(λ)/[1-ρ'1(λ)ρ2(λ)]{ }SλΔλ 2500nm λ=300nm SλΔλ (18) Where. αe1 --- The direct sunlight absorption ratio of the first (outdoor side) glass in the double-layer window glass assembly; λ ---wavelength; α1(λ)---Under the condition that light is emitted from the outdoor side to the indoor side, the direct absorption ratio of the spectrum of the first piece of glass (outdoor side); α'1(λ)---Under the condition that light is emitted from the indoor side to the outdoor side, the direct absorption ratio of the spectrum of the first piece of glass (outdoor side); τ1(λ)---the spectral transmittance of the first piece of glass (outdoor side); ρ2(λ)---Under the condition that light is emitted from the outdoor side to the indoor side, the spectral reflectance of the second (indoor) glass; ρ'1(λ)---Under the condition that light is emitted from the indoor side to the outdoor side, the spectral reflectance of the first piece of glass (outdoor side); Sλ --- the relative spectral distribution of solar radiation; Δλ ---wavelength interval; SλΔλ --- the product of the solar radiation relative spectral distribution Sλ and the wavelength interval Δλ, the value of SλΔλ is shown in Table 2. Under the condition that light is emitted from the outdoor side to the indoor side, the spectral direct absorption ratio α1(λ) of the first piece of (outdoor side) glass is calculated by formula (19). α1(λ)=1-τ1(λ)-ρ1(λ) (19) Where. α1(λ)---Under the condition that light is emitted from the outdoor side to the indoor side, the direct absorption ratio of the spectrum of the first piece of glass (outdoor side); λ ---wavelength; τ1(λ)---the spectral transmittance of the first piece of glass (outdoor side); ρ1(λ)---The spectral reflectance of the first piece of glass (outdoor side) under the condition that light is emitted from the outdoor side to the indoor side. Under the condition that light is emitted from the indoor side to the outdoor side, the spectral direct absorption ratio of the first piece of (outdoor) glass is α'1(λ) using formula (20) Calculation. α'1(λ)=1-τ1(λ)-ρ'1(λ) (20) Where. α'1(λ)---Under the condition that light is emitted from the indoor side to the outdoor side, the direct absorption ratio of the spectrum of the first piece of glass (outdoor side); λ ---wavelength; τ1(λ)---the spectral transmittance of the first piece of glass (outdoor side); ρ'1(λ)---The spectral reflectance of the first piece of glass (outdoor side) under the condition that light is emitted from the indoor side to the outdoor side. The direct sunlight absorption ratio αe2 of the second (indoor) glass in the double-layered window glass assembly is calculated by formula (21). αe2= 2500nm λ=300nm {α2(λ)τ1(λ)/[1-ρ'1(λ)ρ2(λ)]}SλΔλ 2500nm λ=300nm SλΔλ (twenty one) Where. αe2 --- The direct sunlight absorption ratio of the second (indoor) glass in the double-layer window glass assembly; λ ---wavelength; α2(λ)---Under the condition that light is emitted from the outdoor side to the indoor side, the direct absorption ratio of the spectrum of the second (indoor) glass; τ1(λ)---the spectral transmittance of the first piece of glass (outdoor side); ρ'1(λ)---Under the condition that light is emitted from the indoor side to the outdoor side, the spectral reflectance of the first piece of glass (outdoor side); ρ2(λ)---Under the condition that light is emitted from the outdoor side to the indoor side, the spectral reflectance of the second (indoor) glass; Sλ --- the relative spectral distribution of solar radiation; Δλ ---wavelength interval; SλΔλ --- the product of the solar radiation relative spectral distribution Sλ and the wavelength interval Δλ, the value of SλΔλ is shown in Table 2. Under the condition that light is emitted from the outdoor side to the indoor side, the spectral direct absorption ratio α2(λ) of the second (indoor) glass is calculated by formula (22). α2(λ)=1-τ2(λ)-ρ2(λ) (22) Where. α2(λ)---Under the condition that light is emitted from the outdoor side to the indoor side, the direct absorption ratio of the spectrum of the second (indoor) glass; λ ---wavelength; τ2(λ)---the spectral transmittance of the second (indoor) glass; ρ2(λ)---The spectral reflectance of the second (indoor) glass under the condition that light is emitted from the outdoor side to the indoor side. The thermal conductivity Λ between the outdoor side surface and the indoor side surface of the double glazing unit can be based on the sample level specified in ISO 10292.1994. The average temperature is 10℃, and the temperature difference between the inner and outer surfaces of the sample is ΔT=15℃. The protective hot plate method specified in ISO 10291 can also be used Or the heat flow meter method specified in ISO 10293 is recommended to use the calculation method specified in ISO 10292.1994.If in order to meet special The requirements of using other sample inner and outer surface temperature difference ΔT and/or the average temperature of the sample should be stated in the inspection report. 5.8.6 The secondary heat transfer coefficient of the window glass assembly of n (n >2) layer to the indoor side The secondary heat transfer coefficient qi of the window glass assembly of the n (n >2) layer to the indoor side is calculated by formula (23). qi= αe1 αe2 αe3 Λ αen()/he αe2 αe3 Λ αen()/Λ12 αe3 Λ αen()/Λ23 αen/Λ(n-1)n 1/hi 1/he 1/Λ12 1/Λ23 Λ 1/Λ(n-1)n (twenty three) Where. qi ---n(n >2) secondary heat transfer coefficient of window glass components to the indoor side; αe1 ---The direct sunlight absorption ratio of the first glass (outdoor side) in the n-layer window glass assembly; αe2 ---The direct sunlight absorption ratio of the second glass in the n-layer window glass assembly; αe3 ---The direct sunlight absorption ratio of the third glass in the n-layer window glass assembly; αen ---the direct sunlight absorption ratio of the n-th (indoor) glass in the n-layer window glass assembly; he ---The heat transfer coefficient of the outdoor surface of the sample, in watts per square meter Kelvin [W/(m2·K)]; Λ12 ---The heat conduction between the outside surface of the first glass (outdoor side) and the center of the second glass (the center of the glass thickness), single Bits are watts per square meter Kelvin [W/(m2·K)]; Λ23 ---The heat conduction between the center of the second glass (the center of the glass thickness) and the center of the third glass (the center of the glass thickness), The unit is watts per square meter Kelvin [W/(m2·K)]; Λ(n-1)n---The heat between the center of the (n-1)th piece of glass (the center of the glass thickness) and the inside surface of the nth piece (indoor) Guide, the unit is Kelvin per square meter [W/(m2·K)]; hi ---The heat transfer coefficient of the indoor surface of the sample, in watts per square meter Kelvin [W/(m2·K)]; The thermal conductivity Λ12, Λ23, Λ(n-1)n is calculated iteratively according to the calculation process in Chapter 7 of ISO 10292.1994. The direct sunlight absorption ratio αe1, αe2, αe3, and αen are calculated according to the method given in 5.8.5.The calculation consists of the following (n-1) steps. a) The first step. According to 5.1 and 5.2.1, calculate the spectral characteristics of the (n-1) layer component composed of 2, 3, and n pieces of glass, and then compare this The component and the first piece of glass (outdoor side) form a double-layer window glass, and αe1 is calculated according to formula (18); b) Step 2.Calculate the spectral characteristics of the (n-2) layer component composed of 3, and n pieces of glass, and calculate the spectral characteristics of the first piece of glass and The spectral characteristics of the double-layer window glass composed of the second piece of glass, the above two components form a double-layer window glass, through this double For the layer window glass, calculate the sum of αe1 and αe2 according to formula (18). According to the value of αe1 in the first step, αe2 can be calculated, and continue this Steps all the way to the last (n-1) step; c) Step (n-1). Calculate the spectral characteristics of the (n-1) layer component composed of 1, 2, and (n-1) pieces of glass, and then compare this component with The nth piece of glass (indoor side) forms a double-layer window glass, and the sum of αe1, αe2, and αe(n-1) is calculated according to formula (18). According to the known For the values of αe1, αe2, and αe(n-2), αe(n-1) can be calculated, and αen can be calculated according to formula (21). 5.9 Shading factor The shading coefficient SC is calculated by formula (24). SC= 0.87 (twenty four) Where. SC---the shading coefficient of the sample; g ---The total solar transmittance of the sample. 5.10 Light-to-heat ratio The light-to-heat ratio LSG is calculated by formula (25). LSG= τv (25) Where. LSG---the light-to-heat ratio of the sample; τv --- the visible light transmittance of the sample; g ---The total solar transmittance of the sample. 5.11 UV transmittance 5.11.1 Calculation of UV transmittance The ultraviolet transmittance τuv is calculated by formula (26). ......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.