GB/T 2680-2021Glass in building—Determination of light transmittance, solar direct transmittance, total solar energy transmittance, ultraviolet transmittance and related glazing factors (English PDF)

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%.

5.1 Visible light transmittance

5.1.1 Calculation method of visible light transmittance

The visible light transmittance tauv is calculated by formula (1). Slambda --- the relative spectral distribution of solar radiation; deltalambda ---wavelength interval;

Slambdadeltalambda---the product of the relative spectral distribution of solar radiation Slambda and the wavelength interval deltalambda, the value of Slambdadeltalambda is shown in Table 2.

5.5 Direct sunlight reflectance

5.5.3 Outdoor spectral reflectance of multi-layer window glass components

The calculation of the outdoor spectral reflectance rhoo(lambda) 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 alphae is calculated by formula (11).

5.7 Total solar transmittance

The total solar transmittance g is calculated by formula (14). Where. g --- Total solar transmittance of the sample;

taue --- 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

5.8.4 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). he hi (16)

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). (alphae1 alphae2)/he alphae2/Lambda[] 1/hi 1/he 1/Lambda() (17)

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).

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). 4.4epsiloni

(15) Where. hi---the heat transfer coefficient of the indoor surface of the sample, in watts per square meter Kelvin [W/(m2·K)]; epsiloni ---corrected emissivity of the interior surface of the sample chamber. Where. qi---the secondary heat transfer coefficient of the sample to the indoor side; alphae---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)]. Where. qi --- the secondary heat transfer coefficient of the sample to the indoor side; alphae1---The direct sunlight absorption ratio of the first (outdoor side) glass in the double-layer window glass assembly; alphae2---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)]; Lambda ---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 alphae1 of the first piece of glass (outdoor side) in the double glazing assembly is calculated by formula (18). 2500nm alpha1(lambda) alpha'1(lambda)tau1(lambda)rho2(lambda)/[1-rho'1(lambda)rho2(lambda)]{ }Slambdadeltalambda 2500nm Slambdadeltalambda (18) Where. alphae1 --- The direct sunlight absorption ratio of the first (outdoor side) glass in the double-layer window glass assembly; lambda ---wavelength; alpha1(lambda)---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); alpha'1(lambda)---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); tau1(lambda)---the spectral transmittance of the first piece of glass (outdoor side); rho2(lambda)---Under the condition that light is emitted from the outdoor side to the indoor side, the spectral reflectance of the second (indoor) glass; rho'1(lambda)---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); Slambda --- the relative spectral distribution of solar radiation; deltalambda ---wavelength interval; Slambdadeltalambda --- the product of the solar radiation relative spectral distribution Slambda and the wavelength interval deltalambda, the value of Slambdadeltalambda 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 alpha1(lambda) of the first piece of (outdoor side) glass is calculated by formula (19). alpha1(lambda)=1-tau1(lambda)-rho1(lambda) (19) Where. alpha1(lambda)---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); lambda ---wavelength; tau1(lambda)---the spectral transmittance of the first piece of glass (outdoor side); rho1(lambda)---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 alpha'1(lambda) using formula (20) Calculation. alpha'1(lambda)=1-tau1(lambda)-rho'1(lambda) (20) Where. alpha'1(lambda)---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); lambda ---wavelength; tau1(lambda)---the spectral transmittance of the first piece of glass (outdoor side); rho'1(lambda)---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 alphae2 of the second (indoor) glass in the double-layered window glass assembly is calculated by formula (21). 2500nm {alpha2(lambda)tau1(lambda)/[1-rho'1(lambda)rho2(lambda)]}Slambdadeltalambda 2500nm Slambdadeltalambda (twenty one) Where. alphae2 --- The direct sunlight absorption ratio of the second (indoor) glass in the double-layer window glass assembly; lambda ---wavelength; alpha2(lambda)---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; tau1(lambda)---the spectral transmittance of the first piece of glass (outdoor side); rho'1(lambda)---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); rho2(lambda)---Under the condition that light is emitted from the outdoor side to the indoor side, the spectral reflectance of the second (indoor) glass; Slambda --- the relative spectral distribution of solar radiation; deltalambda ---wavelength interval; Slambdadeltalambda --- the product of the solar radiation relative spectral distribution Slambda and the wavelength interval deltalambda, the value of Slambdadeltalambda 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 alpha2(lambda) of the second (indoor) glass is calculated by formula (22). alpha2(lambda)=1-tau2(lambda)-rho2(lambda) (22) Where. alpha2(lambda)---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; lambda ---wavelength; tau2(lambda)---the spectral transmittance of the second (indoor) glass; rho2(lambda)---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 Lambda 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°C, and the temperature difference between the inner and outer surfaces of the sample is deltaT=15°C. 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 deltaT and/or the average temperature of the sample should be stated in the inspection report. alphae1 alphae2 alphae3 Lambda alphaen()/he alphae2 alphae3 Lambda alphaen()/Lambda12 alphae3 Lambda alphaen()/Lambda23 alphaen/Lambda(n-1)n 1/hi 1/he 1/Lambda12 1/Lambda23 Lambda 1/Lambda(n-1)n (twenty three) Where. qi ---n(n >2) secondary heat transfer coefficient of window glass components to the indoor side; alphae1 ---The direct sunlight absorption ratio of the first glass (outdoor side) in the n-layer window glass assembly; alphae2 ---The direct sunlight absorption ratio of the second glass in the n-layer window glass assembly; alphae3 ---The direct sunlight absorption ratio of the third glass in the n-layer window glass assembly; alphaen ---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)]; Lambda12 ---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)]; Lambda23 ---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)]; Lambda(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 Lambda12, Lambda23, Lambda(n-1)n is calculated iteratively according to the calculation process in Chapter 7 of ISO 10292:1994. The direct sunlight absorption ratio alphae1, alphae2, alphae3, and alphaen 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 alphae1 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 alphae1 and alphae2 according to formula (18). According to the value of alphae1 in the first step, alphae2 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 alphae1, alphae2, and alphae(n-1) is calculated according to formula (18). According to the known For the values of alphae1, alphae2, and alphae(n-2), alphae(n-1) can be calculated, and alphaen can be calculated according to formula (21).

5.9 Shading factor

The shading coefficient SC is calculated by formula (24).

(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). tauv (25) Where. LSG---the light-to-heat ratio of the sample;

tauv --- 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 tauuv is calculated by formula (26).