Calculation method of surface radiation absorption coefficient of building materials considering the difference between long and short waves

Abstract

The present invention discloses a method for calculating the surface radiation absorption coefficient of building materials taking into account the difference between long and short waves. Step S1: placing a building material specimen wrapped in a heat-insulating box in an open and unobstructed natural environment, with only the upper surface of the building material specimen in contact with the surrounding environment, and establishing a thermal boundary balance equation; Step S2: recording relevant data; Step S3: selecting a certain time period within a time period when the building material specimen is continuously heated or cooled, and calculating the thermal change Q of the building material specimen s , Convective heat transfer Q c and thermal radiation I sr ; Step S4: In a natural environment where it is cloudy and rainless at night and the surroundings are open and unobstructed, the amount of direct sunlight and scattered radiation is zero, and the long-wave radiation absorption coefficient of the outer surface of the building material test block is calculated by the transformation formula; Step S5: In a natural environment where it is sunny during the day and the surroundings are open and unobstructed, select the system heat exchange in a certain time period, record the relevant data, and calculate the short-wave radiation absorption coefficient of the building material test piece.

Description

Technical Field

[0001] The invention relates to the technical field of engineering building materials, and in particular to a method for calculating the surface radiation absorption coefficient of building materials taking into account the difference between long and short waves. Background Art

[0002] Civil engineering infrastructure not only bears heavy traffic loads, but also bears harsh external environmental effects. External environmental effects include ambient temperature, solar radiation, wind load, climate phenomena such as rain, snow and cold waves, chemical corrosion and freeze-thaw cycles, etc. These effects not only lead to the aging of structural materials, but also have a significant impact on the stress state of the structure. The inner and outer surfaces of the structure continuously exchange heat with the surrounding air medium in the form of convection, short-wave and long-wave radiation and heat conduction. In recent decades, the practice of large-span space steel structures and concrete structures at home and abroad has proved that the temperature changes of the structure caused by the rapid change of solar radiation in a short period of time will aggravate the phenomenon of uneven temperature field and temperature stress inside the structure, and even cause serious deformation of the structure and cause engineering accidents. Determining the temperature field of the structure is the premise for accurately analyzing the temperature effect of the structure (the change of structural mechanical properties caused by temperature) and evaluating the structural state, which directly affects the accuracy and credibility of the subsequent analysis results. For large-span space structures and bridge structures, the temperature effect analysis mainly includes two parts: temperature field calculation and structural mechanical response analysis caused by temperature. Studies have shown that the surface radiation absorption coefficient of building materials has a significant impact on the temperature field and temperature effect of the structure.

[0003] The solar radiation absorption coefficient is used to characterize the properties of the material surface absorbing solar radiation energy. It is the main factor affecting the solar radiation temperature of the space structure. It is related to factors such as the color, roughness, and chemical composition of the structure surface. There is no unified standard for the relevant values ​​of building structural materials. Generally, only a range of values ​​is given for subjective selection. For general engineering building materials such as concrete, long-wave radiation and absorption have the properties of gray bodies. Based on Kirchhoff's law of thermal radiation, the emissivity of the gray body is equal to its absorptivity, and the emissivity of the surface of the object depends on the material composition of the structure, the temperature difference between the structure surface and the surrounding environment, and the surface treatment measures. At present, there is a lack of authoritative data to determine the relevant values, and it can only be subjectively selected within a range of values. At the same time, when selecting the correlation coefficient of the structural temperature field and temperature effect analysis, the influence of structural surface characteristics such as surface roughness, color, type and thickness of coating on the radiation absorption coefficient is often not considered, which will lead to insufficient consideration of the design of environmental loads in the structural design, and bury the potential safety hazards of the structure.

[0004] After being absorbed by the ozone layer, water vapor and atmospheric molecules, the solar radiation that finally reaches the earth's surface is in the wavelength band of 280 to 2500nm, which belongs to short-wave radiation. Long-wave radiation is radiation with a wavelength range of 4 to 120μm. Atmospheric back radiation and thermal radiation of building materials themselves belong to long-wave radiation. Short-wave radiation and long-wave radiation have different absorption and radiation characteristics. Therefore, it is necessary to propose a method for calculating the radiation absorption coefficient that can distinguish between the short-wave radiation and long-wave radiation on the surface of building materials and take the surface characteristics of the structure into consideration based on the differences between the short-wave radiation and long-wave radiation on the surface of building materials. This method is more in line with the need to determine the relevant parameters in the analysis of the temperature field and temperature effect of the building structure, and is in line with the current status of its service environment. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for calculating the surface radiation absorption coefficient of building materials taking into account the differences between long and short waves, which can simulate the service environment of building material specimens and has the advantages of low cost, simplicity and speed, simultaneous measurement and comparison of multiple materials, small size effect of building material specimens and high calculation accuracy.

[0006] The technical solution of the present invention is: a method for calculating the surface radiation absorption coefficient of building materials taking into account the difference between long and short waves, comprising the following steps:

[0007] Step S1: placing the building material specimen wrapped in the thermal insulation box in an open and unobstructed natural environment, with only the upper surface of the building material specimen in contact with the surrounding environment, and establishing a thermal boundary balance equation based on the heat exchange equilibrium state of the building material specimen in the thermal environment;

[0008] Step S2: Record the direct solar radiation I of the surrounding environment m 、Solar diffuse radiation I r and atmospheric back radiation I a , collect the temperature of building material specimens and the surrounding environment, and calculate and collect data once every 10-20 minutes;

[0009] Step S3: Select a certain time period within the time period when the building material specimen is continuously heated up or cooled down, and calculate the thermal change Q of the building material specimen. s , Convective heat transfer Q c and thermal radiation I sr ;

[0010] Step S4: In a natural environment with cloudy sky and no rain at night and open space without any shielding, without the influence of solar radiation, the radiation in the thermal environment of the upper surface of the building material test piece is only long-wave radiation, and the amount of direct solar radiation and scattered radiation is zero. The long-wave radiation absorption coefficient of the outer surface of the building material test piece is calculated by a transformation formula;

[0011] Step S5: In a natural environment with clear sky and open space without any shielding during the day, select a certain time period for system heat exchange and record the direct solar radiation I of the surrounding environment. m 、Solar diffuse radiation I r and atmospheric back radiation I a , collect the temperature of the building material specimen and the surrounding environment, calculate and collect data once every 10-20 minutes, and calculate the short-wave radiation absorption coefficient of the building material specimen through the recorded relevant data;

[0012] Step S6: Replace different building material specimens, repeat steps S1-S5, and calculate the surface radiation coefficients of various building materials taking into account the differences in short-wave and long-wave radiation. When calculating the radiation absorption coefficient of each material, it is necessary to obtain data from multiple time periods for calculation and take the average value.

[0013] Furthermore, the process of establishing the thermal boundary balance equation in step S1 is as follows: heat exchange includes solar radiation, convective heat exchange and radiative heat exchange, with heat flowing from the outside into the structure as positive and heat flowing out as negative; solar radiation includes direct solar radiation and solar scattered radiation; radiative heat exchange includes atmospheric back radiation and thermal radiation of the building material specimen itself, and the thermal boundary balance equation in the thermal environment where the building material specimen is located is established as follows:

[0014] Q s +α(I m +I r )AΔ t +εI a AΔ t =Q c +I sr AΔ t

[0015] Where: Q s Indicates the thermal change of the building material specimen within the selected time period; I m and I r They represent direct solar radiation and scattered solar radiation respectively; α represents the shortwave radiation absorption coefficient; I a represents atmospheric back radiation; ε represents the long-wave radiation absorption coefficient; Q c It represents the convective heat transfer of the building material specimen in the selected time period; I sr It represents the heat radiation emitted by the building material specimen to the surrounding environment during the selected time period; A is the external surface area of ​​the building material specimen; Δt represents the time period selected for calculating the thermal balance, and Δt is 10-20 minutes.

[0016] Further, the empirical formula is used to calculate I m ,I r and I a ;

[0017] The empirical formula for the direct radiation intensity on the surface of the structure with a solar incident angle of θ is:

[0018]

[0019] Where: m = 1 / sinβ, is the distance of the light; β is the solar altitude angle; I o is the solar constant, N is the day number starting from January 1; k a is the relative atmospheric pressure; t u is the Link's turbidity coefficient;

[0020] Solar scattered radiation can be calculated using the following empirical formula:

[0021] I d =(0.271I o -0.294I m )sinβ

[0022] The thermal radiation of the surrounding atmosphere to the building material specimen is I a , also known as atmospheric back radiation, belongs to long-wave radiation, and its empirical formula is:

[0023] I a =E a C s (T k +T a ) 4

[0024] Where: E a is the atmospheric radiation coefficient, E a =1-0.261exp(-7.776×10 -4 T a 2 ), take the approximate value of 0.82, T k =273.15K, used for conversion between Celsius and absolute temperature, T a Indicates the atmospheric temperature.

[0025] Further, in step S3, the heat change of the building material specimen in the selected time period is Q s , and its calculation formula is:

[0026] Q s =c s m s (T s2 -T s1 )

[0027] In the formula, c s Represents the specific heat capacity of the building material specimen; m sIndicates the mass of the building material specimen, T s1 and T s2 They respectively represent the temperature of the building specimen at the beginning and end of the selected time period, and the temperature change can be measured by the thermocouple temperature sensors set inside and on the outer surface of the building material specimen;

[0028] The calculation method of the convective heat transfer between the outer surface of the building material specimen and the air in the selected time period based on Newton's cooling formula is:

[0029] Q c =h c (T s -T a )A

[0030] In the formula, h c It represents the convective heat transfer coefficient of the outer surface of the building material specimen. For concrete materials, h c =6.02+3.46v, where the constant term indicates the consideration of the influence of natural convection heat transfer, and v indicates the wind speed passing over the outer surface of the building material specimen. The average wind speed in the selected time period is taken during the calculation;

[0031] As long as the temperature of an object is above absolute zero, the object will always convert heat energy into radiation energy and emit thermal radiation outward. Therefore, there is thermal radiation between the building material specimen and the surrounding environment. This part of radiation belongs to long-wave radiation. The thermal radiation emitted by the building material specimen to the surrounding environment is I sr , and its calculation formula is:

[0032] I sr =εC s (T o +T k ) 4

[0033] Where: ε represents the long-wave radiation absorption coefficient of the outer surface of the building material specimen. For concrete materials, its long-wave radiation and absorption have the properties of gray bodies. According to Kirchhoff's law of thermal radiation, the emissivity of the gray body is equal to its absorptivity; C s represents the Stefan-Boltzmann constant, which is 5.67×10 -8 W / (m 2 ·K 4 );T k is 273.15K, used for conversion between Celsius and absolute temperature, T o Indicates the outer surface temperature of the building material specimen.

[0034] Further, in step S4, the process of calculating the long-wave radiation absorption coefficient of the surface of the building material specimen is as follows:

[0035] Considering that the building material specimen absorbs external radiation and heats up during the day, and the external environment temperature gradually drops below the specimen temperature at night, causing the building material specimen to release heat to the external environment, in a cloudy and rainless natural environment at night, there is no influence of solar radiation, and the radiation in the thermal environment of the outer surface of the building material specimen is only long-wave radiation, and the amount of direct solar radiation and solar scattered radiation is zero. The long-wave radiation absorption coefficient of the outer surface of the building material specimen can be calculated by the transformation formula:

[0036]

[0037] Furthermore, in step S5, the calculation formula for calculating the short-wave radiation absorption coefficient of the surface of the building material specimen is as follows:

[0038]

[0039] Furthermore, it also includes a simple meteorological station, an anemometer, a solar total radiation sensor, an environmental long-wave radiation sensor and an atmospheric temperature sensor. The simple meteorological station is used to be electrically connected to the anemometer, the solar total radiation sensor, the environmental long-wave radiation sensor and the atmospheric temperature sensor to collect and store data in real time. The anemometer, the environmental long-wave radiation sensor and the solar total radiation sensor are located within 1.5 meters of the building material specimen. The anemometer is used to measure the wind speed passing over the outer surface of the building material specimen. The solar total radiation sensor is used to measure the total radiation of the sun. The environmental long-wave radiation sensor is used to measure the long-wave radiation of the thermal environment in which the building material specimen is located. The atmospheric temperature sensor is used to measure the temperature of the surrounding environment.

[0040] Furthermore, the roughness and color of the outer surface of the building material specimens are changed or different coating treatments are applied to the outer surface to study the influence of different variables on the radiation absorption coefficient of the outer surface of the building material specimens.

[0041] Furthermore, after determining the short-wave radiation absorption coefficient and long-wave radiation absorption coefficient on the surface of the building material specimens, the corresponding total solar radiation, environmental long-wave radiation, and thermal radiation of the building material specimens themselves and the surrounding environment are combined for calculation to analyze the proportion of short-wave radiation and long-wave radiation in the thermal environment of the all-weather building material specimens. Through long-term measurements, the radiation heat behavior patterns of various types of building engineering materials in different seasons can also be fitted.

[0042] Furthermore, the thermal insulation box is made of polyethylene.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1. The present invention can take into account the differences between short-wave radiation and long-wave radiation, calculate the short-wave radiation and long-wave radiation absorption coefficients on the surface of building materials, and is more in line with the needs of temperature field and temperature effect analysis of engineering structures;

[0045] 2. The present invention has the advantages of being simple and practical, having strong operability and low test cost;

[0046] 3. The test conditions in the present invention are controllable, and the calculation of the surface radiation absorption coefficient of building materials with different surface characteristics under different environments can be realized;

[0047] 4. The present invention places the building material specimen in an external environment, constructs a heat balance equation and derives a calculation method for its short-wave radiation absorption coefficient and long-wave radiation absorption coefficient, and the result is more consistent with its actual service status. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a structural diagram of the method for calculating the surface radiation absorption coefficient of building materials taking into account the difference between long and short waves of the present invention.

[0049] Figure 2 It is a structural diagram of the building material specimen of the present invention.

[0050] Building material test piece 1, thermal insulation box 2, thermocouple temperature sensor 3, simple weather station 4, anemometer 5, total solar radiation sensor 6, environmental long wave radiation sensor 7, atmospheric temperature sensor 8. DETAILED DESCRIPTION

[0051] The present invention will be further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0052] Example

[0053] like Figure 1 and Figure 2 As shown, this embodiment provides a method for calculating the surface radiation absorption coefficient of building materials taking into account the differences between long and short waves, including a building material specimen 1, a thermal insulation box 2, a thermocouple temperature sensor 3, a simple meteorological station 4, an anemometer 5, a solar total radiation sensor 6, an environmental long-wave radiation sensor 7 and an atmospheric temperature sensor 8.

[0054] like Figure 1 and Figure 2As shown, the thermal insulation box is made of polyethylene, and the thermal insulation box wraps the building material specimen so that only the outer surface of the building material specimen is in contact with the surrounding environment. Thermocouple temperature sensors are arranged on the outer surface and inside of the building material specimen. The anemometer, the environmental long-wave radiation sensor and the solar total radiation sensor are located within 1.5 meters of the building material specimen. The anemometer is used to measure the wind speed passing over the outer surface of the building material specimen, the solar total radiation sensor is used to measure the total radiation of the sun, the environmental long-wave radiation sensor is used to measure the long-wave radiation of the thermal environment in which the building material specimen is located, and the atmospheric temperature sensor is used to measure the temperature of the surrounding environment. The simple meteorological station is electrically connected to the anemometer, the solar total radiation sensor, the environmental long-wave radiation sensor, the thermocouple temperature sensor and the atmospheric temperature sensor to collect and store data in real time.

[0055] The above-mentioned method for calculating the surface radiation absorption coefficient of building materials taking into account the difference between long and short waves includes the following steps:

[0056] Step S1: placing the building material specimen wrapped in the thermal insulation box in an open and unobstructed natural environment, with only the upper surface of the building material specimen in contact with the surrounding environment, and establishing a thermal boundary balance equation based on the heat exchange equilibrium state of the building material specimen in the thermal environment;

[0057] Step S2: Record the direct solar radiation I of the surrounding environment m 、Solar diffuse radiation I r and atmospheric back radiation I a , collect the temperature of the building material specimen and the surrounding environment, and calculate and collect data once every 10-20 minutes; in this embodiment, calculate and collect data once every 15 minutes;

[0058] Step S3: Select a certain time period within the time period when the building material specimen is continuously heated up or cooled down, and calculate the thermal change Q of the building material specimen. s , Convective heat transfer Q c and thermal radiation I sr ;

[0059] Step S4: In a natural environment with cloudy sky and no rain at night and open space without any shielding, without the influence of solar radiation, the radiation in the thermal environment of the upper surface of the building material test piece is only long-wave radiation, and the amount of direct solar radiation and scattered radiation is zero. The long-wave radiation absorption coefficient of the outer surface of the building material test piece is calculated by a transformation formula;

[0060] Step S5: In a natural environment with clear sky and open space without any shielding during the day, select a certain time period for system heat exchange and record the direct solar radiation I of the surrounding environment. m 、Solar diffuse radiation I r and atmospheric back radiation I a, collect the temperature of the building material specimen and the surrounding environment, calculate and collect data once every 15 minutes, and calculate the short-wave radiation absorption coefficient of the building material specimen through the recorded relevant data;

[0061] Step S6: Replace different building material specimens, repeat steps S1-S5, and calculate the surface radiation coefficients of various building materials taking into account the differences in short-wave and long-wave radiation. When calculating the radiation absorption coefficient of each material, it is necessary to obtain data from multiple time periods for calculation and take the average value.

[0062] The process of establishing the thermal boundary balance equation in step S1 is as follows: heat exchange includes solar radiation, convective heat exchange and radiation heat exchange, with heat flowing from the outside into the structure as positive and heat flowing out as negative; solar radiation includes direct solar radiation and solar scattered radiation; radiation heat exchange includes atmospheric back radiation and thermal radiation of the building material specimen itself, and the thermal boundary balance equation in the thermal environment where the building material specimen is located is established as follows:

[0063] Q s +α(I m +I r )AΔ t +εI a AΔ t =Q c +I sr AΔ t

[0064] Where: Q s Indicates the thermal change of the building material specimen within the selected time period; I m and I r They represent direct solar radiation and scattered solar radiation respectively; α represents the shortwave radiation absorption coefficient; I a represents atmospheric back radiation; ε represents the long-wave radiation absorption coefficient; Q c It represents the convective heat transfer of the building material specimen in the selected time period; I sr It represents the heat radiation emitted by the building material specimen to the surrounding environment during the selected time period; A is the outer surface area of ​​the building material specimen; Δt represents the time period selected for calculating the thermal balance, Δt is 10-20 minutes, and in this embodiment, Δt is 15 minutes.

[0065] In step S2, an empirical formula is used to calculate I m ,I r and I a ;

[0066] The empirical formula for the direct radiation intensity on the surface of the structure with a solar incident angle of θ is:

[0067]

[0068] Where: m = 1 / sinβ, is the distance of the light; β is the solar altitude angle; I o is the solar constant, N is the day number starting from January 1; k a is the relative atmospheric pressure; t u is the Link's turbidity coefficient;

[0069] Solar scattered radiation can be calculated using the following empirical formula:

[0070] I d =(0.271I o -0.294I m )sinβ

[0071] The thermal radiation of the surrounding atmosphere to the building material specimen is I a , also known as atmospheric back radiation, belongs to long-wave radiation, and its empirical formula is:

[0072] I a =E a C s (T k +T a ) 4

[0073] Where: E a is the atmospheric radiation coefficient, E a =1-0.261exp(-7.776×10 -4 T a 2 ), take the approximate value of 0.82, T k =273.15K, used for conversion between Celsius and absolute temperature, T a Indicates the atmospheric temperature. In this embodiment, direct solar radiation and scattered solar radiation belong to short-wave radiation. Although both can be calculated by empirical formulas, the amount of calculation involved is relatively large. They can be easily obtained by on-site collection of the solar total radiation sensor, and the atmospheric back radiation can also be measured by the environmental long-wave radiation sensor.

[0074] In step S3, the heat change of the building material specimen in the selected time period is Q s , and its calculation formula is:

[0075] Q s =c s m s (T s2 -T s1 )

[0076] In the formula, c s Represents the specific heat capacity of the building material specimen; m s Indicates the mass of the building material specimen, Ts1 and T s2 They respectively represent the temperature of the building specimen at the beginning and end of the selected time period, and the temperature change can be measured by the thermocouple temperature sensors installed inside and on the surface of the building material specimen;

[0077] The calculation method of the convective heat transfer between the outer surface of the building material specimen and the air in the selected time period based on Newton's cooling formula is:

[0078] Q c =h c (T s -T a )A

[0079] In the formula, h c It represents the convective heat transfer coefficient of the outer surface of the building material specimen. For concrete materials, h c =6.02+3.46v, where the constant term indicates the consideration of the influence of natural convection heat transfer, and v indicates the wind speed passing over the outer surface of the building material specimen. The average wind speed in the selected time period is taken during the calculation;

[0080] As long as the temperature of an object is above absolute zero, the object will always convert heat energy into radiation energy and emit thermal radiation outward. Therefore, there is thermal radiation between the building material specimen and the surrounding environment. This part of radiation belongs to long-wave radiation. The thermal radiation emitted by the building material specimen to the surrounding environment is I sr , and its calculation formula is:

[0081] I sr =εC s (T o +T k ) 4

[0082] Where: ε represents the long-wave radiation absorption coefficient of the outer surface of the building material specimen. For concrete materials, its long-wave radiation and absorption have the properties of gray bodies. According to Kirchhoff's law of thermal radiation, the emissivity of the gray body is equal to its absorptivity; C s represents the Stefan-Boltzmann constant, which is 5.67×10 -8 W / (m 2 ·K 4 );T k is 273.15K, used for conversion between Celsius and absolute temperature, T o Indicates the outer surface temperature of the building material specimen.

[0083] In step S4, the process of calculating the long-wave radiation absorption coefficient of the building material specimen surface is as follows:

[0084] Considering that the building material specimen absorbs external radiation and heats up during the day, and the external environment temperature gradually drops below the specimen temperature at night, causing the building material specimen to release heat to the external environment, in a cloudy and rainless natural environment at night, there is no influence of solar radiation, and the radiation in the thermal environment of the outer surface of the building material specimen is only long-wave radiation, and the amount of direct solar radiation and solar scattered radiation is zero. The long-wave radiation absorption coefficient of the outer surface of the building material specimen can be calculated by the transformation formula:

[0085]

[0086] In step S5, the calculation formula for calculating the short-wave radiation absorption coefficient of the building material specimen surface is as follows:

[0087]

[0088] After determining the short-wave radiation absorption coefficient and long-wave radiation absorption coefficient on the surface of the building material specimens, the corresponding total solar radiation, environmental long-wave radiation, and thermal radiation of the building material specimens themselves and the surrounding environment are combined for calculation to analyze the proportion of short-wave radiation and long-wave radiation in the thermal environment of the all-weather building material specimens. Through long-term measurements, the radiation heat behavior patterns of various types of building materials in different seasons can also be fitted.

[0089] According to the above calculation method, the roughness and color of the outer surface of the building material specimens are changed or different coating treatments are applied to the outer surface to study the influence of different variables on the radiation absorption coefficient of the outer surface of the building material specimens.

[0090] As described above, the present invention can be better implemented. The above embodiments are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention; that is, all equivalent changes and modifications made according to the content of the present invention are covered by the scope of protection required by the claims of the present invention.

Claims

1. A method for calculating the surface radiation absorption coefficient of building materials taking into account the difference between long and short waves, characterized in that: The following steps are involved: Step S1: placing the building material specimen wrapped in the thermal insulation box in an open and unobstructed natural environment, with only the upper surface of the building material specimen in contact with the surrounding environment, and establishing a thermal boundary balance equation based on the heat exchange equilibrium state of the building material specimen in the thermal environment; Step S2: Record the direct solar radiation I of the surrounding environment m 、Solar diffuse radiation I r and atmospheric back radiation I a , collect the temperature of building material specimens and the surrounding environment, and calculate and collect data once every 10-20 minutes; Step S3: Select a certain time period within the time period when the building material specimen is continuously heated up or cooled down, and calculate the thermal change Q of the building material specimen. s , Convective heat transfer Q c and thermal radiation I sr In step S3, the heat change of the building material specimen in the selected time period is , and its calculation formula is: In the formula, It represents the specific heat capacity of the building material specimen; Indicates the quality of building material specimens, and They respectively represent the temperature of the building specimen at the beginning and end of the selected time period, and the temperature change can be measured by the thermocouple temperature sensors set inside and on the outer surface of the building material specimen; The calculation method of the convective heat transfer between the outer surface of the building material specimen and the air in the selected time period based on Newton's cooling formula is: In the formula, h c It represents the convective heat transfer coefficient of the outer surface of the building material specimen. For concrete materials, The constant term in the formula indicates the consideration of the influence of natural convection heat transfer, v represents the wind speed that passes over the outer surface of the building material specimen, the average wind speed in the selected time period is taken during the calculation, A is the outer surface area of ​​the building material specimen, represents the atmospheric temperature, T o Indicates the external surface temperature of the building material specimen; As long as the temperature of an object is above absolute zero, the object will always convert heat energy into radiation energy and emit thermal radiation outward. Therefore, there is thermal radiation between the building material specimen and the surrounding environment. This part of radiation belongs to long-wave radiation. The thermal radiation emitted by the building material specimen to the surrounding environment is , and its calculation formula is: Where: It represents the long-wave radiation absorption coefficient of the outer surface of the building material specimen. For concrete materials, its long-wave radiation and absorption have the properties of gray body. According to Kirchhoff's law of thermal radiation, the emissivity of gray body is equal to its absorptivity; C s represents the Stefan-Boltzmann constant, whose value is ; T k It is 273.15K, used for conversion between Celsius and absolute temperature; Step S4: In a natural environment with cloudy and rainless night and open space without any shielding, without the influence of solar radiation, the radiation in the thermal environment of the upper surface of the building material specimen is only long-wave radiation, and the amount of direct solar radiation and scattered radiation is zero. The long-wave radiation absorption coefficient of the outer surface of the building material specimen is calculated by the transformation formula; the process of calculating the long-wave radiation absorption coefficient of the surface of the building material specimen is as follows: Considering that the building material specimen absorbs external radiation and heats up during the day, and the external environment temperature gradually drops below the specimen temperature at night, causing the building material specimen to release heat to the external environment, in a cloudy and rainless natural environment at night, there is no influence of solar radiation, and the radiation in the thermal environment of the outer surface of the building material specimen is only long-wave radiation, and the amount of direct solar radiation and solar scattered radiation is zero. The long-wave radiation absorption coefficient of the outer surface of the building material specimen can be calculated by the transformation formula: ； Step S5: In a natural environment with clear sky and open space without any shielding, select a certain time period for system heat exchange and record the direct solar radiation I of the surrounding environment. m 、Solar diffuse radiation I r and atmospheric back radiation I a , Indicates the time period selected for calculating thermal balance, The temperature of the building material specimen and the surrounding environment is collected every 10-20 minutes. The data is calculated and collected once every 10-20 minutes. The short-wave radiation absorption coefficient of the building material specimen is calculated based on the recorded relevant data. The calculation formula for the short-wave radiation absorption coefficient of the building material specimen surface is as follows: ； Step S6: Replace different building material specimens, repeat steps S1-S5, and calculate the surface radiation coefficients of various building materials taking into account the differences in short-wave and long-wave radiation. When calculating the radiation absorption coefficient of each material, it is necessary to obtain data from multiple time periods for calculation and take the average value.

2. The method for calculating the surface radiation absorption coefficient of building materials considering the difference between long and short waves according to claim 1 is characterized in that: It also includes a simple weather station, an anemometer, a solar total radiation sensor, an environmental long-wave radiation sensor and an atmospheric temperature sensor. The simple weather station is used to be electrically connected to the anemometer, the solar total radiation sensor, the environmental long-wave radiation sensor and the atmospheric temperature sensor to collect and store data in real time. The anemometer, the environmental long-wave radiation sensor and the solar total radiation sensor are located within 1.5 meters of the building material specimen. The anemometer is used to measure the wind speed passing over the outer surface of the building material specimen. The solar total radiation sensor is used to measure the total radiation of the sun. The environmental long-wave radiation sensor is used to measure the long-wave radiation of the thermal environment in which the building material specimen is located. The atmospheric temperature sensor is used to measure the temperature of the surrounding environment.

3. The method for calculating the surface radiation absorption coefficient of building materials considering the difference between long and short waves according to claim 1 is characterized in that: By changing the roughness and color of the outer surface of the building material specimens or applying different coating treatments on the outer surface, the influence of different variables on the radiation absorption coefficient of the outer surface of the building material specimens can be studied.

4. The method for calculating the surface radiation absorption coefficient of building materials considering the difference between long and short waves according to claim 1 is characterized in that: After determining the short-wave radiation absorption coefficient and long-wave radiation absorption coefficient on the surface of the building material specimens, the corresponding total solar radiation, environmental long-wave radiation, and thermal radiation of the building material specimens themselves and the surrounding environment are combined for calculation to analyze the proportion of short-wave radiation and long-wave radiation in the thermal environment of the all-weather building material specimens. Through long-term measurements, the radiation heat behavior patterns of various types of building materials in different seasons can also be fitted.

5. The method for calculating the surface radiation absorption coefficient of building materials considering the difference between long and short waves according to claim 1 is characterized in that: The thermal insulation box is made of polyethylene.

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