Building material surface radiation absorption coefficient calculation method considering long and short wave difference

Abstract

The invention discloses a building material surface radiation absorption coefficient calculation method considering long and short wave difference, which comprises the following steps: S1, putting a building material test piece wrapped by a thermal insulation box in a surrounding open and unshielded natural environment, and establishing a thermal boundary equilibrium equation when only the upper surface of the building material test piece is in contact with the surrounding environment; s2, recording related data; s3, selecting a certain time period in the time section of continuous heating or continuous cooling of the building material test piece, and calculating the thermal change quantity Qs, the convective heat exchange quantity Qc and the thermal radiation quantity Isr of the building material test piece; s4, in a natural environment which is cloudy and rain-free at night and is open and free of shielding, the quantity of direct solar radiation and scattered solar radiation is zero, and the long-wave radiation absorption coefficient of the outer surface of the building material test block is calculated through a transformation formula; and S5, selecting system heat exchange in a certain time period in a natural environment which is sunny in the daytime and is open and unshielded in the surrounding, recording related data, and calculating 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, in particular to a method for calculating the surface radiation absorption coefficient of building materials considering the difference between long and short waves. Background technique [0002] Civil engineering infrastructure not only bears the heavy traffic load, but also bears the harsh external environment. External environmental effects include ambient temperature, solar radiation, wind load, climatic 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 internal and external 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 s...

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Problems solved by technology

[0003] The solar radiation absorption coefficient is used to characterize the properties of the material surface to absorb solar radiation energy. It is the main factor affecting the solar radiation temperature of the space structure. It is related to the structure surface color, roughness, material chemical composition and other factors. There is no unified standard, and generally only a value range is given for subjective selection; for general engineering and building materials such as concrete, long-wave radiation and absorption have the properties of gray bodies, and Kirchhoff’s (Kirchhoff ) law, the emissivity of a gray body is equal to its absorptivity, and the emissivity of the object surface depends on the material composition of the structure, the temperature difference between the structure surface and the surrounding environment, and surface treatment measures. At present, there is no authoritative data to determine the relevant values. It can only be selected subjectively 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, coating type and thickness on the radiation absorption coefficient is often not considered, which will lead to environmental problems in structural design. Insufficient load design considerations bury structural safety hazards

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