Comparative study on the infrared radiance field of building surface under sunshine conditions and rainfall conditions

The Monte Carlo method and the region method are combined in this paper, where a high-rise building in Harbin were taken for example to investigate the infrared radiation field of building surface. The calculation models of temperature field and radiation transfer coefficient on the exterior surface were established. Through the self-built Bidirectional Reflectance Distribution Function (BRDF) experimental device, the BRDFs of moorstone, aluminum plate, coated glass and Ethylene-Propylene-Diene Monomer (EPDM) on the surfaces under dry and wet conditions were measured at different incidence angles with respective laser wavelengths of 0.6328 μm and 1.34 μm. For the two wavelengths, the reflection ratios of the material surfaces under dry and wet conditions were calculated respectively. Based on some proper simplifications of the background condition, the simulation analysis of the radiation field of building surface was carried out according to the wetness theory and the measured data. Taking the situation at 9:00 a. m. on the day of summer solstice as an example, this paper made relevant quantitative calculation for the solar radiation, the self radiation of the surface units, the radiating projection between the surface units, and the general infrared radiation of the building surface. Comparisons on infrared radiance field of the building surface were obtained under cloud-free sunshine conditions and rainfall conditions respectively, and the rationality of the results was discussed.