| With the rapid implementation of new rural construction in China,scientific and reasonable planning and construction is particularly important.At present,most of the buildings are in the disordered spontaneous low-level stage,and lack of mature theoretical support and intensive research.Different reflectance underlying surfaces will have a great impact on the outdoor thermal environment of buildings and the microclimate in the personnel activity area.The problems of chaotic layout of underlying surfaces around rural buildings and poor outdoor thermal physical environment need to be solved.Based on this,this paper uses the experimental test research method,through consulting the relevant literature and development status,and visiting and investigating the rural areas around Hohhot,taking the surface reflectivity as the research breakthrough point,carries on the in-depth research on the rural outdoor thermal environment,in order to provide theoretical support for improving the rural thermal physical environment and enhancing the outdoor thermal comfort.This paper mainly carried out the following aspects of research:1.In order to comprehensively analyze the reflectance and influencing factors of underlying surface samples,according to the existing reflectance measurement specifications and methods of curved surface samples,a new type of comprehensive measurement device for solar reflectance of underlying surface is established,which can comprehensively monitoring the reflectance of irregular surface samples,shallow ground temperature field of underlying surface in the target area,thermal environment near the surface and the microclimate physical environment.The reflectance of the reference board is measured,and the results show that the error between the measurement results of the reference board and the standard results of ASTM-E1918-16[62]is between 0-0.04,which verifies the reliability and accuracy of the test method and the reference board.2.In order to accurately quantify the two characteristic parameters of the underlying surface coverage and porosity,the traditional MATLAB image processing method is used for histogram binarization and other operations.And introduce five kinds of gradient operator edge detection are proposed to further refine the edge recognition.According to the verification of correlation and standard deviation,combined with the edge comparison of morphological closed operation map,it is found that Canny operator is the best for grass underlying surface image detection,and Canny operator,Roberts operator and Canny operator are more accurate for porosity and coverage edge detection and recognition of gravel underlying surface,brick underlying surface and grass embedded brick underlying surface.3.In order to quantify the solar radiation absorption capacity of different reflectance underlying surfaces in rural areas and reveal the fluctuation law of reflectance of different underlying surfaces,based on ASTM standard experimental platform,a comprehensive reflectance measurement device and method suitable for typical rural underlying surfaces in Hohhot were developed,and outdoor field grouping experiments were carried out,to monitor four kinds of typical rural underlying surface,grassland,sand,brick and gravel in turn.In order to reveal the relationship between the reflectance fluctuation of underlying surface and the characteristic parameters,accurate edge detection and recognition were used to quantify the characteristic parameters of each group of underlying surface and continuously observe the reflectance fluctuation.The stable fluctuation range of reflectivity of four underlying surfaces is between 11:00 and 15:00,and the law is not obvious in other time periods.At this time,the solar height angle before and after the peak can better reveal the cooling ability of the underlying surface and the difference of the thermal environment.The results showed that the coverage of grass increased by 0.6 and the reflectivity decreased by 0.0290;The porosity of the underlying surface of sand and gravel is increased by 0.0482,and the reflectivity is reduced by 0.0420;The porosity of the underlying brick surface increased by 0.1936,the spectral color changed from lighter to darker,and the reflectance decreased by 0.0477;The underlaying surface of grass-embedded bricks is used as a comparative sample of the characteristic law of reflectivity,and no characteristic parameter grouping experiment is performed.The increase of grassland coverage space and porous structure improves the multiple reflection effect,which leads to more solar radiation being consumed in the surface structure.At the same time,the spectral color of deeper underlying surface will absorb more solar radiation,so the reflectivity will be reduced.4.In order to study the difference of outdoor thermal environment caused by the change of reflectance of underlying surface,the correlation analysis is carried out by monitoring the shallow ground temperature field of underlying surface and bare underlying surface,as well as the thermal imaging array map of near ground surface.It is found that the ability to reduce the surface temperature is grassland>grass inlaid brick>brick>sand.For the grass green underlying surface,with the decrease of reflectance,the increase of grass coverage can reflect less solar radiation,but can effectively reduce the temperature near the ground,which is related to the lighter spectral color of the underlying surface and the increase of water molecular content;For sand and brick hardened underlying surface,the improvement of surface porosity is accompanied by the decrease of reflectivity,but there is little difference in the ability to reduce the near ground temperature,which is related to the irregular change of multiple reflection caused by the diversity of pore structure and shape.The shallow spectral color also has the ability to reduce the near ground temperature,but the high reflectivity will cause glare.Considering the relationship between thermal uniformity,reflectivity and thermal environment of underlying surface,it is helpful to improve outdoor thermal comfort to reasonably use high reflectivity hardened underlying surface and reasonably increase low reflectivity green underlying surface. |
