| In recent years,with the continuous acceleration of urbanization,the compact urban development models based on high-rise and high-density building clusters have become widely accepted.The scale and intensity of the resulting urban heat island effect has also been increasing.The intensification of the heat island effect further leads to the deterioration of outdoor thermal comfort and air thermal environment,while cooling energy consumption increases.In the context of continued temperature rise in the future,the proportion of energy consumption used to improve the thermal environment will escalate,forming a vicious circle with the deterioration of the regional thermal environment.Therefore,it is proposed to use a new type of building finish on the building envelope that can reflect solar radiation in the direction of incidence,the regressionreflective finish,the use of which can reduce the thermal radiation reaching adjacent buildings and roads,thus limiting the impact on the surrounding thermal environment and reducing the urban heat island effect.Based on this,in order to make the architectural retroreflective finishes better applied in the actual building environment,this paper tested the optical stability of architectural retroreflective finishes and their application effects through experiments,and the main research contents and results are summarized as follows:(1)Firstly,the optical properties of two commercially available retroreflective finishes were analyzed.The overall reflectivity of the retro-reflective finish is measured using the integrating sphere with different wavebands as the entry point.At the same time,a new instrument is developed to study the angular distribution and the retro-reflectivity of the two finishes at different incidence angles.The results show that the reflectivity of the prism is 12.56% higher than that of the glass bead.The retro-reflectivity of the finish changes obviously in different wavelength range,and the higher the wavelength,the lower the retro-reflectivity.Increasing the incidence angle will reduce the retro-reflective performance of the finish,and the incidence angle has a great effect on the radiation wavelength less than 1200 nm.(2)Secondly,in order to evaluate the long-term performance of the building’s retroreflective finish,the weather resistance of the finishes under natural conditions was tested.Long-term changes and angular distribution of reflection intensity were assessed by monthly sampling analysis after a year of outdoor exposure to the three finishes with the addition of a highly reflective paint for comparison.The results show that after 366 days of outdoor exposure,the retro-reflective angle distribution of the architectural retroreflective finish has almost no obvious change.The durability of the prism vertebral retroreflective finish against outdoor climate is better than that of the glass bead and is far better than that of the highly reflective coating.The solar reflectivity of the two architectural retro-reflective finish can be almost completely restored by cleaning.(3)Thirdly,through the accelerated aging test box to achieve the determination of the building retro-reflective finish longer-term performance,design accelerated years and different types of building different service life combined,compared and analyzed the accelerated aging of the building retro-reflective finish comprehensive reflectivity and retro-reflectivity changes.The results show that the prism retro-reflective finish have a good performance in the maintenance of material form,angular distribution characterization and the decrease of solar reflectivity.(4)Finally,based on the optical properties and stability of the samples,the prismatic retro-reflective finish was selected to analyze the application effect of architectural retroreflective finishes on improving the thermal environment of high-density enclosed buildings.The design takes regional albedo,wall temperature and air temperature as evaluation parameters,and conducts experiments by establishing a scale-down architectural model and comparing with high-reflective coatings.The experimental results show that the model covered with retro-reflective finish has a better cooling potential with 5.0% higher peak area albedo compared to the model covered with highly reflective coating.The air temperature in the enclosed space of the retroreflective finish model is 2.3°C lower than that of the highly reflective coating model.Compared with highly reflective coatings,the use of retro-reflective finishes can reduce the peak temperature and average temperature of the wall by 2.5°C～15.2°C and 0.3°C～3.8°C in the daytime,and 1.3°C～7.9°C and 0.2°C～4.4°C at night.The best cooling effect of the prismatic retro-reflective facing is on the roof and east wall.The research in this paper clarifies the detailed optical characteristics of architectural retro-reflective finishes at different wavelengths,reveals its material performance stability in outdoor applications and long-term applications,and provides a theoretical basis for its practical application in improving regional thermal environments,providing technical support for the understanding of the thermal environment formation mechanism of high-rise and high-density buildings,and effectively promoting the development and application potential research of architectural retro-reflective finishes in the field of engineering practice. |
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