The Research On Radiation Cooling Of Micro-Nanoparticle Polymer Film

For human survival and social development,energy is the necessary material foundation.With the development of society and People's constant pursuit of life comfort,human consumption in energy is also increasing.On the one hand,the vast majority of the energy used by human beings,such as coal,oil,natural gas and other mineral resources,belongs to Non-renewable sources of energy.On the other hand,the massive burning of these fossil fuels will cause the ecological hazards of air pollution,greenhouse effect and so on.At present,building energy consumption accounts for more than 40 percent of the total energy consumption of the society,and the most important aspect of building energy consumption is the consumption of refrigeration equipment such as air conditioners and refrigerators.Radiative cooling plays an important role in energy conservation.It is considered to be one of the most attractive concepts in twenty-first Century.Radiative cooling mechanism exist widely in nature.However,for ordinary materials,radiative cooling is very inefficient.In order to improve the efficiency and reduce the application cost of radiation cooling techniques,a variety of micro-nanoparticle polymer films with high efficiency of radiative cooling were proposed in this paper.In this paper,the radiation characteristics of particles were calculated by Mie theory,and then the Monte Carlo method(Monte Carlo Method,MCM)was used to solve the problem of light transport in the micro-nanoparticle polymer film.On this basis,a set of calculation method for the radiation characteristics of the micro-nanoparticle polymer film was formed.In this paper,the radiation characteristics of the micro-nanoparticles in the nonabsorbing medium and the absorbing medium were discussed.The spectral radiation characteristics of the non-absorbable particle system and the absorbable particle system were calculated,and the corresponding radiative cooling power was analyzed.On the basis of the traditional Mie theory and MCM,this paper studied the spectral radiation characteristics of Al2O3,SiO2,and TiO2 micro-nanoparticle in nonabsorbing medium and calculated the corresponding radiative cooling.In this paper,the effects of the particle size d,the volume fraction fv and the thickness of the micronanoparticle polymer film h on the cooling effect were investigated by simulating the spectral radiation characteristics of the 0.2~26?m band,and these parameters were optimized.After optimization,the structure of the best efficiency of the radiative cooling was Si O2+Al2O3 micro-nanoparticle polymer film.The average reflectivity of the structure in the 0.2~4?m band could reach more than 0.75.The average emissivity in the 8~13?m band could reach more than 0.95.When the surface temperature of the structure was 300 K,the net power in the daytime could reach 200.49W/m2 and in the night could reach 204.13W/m2.This paper was based on the generalized Mie theory and MCM to study the influence of the absorption properties of the medium on the radiation characteristics of the particles,the spectral radiation characteristics of the absorbable particle medium and the radiative cooling.The generalized Mie theory could correctly calculate the radiation characteristic parameters of particles in absorbing medium in the range of certain absorption index and scale parameter.When the absorption index of the medium was small,the absorption coefficient and scattering coefficient calculated by the traditional Mie theory and the generalized Mie theory were not very different.With the increase of absorption index,the absorption coefficient,scattering coefficient and scattering phase function would be significantly different.However,when the absorption index of the medium studied in this paper was too large(1m? ?0.05)or too small(1m? ?0.001),the radiation characteristic parameters calculated by the traditional Mie theory and the generalized Mie theory had no great influence on the solution of the radiation transfer equation in MCM.Only when 1m? is in the range of 0.005~0.01,the spectral radiating characteristics obtained by the MCM solution would be significantly different.