Experiment Research Of Radiative Cooling On Composite Materials

With the development of economy and the improvement of people's life, there is more and more energy consumption in air conditioning system. It is desired to develop a new refrigeration methodology to decrease the mineral fuel consumption. It is proposed to explore the possibility to make use of the outer space as a cooling source with radiative cooling technology.According to the essence of thermal radiation, the basic mechanism of thermal radiation spectrum and the characteristic of selective thermal radiation are analyzed. The principle of radiative cooling is also probed in order to choose a selective surface with optical properties matched to the atmosphere window 8-13μm.Based on the spectrum-selective-absorption of radiant cooling materials and the concept of infrared radiation coating, a technique of making radiators is developed. A radiation cooling experiment system, which consists of the selective radiator and a transparent cover board, is designed. A corresponding testing temperature system is also constructed.The heat transfer process between the radiator and the sky is analyzed. The heat transfer model is respectively set up under different weather conditions. The cooling temperature of the radiator is derived theoretically on balance condition. It provides a foundation in the application in the following experiment.The experiment is conducted to investigate the radiative properties of the selected material. It proves that the radiator we made shows good cooling effect at night. Due to the effects of solar radiation during the day, its application is limited.Considering the influence of the coating density, an experiment research is made to analyze the changing law. The experiment result shows, in the cooling area 400mm×400mm, when the quality of radiator BaSO₄ is 120g, the cooling effect is the best. But the changing process of cooling temperature difference of various density radiators, which arrives at the maximum, lasts the same time.An experiment research is also made to consider the effect of cooled space height on radiative cooling. The suitable cooled space height is designed at 8cm to achieve the maximal temperature difference.An optimized experiment is set up combining the influence factors above. The maximal temperature difference in the experiment is some 9.4℃.It is possible to achieve the non-energy-consuming refrigeration air-conditioning applying the principle of spectrum selectivity and composite materials. It has the advantage of non-energy, pollution-free, no moving parts, less investment. It is a new technology with practical value and market prospects.