| The energy consumption brought about by economic development has gradually become a hot topic for people to discuss.The strategy of"carbon peaking and carbon neutrality"proposed by our country and the transformation of energy structure are our current key research work.As the most important cold source of the earth,outer space,whose temperature is close to absolute zero,is far less explored than the sun.Space radiation cooling technology is a new type of passive cooling technology that does not consume energy and is pollution-free.It utilizes the high permeability of infrared radiation of objects in the"atmospheric window"band(8～13μm),which can realize the"free"discharge of heat into outer space,thereby achieving the cooling effect,and has a very broad prospect.Based on the basic principle of space radiation cooling,this thesis designs and builds a simple and practical space radiation cooling system,studies the radiation cooling performance of the system itself,different materials,and different structures,and at the same time analyzes different influencing factors and system energy consumption.The test analysis provides a reference for the practical application of radiant refrigeration technology.The specific research contents are:First,the heat transfer model of space radiative cooling technology is analyzed,including the external heat transfer model(solar radiation,atmospheric absorption,convective heat transfer,and environmental heat transfer)and the internal heat transfer model(heat conduction on the outer surface,convective heat transfer between the inner surface and water),summed up the theoretical influence conditions of different outdoor conditions on radiant coolers,and provided a theoretical basis for the next analysis of the influence of different factors on the performance of radiant coolers.Secondly,the structural design of the space radiation refrigerator was carried out.According to the structural combination,the research,analysis and selection of various materials such as RLHY-2 radiation cooling coating,radiation cooling film,PE film and glass cover plate were carried out,and 6 kinds of materials were designed at the same time.Different structures of space radiant refrigerators,and the material collocation of each working condition are analyzed.The original space radiation cooling experiment system was built and modified,and different structures were built and operated for several days to collect experimental data through the design working conditions,so as to make full preparations for the next result analysis.Finally,the refrigeration performance of the experimental system under different working conditions was analyzed,and a comparative analysis was carried out according to the experimental weather and its own factors,and the following conclusions were drawn:(1)Compared with the space radiation cooler with a smooth surface,the experimental conditions after adding materials have different degrees of improvement in the radiative cooling performance at night,and the most obvious performance improvement is the addition of PE film and smearing RLHY-2 and the space radiation refrigerator without the radiation cooling film of the wind screen.The optimal refrigeration performance of the two working conditions is similar,and the refrigeration power of 76.17W/m~2and 75.22W/m~2are increased respectively compared with the stainless steel refrigerator without any material(average refrigeration power of 40.03W/m~2).(2)Different cloud thickness,air humidity,outdoor wind speed,and inlet flow all have certain influences on the cooling performance of the space radiation cooler.The thicker the cloud layer,the worse the cooling performance of the radiant cooler,and the maximum difference in cooling power is 54.54W/m~2.The air humidity has a certain degree of influence on the space radiation cooler.The higher the air humidity,the worse the cooling effect of the radiation cooler.Especially in the process of rising from 78%to 91.6%,the cooling power of the cooler is minimum from 102W/m~2reduced to 42W/m~2,the maximum difference in cooling power is 60W/m~2.The wind speed mainly affects the convective heat transfer between the air and the surface of the space radiant cooler,but it does not mean that the higher the wind speed,the worse the performance of the radiant cooler depends on the combined effects of heat conduction,convective heat transfer and radiative cooling.The larger the inlet flow rate,the worse the cooling performance of the space radiation cooler.When the 0.016kg/s increased to 0.029kg/s and 0.036kg/s,the cooling power of the radiation cooler decreased by 29.52W/m~2and 52.86W/m~2.(3)For the experimental materials,compared with the RLHY-2 radiative cooling coating,the radiative cooling film not only has better cooling performance at night(higher than the coating 32.13W/m~2),but also has a better heat suppression effect during the day(lower than the coating 234.62W/m~2heat),but the price is more expensive.For the wind screen,the glass cover will cause a certain degree of greenhouse effect.Whether the glass cover with radiant cooling film is laid at night,the cooling power will drop by 29.87W/m~2and 52.48W/m~2respectively,but the radiant cover can play a better protective role.PE film is a wind screen with good effect,the difference is not much during the day,and the cooling power is increased by 18.7W/m~2at night,but the protection is relatively poor.(4)Compared with the traditional refrigeration system,the space radiation refrigeration system has better economy.The radiation refrigerator itself does not consume any electric energy.Under the premise of continuous operation for 6 hours,when the power of the internal and external circulation pumps is 31Hz and 41Hz respectively,the electric energy required by the system is 6.85k W·h and 3.32k W·h.At the same time,in cloudy and high wind speed environments,the space radiation cooler can achieve an average cooling power of 59.55W/m~2throughout the day. |
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