Numerical Simulation And Experimental Study For The Radiative Cooling

Energy and environment have been two most important problems in the modern world. Refrigeration and air condition have cost a big part of power supply,and the CFCs which is used in the refrigeration equipment has bad effect on the ozonosphere,so it is not suitable for development.Radiative cooling using the special spectrum of the aerosphere can get cooling through its radiation heat transfer with the outer space.Radiative cooling is passive and worth more research and utilization.In this paper we carry out there parts about the design and utilization of radiative cooling equipment.1) Based on the Kirchhoff's law and the optical films theory,the single and multi-layers films on aluminum substrate are designed by using the optical design software Macleod to satisfy the demand of radiative cooling,hoping to get the ideal selective surface.Firstly,proper film materials are selected.Then the single and multi-layers films are designed on aluminum substrate of high reflectivity in whole wave band.The films are optimized by the Simplex method;the best multi-layers film is obtained.From the reflection curve of the best design,it is found that the film has high emissivity in the wave band of 8～13μm,and high reflectivity in all other bands.And these characters can maintain in a large range of incidence angle(0°-60°).The study provides theoretical guidance for the radiative cooling design.2) In fact the existed raidative cooling is very hard to get cooling result during the daytime in summer.So the radiative cooling device only used in night is designed which called "night radiative cooling".The character standard level of the cooling device decreases,so it is very useful to exploit the potential of radiative cooling.Several materials with high emissivity are tested,and the result showes that the carbon is the best material.Then new radiative cooling device which can be used in practice is designed.Experiment result and discussion show that the "night radiative cooling" can be used in the summer night to get cooling.The efficiency of the device is calculated and the device constucion is optimized using simulation.The optimized potential is also discussed.3) Depend on the selective spectrum of radiative surface of radiative cooling,the author design the cooling-heat equipment which can get cooling during the night due to the radiative cooling and get heat during the daytime due to its reflective solar energy.Three construction of the selective spectrum surface are put forward:trough,arc and parabola,and they are created in the optical software Fred.The constructon is optimized with the optical trace method provided by the Fred.The optimized aim is to maximize the absorbed solar energy.