Experimental Study Of Infrared High-penetration PE For Radiation Cooling Surface

Although radiation cooling air conditioning has high energy-saving benefits and human comfort,the problems such as indoor water dripping and poor cooling capacity caused by condensation on the cooling surface at the end of radiation limit the application and promotion of radiation cooling in life and industry.First of all,this paper analyzes the primary condensation problem on the cooling surface and its causes.Based on the characteristics of radiation and convection heat transfer,a new type of theoretical anti condensation component named "radiation transparent high thermal resistance" is proposed,which is 100% transparent to radiation electromagnetic wave and has high thermal resistance.The transparency of the radiation makes the electromagnetic wave of the cooling surface and the external radiation heat transfer directly pass through the theoretical components without being affected.Theoretically,the theoretical component with appropriate thermal resistance can achieve lower cooling surface temperature,which can not only reduce the risk of condensation on the cooling surface,but also improve the overall cooling capacity of the radiation cooling system.Secondly,this paper selects the PE film(30?m thick)with 87% long wave infrared average transmittance as the experimental base material to prepare the "infrared high permeability and high thermal resistance" experimental anti condensation component(experimental component for short)with double PE film sandwich hollow structure for practical research.A test platform was built to test and characterize the thermal resistance and infrared transmittance of the experimental components.In this paper,an experimental platform is built to study the condensation characteristics of experimental components.Finally,based on the theory of radiant heat transfer and convective heat transfer and the actual transmittance characteristics of the experimental components,this paper simplifies the heat transfer process of the combined cooling surface composed of "experimental components+ cooling surface" and the outside world,obtains the calculation method of the overall emissivity and overall reflectivity of the combined cooling surface,and establishes the combination based on the radiation resistance network method Theoretical calculation method of total cooling capacity of cooling surface.Based on the specific conditions of the simulated radiant cooling experiment platform,the calculation method is verified by experiments.The effects of the experimental components on the radiation and convective heat transfer between the constant temperature cold plate and the thermal environment under four different working conditions are studied through the experimental platform.The experimental results show that in the experimental component,the convective heat transfer surface temperature of the combined cold plate is effectively increased,the condensation risk is reduced,and the radiation heat transfer is less affected,and the original radiation heat transfer on the cooling surface is largely retained.When the sample with different thickness is used,the surface temperature of convective heat transfer When 19?,it is the same as compared with the blank experiment at 19?,the convective heat transfer was the same.With the increase of the thickness of the experimental components,the radiant heat transfer of the sample increased by 10.57%,14.72%,20.54%,23.03% and 25.11%,respectively.The total cooling capacity increased by 21.84%,24.52%,27.28%,30.13% and 36.34%.Based on the above experimental results,it can be seen that the thermal resistance characteristics of the experimental components effectively improve the temperature of the contact surface with the air and reduce the risk of condensation,while the high transmittance characteristics make the radiation heat exchange between the low-temperature surface and the outside weaker.It is expected to achieve low-temperature radiant cooling(lower than dew point)by using appropriate thermal resistance experimental components,which can not only reduce the risk of condensation,but also improve the total cooling capacity of the whole radiant cooling system by improving the radiant heat exchange part.