| With the rapid development of society,our demand for energy is growing,and the problem of environmental pollution has become increasingly prominent by energy consumption.Among of them,building energy consumption accounts for about 1/3 of the total social energy consumption,the building energy efficiency is imminent,and traditional building insulation materials have been gradually unable to meet the demand of building energy of community.It is extremely urgent to develop a kind of insulation material with high performance and low cost for buildings.The research on preparation and thermal insulation performance of vacuum insulation panel will be carried out,including the insulation mechanism,the preparation process,the thermal conductivity,the cost,and service life prediction of vacuum insulation panel,which provides a theoretical basis and test basis for vacuum insulation panel in practical production and large scale application.Vacuum insulation panel(VIP)is a super thermal insulation material with thermal conductivity less than 11.5mW/(m·K)mainly comprised by core material,membrane material and getter.and its insulation effect is 5-10 times than traditional insulation materials.In the aspect of the adiabatic mechanism of VIP plate,the three aspects will be theoretical analysed: gas conduction,convection conduction and radiation conduction.Through theoretical analysis of gas conduction and convection conduction,two points were got that firstly the vacuum of plate must be controlled reasonablely and secondly the core material must be the powder material with larger porosity.Through the theoretical analysis of radiation heat transfer,we can get that the radiation heat transfer coefficient is related to the refractive index,specific extinction coefficient and temperature of the core material.In the process of VIP preparation,the candidate materials would be fumed silica(fs),silica fume(sf),rice husk ash(rha),polypropylene fiber(pp),glass fiber(gf),basalt fiber(bf),glass fiber mesh(gfm)and multilayer metallized film of Hanita(MF).According to the different core material system,the effects of mixing process,molding pressure,holding time,fiber type and content,drying system of core panel and the number of glass fiber mesh on the comprehensive properties of VIP panel were studied.The results showed that: When the mixing speed was 200r/min,and the time was 5-7min;the molding pressure range was 0.3-0.55MPa;the packing time was3-5min;the polypropylene fiber was adopted and the content was 5%;the dryingtemperature was 105oC,the time was 3h,the thermal conductivity of VIP prepared with fs as core material was the lowest,only 7.3mW/(m·K),but the cost was higher.Compared with the fs group,the costs of 1fs 1sf and fs rha groups can be reduced8.27% and 8.17% respectively,and the thermal conductivity increased by 12.33% and2.74% respectively.After comprehensive comparison,the VIP with fs rha as the core material had the highest cost-effective.In the research of VIP's thermal conductivity,the effects of core type,core bulk density,extinction powder type and content,and vacuum degree on VIP thermal conductivity was explored.The results show that the thermal conductivity of VIP prepared with fs as core material was the lowest and the bulk density was the lowest too.The addition of extinction powder can effectively reduce the thermal conductivity of VIP,the commonly used extinction powder is carbon black,and the content is usually 5%-10%;The thermal cutoff values of different core materials were different,the vacuum value must be controlled reasonably in the tests.The effects of different physical properties were different,it can provide some theoretical and experimental basis for the preparation and the predicted service life of VIP. |
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