| The initial thermal conductivity of vacuum insulation panel with glass wool as core material is as low as 1.5mW/(m·K),which is the lowest thermal conductivity material,and has important application prospects in the field of building insulation and cold chain insulation.However,the thermal conductivity of VIP rises slowly with time,which is called VIP aging in the industry.Internationally,the engineering application of glass wool core material VIP has been less than 10 years.Theoretically estimate VIP service life over 70 years.Unable to evaluate VIP aging performance and life through actual engineering applications.However,the research on VIP aging of glass wool core materials at home and abroad is almost in the blank stage.Therefore,this paper studies the aging performance of VIP and predicts its service life,in order to provide theoretical basis for VIP improvement and engineering application.Firstly,according to the characteristics of VIP,different core materials,different film materials and VIP with or without getter were prepared,and the accelerated aging experiments were carried out to explore the influence of various factors on the aging performance of VIP.The results show that core material,film material,getter and ambient temperature all have great influence on the aging properties of VIP.The refinement of core material can reduce the inner pore size of core material and improve the anti-aging performance of VIP.However,when the diameter of fiber is less than 3.99 microns,the effect of refinement of fiber diameter to enhance the anti-aging effect of VIP is not obvious;The lower the gas permeability and the higher the getter,the better the aging resistance of VIP;Ambient temperature has a great influence on the aging properties of VIP,mainly on the gas permeability of the film;Environmental humidity has little effect on VIP containing getter,because the main component of getter is CaO,which can effectively absorb water vapor into VIP and reduce the influence of environmental humidity on the aging performance of VIP;The aging properties of VIP were almost unaffected by high and low temperature shocks in the range of-20 ~77?.In terms of VIP life prediction,this paper proposes an experimental prediction method with internal pressure as an intermediate variable and a mathematical model based on Gaussian distribution function to predict VIP service life.The prediction method with internal pressure as the intermediate variable first determines the relationship between the thermal conductivity of VIP and time,the relationship between VIP internal pressure and thermal conductivity.Establishing the relationship between the timeVIP internal pressure and the VIP thermal conductivity,and predicting the VIP life with a linearly varying internal pressure instead of a nonlinearly varying thermal conductivity.The prediction results show that the VIP service life is seriously affected by temperature.The VIP life can reach 70 years at 7 ?,but the VIP life is only about 3 years when the ambient temperature rises to 77 ?.Life prediction model based on Gaussian distribution function uses Gaussian distribution function to weight gas thermal conductivity in each aperture.The integral formula of the relationship between the thermal conductivity of the internal gas of VIP and time is obtained.A VIP aging mathematical model of glass wool core material was established by coupling the thermal conductivity of gas phase and solid phase.Compared with the actual monitoring data in two years,the predicted results of the model are in good agreement. |
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