Study On Heat Storage Characteristics Of Carbon Fiber Skeleton Composite Phase Change Materials

As a country with a large population,the development in China has caused energy to be continuously consumed in various aspects.Especially in the era of rapid development of the automotive industry,the problem of insufficient energy supply has become increasingly apparent.As a result,new energy vehicles have gradually emerged,and the research on various aspects of batteries has become more and more in-depth.Battery thermal management systems have always been the focus of scholars at home and abroad.In order to improve the performance of the battery and control the temperature of the battery in an ideal range,a high-tech thermal storage technology which is phase change thermal storage has appeared.Phase change thermal storage materials can absorb and release heat,keep the overall temperature of the system within a stable range,and store energy.Phase change materials have high latent heat,green environmental protection and other characteristics,which makes them have good advantages in battery thermal management.The purpose of this study is to develop a new type of carbon fiber composite phase change thermal storage material with low cost,good thermal storage performance and thermal cycle stability.It is suitable for use in automotive power batteries,HVAC or solar latent heat storage systems.The application provides a more reliable experimental basis and technical basis.In this paper,two kinds of inorganic hydrated salts,aluminum potassium sulfate dodecahydrate?KAl?SO₄?₂·12H₂O?and sodium decahydrate?Na₂SO₄·10H₂O?,are melt-mixed and formulated at different mass fraction ratios to find out the proportion of formulations with optimized performance.Because the melting point of potassium aluminum sulfate dodecahydrate is high and the melting point of sodium sulfate decahydrate is low,it is possible to obtain a mixed salt with a phase transition temperature within a reasonable range after compounding the two,and make a single inorganic salt appear.The undercooling phenomenon has been alleviated.Due to the low thermal conductivity of these two inorganic hydrated salts,we add nano-carbon powder as a thermally conductive active agent to improve the thermal conductivity of the material,and use the dispersant PVP to reduce the agglomeration of the nano-carbon powder so that it is evenly mixed in the solution to obtain composite phase change material with higher thermal conductivity,simultaneously solving the phenomenon of phase separation of inorganic salts,and prepared an inorganic mixed phase change material with a high phase change enthalpy.Then,carbon fiber with high thermal conductivity and porous structure was selected as the support material,and the prepared sample was packaged and shaped to prepare a carbon fiber skeleton composite phase change heat storage material.Finally,the prepared composite phase change material was wrapped around a heating rod.The heating rod was used to simulate the heating of the battery,and the thermal storage characteristics of the prepared composite material were tested and verified.The results show that when the mass ratio of aluminum potassium sulfate dodecahydrate to sodium decahydrate is6.5:3.5,phase change temperature of the mixed salt was approximately 36.47°C and phase change enthalpy was approximately 220.84 J/g.Adding 1wt%of nano-carbon powder increased the thermal conductivity of the mixed phase change material by about 81.0%and reduced the subcooling by about 37.9%.The addition of carbon fibers also improved the thermal conductivity by 1.3 times.After 100 cycles of performance tests,the material still has good phase change properties.After simulation application,it was found that this phase change heat storage material can effectively reduce the temperature and heat flow of the surface of the simulated battery,and the heat storage effect is significant.