Research On The Preparation Of Graphene Based Phase Change Energy Storage Composites And The Analysis Of Thermal Conduction Mechanism

Phase change materials with latent heat storage mode have great advantages in thermal control of spacecraft,but the disadvantages of low thermal conductivity and easy leakage greatly restrict the application of phase change materials in energy storage and thermal management.Graphene materials with high thermal conductivity provide new opportunities for the development of high-performance phase change composites.In this paper,macroscopically conductive skeleton structure was constructed from graphene materials,and the promotion of thermal conductivity and encapsulation of liquid phase were realized simultaneously.The graphene-based phase change energy storage composites were successfully prepared.In view of the characteristic morphology of graphene foam,the representative elementary volume is constructed,and the thermal conduction mechanism of the composite material is studied by the finite element method.Firstly,a graphene foam-based phase change energy storage composite material was prepared and its thermal conduction mechanism was analyzed by finite element method.Using graphene oxide aqueous solution as raw material,graphene foam was prepared by directional solidification ice template method combined with reduction and heat treatment technology.The paraffin wax was used to obtain the composite material.Graphene foam exhibits an ordered distribution of honeycomb-like microporous structure.The unit mass fraction of graphene foam can bring about a 214% increase in thermal conductivity to the matrix PCM,while the microchip thermal conductivity of the graphene foam cell walls can reach 74.06-110.94W/mK,thereby increasing the phase change material heat absorption/ release rate.The simulation results show that the thermal conductivity of the hole wall and the thermal interface resistance are the key factors affecting the thermal response of the composite energy storage material.Then,a graphene film with super high thermal conductivity was introduced into the structure to obtain a composite material embedded with a directional thermal conductive film to further strengthen the heat transfer process in the composite material.The material obtained 24.71 times of thermal conductivity increase with the mass cost of 0.94 wt%,which is equivalent to that the unit of graphene content increased the thermal conductivity of the phase change material by 2628%,and the heat transfer enhancement effect of the phase change material was remarkable.Finally,using the melting /solidification model in Fluent software to simulate the phase change heat transfer process of composite materials under given conditions,the influence of different graphene skeletons on the thermal response rate of phase change materials was analyzed.The results show that the addition of graphene film greatly reduces the temperature gradient in the direction of the thickness of the composite and greatly improves the thermal response efficiency.