Study On The Influence Factors And Mechanism Of Heat Transfer Of Composite Phase Change Materials Of Thermal Conductivity Enhancement

Paraffin/polymer composite phase change materials have the advantages of accurate temperature control, heat content, stable work, and so on, while the thermal conductivity of composite phase change material is low, which leads to low utilization rate of phase change heat in the process of phase transition. As a result, how to improve its applicability through the heat conduction mechanism research and thermal network system design are the key to improve the ability of the new composite phase change materials.Hierarchical porous carbon aerogel blocks, graphitization hierarchical porous carbon aerogel blocks, and graphitized carbon aerogel microspheres were designed to research the influence of carrier structure to thermal conductivity of PCMs. PCMs were fabricated with paraffin and different carbon aerogels through atmospheric melt infiltration method. Three kinds of carbon aerogels were tested by TG-DSC, SEM, XRD, and N2 adsorption- desorption detection method. Besides, preparation methods and basic performance were mastered. PCMs were detected by SEM, DSC, and Hot-disk. Results show that carbon aerogels are great carrier material, paraffin wax was well-distributed in the carbon aerogels.Melting temperature of CPCM-1 å'Œ CPCM-2 rise because of microporous structure in the blocks, phase change temperature increased by 3,while the spherical structure leads to a narrow phase transition temperature range of CPCM-3.And with the increase of the content of the paraffin, the phase change enthalpy of PCMs increased. And the thermal conductivity of the composite phase change material can be improved remarkably by the structure of the graphite carbon aerogel carrier.Heat transfer mechanism of CPCM-1 and CPCM-2 were studied by approximate analysis method.The heat transfer mechanism of PCMs were analyzed by comparing steady state heat conduction with internal heat source and transient heat transfer of paraffin solid liquid phase change, provided that paraffin convection is equivalent to internal heat source in the carbon aerogel. It turned out that the factors affecting the heat transfer rate of PCMs were: thermal conductivity of carbon aerogel carrier k, cylinder length, phase transition temperature and phase interface position, and so on.Heat transfer mechanism of CPCM-3 were analysed according to the H-C model theory. The results show that the higher content of graphitized carbon aerogel microspheres, the higher thermal conductivity in the PCMs, and the higher thermal conductivity of graphite carbon aerogel microspheres, the higher thermal conductivity in the PCMs, on the condition of the same volume fraction of the graphite carbon aerogel microspheres.