Preparation And Analysis Of Nanoparticles Containing Enhanced Heat Transfer Phase Change Composite Energy Storage Component

Currently,the most of the phase change material has supercooling and low thermal conductivity,severely restricted the phase change thermal control system applications.In this article,there types of high thermal conductivity nanoparticles(SiO2,AlN and graphene)were added to four types of PCMs(paraffin,acetamide,erythritol and mannitol).The high thermal conductivity nanoparticles could reduce the supercooling and improve the thermal conductivity of the PCMs.Then the supercooling and thermal conductivity of the nanoparticles modified PCMs were were simulated.Nano-modified PCMs(PCM-nanoparticles)were prepared with the magnetic stirrer and ultrasonic dispersion.Nanoparticles containing enhanced heat transfer phase change composite(PCM-nanoparticles-graphite foam)were prepared with the mothed of vacuum melt infiltration.The properties of the raw materials and the composites were investigated by scanning electron microscopy,X-ray spectrometer and X-ray diffraction.The supercooling,phase transition temperature and enthalpy of the PCM-nanoparticles and PCM-nanoparticles-graphite foam samples were investigated by differential scanning calorimeter.The influence of the nanoparticles and graphite foams on the phase change properties of PCMs was investigated.The supercooling degree of acetamide was successfully reduced from 38.4 ? to 7.7 ? and the supercooling degree of erythritol was reduced about 36 ?,and the solidification enthalpy of the PCMs were improved.A molting-solidification device was self made and the acetamide composite samples were subjected to melting-solidification cycles 50 times,measuring the macroscopic supercooling and the stability of the melting-solidification cycle performance of acetamide.A set of algorithms was derived using MATLAB software for simulating the crystallization of samples based on the classical nucleation theory.The results of the simulation agreed with the experiment results.The influence of the cooling rate,the concentration and the size of the nanoparticles on the supercooling of the samples was studied with simulation.With grain boundary simulations,using the grain boundary adjustment theory well explained an experiment phenomenon that the PCM solidification latent heat far less than melting latent heat and the secong melting point and melting latent heat lower than nomal.The thermal conductivity of each sample were measured by transient hot-wire tests and the influence of the nanoparticles and graphite foam on the thermal conductivity of the PCMs was also been investigated.The heat transfer process of the graphene modified PCMs and the PCM-graphite foam were simulated by finite element software.The simulation results showed that the two-dimensional sheet structure of graphene contribute to form the heat conduction pathway and greatly increase the thermal conductivity.Measurements and simulation results showed that the increase of PCM-graphite foam thermal conductivity was greater than PCM itself.A concept of "zoom factor K" was presented for this phenomenon.The influence of PCM thermal conductivity and thermal contact resistance on the "zoom factor K" was studied,this was very important to the research of heat transfer for the foam structure(such as graphite foam,foam copper,etc.).