Study On Heat Storage Characteristics Of Erythritol In Energy Storage Device Based On Different Heating Modes

Phase change energy storage technology plays an extremely important role in the field of energy storage.Phase change material is the basis of phase change energy storage technology.In the process of energy conversion and utilization,it has the advantages of ultra-high volume energy density and narrow temperature distribution range.It can effectively improve energy utilization efficiency and eliminate the contradiction between energy supply and demand in time and space.Therefore,phase change energy storage technology has been widely used in industrial and civil fields.At present,the domestic and foreign scholars mainly focus on the field of low temperature and high temperature,and less on the energy storage process of medium temperature phase change materials,and the volume change of solid-liquid phase change materials is often ignored in the process of numerical simulation.Therefore,this paper takes the medium temperature phase change material erythritol as the research object,considering the natural convection and volume expansion phenomenon,carries out the numerical research on the heat transfer characteristics of erythritol energy storage process in the rectangular cavity energy storage device by FLUENT software,and the research results provide a certain reference for the medium temperature phase change field and the structural design of energy storage device.The main contents and conclusions of this paper are as follows:1.In the bottom heated rectangular cavity energy storage device,the influence of the volume fraction of phase change material(PCM)cavity on the flow and heat transfer of PCM is mainly considered.The results show that the larger the volume fraction of PCM cavity is,the longer the total latent heat energy storage time is,and the smaller the PCM volume expansion rate is,and the maximum volume expansion rate is less than 20%.When the volume fraction of the cavity is 80%,there is a pinnate structure formed by the rapid development of Rayleigh convection at the bottom of the intermediate shaft,which makes the internal temperature distribution and phase interface distribution more uniform.2.The influence of changing the aspect ratio of the bottom heating energy storage device on the energy storage characteristics is discussed when the total energy storage area remains unchanged.The results show that with the increase of aspect ratio,the total melting time first increases,then decreases and then increases,and the volume expansion rate of PCM first decreases,then increases and then decreases.3.The energy storage characteristics of PCM in rectangular cavity energy storage device with central tube heating are studied.The results show that during the melting process,the natural convection mainly strengthens the heat transfer of PCM above the central tube,increases the melting rate of PCM above the central tube,makes the PCM phase interface present the shape of up and down asymmetry,and makes the isotherm of liquid region bend,resulting in thermal stratification.4.The effects of changing the aspect ratio and the arrangement of heating rods on the energy storage characteristics of erythritol in rectangular cavity energy storage device heated by central tube were studied.The results show that when the aspect ratio increases,the total melting time of PCM first decreases and then increases,and the volume expansion rate of PCM first increases and then tends to be stable.When the aspect ratio is 0.88,the total melting time is the shortest,and the volume expansion rate of PCM with the aspect ratio of0.64 is the smallest.When two heating tubes are arranged in the radial direction,the total latent heat storage time is the shortest,and the energy storage effect of erythritol is the best,which is 36% shorter than the melting time of erythritol with one heating tube in the center.5.the results show that the energy storage effect of the energy storage device with bottom heating is the best.