Preparation And Performance Study Of Erythritol-based Phase Change Energy Storage Composites

As a medium temperature solid-liquid phase change material,erythritol(E)have been received widespread attention because of its high enthalpy values.In order to further broaden the scope and application of erythritol,eythritol(117.42℃)was selected as a basic to develop and prepare erythritol/thiourea(TU)and erythritol/xylitol(X)binary eutectic PCMs by theoretical calculation and experiment,and to prepare phase change composite fibers in which erythritol and two eutectics as PCM.PVA as supporting material by electrospinning.Adopt to add variety of nanoparticles and graphene to explore and improve its thermal conductivity.Chemical structure,morphology and thermal properties of phase change composite fibers by FTIR.XRD.SEM.DSC and thermal conductivity test.Finally,using erythritol as the PCM to study the effects of the structure and heat transfer parameters of the two hase change thermal storage units on the thermal storage efficiency of the thermal storage unit are analyzed by numerical simulation.The main results are as follows:Phase transition temperatures(enthalpy values)of(E-TU)and(E-X)two eutectic phase change materials are 98.63℃(274.5 J/g)and 81.98℃(272.9 J/g),respectively.The average diameters,phase transition temperatures,enthalpy values and thermal conductivity of phase change composite fibers prepared by electrospinning increased with the increase content of PCMs.The content of PCMs in composite fibers could reach high of 80%,and could maintain good morphology and thermal stability.The AFDs,phase transition temperatures and phase change enthalpy values of the phase change composite fibers with adding nano-additives decreased with the increase of the content of additives.The AFDs of the E/PVA composite fibers decreased to 0.56 μm with the addition of 4%nano-carbon,and the average diameters of the two eutectic composite fibers decreased to 0.59 μm and 0.58 μm,respectively,at the addition of 10%graphene.The maximum heat loss rates of composite fibers was 4.8%.However,the thermal conductivity of the composite fibers can be increased by 167%in the case of 4%nano-carbon,and the thermal conductivity of the phase-change composite fiber can be increased by 312%and 260%respectively when the content of graphene is 10%.Numerical simulation results show that the circle-shaped phase change unit is faster and more efficient than the cylindrical phase change unit,and the heat storage and exothermic completion time are reduced by 12.5%and 11.6%respectively.The smaller ratio of the outer diameter to the inner diameter of the circle,the higher heat storage efficiency.During the melting(solidification)process,the phase change complete time decreased by 13.5%(9.7%)when increasing the fluid temperature,and decreased by 6.1%(4.6%)when increasing the fluid flow rate,the effects of fluid temperature on efficiency of phase change units were stronger than fluid flow rate.