相变材料对储热系统换热速率的影响

Effects of Phase Change Materials on the Heat Transfer Rate of Thermal Energy Storage System

相变材料(PCMs)是潜热储热系统的核心媒介,而相变温度、导热系数及储能密度是选择PCMs的最关键三大因素.通过热阻模型相对热阻变化,对PCMs以上三个因素分别对储热系统换热速率的影响进行了分析.结果表明,PCMs的导热系数提高到2倍时对系统的换热效果提升显著,提高到5倍以后继续提高导热系数增强系统换热速率效果几乎已失效;在蓄热过程中PCMs相变温度越低,换热速率越快,在释热过程中恰好相反;提高储能密度对系统的换热速率并没有影响,只是相应倍数地延长了蓄/释热功率的时间.

Phase change materials(PCMs)are the core media in latent heat thermal energy storage system,and phase change temperature,thermal conductivity and energy storage density of PCMs are the three most critical factors for selecting PCMs.These effects of three key factors of PCMs on heat transfer rate of thermal energy storage system are analyzed by means of relative thermal resistance variation according to thermal resistance modeling,respectively.The results indicate that when the thermal conductivity of PCMs is increased to about 2 folds,the heat transfer improvement of the system is significantly effective.After increasing to 5 folds,the effect of increasing the thermal conductivity to enhance the heat transfer rate of the system is almost invalid.During the charging process,the lower of PCMs’phase change temperature is,the higher heat transfer rate becomes,and it’s just on the contrary during the discharging process.The increase of energy storage density has no effect on the heat transfer rate of the system,but the time of heat charging/discharging power is extended by corresponding multiple.