双翅片矩形相变储能单元蓄热性能实验研究

Experimental study on heat storage performance of a doublefin rectangular phase change energy storage unit

以双翅片矩形相变储能单元为研究对象,开展不同边界温度下(50℃、55℃、64℃、69℃、73℃)相变材料熔化过程的可视化实验,通过观察相变材料固液相变界面、温度和液相率变化分析储能单元内相变材料的熔化行为和传热规律,探究不同边界温度对储能单元蓄热性能的影响。研究表明:熔化后期储能单元内出现的熔化死角极大延长了蓄热时间,熔化死角用时比均大于30%;边界温度增加,固液相界面形状无明显变化,相变材料内温度分布及变化趋势相似,但固液相界面演化进程加快,自然对流加强,相变材料内温度分布不均匀性最大增加60%,相变温度最大增加2.9℃;边界温度从50℃提高至73℃时,完全熔化时间缩短510 min,且边界温度越低时(Fo)/(Ste)越大,表明在边界温度较低时,增加边界温度对相变材料的强化传热效果更明显。

This study aims to investigate the influence of different boundary temperatures on the heat storage performance of the phase change energy storage unit(PCESU)by conducting visual experiments on the melting process of phase change material(PCM)in a double-fin rectangular PCESU at different boundary temperatures.The analysis involves examining the melting behavior and heat transfer process based on the observation of the solid–liquid interface,PCM temperature,and liquid fraction.The results show that during the late melting stage,solid PCM accumulated at the right-bottom of the PCESU,extending the heat storage time,with the melting time ratio of the PCM at this stage exceeding 30%.With the increase of boundary temperature,the shape of the solid-liquid interface remains considerably constant,with temperature distribution variation being similar.However,the evolution process of the solid-liquid interface accelerates,and natural convection is enhanced,leading to a 60%increase in the nonuniformity of the temperature distribution in the PCM.Moreover,the phase transition temperature increases by a maximum of 2.9℃.The results demonstrate that when the boundary temperature increases from 50℃to 73℃,the complete Fo melting time is shortened by 510 min.Lower the boundary temperature,greater the Ste,indicating that increasing the boundary temperature has a pronounced effect on heat transfer enhancement of the PCM at a lower boundary temperature.