中文摘要：

为了揭示周期性热作用下相变材料内部相变传热特征,为建筑外表相变隔热设计和计算提供支撑,本文设计制作了能模拟太阳运行、提供周期性加热的装置,并将正18烷封装于塑料圆桶容器中,使容器底部和侧面绝热,制作了测试试件。利用热电偶和巡检仪自动记录了周期性热作用下相变材料内部各层温度的变化。测试结果表明,在稳定周期性热作用下,材料内部相变传热特征主要可表述为：1）材料在非稳态周期性相变传热阶段,各层温度在达到相变温度点之前,温度变化明显;相界面会随着周期性加热次数的增加间断性地向内部扩展;温度平均值和振幅值向稳态周期性相变传热时的平均值和振幅值靠近。2）材料在稳态周期性相变传热阶段,内部各点温度也表现出与外界热作用等周期性变化,温度振幅从外到内依次减小。这与发生在固体中的周期性传热特性类似。但材料内温度变化呈现折转现象,在温度明显升高前出现等温滞后,在温度降低时会出现等温冷却。这与发生在固体中的传热现象有很大的区别。3）材料在稳定周期性热作用下,内部不会出现多个相界面共存现象。4）空气流速对相变材料中温度振幅和相界面移动速率都有较大影响,提高空气流速可以降低温度振幅和减慢相变进程。这意味着当相变材料用于建筑外表进行相变隔热时,可以通过组织自然通风减少其用量。

英文摘要：

In order to reveal the phase change heat transfer characteristics in PCM with outside steady periodic heating and cooling,and provide some suports for thermal insulation of building skin with PCM,an apparatus which can simulate the sun running and provide periodic heating was designed and made in this paper;a test specimen was also fabricated by encapsulating the octadecane into a plastic circular container with its bottom and side thermal insulation.The temperature variations of each layer in the PCM were automatically recorded by thermocouples and instrument during the steady periodic heating and cooling process.The test results show that the characteristics of phase change heat transfer in PCM can be mainly described as followings：1） at the unsteady periodic phase change stage,the temperature of each layer in PCM changes obviously before it reach es the phase transformation point;the phase change interface movies intermittently from outside to inside with the increase of times of periodical heating and cooling;the value of average temperature and temperature amplitude in PCM changes gradually closing to the value of that at the steady periodic phase change stage.2） at the steady periodic phase change stage,the temperature of each layer in PCM changes periodically with the same period of outside heating and cooling;the temperature amplitude in PCM decreases from outside to inside.Those are similar to that occurred in solid.However,the temperature changes with folding phenomena;the isothermal lag occurs before temperature obviously rising and isothermal cooling occurs during temperature dropping.This is quite different from that occurred in solid.3）with outside steady periodic heating and cooling,multiple phase change interfaces will not happened in PCM.4） The air velocity has great influence on the temperature amplitude and the moving rate of the phase change interface,increasing the air flow rate can reduce the temperature amplitude and slow the phase change process.This means that when the PCM is us