高温相变石蜡复合微胶囊的制备及其悬浮液的传热机理

Microencapsulated phase change material suspension is a kind of heat transfer media for heat storage and heat transportation. It can store and release latent heat during phase change process. So, its heat storage density and heat carrier density are higher than those of water. Based on that, latent heat transportation using microencapsulated phase change material suspension can cut energy consumption of pumps, so the energy saving can be achieved. In view of the application prospect in waste heat recovery, cooling system of high power diesel engine or solar energy utilization, and the drawback of normal microencapsulated phase change material suspension in heat transfer, the composite phase change microcapsule will be prepared with the phase change paraffin with high melting-point (phase change temperature range from 80?C to 90?C) as the core material, polymer filled with nanoparticles as the wall material. Based on that, physical properties of the composite microcapsule and its suspension will be tested. To study the thermal conduction mechanism, the theoretical model for predicting thermal conductivity of the composite microcapsule and its suspension will be established. Then, a numerical model for the forced convective heat transfer of the composite microcapsule suspension flowing in a circular tube will be set up. The heat transfer characteristic and mechanism of the composite microcapsule suspension will be investigated using experimental and numerical simulation methods. This project will expand the application of microcapsule suspension, and also can provide a useful scientific proof and theoretical guidance to low melting-point paraffin microcapsule suspension.

相变微胶囊悬浮液是一种集储热与热输运于一体的传热介质。在相变温度范围内，与水相比，其储、载热密度大，能大幅度降低输运功耗，具有很大的节能意义。本项目针对微胶囊悬浮液在废热回收系统、大功率柴油机冷却系统、太阳能利用等方面的应用背景和传统微胶囊悬浮液传热性能的不足，拟以相变温度在（80-90℃）内的高温相变石蜡为芯材，掺杂纳米粒子的高分子聚合物为壁材，研制具有较高热导率的复合微胶囊。在此基础上，获得该复合微胶囊及其悬浮液的基础物性数据。建立复合微胶囊及其悬浮液的热导率模型，揭示其热传导机理；建立复合微胶囊悬浮液的管内对流换热模型，通过数值模拟与实验研究相结合的方法，获得该复合微胶囊悬浮液的对流换热特性并揭示其强化传热机理。本项目对拓展微胶囊悬浮液的应用领域具有重要意义，同时为低温相变石蜡微胶囊及其悬浮液的传热强化研究提供科学依据和理论指导。

相变微胶囊悬浮液是一种集储热与热输运于一体的传热介质。在相变温度范围内，与水相比，其储、载热密度大，能大幅度降低输运功耗，具有很大的节能意义。本项目通过原位聚合法合成了以高温相变石蜡（相变区间为75-85℃）为芯材，改性脲醛树脂为壁材的相变微胶囊。采用差式扫描量热仪（DSC）、扫描电子显微镜（SEM）、导热系数仪等分别对微胶囊的形貌、热性能等进行了表征。分析了NaCl溶液、三聚氰胺以及石墨烯的添加对微胶囊的影响。结果表明，NaCl的添加能改善微胶囊表面形貌及机械性能，三聚氰胺的添加能提高微胶囊的包埋率。添加质量百分含量为0.03 %的石墨烯时，在80℃时微胶囊的导热系数提高了55.56%，而且其热稳定性有所提高。建立了复合微胶囊及其悬浮液的热导率模型，建立了复合微胶囊悬浮液的管内对流换热模型，通过数值模拟与实验研究相结合的方法，获得该复合微胶囊悬浮液的对流换热特性并揭示其强化传热机理。本项目对拓展微胶囊悬浮液的应用领域具有重要意义，可为微胶囊及其悬浮液的传热强化研究提供科学依据和理论指导。