Thermal Transport in Nano-Enhanced Phase Change Materials

0931507Fleischer相变材料(PCM)用于在瞬时加热过程中吸收和释放热能。相变材料已成功地在小范围内用于太阳能储存、节能建筑材料和冷却便携式电子产品。然而，在许多较大的系统中，大多数相变材料的导热系数较低，导致相变材料的质量利用率较低。最近，一种嵌入低成本石墨纳米纤维(GNF)的纳米增强型相变材料(PCM)已经被开发出来，该纤维具有大的热导率。独特的纳米纤维是通过催化分解过程合成的，并沿着纤维轴呈同心基面的形式。初步结果表明，当纳米纤维混合到相变材料中时，可以改善相变材料的热性能。这项研究考察了纳米增强型相变材料在熔融和凝固过程中热传输的基本性质，包括(1)用于建筑材料、热接口材料以及其他薄膜应用的薄层(0.5 mm至5 mm)，以及(2)用于太阳能储存、电子热管理和其他高功率能源系统的较厚层(20 mm至200 mm)。智能优点：将确定导致观察到的纳米增强型相变材料热性能改善的基本能量传输机制。计算研究将通过将分子动力学(MD)模型应用于各种类型的纳米纤维来进行。分子动力学模型将被用来预测不同纤维类型中能量传输的性质，并表征单个纤维的导热系数。将进行涉及特定基质构型的随机模拟，以确定纤维类型如何影响纳米增强相变材料的热性能。将进行涉及嵌入不同类型纳米颗粒的相变材料的实验，以便直接比较每种纳米颗粒类型对相变材料有效导热系数的影响。这为GNFS在提高有效热量方面的影响提供了基础，可将其与其他更昂贵的纳米粒子带来的影响相比较。广泛影响：该项目涉及通过传统的会议和期刊出版物以及通过在线社区，如NanHUB和therMalHUB来传播结果。该项目为几名本科生和研究生提供了研究机会。这项研究将通过新的和现有的纳米行为课程整合到维拉诺瓦大学机械工程和化学工程系的课程中。最后，PIS将与维拉诺瓦工程学院V.E.S.T.E.D.学院合作，该学院为有风险的初中生和高中生推广数学、科学、技术和工程方面的学术成就，并在当地中学推广。

0931507FleischerPhase Change Materials (PCMs) are used to absorb and release thermal energy during transient heating. PCMs have been used successfully at small scales for solar energy storage, in energy efficient building materials, and in cooling portable electronics. In many larger systems, however, the low thermal conductivity of most PCMs results in poor utilization of the PCM mass. Recently, a nanoenhanced PCM with embedded, low cost graphite nanofibers (GNF) characterized large thermal conductivities, has been developed. The unique nanofibers are synthesized using a catalytic decomposition process and take the form of concentric basal planes along the fiber axis. Preliminary results have shown that, when blended into a PCM, the nanofibers improve thermal performance of the PCM. This research examines the fundamental nature of thermal transport in nanoenhanced PCMs during melting and solidification in (1) thin layers (0.5 mm to 5 mm) for use in building materials, thermal interface materials as well as other thin film applications, and in (2) thicker layers (20 mm to 200 mm) for solar energy storage, electronics thermal management and other high power energy systems. Intellectual Merit: The fundamental energy transport mechanisms responsible for the observed improvement in thermal performance of the nanoenhanced PCM will be determined. Computational research will be conducted by applying molecular dynamics (MD) modeling to various nanofiber styles. The MD model will be used to predict the nature of energy transport in the different fiber styles, and characterize the thermal conductivity of a single fiber. Stochastic simulations involving specific matrix configurations will be conducted to determine how the fiber styles affect the thermal performance of the nanoenhanced PCMs.Experiments involving PCMs that are embedded with different types of nanoparticles will be conducted to allow direct comparison of the influence of each nanoparticle type on the PCMs effective thermal conductivity. This provides the basis for which the influence of GNFs on the enhancement of the effective thermal may be compared to that brought about by other more expensive nanoparticles.Broader Impact: This project involves dissemination of results through both traditional conference and journal publication, as well as by way of online communities such as nanoHUB and thermalHUB. The project provides research opportunities for several undergraduate and graduate students. The research will be integrated into the curricula of both the mechanical engineering and chemical engineering departments at Villanova University through new and existing courses in nanoscale behavior. Finally, the PIs will partner with the Villanova College of Engineerings V.E.S.T.E.D. Academy which promotes academic achievement in mathematics, science, technology, and engineering for at risk middle and high school students and outreach at local middle schools.