Phase 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.
