Mechanism of Fume Suppression and Performance on Asphalt of Expanded Graphite for Pavement under High Temperature Condition

Fume suppression mechanisms and the effect of expanded graphite on the performance of asphalt were studied by applying infrared spectroscopy（FT-IR）, X-ray diffraction（XRD）, scanning electron microscopy（SEM） and comprehensive thermal analysis（TG, DSC）. The experimental results confirm that asphalt which is mixed with expandable graphite will expand in the process of hot mix, and the expanded graphite layer will swell by the light component in the asphalt. The light component in the asphalt and PAHs adsorption on expanded graphite surface or part of the plug in the expanded graphite layer between plates made nucleation crystallization growth. And the Van der Waals force and the bonding of the lattice can effectively restrain the asphalt fume release. Meanwhile, the expanding agent with oxidative can spread into the asphalt, leading to asphalt oxygenated and plastic abate, while the ductility decreases. Expanded graphite, SBS modifier and environment- friendly plasticizers are used to composite modified asphalt. According to asphalt fume release experiment, normal test of asphalt performance, Brookfield viscosity test, RTFOT test and asphalt mixture tests（high temperature stability, low temperature stability, water stability）, it has been proven that the modified asphalt’s performance is better than that of matrix asphalt and equivalent to that of SBS modified asphalt. Furthermore, it has good fume suppression effect.

Experimental research and numerical simulation of the thermal performance of a tube-fin cold energy storage unit using water/modified expanded graphite as the phase change material

In this study,experimental and numerical investigations were conducted on a tube-fin heat-exchanger latent-heat cold energy storage unit.The fin side of the heat exchanger was filled with water as the energy storage medium,and modified expanded graphite(MEG)was employed to improve the thermal characteristics of water.The water contact angle of the expanded graphite decreased from 106.31°to 0°,and the hydrophilicity and the absorption rate of water significantly improved after the modification.Moreover,the experimental analyses of the charge/discharge process showed that the cooling capacity of the system filled with 90 wt.%water/MEG was 80.8%of that of pure water,whereas its cooling time was only 69.7%of that of pure water.The average power increased by 15.9%compared with that of water.The system filled with 90 wt.%water/MEG completed two energy charging and discharging cycles,whereas the system filled with water completed only 1.5 cycles within 15000 s.Furthermore,the effects of the flow rate and inlet temperature of the heat transfer fluid on the charging process were explored.Finally,a numerical model was built and validated to investigate the phase change behavior and the effect of the structure size on the performance of the system.The heat-exchanger fin spacing had no significant effect on the cold energy storage unit,whereas the vertical spacing of the tube pass had the highest effect.It can be concluded that the heat exchanger combined with high-thermal-conductivity water/MEG exhibits better energy storage capacity and working power,showing a wide application prospect in the field of cold energy storage.