| Biography | |
|---|---|
 Prof. Zhen Yang Department of Energy and Power Engineering, Tsinghua University, China |
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| Title: Molecular dynamics simulation on evaporation of suspending difluoromethane nanodroplets | |
| Abstract: Nanodroplet evaporation is a basic process widely existing in nature and industrial applications. Difluoromethane (CH2F2, also called “R32”) has attracted more and more attention in refrigeration, heat pump, power cycle and other fields because of its excellent thermophysical characteristics. In this talk, the evaporation process of R32 nanodroplet is studied by means of molecular dynamics simulation. The dynamic evaporation characteristics of droplet under different conditions (droplet size, initial temperature, and ambient temperature) and the effects of different parameters on the evaporation rate are quantitatively analyzed. The simulation results were compared with the calculation from the diffusion-based model and the kinetic model. The calculation accuracy of each model is evaluated and the reasons for the deviation between the model predictions and the simulation results are also discussed. The results show that the increase of ambient temperature and initial saturation temperature can lead to a significant increase of droplet evaporation rate, and shorten the pre-heating time needed for the droplet to reach the quasi-steady evaporation stage. The increase of droplet size also increases the pre-heating time, but has no significant effect on the evaporation rate. For the evaporation scenario studied (Knudsen number (Kn) ~ 1), the existing modification for the kinetic model can be well applied to the calculation of the evaporation rate of R32 droplets in the quasi-steady evaporation stage. The deviation between the simulation and the diffusion-based model is large, however the accuracy of the diffusion-based model can be significantly improved by correcting the thermal conductivity considering the scale effect. Key words: molecular dynamics, evaporation, nanodroplet | |
| Biography: Dr. Zhen Yang is an associate professor at Department of Energy and Power Engineering, Tsinghua University. He received his B.E. and Ph.D. degrees in Power Engineering and Engineering Thermophysics from Tsinghua University, Beijing, China in 2002 and 2007, respectively. He was a post doctor at School of Mechanical Engineering, Purdue University, West Lafayette, USA during 2008-2010. He joined Tsinghua University in 2010. His research interest includes Thermophysical properties of fluids, Thermal Energy Storage, Solar Thermal Power System, Boiling & Condensation, Flow and Heat Transfer in Porous Materials. He has published over 100 peer-reviewed articles in leading international journals, including Applied Energy, Energy Conversion and Management, Energy, etc. He was the Keynote Speakers at 2012 Annual Conference of Heat and Mass Transfer of China Society of Engineering Thermophysics, the 6th International conference on cooling and heating technologies (2012), the 12th Asia Thermophysical Properties Conference (2019), 2019 Heat and Mass Transfer Academic Conference of China Society of Engineering Thermophysics, and 2019 International Conference and Expo on Nanotechnology & Nanomaterials. He served as the Session Chairs of the 16th International Heat Transfer Conference (2018) and the 12th Asia Thermophysical Properties Conference (2019). He served as the Scientific Committee Member of the 7th International Symposium on Micro and Nano Technology (2019). He served as the Technical Members of the 5th International Conference on Renewable Energy Technologies (2019), the 4th IEEE International Conference on Green Energy and Applications (2020), 2020 International Conference on Energy, Material Science and Environment Engineering, and the 6th International Conference on Renewable Energy Technologies (2020). | |
