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On-going Research
Wetting Dynamics of Droplets with Interfacial Phase Change
Wetting processes usually come with interfacial phase change as most of the liquids in nature exhibit volatile characteristics. Droplets, due to its widely existence and representative geometry, serve as an idea object to study the combined effect of wetting and interfacial phase change.
This research aims to comprehensively reveal the wetting dynamics of droplets along with interfacial phase change. The joint effect of capillary stress, viscous dissipation, thermal and solutal Marangoni flow will be investigated through both experimental and numerical approaches.
Videos and Figures in this page provide some demonstrations of the simulation results of pure volatile droplets.
Phase change driven instability in multicomponent fluid systems
Nonuniform distribution of interfacial mass flux can induce concentration gradient within multicomponent fluids, generate solutal Marangoni stress, and result in flow instablity. Such phenomena, whether on a solid base or on a liquid (oil) base, indicate great potentials for fast liquid atomization and advanced surface patterning technologies.
This research will focus on the phase change driven instablity in multicomponent fluid systems, aiming to fully reveal the underlying physics, arrive at a general principle for controllable and repeatable generation of flow instability, as well as to develop robust techniques for fast liquid atomization and high quality surface patterning.
Marangoni Bursting: A demonstration video of phase change driven instability by Tomoya NAGATA (B4) with post process by Tenshiro ICHIMURA (M2) in our lab.
Funding
Projects on and before PhD
Vapor absorption/desorption into hygroscopic ionic solution droplets
The study of vapor absorption into liquid desiccant droplets is of great significance for better understanding the oriented moisture transport in various dehumidification and desalination processes. This project aims to fully reveal the fundamentals of vapor absorption or desorption into hygroscopic ionic solution droplets, including droplet dynamics and contact line motion, the evaporative cooling or absorptive heating effect, the solutal and thermal Marangoni effect, etc.
Investigations are carried out combining experimental study (optical microscopy, infrared microscopy, microPIV) and numerical simulation (DNS). The conclusions help to clarify the phase change phenomena of binary droplets, and provide direct instructions to the design and optimization of different dehumidificaiton devices.
Waste heat and water recovery from industrial flue gases
In this project, we propose an open absorption system for both heat and water recovery from fossil fuel boilers using the high temperature flue gas as the regeneration heat source. In this system, liquid desiccant serves as the recycling medium, which absorbs waste heat and moisture contained in the low temperature flue gas in the packed tower and then regenerates in the regenerator by the high temperature flue gas. Water vapor generated in the regenerator gets condensed after releasing heat to the heating water system and the condensing water also gets recycled. The return water collects heat from the solution water heat exchanger, the flue gas water heat exchanger and the condenser respectively and is then used for district heating.
A prototype system is established to evaluate the system performance for different type of flue gases and in different application scenarios. The heat and mass transfer within dehumidifiers (key component) is investigated in details for system optimization.
Integrated heat pipe system for efficient cooling of data centers
With the wide application of telecommunications and internet systems, data centers have been rapidly developing in recent years and have already caused energy and environmental problems. The power density in data centers is usually high. According to a survey by Greenburg, data centers can be over 40 times as energy intensive as conventional office buildings.
This project works on an integrated cooling system for data centers which combines a heat pipe cooling cycle and a vapor compression cooling cycle. The operating mode of the system changes with the outdoor temperature. Key problems of the integrated system were solved such as the mix of the refrigerant and lubricant, the match of heat exchange areas and the durability of valves. A thermal equilibrium test was carried out to evaluate the system performance. Thermodynamic analyses based on experimental data show that the PUE (Power Usage Effectiveness) of data centers using the integrated heat pipe system can be 0.3 lower than using the conventional air cooling systems in cold areas like Beijing and Harbin. The energy saving potential of the integrated heat pipe system varies with seasonal and regional climate changes.
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