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Roadmap
Topics
① Predictable Wetting (Fundamental Research)
- Generalizing classical theories from ideal to real liquids
Wetting widely exists in nature, and plays significant role in our daily life and in cutting-edge industries. Over the past two hundred years, scientists have been exploring the secrets of wetting and developed classical theories to describe the state of wetting, represented by the Young's equation (contact angle), the Tanner's law (spreading), the Jurin's law (capillary), etc. However, these classicial theories are largely limited to ideal cases, i.e., pure liquids without phase change. While in real world, nearly all liquids are volatile (they can evaporate) and not pure (they are multicomponent), it is therefore highly required to develop a comprehensive framework of wetting that can describe the real world, so that we can understand liquid wetting from Ideal to Real, and utilize wetting from Theory to Practice!
We will make continuous efforts towards this goal through experimental, theoretical, and numerical approaches!
② Controllable Wetting (Application Research)
- For advanced cooling, portable diagnosis, and controllable electrochemical reactions
Supported by a rich set of external fundings, we will explore the power of controllable wetting for a wide range of cutting-edge applications, including disease diagnosis with minimal volume of liquid samples, separation of expensive elements, advanced cooling, and self-assemply of functional molecules with tunable microflow and contact line dynamics.
We will make whimsical ideas come true through enterprising interdisciplinary collaborations!
③ Visualization and Numerical Techniques (Technical Development)
- High space-time resolution visualization, image processing, and numerical methods
We will explore new techniques for fully revealing complex interfacial dynamics, with record-high spatiotemporal resolutions. We are especially interested in new visualization techniques, new image tracing and processing methods, and innovative numerical approaches to address complex boundary problems.
We look forward to direct, frank and efficient communications with industrial partners and peer researchers that share common technical interests and demands!
Experimental Approach
e.g. simultaneous LIF-PIV measurement based on wavelength selection
Numerical Approach
e.g. mathematical formulation of real liquid spreading with lubrication theory
Acknowledgement
Past Projects
Vapor absorption/desorption into hygroscopic saline solution droplets
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Wang, Z., Karapetsas, G., Valluri, P., Sefiane, K., Williams, A., & Takata, Y. "Dynamics of hygroscopic aqueous solution droplets undergoing evaporation or vapour absorption." Journal of Fluid Mechanics 912 (2021): A2.
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Wang, Z., Orejon, D., Sefiane, K., & Takata, Y. "Water vapor uptake into hygroscopic lithium bromide desiccant droplets: mechanisms of droplet growth and spreading." Physical Chemistry Chemical Physics 21 (2019): 1046-1058. （Back Cover）
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Wang, Z.*, Orejon, D., Sefiane, K., & Takata, Y. “Coupled thermal transport and mass diffusion during vapor absorption into hygroscopic liquid desiccant droplets.” International Journal of Heat and Mass Transfer 134 (2019): 1014-1023.
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
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Wang, Z., Zhang, X., Han, J., & Li, Z. "Waste heat and water recovery from natural gas boilers: Parametric analysis and optimization of a flue-gas-driven open absorption system." Energy Conversion and Management 154 (2017): 526-537.
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Wang, Z., Zhang, X., & Li, Z. "Investigation on the coupled heat and mass transfer process between extremely high humidity air and liquid desiccant in the counter-flow adiabatic packed tower." International Journal of Heat and Mass Transfer 110 (2017): 898-907.
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Wang, Z., Zhang, X., & Li, Z. "Evaluation of a flue gas driven open absorption system for heat and water recovery from fossil fuel boilers." Energy Conversion and Management 128 (2016): 57-65.
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.
Thermal management of high power density data center
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Wang, Z., Zhang, X., Li, Z., & Luo, M. "Analysis on energy efficiency of an integrated heat pipe system in data centers." Applied Thermal Engineering 90 (2015): 937-944.
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Wang, Z., Cao, H., & Li, Z. Cold source selection and efficiency analysis of data center cooling systems. Journal of Engineering Thermophysics, 38(2) (2017): 326-333.
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 climate regions. The energy saving potential of the integrated heat pipe system varies with seasonal and regional climate changes.
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