Lehigh Mechanical Engineering Seminar Series: Dr. Jianxing Sun

Controlling phase change is crucial for optimizing multiphase energy conversion and storage systems. Processes like condensation and boiling, heat release or absorption, are central to heat exchangers in power plants, HVAC systems, and chemical processing. Enhancing phase change rate can greatly improve energy efficiency. However, undesirable phase transitions, such as frost formation on heat exchangers in heat pumps, can disrupt equipment operation and increase energy consumption. Spanning from nanoscale nucleation to meter-scale accretion, phase change phenomena involve complex multiphase interactions across broad temperature ranges. Effective control demands a deeper understanding of nucleation and growth dynamics, heat transfer mechanisms, and advanced surface engineering to promote beneficial transitions and mitigate unwanted ones.

 

In this talk, I will explore microdroplet dynamics and their thermal signatures during dropwise condensation on lubricant-infused surfaces (LISs), as microdroplets contribute over 90% of the total heat transfer. Using advanced imaging techniques and simulations, I will highlight two distinct size-dependent droplet motions driven by the competition between unbalanced capillary forces and shear forces from Marangoni flow, demonstrating their role in enhancing condensation rates and guiding LIS design for improved thermal performance. I will introduce innovative zwitterionic materials with unprecedented anti-icing performance, where a unique combination of positively and negatively charged groups bonds with water molecules to form a non-freezing layer. Finally, I will discuss challenges and opportunities in phase change-driven energy applications and material design strategies for improved phase change control.