LAUSR

Transient convective droplet removal from condenser surfaces has the potential to significantly enhance thermal transport. Despite a century of progress in understanding of steady-state condensation, less is known about transient condensation. Here, we study transient pulse condensation of ethanol vapor. Using rigorous two-phase heat transfer measurements, we characterize transient heat transfer performance for filmwise and dropwise condensation of ethanol on smooth copper and nanostructured copper oxide lubricant-infused surfaces, respectively. We demonstrate an 8X and 5X enhancement in the condensation heat transfer coefficient during transient operation for dropwise and filmwise modes, respectively, when compared to the steady state. Beyond transient heat transfer enhancement, repeated cycles or pulses of dropwise condensation led to 30% higher time-averaged heat transfer performance due to higher nucleation site density and convective effects. Our work not only demonstrates transient condensation as a method to enhance heat transfer but also develops a methodology for enabling enhanced condensers for high power density thermal management systems for applications employing transient energy dissipation.