Enhancing condensation heat transfer via vapor phase engineering

Abstract

When water condenses on surfaces, two distinct condensation modes, termed filmwise and dropwise condensation modes, appear depending on the surface wettability. Due to the continuous surface refreshment by droplet shedding, dropwise condensation mode typically has a 5 to 7 times higher heat transfer coefficient when compared to filmwise condensation mode. Therefore, previous researchers have focused on developing surface coatings to sustain dropwise condensation mode, where durability is the limiting factor. In this thesis, a new strategy that utilizes volatile amphiphilic surfactants, which have the capability to adsorb to the liquid-vapor interface and reduce the interfacial tension of water, is demonstrated. The vapor phase volatile surfactants induced a transition from filmwise mode to the more efficient dropwise condensation mode. Enhanced droplet mobility was also observed, similar to the condensation behavior on lubricant-infused surfaces, upon a constant supply of volatile amphiphilic molecules. The suggested approach, which does not require surface treatment, shows strong applicability to real-world industrial applications to increase heat transfer efficiency.