A Novel Inorganic Aqueous Solution and its Effect on Liquid Spreading and Freeze/Thaw Processes

Abstract

Frozen startup of phase change heat transfer devices is a complex problem that can have a large impact on heat transfer systems. A patented novel working fluid developed at UCLA comprised of an inorganic aqueous solution (IAS) was investigated for potential effects on the freeze/thaw capabilities in phase change heat transfer devices by examining the melting process of droplets. Preliminary visual tests were conducted to gain insight into any physical processes that surface augmentation created by this fluid may have on the freezing and melting process. These tests demonstrated significant differences in liquid spreading, the melting process, and the melting rate of droplets on surfaces pre-treated with IAS. Contact angle measurements exhibited enhanced wetting properties. SEM images of frozen droplets showed that liquid freezes in the small capillary wick formed by the initial evaporation of IAS. Video of melting droplets showed a significant increase in melting rate when the surface was first treated with IAS due to superior liquid spreading.

Experimental investigation of designer working fluids in a flat heat pipe

“…The performance increases are due to the wetting and wicking nature of the coating. Supowit et al [15] showed that the coating acts as a micro-wick that can maintain a wetted surface. When dry-out occurs, the capillarity of the large grooves cannot withstand the required flow rate.…”

Designer fluid performance and inclination angle effects in a flat grooved heat pipe

“…Various studies have exemplified the thermal improvement potential of the IAS designer fluids through surface wetting and capillarity of the surface augmentation. By examining the thawing process of droplets, Supowit et al [13] demonstrated that the surface features created by the IAS fluid wicked liquid water from underneath the frozen droplet as it thawed. The spreading phenomenon is a result of hemi-wicking, a concept developed by Bico et al [14].…”