Wettability analysis of coated plates for indirect evaporative cooling systems

Indirect Evaporative Cooling (IEC) is a very promising solution to substitute and/or integrate traditional air conditioning systems, due to its ability to maintain comfort conditions in the air-conditioned environment. Literature studies proved that a higher wettability of the IEC plates corresponds to better performance of the system. In this work, wettability of three different surfaces used for IEC systems plates are analyzed: the uncoated surface (AL), the surface covered with a standard epoxy coating (STD), and the one covered with a hydrophilic lacquer (HPHI). The wettability analysis was performed by evaluating: the static contact angle, its trend over time, the dynamic contact angles (advancing and receding), and their transient behavior. The static contact angle resulted to be the lowest for the HPHI surface, intermediate for the STD surface, and the highest for the AL surface, while its trend over time turned out to be decreasing for all the surfaces. The analysis of the dynamic contact angles showed that their transient behavior is similar for all the surfaces, and the dynamic contact angles reached at the end of the transient are consistent with the results of the static analysis. These results will be useful to extend the correlation between plates wettability and IEC system performance parameters.