Surface Engineering in Heat-Transfer Applications

The purpose of this dissertation is to show the effectiveness of surface engineering (wettability patterning) in thermal management applications. The study is centered on redesigning an existing thermal-management system, the vapor chamber, using an innovative concept to improve its performance. The study was inspired by the tremendous potential of surface-energy patterning to provide a platform for harnessing surface-tension forces to transport fluids in a pumpless and rapid manner, which resulted in the development of a pattern combination that improves the condensation heat transfer of a metallic surface. The following steps were taken to accomplish this goal; initially, the conventional vapor-chamber heat-spreader was modified by replacing a portion of the totally wick-lined system (condenser) with a wickless and wettability patterned one, resulting in a hybrid vapor chamber. Furthermore, the hybrid vapor-chamber's capacity to serve as a passive thermal diode was demonstrated. Moreover, an attempt was made to completely reap the benefits of the wettability-patterning process by fabricating a quite effective wick-free vapor chamber. This system constitutes the first completely wick-free thermal-management apparatus. Additionally, femtosecond laser processing technology was applied on the wick-free system to develop a wickless and laser-fabricated vapor-chamber thermal diode, which takes advantage of the extreme limits of wettability. Finally, in order to further investigate the condensation phenomena that occur on the novel vapor-chamber's wickless and wettability-patterned condenser, a unique experimental setup was developed that focuses solely on steam dropwise condensation on metallic surfaces in an environment similar to the vapor chamber’s interior.