title: Dynamic Evolution of the Evaporating Liquid-Vapor Interface in Micropillar Arrays.
abstract: Capillary assisted passively pumped thermal management devices have gained importance due to their simple design and reduction in energy consumption. The performance of these devices is strongly dependent on the shape of the curved interface between the liquid and vapor phases. We developed a transient laser interferometry technique to investigate the evolution of the shape of the liquid-vapor interface in micropillar arrays during evaporation heat transfer. Controlled cylindrical micropillar arrays were fabricated on the front side of a silicon wafer, while thin-film heaters were deposited on the reverse side to emulate a heat source. The shape of the meniscus was determined using the fringe patterns resulting from interference of a monochromatic beam incident on the thin liquid layer. We studied the evolution of the shape of the meniscus on these surfaces under various operating conditions including varying the micropillar geometry and the applied heating power. By monitoring the transient behavior of the evaporating liquid-vapor interface, we accurately measured the absolute location and shape of the meniscus and calculated the contact angle and the maximum capillary pressure. We demonstrated that the receding contact angle which determines the capillary pumping limit is independent of the microstructure geometry and the rate of evaporation (i.e., the applied heating power). The results of this study provide fundamental insights into the dynamic behavior of the liquid-vapor interface in wick structures during phase-change heat transfer.
authors.affiliation: Device Research Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Dion S
authors.initials: DS
authors.lastname: Antao
authors.affiliation: Device Research Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Solomon
authors.initials: S
authors.lastname: Adera
authors.affiliation: Device Research Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Yangying
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Device Research Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Edgardo
authors.initials: E
authors.lastname: Farias
authors.affiliation: Thermal and Fluid Transport Laboratory, Department of Mechanical Engineering, Indian Institute of Technology , Patna, Bihar 00013, India.
authors.forename: Rishi
authors.initials: R
authors.lastname: Raj
authors.affiliation: Device Research Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Evelyn N
authors.initials: EN
authors.lastname: Wang