Characterization of thin film evaporation in micropillar wicks using micro-Raman spectroscopy

Abstract

Thin film evaporation on microstructured surfaces is a promising strategy for high heat flux thermal management. To enhance fundamental understanding and optimize the overall heat transfer performance across a few microns thickness liquid film, however, requires detailed thermal characterizations. Existing characterization techniques using infrared thermometry or

Passive, high-efficiency thermally-localized solar desalination

“…Similar to most studies on evaporator design, we consider an evaporator as an open system, i.e., vapor transport is from the evaporator to the far-field air ambient. [72][73][74][75][76] According to the energy balance, the total input solar energy (units: W) is converted into thermal energy driving evaporation and heat loss ,…”

Stefan flow induced natural convection suppression on high-flux evaporators

“…We considered a two-dimensional, steady, laminar boundary layer on a horizonal evaporator. As many high-performance evaporators are operated in a planar configuration [4,28,30], we modeled the evaporator as a semi-infinite flat hot plate with a uniform temperature T s and the half length of L. To further simplify the problem, we made the following assumptions: (1) The Stefan flow velocity V 0 is reasonably small compared to the horizontal characteristic velocity U so that the boundary layer assumption is still valid. (2) No-slip boundary condition can be applied to the air flow at the liquid-vapor interface as the dynamic viscosity of liquid water is one order of magnitude larger than that of the air (e.g., 8.9 × 10 −4 Pa • s compared to 1.8 × 10 −5 Pa • s at 25°C, respectively).…”

“…We calculated the Stefan flow velocity as a function wall superheat. We chose two representative effective diffusion boundary layer thicknesses i.e., δ c = 0.1L and δ c = L which match different experimental conditions [28,30]. The relatively large effective diffusion boundary layer thickness is achieved by directly exposing the evaporator into a quiescent ambient, whereas the smaller diffusion boundary thickness typically occurs when the vapor at the far field removed (i.e., convected) by a weak flow.…”

Enhanced Liquid Propagation and Wicking Along Nanostructured Porous Surfaces

“…Inspired from water transpiration in plants, [1,2] capillary-fed evaporators are widely used for many industrial applications such as water filtration, [3,4] electronics cooling, [5][6][7] heating, ventilation, and air conditioning, [8][9][10] fuel cells, [11,12] and biomedical applications. [13] Due to its essential role in the earlier processes, passive capillary pumping, which effectively transports liquid through a wick without any need for external forces, has attracted broad interest.…”