Evaporation inside microchannels

From Thermal-FluidsPedia

Figure 9.18 Evaporation of liquid from cylindrical pores: (a) low or moderate evaporation rates, and (b) high evaporation rates.

Heat transfer during the evaporation of liquid from a liquid/vapor meniscus heated from solid wall plays an important role in predicting the performance characteristics of various two-phase devices with capillary structures such as heat pipes, evaporators, heat sinks, and separators. Heat transfer during the evaporation of liquid from cylindrical and/or hemispherical liquid-vapor menisci in pores or slots is shown in Fig. 9.18. During evaporation from a pore with small wall-liquid temperature drops, the vapor flow does not affect the morphology of the liquid-vapor interface. It can be considered to have nearly-constant curvature except for the microfilm region [see Fig. 9.18(a)]. For extremely high heat flux, on the other hand, the vapor flow can significantly affect the morphology of the liquid-vapor interface, as shown in Fig. 9.18(b). Analytical and numerical solution of evaporations inside cylindrical pores under moderate heat fluxes will be considered in Sections 9.6.1 and 9.6.2. Evaporation inside microchannels under high heat flux will be discussed in Section 9.6.3. Section 9.6.4 discusses evaporation in an inclined micro channel.