Numerical Study Of Flow And Heat Transfer Characteristics Of Evaporating Thin Liquid Film For Binary Fluids

The heat transfer of the evaporating thin film widely exists in phase transition.It obtains a very high heat transfer coefficient.The research of the conjugated heat transfer in evaporating thin film and intrinsic meniscus is helpful to understand the heat and mass transfer characteristics of evaporating thin film and improve the thermal performance of phase-change heat transfer devices.At present,the thin film evaporation mechanism is not well understood.Related research is confined to pure fluids,rarely considering the influence of binary fluids,size and non-condensable gas.A generalized conjugated heat transfer model is developed,with an augmented Young-Laplace equation and the kinetic theory,for the conjugated heat transfer in evaporating thin liquid film and intrinsic meniscus.The Fluent software and UDF are used to solve the coupling model.The heat and mass transfer process for the binary fluids(5^wt% n-butanol aqueous solution)and pure fluid in the closed microcavity,the evaporating droplet and microchannel are studied.And the temperature distribution,flow field and evaporation differences for 5^wt% n-butanol aqueous solution are compared.Meanwhile,the effect of non-condensable gas in closed environment is discussed.Further,the impacts of fluid properties,structure size and wettability on heat transfer of the evaporating thin film are analyzed.The main conclusions are as follows:?1?5^wt% n-butanol aqueous solution has special surface tension characteristics when temperature is sufficiently high,so it is beneficial for fluid circulation and heat transfer.Compared with pure water,5^wt% n-butanol aqueous solution has longer thin liquid film and stronger interfacial heat transfer.?2?The thin film heat transfer contribution in higher environment is lower than that in relatively lower environment.?3?the total heat transfer can be deteriorated and the thin film contribution to the net heat transfer rate will be reduced if there exists the non-condensable gas in the close environment.?4?With the decreasing size,the total heat transfer for 5^wt% n-butanol aqueous solution is reduced,while the thin film heat transfer contribution increases.?5?Better wettability,smaller contact angle.The thin film heat transfer is enhanced and its heat transfer contribution to the net heat transfer rate increases.?6?The capillary pressure and disjoining pressure can inhibit evaporation of 5^wt% n-butanol aqueous solution droplet and weaken its interfacial heat transfer.