Influence Of Evaporating Meniscus On Heat And Mass Transfer Of The Capillary Phase Change Devices

In recent years, with the miniaturization of electronic devices and power increasing,demands for thermal control technology are highly rising. As the two-phase capillary heattransfer devices(such as loop heat pipe, etc)have the advantages of no moving parts, highefficiency, better isothermal and low thermal resistance in thermal control, they are hottopics for many domestic and foreign researchers. But some key issues severely limit thepractical application of such a device(such as failure of the system far below the theoreticallimit), it has a great relationship with people lack of understanding of heat and masstransfer mechanism in meniscus evaporation which plays a key role in evaporator wick.Firstly, from the augmented Young-Laplace equation, a evaporation meniscus heatand mass transfer model is established, through evaporation meniscuscontinuity,momentum and energy equation. Under this model, the impact of thermalboundary conditions, geometry and working fluid thermal parameters on evaporationmeniscus is researched. The results show that the meniscus in evaporation and static stateare quite different; evaporation in thin film region takes a large proportion of the entiremeniscus evaporation, while the heat transfer in this region are easily overlooked. Theimportant parameters under thermal load variations, such as the apparent contact angle andthe effective radius, are obtained.Based on the evaporation meniscus research results, heat transfer model and pressureloss model in the two-phase capillary heat and mass transfer devices are established, thenthe capillary limit of the loop is got. Numerical methods are taken to analyze the factorsaffecting the capillary limit. The differences of the capillary limit adding and ignoring thefilm evaporation heat and mass transfer are considered.The cotter capillary limit is alsodiscussed which always thinks meniscus is static.The study plays an important role in improving the capacity of the capillary loop, andalso has certain extent for the stability research of the capillary loop. Due to the study, thedesign of the capillary loop with larger capacity can be better guided.