Understanding the evaporation of spherical drops in quiescent environment

作者：Chini S Farshid; Amirfazli A^*

来源：Colloids and Surfaces A: Physicochemical and Engineering Aspects , 2013, 432: 82-88.

DOI：10.1016/j.colsurfa.2013.05.013

• Evaporation
• Maxwell assumptions
• Convection
• Diffusion
• Transient
• Suspended drops
• Micro-liter drops

Evaporation of suspended micro-liter drops in room temperature, atmospheric conditions and in quiescent air is not controlled by liquid transport across the drop interface (phase change) but by vapor transport from the drop surface to the surrounding. The vapor transport can be decomposed into convection and diffusion. Literature assumes the convection is negligible, also the evaporation process is assumed as quasi-steady (Maxwell assumptions). Although, the Maxwellian models are relatively accurate, the validity of the assumptions was never investigated independently. In this paper, it was shown that relaxing the steady-state assumption alone results in 60% error in predicting the evaporation rate. Also, using the Peclet number concept, it was found the evaporation is not purely diffusive. This means that evaporation is not a steady-state nor pure-diffusive process. Relaxing both Maxwell assumptions together, a transient and diffusive-convective (TDC) model was developed. It was found that only for liquids with small vapor concentration values (e.g. water), the TDC and Maxwell based models provide similar results (likely due to fortuitous cancelling of transient and convective effects for such liquids). For liquids with large vapor concentration values the TDC should be used.

• 出版日期2013-9-5