A Theoretical and Experimental Investigation of Evaporation From Drops Containing Nonvolatile Solutes
Gavin, Patrick Michael
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https://hdl.handle.net/2142/70116
Description
Title
A Theoretical and Experimental Investigation of Evaporation From Drops Containing Nonvolatile Solutes
Author(s)
Gavin, Patrick Michael
Issue Date
1983
Department of Study
Mechanical Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Mechanical
Abstract
The many and varied applications in which droplets are encountered have fostered the development of an extensive body of literature on drop dynamic and thermodynamic behavior. An extensive review of this literature showed that current understanding of the physics of evaporation from drops containing nonvolatile solutes is incomplete, preventing the establishment of viable vaporization models for such drops.
In order to improve this situation, an experimental investigation of the vaporization of drops containing a single nonvolatile solute was conducted. Free-fall conditions were simulated by suspending the drops, free of any attachments, on an upward flowing air stream in a vertical wind tunnel. Measurements of drop velocity histories and examination of photographs of final dry particles revealed that, although the vaporization process and final particle structure are strongly solute-dependent, consistent regimes of drop behavior can be identified.
A theoretical model of the vaporization of a drop containing a single nonvolatile solute was also developed. Excellent agreement was found between theoretical predictions and experimental data for evaporation before the onset of solute precipitation (Phase I). Model/data comparisons also revealed that high levels of supersaturation exist in solution drops before component separation begins. The period of evaporation during solute precipitation (Phase II) was modeled in two limiting cases. The core scenario model assumes that precipitation occurs inside the drop and has negligible impact on evaporation. The cap scenario model assumes that precipitation forms a solute cap on the drop which acts as an additional diffusion resistance in the mass transfer path. For most of the solutes studied, both models gave excellent predictions of the time required for the drop to reach its final, dry state (Phase III). In cases where solute precipitated on the drop surface, the cap scenario model gave better predictions of drop dynamic behavior and final particle size. In the absence of surface precipitation, drop velocity and final particle structure as predicted by the core scenario model were in good agreement with experimental data.
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