Drop Removal from Solid Surfaces: Shedding and Evaporation

• Author / Creator

  Chini, Seyed Farshid

• Removal of a drop from its substrate may be gradually (e.g. evaporation) or all at once (e.g. shedding). In this thesis, drop adhesion force as a base for understanding the all at once removal of a drop from its substrate, and drop evaporation in room temperature as one of the gradual removal mechanisms are studied in details. The drop adhesion force is found by calculating the summation of surface tension forces along the contact line. The developed model is applicable to any shape drop as long as contact line is convex everywhere. The model requires the value of left and right contact angles observed in the 2-D side view images which was found using the in-house developed software (i.e. SPPF). Regarding the evaporation study, as a first step and to minimize the number of parameters, evaporation of suspended micro-liter drops is studied. Evaporation of such cases is restricted by movement of vapor from the drop surface, and not the phase change. Literature studies assume the evaporation process is steady-state and convection is small (Maxwell assumptions). It is found that none of the two assumptions are valid. However, for the range of parameters for micro-liter drops, the effect of transient term cancels the effect of convection, and Maxwell assumptions yield accurate results. It was also found that buoyancy, which is different from convection, is not a dominant factor on evaporation of drops, and the difference between the evaporation of sessile and pendant drops has a different source (i.e. evaporation modes). Uneven evaporation flux distribution along the sessile drop surface was also studied using an electrostatic analogy (exterior Dirichlet).

• Subjects / Keywords

  • Drop adhesion
  • Contact angle
  • Drop evaporation

• Graduation date

  Spring 2013

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R35415

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.