Design of evaporation rig for sessile drops

• Main Author: Abdul Hamid, Shahnawaz
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Mechanical engineering::Machine design and construction
• Online Access: http://hdl.handle.net/10356/40388
• Institution: Nanyang Technological University

Much research has been conducted in the field of droplet evaporation, of which the possible applications include ring stain formation and thin film coating. However, many uncertainties with regards to conditions at the liquid-vapor interface during a phase change process still exist. This report presents an initial experimental study that serves to investigate the temperature gradient at this liquid-vapor interface when the evaporating droplet is placed on a heated surface. To perform the study an evaporation rig was designed using SolidWorks 2009 and subsequently manufactured. The rig was to meet several criteria among which was to provide continuous flow of fluid from a reservoir to a heated surface and allow fluid to form sessile drops without leakage into rig itself. Also, the rig was to be vacuumed to remove any buoyancy-driven convection. To measure the temperature and pressure of the rig‟s surroundings, a thermocouple and pressure transducer were calibrated and included in the final set-up. Both calibration processes are elaborated. Several other apparatus, such as a vacuum pump and syringe driver, were also loaned. A description of the role played by each apparatus is included. Finally, the setup was tested with the use of de-ionized water. The steps undertaken in the test are listed clearly, allowing for future repetitions. Also, several troubleshooting techniques with regards to the setup are shared with the reader. Finally, the results of the test conducted were recorded and discussed. Primarily it was found that the temperatures recorded for the liquid droplet were significantly higher than that of the vapor in several experiments, with an approximately 0.5⁰C difference in the case of no heating and 0.25⁰C in the case of heating.