Marangoni Flow Induced Evaporation Enhancement on Binary Sessile Drops

Area of Science:

• Fluid Dynamics
• Heat and Mass Transfer
• Surface Science

Background:

• Drop evaporation behavior is influenced by substrate temperature and fluid properties.
• Marangoni effects, driven by surface tension gradients, significantly impact evaporation dynamics.
• Understanding these phenomena is critical for applications involving liquid droplets on heated surfaces.

Purpose of the Study:

• To investigate the effect of temperature on the evaporation of pure water, pure 1-butanol, and 5% 1-butanol aqueous solution drops.
• To analyze the role of thermal and solutal Marangoni effects during drop evaporation.
• To develop empirical equations for predicting evaporation rates.

Main Methods:

• Utilized a drop shape analyzer to measure contact angle, diameter, and volume evolution.
• Employed infrared thermal mapping to record surface temperature distributions.
• Analyzed the relationship between evaporation rate, Marangoni number, and experimental data.

Main Results:

• Pure 1-butanol drops showed no thermal instability.
• Thermal Marangoni convection cells appeared on pure water drops above 50 °C.
• Solutal Marangoni effects were observed in 1-butanol solutions at all temperatures, with coexistence of thermal and solutal effects above 50 °C.

Conclusions:

• Temperature significantly influences Marangoni effects during drop evaporation.
• Developed empirical equations accurately predict evaporation rates for water and 1-butanol solutions.
• Findings provide valuable insights into droplet behavior on heated hydrophobic substrates.