Numerical Study of Bacteria Containing Droplets Aerosolized From Hot Surfaces

Area of Science:

• Fluid dynamics
• Aerosol science
• Microbiology

Background:

• Water droplet interaction with hot surfaces can lead to aerosolization of microorganisms.
• Film boiling regime is critical for droplet departure and airborne contamination.

Purpose of the Study:

• Investigate water droplet behavior on heated surfaces in film boiling.
• Model droplet departure conditions and airborne evolution.
• Evaluate bacterial survival post-aerosolization.

Main Methods:

• Developed a mathematical model for droplet shooting-off conditions and cooling.
• Experimentally determined critical droplet sizes for departure.
• Assessed survival rates of Escherichia coli and Bacillus subtilis under varying cooling times.

Main Results:

• Droplets up to 1mm in size were observed to depart from hot surfaces.
• Liquid-hot surface interaction is inefficient for microbial inactivation.
• Shorter cooling times correlated with higher bacterial survival rates.

Conclusions:

• Aerosolization of bacteria from contaminated water on hot surfaces is a significant concern.
• Cooling time, not just departure, is crucial for bacterial inactivation, but often insufficient.
• Substantial bacterial recovery rates (approx. 50% for B. subtilis) observed even after 15 seconds of cooling.