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Viability of basic heterogeneous nucleation studies with thermally diffusive condensation particle counters
1Yale University, Department of Mechanical Engineering and Materials Science, New Haven, CT 06520-8286, United States.
Journal of Colloid and Interface Science
|August 14, 2020
Summary
Researchers have found two ways to minimize supersaturation variation in diffusive condensation particle counters (DCPCs), enabling better heterogeneous nucleation studies. These methods involve flow sampling and specific gas-vapor mixtures, making DCPCs more useful for experiments.
Area of Science:
- Aerosol Science and Technology
- Physical Chemistry
- Thermodynamics
Background:
- Heterogeneous nucleation studies are crucial for understanding atmospheric processes and material science.
- Existing tools like diffusive condensation particle counters (DCPCs) have limitations due to significant supersaturation variations.
- Controllable and uniform supersaturations are essential for accurate and reproducible nucleation experiments.
Purpose of the Study:
- To identify methods for minimizing supersaturation variation within diffusive condensation particle counters (DCPCs).
- To enable the use of DCPCs for basic experimental heterogeneous nucleation studies.
- To explore conditions that lead to uniform maximal supersaturation (Smax) distributions.
Main Methods:
- Calculated spatial supersaturation (S(x,y)) distributions in a 2D parabolic flow with discontinuous wall temperature changes.
- Determined maximal supersaturation curves (Smax(Ψ)) as a function of streamline (Ψ).
- Computed activation probability curves (P(Ts,Tc)) based on critical supersaturation (S*).
Main Results:
- Discovered two novel approaches to achieve nearly constant Smax(Ψ): sampling the central 50% of the flow or ensuring the Lewis number (Le = α/D) is unity.
- The central flow sampling method is particularly effective in 2D parabolic flow, a benefit lost in axisymmetric configurations.
- A Lewis number of unity, achievable with specific vapor/gas mixtures (e.g., ethanol/CO2, H2O/air), results in a generally constant Smax(Ψ), even in turbulent flows.
Conclusions:
- Diffusive condensation particle counters (DCPCs) can be adapted for reliable heterogeneous nucleation studies.
- Minimizing supersaturation variation through flow control or specific gas properties enhances the utility of DCPCs.
- These advancements open possibilities for using newly available seed particles of fixed size and composition in nucleation research.
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