Exploring the Taste of Electronic Cigarettes - Aerosol Chapter (1)

Summary:
This article is the aerosol part of the electronic cigarette taste exploration series, discussing the factors that contribute to the formation of electronic cigarette taste. The formation, evolution, and transportation of aerosols are key to taste, including processes such as nucleation, condensation and evaporation, and polymerization and fragmentation. The article also introduces that electronic cigarette aerosols are mainly composed of two parts: small particles and liquid particles, which helps to deepen the understanding of the formation mechanism of electronic cigarette taste.
With the rapid development of the new atomization industry, users have long abandoned the stage of "smoking is enough" for electronic cigarettes. Today, users pursue electronic cigarette products with high fidelity, high satisfaction, and full and smooth suction. Therefore, taste becomes the ultimate criterion for judging the quality of electronic cigarettes, and what factors affect the taste?
This topic will start from the mechanism and explore the various factors that affect the formation of electronic cigarette taste, in order to deepen your understanding of the mechanism of taste formation.
Topic 1: Formation, Evolution, and Transport of Aerosols
Firstly, we introduce a concept that aerosol refers to a gaseous dispersion system composed of solid or liquid particles suspended in a gas medium. The smoke of traditional cigarettes is solid particles generated by the combustion of tobacco, while the smoke of electronic cigarettes is liquid particles formed by the evaporation and condensation of atomized liquid. The two are suspended in the air medium to form aerosols, but their formation mechanisms and research methods are different.
(1) The formation and evolution of aerosols
Nucleation: In a mixture composed solely of vapor, one or more chemical components may be in a supersaturated state, which means that the partial pressure is greater than the equilibrium vapor pressure of the mixture. From an energy perspective, it is beneficial for vapor molecules to recombine into the liquid phase. If the supersaturation is high enough, it can overcome the energy barrier associated with the formation of the droplet surface, leading to droplet nucleation;
Condensation evaporation: Steam molecules are more likely to change phase and condense onto existing surfaces. This process is driven by the saturation of steam and the fluidity of steam molecules relative to the mixture. If the vapor becomes unsaturated, aerosol droplets may begin to evaporate and disappear;
Aggregation fragmentation: In dense aerosols, particles may collide with each other. Along with these collision events, two particles may merge into one; They aggregate. On the contrary, there is also a probability of particles being scattered into multiple particles, that is, particle splitting;
(2) Transport of aerosols
Drift: Particles have properties different from those of the carrier gas, such as density or viscosity, which may cause the movement of the particle phase to deviate from the movement of the carrier gas. This motion can be caused by inertia, for example, when a droplet carries too much momentum to adapt quickly enough to the local acceleration felt by the carrier gas.
Diffusion: When the particles are small enough, this Brownian motion leads to the diffusion of droplets. From a macro perspective, this diffusion is like a "regular" molecular diffusion, making aerosols quickly appear more dispersed.
Sedimentation: The velocity of the carrier gas on this surface is zero, which means that no gas molecules can pass through the surface. If aerosol particles precisely follow the streamline of the carrier gas, their motion will also stagnate on the surface, thereby preventing deposition. However, aerosol drift and diffusion may cause net transport of particles deviating from the carrier flow line. Therefore, drift and diffusion are both mechanisms that cause aerosol deposition, and in this sense, deposition can be seen as a result of the dispersion characteristics of aerosols.
From this, we can infer that the electronic smoke aerosol mainly consists of two parts:
When the surface of an atomized liquid is in a heated state and has not reached the temperature of evaporation, it breaks through the constraint of liquid surface tension and detaches from the small particles on the liquid surface (diffusion)
2. When the atomized liquid is heated and reaches the evaporation temperature, the high-temperature vapor condenses when encountering a normal temperature airflow, resulting in liquid particles (evaporative condensation)