Hello Friends, I have a question that is stated in the title. I saw many papers trying to introduce moisture in a system by bubbling the air through it first. How much exactly moisture is introduced to the system using this way? Is there scientific reasoning how air is carrying water molecules with it?
Well, normally gas bubbling is used to saturate the gas to prevent evaporation inside for instance a fermentation. In short, the bubble is saturated vèry fast with water in case of clean water since mass transfer limitations (in the gas phase) can be neglected and non-existent in the water phase. The amount of water is then simply the gas flow rate through the upper surface (temperature and pressure) containing water fraction according to the vapour pressure at those pressure and temperature.
When a bubble collapse at the surface, a very small droplet may form. If you want to be accurate use a filter as Navid mentions. But there are more complications such as saturation of the filter with water, changing pressure. Atmospheric pressure changes. Accurate determination of the gas flow rate. Condensation of water at the inside of the (colder) tube to the 'reactor', changing saturation conditions. And, not unimportant, contamination of the water with oil like stuff, forming a microlayer at the bubble surface, creating a mass transfer limitation at the liquid side. It all depends on how accurate you want to know the amount added.
Vapor is gas. When you introduce a gas bubble in water interfacial mass transfer will occur according to Henry and Dalton Laws. This mass transfer will depend on the gas composition of the bubble and on the dissolved gases in water.
For water/vapor thermostatic equilibrium see:
(PDF) AD-Chapitre 2 : Dynamique et thermodynamique des Géo-Fluides (researchgate.net)
Other academic resources are provided within the project references:
SINGLE PHASE AND MULTIPHASE TURBULENT FLOWS (SMTF) IN NATURE AND ENGINEERING APPLICATIONS | Jamel Chahed | 3 publications | Research Project (researchgate.net)
Dear Jamel, please tell me what is the Henry coefficient of water vapor in water?
Dear Rob van der Lans Henry Law applies to varous gases forming the bubble and defines interfacial gas-liquid mass transfer according to partial pressure of each and liquid concentration in gas. Dalton Law applies to gas mixtures and gives a relation between partial pressures to total pressure.
Water/Vapor equilibrium in governed by constitutive relations driving from thermostatic analysis.
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