Modeling Aluminum particle vaporization

[Swagnik]

Hello All,

I am trying to model the combustion of Aluminum particles in air. The first step is to vaporize the particles according to the equation Δc=(3Φ_s*ρ_s/τ)*(1+0.276*sqrt(Re)), which describes the inter-phase mass transfer rate. Something that I am trying to understand is, whether the heat of formation of Aluminum vapor should be added to added to/subtracted from the gas phase total energy, and why? Also, what about the total energy/internal energy for the particle phase? Does it not change? I am only talking about the effect of the heat of formation. I understand the changes in energy due to change in Kinetic energy and Pseudo Thermal Energy.

In order to make the problem description more clear, I am modeling the burning of Al in air inside a closed domain. So the vaporization occurs only due to either the burning of Al or some shock passing through the domain, etc., i.e., there is no external heating.

I would really appreciate it if someone can provide me with some insight on this.

Regards,

Swagnik

 

[georgeverghese]

Presume you are atomising aluminium liquid particles in this closed domain prior to combustion to aluminium oxide. In most texts, the heat of formation of aluminium oxide would reference the reactant aluminium particles in their standard state at room temp, which in this case would be solid aluminium. Since you are now combusting aluminium vapor, you have to add the heat of fusion (solid to liquid) and heat of vaporisation (liquid to vapor) to the heat of the combustion ( or heat of formation ) reaction.
So, in your case, Hr = Hc + Hsl + Hlv - H1 - H2 , where Hc identical to the std. heat of formation of solid aluminium oxide. H1 is the heat required to raise the temp of aluminium oxide solid from 25degC to your closed domain conditions. H2 is the heat required to raise the oxygen required for this reaction from 25degC to combustion temp. We are assuming here this combustion reaction occurs at isothermal conditions.