For a solely water vapor condensation thermal hydraulic ANSYS Fluent CFD problem, I have defined a 'hybrid' fluid for which all necessary fluid properties are defined as temperature dependent piece-wise-linear distribution.
The hybid fluid bears fluid properties of both the phases (gas and liquid); i.e. for fluid temperatures>saturation temperature, the hybrid fluid has properties of gas phase and for fluid temperatures
I would have one question: How you determine in this approach the interfacial area density (IAD)? IAD has the unit of measure of [m^-1] and is the inverse of the ratio of a balance volume to the amount of interfacial area (in m^2) being enclosed in that balance volume. With a classic multiphase flow approach we can calculate IAD from an assumption about the shape of interfaces (e.g. bubbles, droplets), characteristic length scales of the disperse phase and the local volume fraction. But how do you do this calculation for your approach? Essentially all mass, momentum and energy transfer processes are dependent on IAD.
Best regards,
Dr. Th. Frank.
I got my answer Dr. Thomas Frank .
I foolishly ignored interfacial area density calculations, which I know are ultra important in multiphase simulations. In my case, the only parameters to compare from the experiment are temperature and pressure drops along tube length. Maybe its a coincidence or rather effect of some other assumptions in my simulation setup that caused the respective results to match with the experiment.
Thank You.
The sharp gradient of the density along the interface is important for accurate simulations of multiphase flows. That is why fine meshes are needed at the interface. Approximating this sharp interface with hybrid or average properties won't yield accurate results in most cases.
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