Hi everyone. I have some problems about evaporation - condensation. (This is very long question :) )
I am trying to simulate water evaporation for different designs but actually I can't.
I'm a relatively newbie in liquid-gas two-phase simulations, especially in Fluent. I'm trying to simulate evaporation and condensation that occurs at every temperature, not boiling. I can't get the right result when I run my models by trying the VOF and mixture models.
The methods I have tried so far and the methods I did not get results:
I defined three phases (air, water-liquid and water-vapor).
1. I created a piecewise - linear graph for saturation temperature by choosing water to steam as the mass transfer. There was no evaporation. Also, if I choose steam to water, I got a negative latent heat error.
2.While researching, I tried creating source terms for cell zone, liquid and vapor. Simply, if t>t_sat was evaporation, if t
Greetings. Before doing your own simulations it is important to know how mass transfer models work, especially before making a UDF, which would substitute frequency, mass transfer, phase shift at the desired temperature, etc. For your model to work it is essential to verify that the energy equation is selected, some mass transfer model (evaporation-condensation) as well, and the correct selection of the energy model for evaporation, Ranz-Marshall or double resistance. In order to know with certainty what the omission could be or why the simulation is not being executed, it would be desirable and convenient to give a little more detail. The use of a UDF is for experienced users and not everyone can make it work, especially since the modifications and names often conflict with the names of the designated variables. In newer versions to 2021 it is more feasible to use mathematical expressions, as is done in Comsol instead of the UDF itself while the user gets used to correctly programming the UDFs. It is always advisable to do a tutorial, either from the official page or from those found on YouTube, but verbatim to understand how the software works. For step-by-step, more details are needed. In fluent models, evaporation is always used as the saturation temperature for the model to work. My apologies if it was not the answer you expected. (these really work, but are in 2d https://www.youtube.com/watch?v=o2cFA97LDJk https://www.youtube.com/watch?v=Q8rJp9HH9TA )
I would first recommend you validate your numerical model with existing literature. Once you identify a good reference, you can use their boundary conditions, and numerical setup to generate the results. Make appropriate changes until you get within acceptable accuracy limits. Once you are done with validation you can use it for your own purpose. The validation will help you choose the right models, equations, etc for the evaporation-condensation process.
- Badges
- Science topic
- Similar topics
- Agriculture
- Horticulture
- Seeds