Drying process (evaporation in porous)
 

Helo everybody

I trying to model a drying process. Hot air from nozzle come throught porous domain. Porous material (straw) contains water (modeled as morphology- dispersed fluid). To model water evaporation i used tips from Solver modeling guide. It seems that evaporation working corectly. Problem is with water-liquid in straw. When simulation starts after few seconds all water goes out.

My question is how to stop/fix water in porous region? I want evaporate it not blow out.

Hi, im interested on drying Model for biomass combustion. Would you be so Nice to share the model or some instructions??
Please!!

Tomasz - it sounds like your physics is wrong then. Can you post your CCL?

we generally don't like to download *.zip files from random people from the internet. You should post your CCL in here directly into an [*CODE] [*/CODE] wrapper (without the *)

Is it okey in .txt file?

I can't use [*CODE] [*/CODE] - too many characters

I think you need to have a careful think about what you are trying to do here. You appear to be modelling the gas as a air/water vapour mixture, and then a multiphase model with water droplets. Please correct me if I am wrong but I don't think a eularian droplet multiphase model is appropriate to model the evaporation process in this application.

Modelling the detailed physics in this as you are attempting appears very challenging to me. So do you really need the detailed physics? I would consider doing a much simpler additional variable approach where you use an additional variable to track the water content of the straw, and have an empirical model to remove the water based on the local conditions. Then the details of the physics are covered in the empirical model. This sounds far simpler to apply to me.

ghorrocks do you know any easier way to model drying proces? I don't need very detailed model. I found this solution in Ansys CFX Solver modeling guide (realise 17.0).

The additional variable approach I suggested is very simple.

You need to state what is the important physics in your case before we can recommend a model. Is the change of mass important? Heat gain/loss due to evaporation? Humidification of the air leaving the area? Temperature profiles? etc etc. The more of these things you want to model, the more complex it gets.

Most important is get to know water mass change in time. I want to estimate optimal time for drying straw for combustion. In addition i want get temperature profile.

I have a real size empirical model and measurement data to compare with simulation.

So then I guess that important physics would be:

* evaporation rate versus water content, air humidity and temperature data
* specific heat loss/gain due to phase change

Do you have this data? The specific heat loss/gain would just be standard water data. But I suspect the evaporation rate one is dependant on the straw material so you will need to provide this data. Do you have it?

Ok, I found specific heat loss/gain. Evaporation rate, air humidity and temperature (temperature of hot air? Or straw before heating?) - i can gain this data in experiment. But what next? Could You describe Your idea? Is it include a hot air flow?

I would be thinking about using a additional variable to track the water content in the straw, and a multicomponent mixture for the air. You then need to couple the AV to the mixture using source terms.

Drying of brick (half porous)
 

Helo everybody

Would this case fit considering the 8-hole brick as a porous medium? because I'm trying to seize this case and I'm not getting it.

It is important to understand what you are trying to do before we suggest approaches to model it. Please answer the questions on your other thread and we will discuss it there.