[Kummi]

Hello Foamers,
I met a problem that I can't solve, please help me with it. My topic of research is to build the 1D mathematical model for simulating the coal pyrolysis in OpenFOAM. Based on fireFOAM, I developed my own solver extracting only solid region for pyrolysis. After then, Im stuck here with phase change.
As explained in attachment (figure), due to supply of heat from the wall ==> the moisture (1st phase) content embedded in the coal particle boils to give steam (phase 2) at 100deg . In my case, the moisture and steam are not treated as separate phases (there are no two phases defined explicitly), so that eliminates multiphase (interFoam) methods which is basically defined with two phases explicitly (as phase 1 and phase 2 in transport properties).

On cross check with other solvers like "lagrangian", there found LiquidEvaporationBoil >> under PhaseChangeModel, which is basically defined under injection model in openFOAM, but in my case I dont need injection, so is it possible to implement LiquidEvaporation in OpenFOAM (without injection based)?

My problem is solely dependent on main variable temperature (T) with no pressure and velocity terms. Finally, the calculated rate of boiling (r)due to moisture boiling as shown in figure will be manipulated in ENERGY equation as a source term. However, I understand the flow physics, I am not sure about where should I start, based on which solver and move on..
Kindly someone share their ideas please. Thank you !!!

[nimasam]

i guess you may start with icoFoam, then add energy equation + variable density

[Kummi]

Hello Mr. Nimasam,
Firstly, thank you for your response.
As mentioned above, I have already created my own solver based on fireFOAM for only pyrolysis (only solid region).

There is a source term called rgas*cgas*(∂T/∂x) realted to gaseous species in the main energy equation as shown in the figure. I guess that I should attack this source term for phase change by including the gas chemistry. I am giving my try to solve it.

Some help related to it will be highly useful.
Thank you ^^

[Kummi]

Hello Mr. Nimasam,
To make it simple, my question is, how the moisture in the wet coal can be evaporated using OpenFOAM?
Is there any evaporation model or solver related to such problem?
Because in my case, the moisture and vapor are not defined explicitlyas how it is defined in multiphase problem. (the moisture and steam are not treated as separate phases)

Kindly share your ideas.
Thank you

[wyldckat]

Quick answers:

1. interPhaseChangeFoam is the main solver for phase changes...
2. OpenFOAM-v1812 also has the solver interCondensatingEvaporatingFoam: https://develop.openfoam.com/Develop...vaporatingFoam

[Kummi]

Dear Mr. Bruno and Mr. Nimasam,

Big thanks for your resonses.
I took some time to explore my problem. I have gone through interPhaseChangeFoam, added Transport Equation for Temperature, compiled and run the problem, which is built based on mass transfer model with alpha and pressure loop.

Whereas in my case, I found that I need to solve a type of 1D STEFAN problem (solved based on MASS and HEAT BALANCE EQUS. as shown in ATTACHMENT).In reality, the moisture is embedded within the WET COAL, but in this case (as per my understanding), it should be assumed for 1D PROBLEM that the moisture (as liquid) will be filled in the entire chamber initially @ t=0 (for wet coal basis). Heat is transferred by wall conduction only. When the temperature reaches T=100deg (heating wall -left), the surface (near the wall as show in figure) reaches above the saturation temperature, and so liquid (moisture) evaporates leading to the motion of vapor-liquid flat interface from left (flat-isothermal surface) to the right of the chamber. If the vapor-liquid interface moves to the complete right, then the chamber is saturated with only evaporated vapor (considered as dry coal in real basis). Interface stays flat for 1D PROBLEM. Once after the moisture evaporates at T=100deg, the wet coal turns into dry coal and then the coal pyrolysis process takes place.

And further, the moving boundary (boiling plane- xb) and saturation temperature (@boiling temp = 100deg) are not defined with any expressions.

REF - STEFAN problem - SECTION 4.1 ~ https://www.sciencedirect.com/science/article/pii/S0021999108001228

REF - MANUSCRIPT which I am focussed with based on GOVERNING EQUATIONS and SOLUTIONS ~ https://sci-hub.tw/https://doi.org/10.1016/0016-2361(83)90225-9
Focussing on my objective, I should reproduce the Figure 1 given in above attached manuscript, "Mathematical models of the thermal decomposition of coal - 4. Heat transfer and temperature profiles in a coke-oven charge". I have already created my own solver based on fireFOAM for only pyrolysis [considering as dry coal]. Now, I should create a SUBMODEL considering moisture evaporation [wet coal] and couple with my pyrolysis solver.

On the whole, the above problem for MOISTURE EVAPORATION looks to be SIMPLE with simplified equations based on 1D STEFAN problem , but I am unable to find a way in OpenFOAM.

Kindly guide me how to proceed on. Thank you

[Pavithra]

Hi Everyone,

I want to simulate a closed heat pipe where evaporation takes place at the lower end of the pipe and condensation takes place at the top end of the pipe.

I am aware that interCondensatingEvaporatingFoam or icoReactingMultiphaseInterFoam can handle evaporation or condensation. But, can they handle evaporation and condensation simultaneously ?

Thank You.

With Thanks,
Pavithra.