Learning Forum

[FaizanYounas]

Hello there. I just have one confusion about adding the latent heat in the energy equation. I know that it can be done by enabling the following command:

solve/set/multiphase-numerics/heat-mass-transfer/alternative-energytreatment (yes)

After enabling it the difference between the SSE of liquid and vapor is considered as the latent heat. So, I'm keeping the SSE of liquid as zero and giving an "x" SSE value to the vapors. My question is do I have to multiply or divide that "x" value to the molecular weight of the liquid? or the exact value of "x" is taken as the latent heat by the fluent?

I have to put 175000 as latent heat, should I put the 175000 as the SSE or multiply it by molecular weight and then add it as SSE?

[Rob]

It depends on what units you got your latent heat in when compared to the Fluent data entry. To note, kgmol is kmol in American.

[FaizanYounas]

My latent heat is in J/kg. Right now I'm running with liquid SSE as 17500 and the vapor SSE as 0. I don't know should I multiply or divide it by some factor (maybe molecular weight). I'm running the condensation case.
I know the other way to do it is with the DEFINE_SOURCE macro. But, I'm already using DEFINE_MASS_TRANSFER macro and in new fluent, both these macros don't work well if used together.

[Rob]

Then you'll need to change the units and convert your values. Check the enthalpy units in Fluent just in case you can change those rather than looking up the conversion factors.

[FaizanYounas]

means I have to divide the SSE value with the molecular weight to get the equivalent latent heat. Okay. Anyways, thank you. I just wanted to ask why the two macro's DEFINE_SOURCE and DEFINE_MASS_TRANSFER don't work together in new fluent?

[Rob]

Where does it say you can't use both? I can see there being a conflict if they're effecting the same cells but not anything in DOC about it.

[FaizanYounas]

I was suggested on this forum to not use both the macros in the new fluent. I was solving the Stefan condensation problem. When I only used one macro instead of both two. I got good results and both this macro's worked perfectly fine in the old fluent. Anyways, thank you very much.

[Amine Ben Hadj Ali]

Yes I suggest to use either the concatenated Multiphase mass transfer macros or the define source ones. Better not both for the same pupose but you combine for all other purposes .