topic Re: moist air simulation question in CFD Forum

moist air simulation question

rkd3456 — Wed, 22 Jun 2022 07:17:01 GMT

Hello. I am a graduate student studying in Korea.

I am trying to study the interpretation of wet air.

I want to simulate that humid air with humidity 100%RH inside is rising to 100℃, and humid air with humidity 0%RH coming in from outside.

As shown in the picture, the material is
Object (pipe): Aluminum
Internal fluid: moist air (variable)
External fluid: air

boundary condition as shown in the capture_1
I gave Inlet_1, Inlet_2, Outlet

Initial conditions were given as temperature and humidity conditions.

However, the simulation does not proceed.

Only automatic mesh was given for the mesh, and when boundary conditions and initial conditions are set, I plan to finely mesh them.

Any help would be appreciated.

cfz file is not uploaded, so I upload it as a zip.

Re: moist air simulation question

karol.suchon — Wed, 22 Jun 2022 12:31:49 GMT

Hello,

with the applied conditions the phase change appears so the moist solver is not able to compute humidity.

You could try to set the fluid with saturated steam and compute quality analysis or decrease the temperature to 99 degrees.

Best regards,

Karol

Re: moist air simulation question

rkd3456 — Thu, 23 Jun 2022 04:48:09 GMT

Hello, Karol
Thanks for replying.
I understand that the phase change cannot be simulated in Humidity because evaporation occurs at 100°C.
If so, does the analysis not proceed even if the initial temperature exceeds 100 degrees due to heat generation at the initial temperature of 25 degrees? I wonder.

First, as Karol's advice, I used saturated steam and changed both the boundary condition and
the initial condition to Quality (0=only water, 1=air).
But the solver stopped as shown.
I've tried a number of things, but it doesn't work, so any help would be appreciated.

Re: moist air simulation question

rkd3456 — Thu, 23 Jun 2022 08:12:51 GMT

any help would be appreciated.

Re: moist air simulation question

karol.suchon — Thu, 23 Jun 2022 10:26:02 GMT

I forgot that there is a defect with the boiling initialization in CFD 2021.

Decrease the temperature and use the humidity analysis, the quality analysis is much more complicated.

If you really want to use quality analysis, please instal the previous version.

Re: moist air simulation question

rkd3456 — Mon, 27 Jun 2022 03:32:26 GMT

Are there any problems with the analysis conditions I have set?

The current 2019 version doesn't seem to be for students, so I can't try it.

I tried the 2023 version but it didn't work.

Re: moist air simulation question

karol.suchon — Thu, 30 Jun 2022 09:02:47 GMT

So you will need to use the humidity solver, so please decrease the temperature below the boiling point.

best regards,

Karol