how to set the constant value of outdoor temperature of a chamber in FDS?

[Dahai Qi]

Hi all,

I am simulating the air flow of an air conditioning chamber using FDS. I want to use outdoor temperature as the boundary condition that is constant all the time. In the FDS user guide, it was suggested to use exposed and initial temperature of the chamber wall that contacts with the outside air. However, I found the outside air (outdoor temperature) would be changed when i did as the user guide said. Could you help me how to set in FDS to make outdoor temperature constant?

Thanks!

Dahai

[Kris]

You could try setting the ambient temperature (TMPA on the MISC line)
to the outdoor temperature, and then using an INIT line to set the gas
temperature inside (and TMP_INNER for solid abostructions) - See
Section 6.5 of the User Guide.

Kris

[Dahai Qi]

Thanks for your help! Your information is useful for me. But I cannot understand the exact meaning of the TMP_INNER for solid obstructions. I tried some examples about the effect of TMP_INNER on the temperature distribution. However, I cannot see any different phenomena about different TMP_INNER. The temperatures are all decided by the ambient temperature (TMPA on the MISC line). So could you tell me what is the TMP_INNER meaning when use it?

Dahai

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Dahai (Darren) Qi

Ph.D. Student

Dept. of Building, Civil & Environmental Engineering
Concordia University, Rm: EV-10.221

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[Kris]

As you've noted, the initial temperature of solid obstructions is set
to TMPA from the misc line by default. However, if you want a solid
obstruction to have a different initial temperature, you can set that
use TMP_INNER on the SURF line used for that obstruction. This is
explained in Section 8.4.6 of the User Guide. You will need to set
all of the following:

On the MISC line: TMPA=40 (or whatever your outside temp is)

An INIT line that has the xb of the inside of your building with
TEMPERATURE-20 (or what ever your inside temperature is). This may be
the whole domain if you aren't modelling beyond your building.

SURF lines for any of the solid obstruction types inside your building
(eg floors, walls) that have the TMP_INNER=20 (or whatever your inner
temperature is) (See Section 8.4.6 for other restrictions - eg SURF
line must have THICKNESS and MATL_ID parameters specified)

Define your blockages within your building with SURF_ID referring to
SURFs that have the TMP_INNER set to the inside temperature

If you have solid obstructions that you want to be initially at the
outside temperature, you will need to have SURF lines for these that
don't have the TMP_INNER parameter set.

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[Dahai Qi]

Thanks for your help! I see.

Dahai