Issue with inlet/outlet air flow to thermal model

[Anonymous]

Hi,

I'm trying to perform a study of thermal comfort in a conference room with slot inlets and a central outlet point. I've done both a simple model with a small room with 1 inlet and 1 outlet and a 'full scale' model with a large room and 30 inlets and 1 outlet.

I expect inlet velocity speeds over each inlet slot to be approx. 1.1 m/s. This is achieved well with no problem in the simple model with the inlet plume acting as expected. However, when trying to apply the principle to the 'full scale' model I get close to zero velocity speed values  over the inlets (0.0005 m/s etc.), i.e. close to no inlet air to the model. Convergence is still fine though, but the model seems to neglect to BC's in question. I've tried optimizing the grid sizing for the inlet slots, so it is much finer for the 'full scale' model than for the simple one. Any ideas for what might be wrong? Should I try applying som inlet conditions (e.g. air velocity over the inlet slots) in order to help the model 'notice' the applied air flow BC's? I've attached both support-files:

- Simple room: 'Komponenttest-06_1_support'

- 'Full scale' room: '7350-01A - HSS_1_support'

Can you help me out please? Thanks!

[Anonymous]

Also including the attachments.

[marwan_azzam]

Hello,

I opened the file "7350-01A - Ballroom-07_1_support.cfz"

My hand calculations indicate an inlet velocity of 6.627e-7 m/s.

You are getting 0.0005 m/s so I'd say you are way ahead of the game here.

I looked at a random inlet surface:

Q=VA

Q = 167 m3/h

A = 1000m x 70m = 70,000m2

V = 167/70,000 m/h

You've got one huge building.

Check your units.

cheers,

Marwan

[Anonymous]

Hi Marwan,

You are completely right. It does indeed look like I made a "small" a scaling factor (of 1000).

Thanks for the input!

Cheers,

Rasmus