Stairwell pressurization.

[Siva D]

Hi greetings everyone

I have been trying to model a stairway pressurization scenario. I tried to obtain some previous studies regarding stairwell pressurization using FDS for validation purpose and unfortunately, I could not find any. 

My question really is, how stairway pressurization is done using CFD. On my quest to unravel this, I created a simple geometry and I simulated the smoke.

I understand the fact when pressure increases in the domain in such a way that no more smoke can be accommodated in domain, numerical instability arises. So, how is a stairwell pressurization study done using CFD ? 

Is the fire zone connected to the ambient for pressure relief? Can someone please guide me towards some document which says how SP is done ? 

Sadly, I could not find any documents related to Stairwell Pressurization done using CFD on the NIST website either. 

Thank you

[Salah Benkorichi]

I used this few days ago,

What I have done is simply adding an HVAC system on the top head of stair. You use curved fan (check user guide) you also need to set max pressure value that will correspond to you flow rate. And it should make pressurised zone in stair and prevent smoke from spreading into staircase due to the pressure differences.

Sent from my phone

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From: fds...@googlegroups.com <fds...@googlegroups.com> on behalf of Siva D <sivaa...@gmail.com>
Sent: Tuesday, April 24, 2018 12:17:53 PM
To: FDS and Smokeview Discussions
Subject: [fds-smv] Stairwell pressurization.

 

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[Siva D]

Thank you for your response. I have done that.

However, there comes a point where smoke can no longer remain in the volume from where it originates because it gets filled completely. So numerical instability occurs.

I would like to know if there is any CFD study based study for stairwell pressurization. I want to know about the minimum boundary conditions I need to apply to perform a reasonable study.

Thank you  

[Salah Benkorichi]

It is good thing to have a numerical instability at such condition, imagine having a sealed box and keep filling it, at certain point you can no longer as the fluid is no longer compressible. 

I don't know what you are trying to achieve, but you should find recommendations in your local guidance and regulation. 

A vent is expected in a fire room in order to maintain your HRR, this might provide some relief for this smoke, similarly with leakage areas.. 

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[Siva D]

I understand. I was unable to find local guidance. Hence I came here. Thank you for your wonderful support. 

[Salah Benkorichi]

Your corridor would generally requires either a natural shaft or an mechanical extract depending on your local guidance and what design you are working for. So, that would also help your smoke to be sucked out, and clear your means of escape.

On 24 April 2018 at 13:43, Siva D <sivaa...@gmail.com> wrote:

I understand. I was unable to find local guidance. Hence I came here. Thank you for your wonderful support. 

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[Siva D]

Thank you. I was also confused regarding something. I had been referring BS EN 12101-6 standard for stairwell pressurization.

1. For example if you check out page 21 of that standard, for class C stairwell pressurization systems, the standard recommends the stairwell to be 50 pascals more than the other zones when all doors are closed. 
2. My question is, does this criteria apply when there is a fire or it is just a design condition that has to be maintained for testing stairwells when there is no fire ?
3. I am sure that the pressure in the zone increases rapidly with the presence of fire and there is no way we can maintain 50 Pa difference and even if we wanted to do it, it might take a fan with a very large CFM value. 
4. However, the standard does not mention anything about fire. Could you please share your insight on this ? I just want someone to throw some light on this.

Thank you. 

[Salah Benkorichi]

This is part of design for fire strategy. In case of fire is where generally the pressure increases.

50pa because the general rule recommend to not pass 100N so the doors can be opened. P,,=force/area, i.e. 50=100/2 where 2 is the area of the door.

You might consider consulting senior engineers elsewhere than this group who have more experience in term of norm and standards.

Sent from my phone

From: Siva D

Sent: Friday, 27 April, 06:48

Subject: Re: [fds-smv] Stairwell pressurization.

To: FDS and Smokeview Discussions

Thank you. I was also confused regarding something. I had been referring BS EN 12101-6 standard for stairwell pressurization.

For example if you check out page 21 of that standard, for class C stairwell pressurization systems, the standard recommends the stairwell to be 50 pascals more than the other zones when all doors are closed. My question is, does this criteria apply when there is a fire or it is just a design condition that has to be maintained for testing stairwells when there is no fire ?I am sure that the pressure in the zone increases rapidly with the presence of fire and there is no way we can maintain 50 Pa difference and even if we wanted to do it, it might take a fan with a very large CFM value. However, the standard does not mention anything about fire. Could you please share your insight on this ? I just want someone to throw some light on this.

Thank you. 

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[Siva D]

Thank you Salah.

So basically a stairwell pressurisation system or any fire protection system for that matter is designed with the knowledge of the maximum pressure that can develop in case of a fire ?

[luca.mi...@gmail.com]

Hi,

sorry if I use this post to ask a question, but I am facing a similar situation, i.e. I am trying to design a stairwell pressurization with BS EN 12101-6.

I am reproducing the airflow criterion case (open door on the floor where the fire start). In this case, since the corridor and the staiwell are not separated, I have not specified any pressure zone. Is this correct?

Luca