Underfloor Distribution of Auditorium 2

[walz]

Hi all

I have an underfloor distribution system to be designed to serve an auditorium, in the seating area, i am already using underfloor system for which i have raised floor, and return from top. While for the stage area, i have both options available i.e., i can either do underfloor or can do mixed air system (supply from top / return from below).

The question is that wheather this arrangement can work. As a whole there is one volume. the reason for this is because im skeptical about underfloor system for stage area. it can work or not. if not then i have to use mixxture system for stage area.

appereciate any response in advance

 

[SAK9]

With UFAD,supply air temperature will be around the 18~19 C mark.This temperature is too high for a mixed air distribution.Air flow requirement for the stage will be high due to high lighting load. So UFAD will be difficult for the stage from an air distribution point of view.Further latent load on stage can be high depending on activities undertaken.This would need a lower supply air temperaure.

A dedicated unit for the stage is the normal solution.The performers will have better control over temperature as well.

 

[ChasBean1]

Agree with SAK9, good post. Architecture permitting, I'd stick with UFAD throughout. Warmer DATs to prevent cold legs require dehumidification controls, such as a wrap-around cooling coil heat pipe or reheat of some sort.

 

[cdxx139]

With the excessive light load, I would guess it would make the most sense to return high, that way the coil sees the light load instead of distributing it into the space.

Whatever you supply behind the curtain, also return behind the curtain, the owners will not like it when the curtains sway due to airflow.

knowledge is power

 

[walz]

SAK9 and Chasbean

If i put both systems in auditorium, will there be some problem?

The whole auditorium is UFAD except the stage where its mixture. and if i do, can i do the stage with top supply, bottom return? (keeping in mind that rest of the area is supply at bottom).

or if i have to go for mixture system at stage, i have to have both supply / return from top?

 

[SAK9]

I do not see any issues in having different systems.It is going to be a challenge doinga UFAD on stage given the high air flow requirements and constraints to floor diffuser locations(never know what equipment,furniture is going to be on stage).If the theatre is not for professional performances you might get away with UFAD on stage as well.

In regards to the stage,you need to have supply and return at high levels, the return going past the light bar so that you can account for atleast 70% of lighting load in return air load.As CB noted be mindful of humidity issues when using a displacement system.Cooling and reheating will be required.Given the large ventilation requirement,the theatre UFAD will most likely be a full fresh air system with scope for energy recovery.

 

[GMcD]

Think about what happens on the stage. Trying to supply air from the top, and using a mixing strategy will cause anyone with smoke effects to go mental. Don't Do It !. UFAD/Displacement has been used for a hundred years for theatres, including the stage conditioning. If it ain't broke, don't fix it. Any type of mixing or high level air supply will need a high delivery velocity to get air down at the people zone: high velocity = air motion = waving curtains and backdrops. Not Good.

Yes, there may be some stage lighting heat, but think about the fundamentals - there will be some radiant heat from the spotlights, but 90% of the heat rises up off the lamps in the bouyant plumes, so a lot of the heat from the lights does not become part of the comfort cooling load on the stage.

Just google ASHRAE's UFAD and DV Guide as well as the REHVA DV Guidebooks.

 

[SAK9]

I have not noticed any curtain flutter in any of the projects I have worked on or that i have visited.Heard about this argument many times before but there is no truth in it.Based on my experience the air flow from a diffuser is not strong enough to cause fluttering of the heavy curtains.