cable tunnel ventilation

[HVAC68]

I have a cable tunnel which is 500m long and 2m x 2m cross-section. What's the air changes per hour to be considered for ventilation in normal mode and in smoke mode ?

HVAC68

 

[SAK9]

For the normal mode, you need to calculate air quantity based on heat dissipation from cables(which is available based on watt/m).

For the smoke purge a velocity of 2.5 m/s is recommended across the tunnel cross section.Anything greater may impede escape from the tunnel.

I came across these figures while bidding for a cable tunnel project.

You would need to consult your local fire authority whether these figures can be used

 

[SAK9]

http://www.arup.com/industrial/project.cfm?pageid=5659

Please check the above link which will give you some helpful guidelines.Looks like the figure I gave in previous post is wrong!

Arup recommends 5 m/s for smoke purge mode.

Also note that a cable cooling system is to be used(which is done with the help of a cooling tower circuit).These pipes are buried next to the cables in a sand trench.Therefore the ventilation system needs to remove only a portion of the heat generated by the cables.I can not remember what percentage I had apportioned for the cooling system .

A CFD model is required for the detailed design.


This could prove to be a lot trickier than you would have imagined!