CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > ANSYS > FLUENT

Car park ventilation and impulse fans

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Search this Thread Display Modes
Old   May 11, 2008, 19:59
Default Car park ventilation and impulse fans
Posts: n/a

I'd like to get the opinion of car park designers on the following point:

Impulse fan manufacturers claims that the instalation of impulse fans reduces dramaticaly the flow rates of exhaust and supply fans of the car park.

My model consistently showed that the tunnel analogy doesn't work in a car park and the CO concentration is very much set by the average air velocity throughout the carpark created by the exhaust/supply velocity in a car park of rectangular shapes with exhaust on one side and supply on the opposite side. The higher velocities created in the fan areas are only mixing the pollution, create recirculation zones, and destroy the vertical stratification of CO concentration.

In my opinion, impulse fans are only usefull for smoke dilution in the case of a rectangular car park. They can help with CO only when there are stagnation areas in car park with a complex shape (by bringing some fresher air in the stagnation area) or when the sides of the carpark are open and thus the impulse fans set the average velocity of the air through the car park (tunnel analogy is valid in this case).

Anybody to agree or disagree?
  Reply With Quote

Old   May 18, 2008, 08:14
Default Re: Car park ventilation and impulse fans
Posts: n/a
  Reply With Quote

Old   August 13, 2009, 04:08
New Member
Join Date: Aug 2009
Posts: 1
Rep Power: 0
Flakt is on a distinguished road
A well designed Jet thrust system will ventilate an are in both pollution and smoke modes. You are correct in the fact that the air change rate within the are is achieved with the main extract fans and this will not change from a ducted system, however where a ducted system has both high and low level grilles placed evenly around the car park, the jet thrust system uses impulse fans to distribute the air.
The advantages of a Jet thrust system is that the main extract fans have far less resistance to overcome due to not having associated duct work, and therefore have smaller motors, have to do less work and in turn consume less power, the volume flow rate remains the same.
Jet fans also have the advantage of being directional. this allows individual areas, also known as zones, to be defined, allowing selective oporation of jet fans in polluted areas. This methodology also translates into an emergency scenario where fans can be run strategicaly depending on the location of the fire, allowing the smoke to be directed to the closest extract point within the car park, helping tto keep the rest of the area free of smoke to allow fire fighters to tackle the fire safely.
Flakt is offline   Reply With Quote

Old   June 27, 2011, 11:17
New Member
Join Date: Jun 2011
Posts: 7
Rep Power: 14
trulytrue is on a distinguished road
Dear ALL.
I want to simulate in fluent Combustion of polyurethane with power of combustion of 4 MW. the area of the source of combustion is 2mX5m.

The time of combustion is 20 min. The use of this simulation is for carpark ventilation system.

It will be fine if some can help me to estimate the visibility as well.

THank you .

trulytrue is offline   Reply With Quote


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Car park ventilation and impulse fans guillaume Phoenics 9 October 27, 2015 05:57
Car park ventilation and impulse fans guillaume Main CFD Forum 12 June 27, 2011 11:16
Validation of carpark impulse/jet fans Henry Ho Phoenics 3 July 6, 2009 06:59
Car park ventilation and impulse fans guillaume Siemens 0 May 11, 2008 20:00
Car park ventilation and impulse fans guillaume CFX 0 May 11, 2008 19:59

All times are GMT -4. The time now is 15:40.