Jet fans for car parks - cost justification 2

[Drazen]

I am consulting design development of several underground car parks.

My client heard from several sources about "fantastic innovation", that is jet fan ventilation instead of classical system with ductwork. He asked me to make investigation.

I found 4 such systems within my small country, all installed by same manufacturer.

As it is usual for this small market, I also made investigation in several neighboring countries and contacted some manufacturers directly.

What did I find? Some designers and sales engineers praise jet fans and call that system indispensable. But when I ask for some specific cost justification exercise, loud voices turn to silence. I spend several weeks in conversation with some manufacturers reps, but still don't have any specific answer to my very simple question: How jet fans save the money"?"

The problem is that I cannot do analysis myself, selection and specificattion of jet fans is based on computational flow analysis, and some manufactuters offer their calculations IF you make contract with them and include their producats in your design (it is additional question how to validate their software - I would never put my stamp on their calculation before they provide me with their full numerical iteration process and I check it throughly).

Does somebody have ideas about this?

 

[IRstuff]

Have you talked to the 4 customers? What do they say about their cost savings?

Some interesting reading:

http://www.cdc.gov/niosh/mining/pubs/pdfs/ri9399.pdf

http://www.aggman.com/0402_pages/0402operations.html

The main apparent advantage, for mines, is more mining vs people moving time, since the crosscuts can be made longer.

TTFN

 

[KiwiMace]

I don't think you ever have to worry about a supplier UNDER-supplying your project I've seen these systems done before (in Singapore) and all with CFD as part of the authority submission, pretty sure the calcs were done by the vendor. Save on overhead height and ducting, but lots of little motors to maintain.

 

[MintJulep]

The only thing that comes to mind is that without ductwork there is no duct friction loss.

 

[IRstuff]

Oh, I had forgotten that this has to do with a car park. I'm not even clear how this work in a car park.

Surely, the noise and wind alone would deter any real people from using a car park so equipped.

TTFN

 

[SAK9]

I have seen such systems in basement car parks.Obviously savings are there because no duct work is required.An indirect saving is there on the building construction cost as carpark height can be reduced.

Careful analysis is required as to how the system works in smoke purge mode so a CFD model is a must to convince your local authorities

 

[Drazen]

Yes, thanks, that's my problem: allmost everybody among colleagues tells that jet fans must be cheaper, but I cannot find any single case study, cost comparison...

 

[SVBNOVENCO]

Hello Drazen,

Let me introduce myself first, I work as a international technical/commercial engineer for a company (Noveco Netherlands) who designs and built the jet fan systems into car parks for more than 10 years now. They are also the founder of this system into car parks.

I understand that;"you are looking for some cost compartment duct versus jet fans, right?"

Is not so easy to give, the cost varies by country because the regulations varies and labour cost is also a big factor. In some countries you have to use fire rated duct and high temperature fans, sprinkler, normal duct or a combination of these.

With the experience I have, I will not say that jet fans saves money, it depends on the requirements of the client, regulations of that country or even state. I even dare to say that in most occasions it is more expensive.

About some things I am sure; for example it is more ( ca. 20%) efficient than duct work. The principle of mixing ( jet fans) is better than duct work (supply/extract). So less power consumption. Due to the small height of the jet fans, the constructor can save some height of the car park.

The other item, maybe even more important; "the jet fan system is far more saver than a traditional ductwork system."You can provide a good visibility, low smoke temperature and even smoke control in a car park, we call it a engineered solution /a live safety system. This system is a big step forward in offering a safe solution in a enclosed car park, for users and fire fighters.

If you require further information are help please contact me ore look at

http://www.novenco.nl

Sander

 

[Drazen]

Thanks for realistic advice, I consider it much more valuable then some reports that tend to be adjusted to client's initial needs, but have no enough support data.


At this moment my client is fully focused on jet fans as a means of cost saving, I need to convince him somehow that it is not basic criteria for selecting jet fans options.

Anyhow I will contact you in due course, thanks.

 

[ChasBean1]

Good for you Drazen for being skeptical and you should be. Running a fan without an attached system often costs more with a high volume flow and low DP. I’ve seen these installed in Boston’s Central Artery Tunnel Project as well as other jobs only recently. I’m very skeptical about their contaminant removal efficiency with respect to short-cycling of air and mixing effects at the inlet and outlet.

Very basically, a fan is supposed to take air from A and move it to B. If there’s no (or very little) differentiation between A and B, what’s the point?

-CB

 

[VEEKRISH]

As I have understood it, the mmajor tangible advantages of the Jet fan system are :

(1) No Ducting.
(2) Saving in height (from construction point of view) since ducts need not be factored in.

The other more significant advantage is -

In conventional system you would have a supply air fan and an extract air fan supplying and extracting the air via a dutct work system. These systems will have a fairly large fan motor to move the air around.

As against this, using the Jet Fan System, we will have a number of Jet Fans installed, the locations based on CFD analysis. This will mean a number of small motors all over the place. The philosophy of the Jet Fan system is that each zone covered by the Jet Fan will monitor the air quality in that zone. When the CO / CO2 concentration increases beyond the threshold limit, the Jet Fan in that zone will come on and stay on till the level is diluted. So in effect, you will have the individual fans cycling On and OFF to mainatin the air quality level. This is where the real saving is effected.