March 12, 2025
192 - Fire Fundamentals pt. 14 - Jet fan systems for car parks
The player is loading ...
Jet-fan systems effectively control smoke in car parks by creating directed airflows that transport smoke from one point to another, similar to how longitudinal ventilation works in tunnels. These systems offer cost-effectiveness and simplicity by eliminating ductwork while providing powerful smoke management capabilities when properly designed and understood.
• Jet Fans create momentum transfer through air entrainment rather than directly moving smoke
• Two distinct operational modes exist: smoke clearance (reducing thermal stress) and smoke control (maintaining clear firefighter access)
• Systems require careful balancing of extraction capacity with Jet Fan thrust force
• Optimal design typically requires CFD modeling followed by hot smoke testing for verification
• Jet Fan activation timing presents challenges for evacuation - usually delayed until occupants exit
• Systems excel in tunnel-like geometries but struggle with complex layouts (the "Tetris rule")
• Particularly effective against heavier-than-air gases like LPG or EV battery fire emissions
• European standards now available through EN 12101 family for design guidance
If you need design assistance with Jet Fan systems for your projects, email me directly at w.wegrzynski@itb.pl.
Further reading:
- Jet-Fan Systems in Car Parks Design Methods: an Overview and Assessment of Performance
- Our in-depth multiparametric study on car park ventilation
- A. Król and M. Król, Study on numerical modeling of jet fans
- Thunderhead's guide to modelling jet-fans in FDS
Fire Science Show has been named the top podcast in Fire Protection and Safety by Feedspot. Check the list below, and you will also discover a lot more podcasts in our space!
https://podcast.feedspot.com/fire_protection_and_safety_podcasts/
Thank you for your continuous support, and to the OFR for making it possible to create this content!
----
The Fire Science Show is produced by the Fire Science Media in collaboration with OFR Consultants. Thank you to the podcast sponsor for their continuous support towards our mission.
Chapters
01:48 - Introduction to JetFan Systems
04:06 - What is a JetFan System?
09:25 - Clearance vs. Smoke Control
13:13 - System Components and Operation
20:26 - Velocity Requirements and Space Impact
27:20 - Design Challenges and Evacuation Considerations
34:24 - CFD Modeling and Testing
37:51 - Design Factors and Final Remarks
Transcript
WEBVTT
00:00:00.541 --> 00:00:02.208
Hello everybody, welcome to the Fire Science Show.
00:00:02.208 --> 00:00:08.173
You know that I love exposing engineers to fire science and I like to do it otherwise as well.
00:00:08.173 --> 00:00:18.592
I love to expose my fellow fire scientists to some solid fire safety engineering concepts that go probably a little bit deeper than what's mostly thought at different universities.
00:00:18.592 --> 00:00:22.731
And some time ago I've published an episode on pressurization systems in stairwells.
00:00:22.731 --> 00:00:23.870
It was well received.
00:00:23.870 --> 00:00:24.760
A lot of people commented.
00:00:24.760 --> 00:00:32.070
It made me organize like 20 different private meetings with people, so a lot of you have enjoyed that episode.
00:00:32.109 --> 00:00:42.887
I thought let's share another piece of technology that I think in Poland is way, way, way more popular than in other parts of the world and that is the Jetfan systems in car parks.
00:00:42.887 --> 00:00:45.353
I like car parks, I like Jetfan systems.
00:00:45.353 --> 00:00:51.250
They are a big part of my professional career, even before I have became a fire scientist.
00:00:51.250 --> 00:00:55.947
First I was an engineer designing them, later I became a scientist studying them.
00:00:55.947 --> 00:01:02.533
So yeah, I've seen some car parks and I would love to share with you the experience that I've gained over the years.
00:01:02.533 --> 00:01:05.254
Jetfan systems they have mixed opinions.
00:01:05.254 --> 00:01:11.451
Some people swear by them that it's the best ventilation system you can have in a car park.
00:01:11.451 --> 00:01:13.203
I believe they are a very good solution.
00:01:13.203 --> 00:01:28.087
If you understand what you want to achieve and if you're realistic about the goals that you want to achieve and you're very mindful about what is the expected outcome of the system operation, you can have a very, very good system for very, very good money.
00:01:28.087 --> 00:01:32.027
And those who don't believe in them well, they simply don't believe in them.
00:01:32.027 --> 00:01:36.242
I don't think engineering systems are stuff that you either believe or not believe in.
00:01:36.242 --> 00:01:42.284
I think it should be discussed on engineering grounds, and this is what we're going to do in this podcast episode.
00:01:42.284 --> 00:01:43.528
So stay with me.
00:01:43.528 --> 00:01:45.492
Let's spin the intro and jump into the episode.
00:01:49.921 --> 00:01:51.466
Welcome to the Firesize Show.
00:01:51.466 --> 00:01:54.981
My name is Wojciech Wigrzyński and I will be your host.
00:01:54.981 --> 00:02:18.072
This podcast is brought to you in collaboration with Ofar Consultants, a multi-award-winning independent consultancy dedicated to addressing fire safety challenges.
00:02:18.072 --> 00:02:29.734
Established in the UK in 2016 as a startup business of two highly experienced fire engineering consultants, the business has grown phenomenally to eight offices across the country, from Edinburgh to Bath.
00:02:29.734 --> 00:02:39.240
Colleagues are on a mission to continually explore the challenges that fire creates for clients and society, applying the best research experience and diligence for effective, tailored solution.
00:02:39.240 --> 00:02:43.230
In 2025, there will be new opportunities to work with OFR.
00:02:43.230 --> 00:02:51.110
Ofr will grow its team once more and is keen to hear from industry professionals who would like to collaborate on fire safety features this year.
00:02:51.110 --> 00:02:54.147
Get in touch at ofrconsultantscom.
00:02:54.147 --> 00:02:55.411
Okay, let's go.
00:02:55.560 --> 00:02:58.729
So first question what the hell is a JetFan system?
00:02:58.729 --> 00:03:02.090
Well, it's a system that employs JetFans.
00:03:02.090 --> 00:03:13.473
Jetfan is an axial ventilator, not a very large one, that you put underneath the ceiling of your car park and it simply blows air forward.
00:03:13.473 --> 00:03:24.550
They're like those tubes that you see on the cover of the episode that you install underneath your car park ceiling to transport air through your car park and with that air you transport smoke through your car park.
00:03:24.550 --> 00:03:32.133
It's a very interesting way of operation, very similar to the operation of longitudinal systems in road tunnels.
00:03:32.133 --> 00:03:55.835
Actually, from what I've learned, the jet fans were introduced by a company, novenco, in 1990s, and one of the directors in that company, rudvan Beke, is a good friend of mine and I've spent more than a decade working with him, and I've been told a story that they just thought that perhaps the same idea of operation as you would have in a road tunnel could be actually employed in a car park.
00:03:55.835 --> 00:04:03.293
If we could blow the smoke through the car park in a way like you blow away candles on your birthday cake.
00:04:03.293 --> 00:04:04.514
Perhaps that would work.
00:04:04.514 --> 00:04:06.180
They've tried and actually it worked.
00:04:06.180 --> 00:04:14.507
They developed a solution for that called the jetfan Carpark jetfan and this has been since then a common solution used in the Netherlands.
00:04:15.068 --> 00:04:16.740
It's a very common solution in Poland.
00:04:16.740 --> 00:04:19.750
I know that those systems are used all around the world.
00:04:19.750 --> 00:04:25.569
I said mixed opinions and also legislations show that mixed opinions.
00:04:25.569 --> 00:04:27.286
In some countries it's possible to use them.
00:04:27.286 --> 00:04:29.307
In some countries it is not possible to use them.
00:04:29.307 --> 00:04:42.353
But in general, instead of extracting your smoke upwards through a layer of ducts, you simply blow smoke from one point to another and happily extract it at the end of the pathway where you are blowing at it.
00:04:42.353 --> 00:04:44.307
It's a very simple concept of operation.
00:04:44.920 --> 00:04:47.730
Now, I said those systems are popular in Poland.
00:04:47.730 --> 00:04:53.449
There's also a story behind that and it's kind of funny, like how a wrong legislation builds a market for you.
00:04:53.449 --> 00:05:06.752
So in Poland, before 2009, I believe, we had a law that said that in a car park of a specific size, you are required to have extraction point every 10 meters.
00:05:06.752 --> 00:05:09.228
This was made for duct systems.
00:05:09.228 --> 00:05:17.952
You need an extraction point every 10 meters and because jet fan systems obviously do not have ducts, you don't have extraction points.
00:05:17.952 --> 00:05:23.069
So whenever someone came and wanted to make a ductless system.
00:05:23.069 --> 00:05:25.814
They were called the ductless systems back then, the jet fan systems.
00:05:25.814 --> 00:05:38.086
You actually had to apply for a national derogation from that and to get that you had to run some CFD simulations to prove that your concept is actually working on par with the traditional system.
00:05:38.086 --> 00:05:40.620
And boy, that has built the industry in Poland.
00:05:40.620 --> 00:05:46.963
And my institute, itb, also participated in that early Russia for CFD simulations in compact systems.
00:05:46.963 --> 00:05:50.607
And well, that's kind of how we got answers fluent for our simulations.
00:05:50.911 --> 00:05:57.927
If anyone wondered how we can afford that, it was the golden era of Jetfan systems that enabled us to do that.
00:05:57.927 --> 00:06:05.685
But anyway, the Jetfan systems stoned Poland because at that time it was very expensive to build the duct systems.
00:06:05.685 --> 00:06:13.983
There were not that many approved systems, they were in general very expensive and for jet fun systems you did not need any ducts.
00:06:13.983 --> 00:06:28.225
Therefore you saved a ton of money in your buildings and usually the savings on the jet fun were sufficient to pay for the CFD, additional engineering, all the hassle, and you would still save some.
00:06:28.725 --> 00:06:29.949
Since then it has changed.
00:06:29.949 --> 00:06:31.940
The duct system also evolved.
00:06:31.940 --> 00:06:36.050
There are so many new solutions that you can use in your car products.
00:06:36.050 --> 00:06:42.422
I'm not sure if this economic argument still holds, but there are still benefits, other than economic, for use of jetfan systems.
00:06:42.422 --> 00:06:57.567
Now, as we're talking about jetfan systems, it's necessary to put it straight, like what they can do, what they cannot do, and I think this is the most fundamental problem people have with jetfans they don't understand what you can do with the system and sometimes they have wrong expectations.
00:06:58.048 --> 00:07:07.822
So in our book on designing jetfan systems in for polish market 2015, we've defined two ways of operation of the jet fan system.
00:07:07.822 --> 00:07:14.382
One we call the clearance it's inspired by the British nomenclature and one we call the smoke control.
00:07:14.382 --> 00:07:38.942
In a clearance system, what you want to achieve with your jet fan system is to remove the majority of hot gases from your car park and significantly reduce the thermal stress you impose on the structure and on the people in the car park by blowing air through the fire, through the smoke layer and removing the smoke with the air and, first and foremost, mixing all of that together.
00:07:38.942 --> 00:07:49.250
And in this clearance system, you would not care about the visibility of the fire source, so you would expect that there could be a whole smoke control compartment full with smoke.
00:07:49.250 --> 00:08:00.894
So basically, you're focused on reducing the hazards coming from the heat and after the fire, when, when the fire is extinguished, this system will will very quickly manage to clear the car park from the smoke.
00:08:00.894 --> 00:08:02.480
Hence the name smoke clearance.
00:08:03.081 --> 00:08:04.886
In smoke control it's different.
00:08:04.886 --> 00:08:07.952
It's more like longitudinal ventilation in the tunnels.
00:08:07.952 --> 00:08:15.689
So you would like to have a sharp boundary between the space in which there is smoke and space in which there is no smoke.
00:08:15.689 --> 00:08:20.879
So you'd really want to stop the smoke at the level where the fire is Like.
00:08:20.879 --> 00:08:24.370
You would create a wall of air that's impenetrable for the smoke.
00:08:24.370 --> 00:08:25.685
So always coming from the fresh air side, you would see the fire.
00:08:25.685 --> 00:08:26.312
You would create a wall of air that's impenetrable for the smoke.
00:08:26.312 --> 00:08:28.235
So always coming from the fresh air side, you would see the fire.
00:08:28.235 --> 00:08:29.817
You would, you would be able to reach it.
00:08:29.817 --> 00:08:33.505
In fact, there are some criteria defined in the new ian standard.
00:08:33.505 --> 00:08:37.261
I was also very pleased to participate in that standard writing.
00:08:37.942 --> 00:08:41.450
Shout out to the previous episode on the committees.
00:08:41.450 --> 00:08:47.652
Perhaps that made the link in my brain to do the jet fan episode, because the jet fan committee is the one I've spent the most time in.
00:08:47.652 --> 00:08:51.750
Anyway, you want to have a wall of air that's clear.
00:08:51.750 --> 00:08:58.369
The smoke is stopped, literally at a line almost, and you have an access to the fire.
00:08:58.369 --> 00:09:01.328
There are more ways you can distinguish those systems.
00:09:01.328 --> 00:09:05.068
Some of them should include for human evacuation.
00:09:05.068 --> 00:09:09.149
This is very challenging in jet fun systems and we'll come back to that in this podcast episode.
00:09:09.149 --> 00:09:12.145
Some of them are meant just as a tool to assist firefighting.
00:09:12.145 --> 00:09:16.205
Some of them are just meant as a tool to clear the car park after the fire from the smoke.
00:09:16.647 --> 00:09:28.975
So there are many ways to cut this cake and it's important that your expectations are set beforehand, especially in regards of the clearance and control, because that's going to have large differences.
00:09:28.975 --> 00:09:31.467
Now where do those differences would come?
00:09:31.467 --> 00:09:35.851
How does the smoke clearance system differ from the smoke control system?
00:09:35.851 --> 00:09:41.230
The main thing comes down to the volumetric capacity of your extraction shafts.
00:09:41.230 --> 00:09:43.807
Pretty much, I would say that's the defining factor.
00:09:43.807 --> 00:09:48.828
So how much air in the end you're capable of extracting from the car park?
00:09:49.299 --> 00:10:02.586
Obviously, for smoke control you need more air than for smoke clearance, because you care about moving all the smoke, not just most of the smoke, and the differences in velocities that you need to achieve in a car park are quite significant.
00:10:02.586 --> 00:10:12.261
Usually, for smoke control in a car park of a height of, let's say, three meters, what you would be aiming for is approximately 0.9, maybe one meter per second.
00:10:12.261 --> 00:10:13.465
That usually would be sufficient.
00:10:13.465 --> 00:10:22.804
If you have average velocity like that in the cross-section of your car park, you should be able to achieve the smoke control operation really, and that's very low velocities.
00:10:22.804 --> 00:10:30.662
If you look at tunnels, we're talking about two and a half, three and a half meter per second.
00:10:30.662 --> 00:10:32.826
Here just around one meter per second would be sufficient for smoke clearance.
00:10:32.826 --> 00:10:35.852
This velocity would be perhaps lower, maybe as low as 0.5, 0.6 meter per second.
00:10:35.852 --> 00:10:45.095
Those numbers sounds very low, but if you multiply them by the cross section of your car park, you have one meter per second.
00:10:45.095 --> 00:10:47.708
Your car park is 32 meters wide.
00:10:47.708 --> 00:10:49.386
You have three meters of height.
00:10:49.386 --> 00:10:52.860
Suddenly you have 96 cubic meters per second to remove.
00:10:52.980 --> 00:10:59.951
If you want to have an average of one meter per second in that car park, 100 cubic meters per second, that's quite a big system already.
00:10:59.951 --> 00:11:05.773
That means you need at least 10 square meters of extraction shaft in your building.
00:11:05.773 --> 00:11:09.591
You will need 10 square meters of your inlet shaft in your building.
00:11:09.591 --> 00:11:14.631
This means you just lost 20 square meters of leasable area on every floor of your building.
00:11:14.631 --> 00:11:18.890
So yeah, that's where expenses come in in the safety systems.
00:11:18.890 --> 00:11:30.590
People often think that the expensive part of your systems are the systems that you're designing, but no, really the expensive part is the space they take and the cables that you need to plug them in.
00:11:30.590 --> 00:11:34.951
Anyway, those differences in velocities going up from 0.6 to 1 meter.
00:11:34.951 --> 00:11:53.988
What will happen is that you will start removing more and more air, you will start clearing more and more of your car park and eventually you will reach that point where you have a wall of air that prevents any backfiring of the smoke, that prevents the movement of the smoke back upwind and will protect your car park a low, free path of entry.
00:11:54.469 --> 00:12:07.041
Now there's also one thing about jet systems that made them so popular in here is that in poland we had a lot of lpg powered vehicles and that's a very popular alternative fuel used in Poland for decades.
00:12:07.041 --> 00:12:15.908
And LPG is a nasty thing because if it spills in your car park from your vehicle, it's heavier than air, so it would spill along your floor.
00:12:15.908 --> 00:12:20.085
So the normal duct systems were not that effective on removing that.
00:12:20.085 --> 00:12:31.280
You would have to have separate grills closer to your floor to remove that Very challenging remove that very challenging design, very expensive design, and with jetfan systems you just mix the air through the entire cross-section of your car park.
00:12:31.280 --> 00:12:32.725
So you're very effectively.
00:12:32.725 --> 00:12:46.090
We can remove hazards like like lpg and perhaps in the age of electric vehicles we also see there are clouds forming with gases that are obviously heavier than air because they are spilling along the floor.
00:12:46.090 --> 00:12:57.168
So I would assume the operation of jet fan system would also be quite good against those, especially if you design the smoke control mode where your people would not be exposed to any smoke from the electric vehicle.
00:12:57.168 --> 00:13:00.590
Anyway, you don't need fire to benefit from that.
00:13:01.179 --> 00:13:03.386
Car parks means vehicles operating in them.
00:13:03.386 --> 00:13:06.969
That means a lot of fumes, that means a lot of gases already in the car park.
00:13:06.969 --> 00:13:10.669
So they are also great for sanitary mode operations.
00:13:10.669 --> 00:13:12.828
Very cheap, very comfortable.
00:13:12.828 --> 00:13:17.519
You need perhaps 0.2, 0.3 meter per second and you're good with those operations.
00:13:17.519 --> 00:13:23.312
So sometimes they would be run on a low energy setting just to clear the car park from the fumes from the cars.
00:13:24.164 --> 00:13:27.306
Next thing about JetVent systems that you can have different systems.
00:13:27.306 --> 00:13:38.368
You could have a system in a completely open car park like imagine hundreds of meters of car park without any walls, without any boundaries, just a set of columns and a massive building above them.
00:13:38.368 --> 00:13:39.792
We've done car parks like that.
00:13:39.792 --> 00:13:48.408
Or you could have car parks that are literally a collection of smaller compartments, few hundred square meters each, and from one compartment you go to another, to another, to another.
00:13:48.408 --> 00:13:57.695
That's a popular way to design the car parks in Belgium, for example, and in that case in a very large car park you would like to have most of the car park empty, free of smoke.
00:13:57.774 --> 00:14:11.520
With your JetFan system we would usually design the smoke control compartments with a size of up to two and a half thousand meter square, perhaps up to five thousand square meter if it's really really challenging project with a massive car park.
00:14:11.520 --> 00:14:13.004
But that comes with additional cost.
00:14:13.004 --> 00:14:18.104
So that would be our usual design for compartments in those large car parks.
00:14:18.104 --> 00:14:21.942
You'd also like to have the system reversible so it can go both directions.
00:14:21.942 --> 00:14:25.312
So you always extract to the shaft closer to the fire.
00:14:26.081 --> 00:14:33.828
And if it's really really large car park and you have to separate it into multiple smoke compartments, not always you have to put physical boundaries between them.
00:14:33.828 --> 00:14:38.427
Sometimes it's possible to create those invisible walls with just the jet fan system operation.
00:14:38.427 --> 00:14:40.307
But again that's another challenge.
00:14:40.307 --> 00:14:47.005
For smaller compartments there is a strategy where you would just transport the smoke from one compartment to another with the JetVan system.
00:14:47.005 --> 00:14:50.562
So it's also like an interesting way of operation not very popular in here.
00:14:51.245 --> 00:14:55.173
And finally, a lot will depend on your inlets and outlets.
00:14:55.173 --> 00:15:00.879
The easiest is if you have open facades and you have, like, unlimited source of air on one facade.
00:15:00.879 --> 00:15:04.625
You have unlimited extraction space on your external facade.
00:15:04.625 --> 00:15:14.788
Then you can make a really efficient, really cheap jet vent system that will beat any other smoke control way really, and they can also beat the wind quite easily.
00:15:14.788 --> 00:15:26.451
Actually, I've had an episode about open car parks with wind a year ago and we've noted that if you just have an open car park, in some wind scenarios you get very bad conditions inside the car park in fire.
00:15:26.451 --> 00:15:33.312
With JetFan systems in such an open car park I would assume 95% of scenarios you would easily beat the wind.
00:15:33.312 --> 00:15:40.289
It's something that we are currently researching so I can just tell you work-in, work in progress results, but it's looking very promising.
00:15:40.309 --> 00:15:42.962
Jetfan systems are really good enhancement for open car parks.
00:15:42.962 --> 00:15:45.107
For wind conditions in particular.
00:15:45.107 --> 00:15:49.342
If you have an enclosed car park, you need an extraction shaft.
00:15:49.342 --> 00:15:56.927
You need an air inlet shaft because you need to supply the air that you're extracting and this is when it becomes challenging.
00:15:56.927 --> 00:16:06.306
The inlets and outlets can become quite large if you need large quantities of air and you also cannot really supply air with too high velocity.
00:16:06.306 --> 00:16:13.730
So every time you think about it, if you supply air with high velocity, the air has some kinetic energy in it.
00:16:13.730 --> 00:16:14.714
Inevitably.
00:16:14.714 --> 00:16:21.270
If you supply air with 5 meters per second 10 meters per second that's a lot of kinetic energy the air will fly very, very far.
00:16:21.270 --> 00:16:27.471
And in jet-fed system we need to direct air through a very specific pathway to clear the car park from the smoke.
00:16:27.471 --> 00:16:41.831
If I have a very strong stream of air, I need to use a lot of force to push that jet stream in the place where I want it to be, and in most cases it's even impossible if you have more than five meters per second inlet.
00:16:41.831 --> 00:16:47.889
So the inlet strategy in the JetFan system will be as important as your extraction strategy.
00:16:48.510 --> 00:16:57.836
Okay, now let's go to some technicalities of JetFan systems and shortly after we'll go into scenarios, because that's perhaps the most controversial part of a jet fan system design.
00:16:57.836 --> 00:17:14.125
So for components you would have your inlet and extraction fans, that those would be a very large, usually axial fans that operate for even hundreds of cubic meters per second that provide you the air supply and extraction from your car park.
00:17:14.125 --> 00:17:15.930
They obviously need to be fire rated.
00:17:15.930 --> 00:17:21.530
It's best if they're reversible, so you can have two directions of operation of your JetFan system.
00:17:21.530 --> 00:17:23.482
In that way they are the most useful.
00:17:23.482 --> 00:17:31.309
And other way to define the JetFan systems, whether they are one directional or reversible you also need JetFans obviously.
00:17:31.309 --> 00:17:33.844
Jetfans would also be axial fans.
00:17:33.844 --> 00:17:37.397
They will also be fire rated and they are usually in Europe.
00:17:37.397 --> 00:17:43.271
They're tested according to EN 12101, part three, a very important standards that actually includes.
00:17:43.311 --> 00:17:48.509
For jet fans, they are tested within furnaces like normal fans would be.
00:17:48.509 --> 00:17:50.894
Well, not exactly like normal fans.
00:17:50.894 --> 00:17:53.569
Normal fans would have an installation connected to the furnace.
00:17:53.569 --> 00:18:00.946
You would extract this hot gases from your furnace, transfer them through your fan and that's how you would expose it to temperature.
00:18:00.946 --> 00:18:13.089
For jet fans, we simply hang them inside the furnace, we set the temperature on the oven to 400 degrees and they operate 15 minutes later, shut them down two minutes, wait, turn them on again and let's go.
00:18:13.089 --> 00:18:17.911
They have to survive the remaining time for the specific class that they are exposed to.
00:18:17.911 --> 00:18:21.166
Very nice experiment that I'm very used to.
00:18:21.166 --> 00:18:23.471
I used to be doing a lot of those now.
00:18:23.471 --> 00:18:30.332
One thing that actually I I took off my table very few of those is is the the component testing.
00:18:30.332 --> 00:18:32.520
I'm not doing those that much anymore.
00:18:32.820 --> 00:18:35.923
Um, and there will be auxiliary components in the jet fan system.
00:18:35.923 --> 00:18:38.244
Sometimes you would use some smoke curtains.
00:18:38.244 --> 00:18:41.548
They could be a part of your smoke control strategy.
00:18:41.548 --> 00:18:52.615
You of course, need to supply power to your jet fans, so you need some sort of cabinets, smoke control panels to steer the jet fans, to trigger the correct jet fans at the correct time.
00:18:52.615 --> 00:18:54.396
You would need smoke detection.
00:18:54.396 --> 00:19:01.269
Some people ask me how the hell the jet fan knows that there's a fire in the car park and it has to have a smoke detection system.
00:19:01.269 --> 00:19:04.931
You need to trigger it with something, preferably automatically.
00:19:04.931 --> 00:19:07.047
So there needs to be smoke detection.
00:19:07.047 --> 00:19:12.465
There needs to be some redundant power source, usually there, and that would be pretty much it.
00:19:12.465 --> 00:19:14.806
Those are fairly simple systems in the end.
00:19:15.327 --> 00:19:20.987
The jet fans themselves they are characterized not by flow, like normally you would think about a ventilator.
00:19:20.987 --> 00:19:25.125
You would like to quantify the ventilator by the flow that it has.
00:19:25.125 --> 00:19:29.824
In case of a jet fan, we use a different property In jet fan systems.
00:19:29.824 --> 00:19:32.071
We talk about the thrust of the jet fan.
00:19:32.071 --> 00:19:41.648
So you can calculate the thrust if you multiply the air density by the velocity in the jet fan by the volumetric capacity of the jet fan.
00:19:41.648 --> 00:19:52.230
That's an approximation of the thrust of the jet fan and for car park systems we would normally get jet fans that would be 35 newton to perhaps 55 newton for axial fans.
00:19:52.230 --> 00:19:58.393
And there are also those centrifugal fans that could have like 100, 110 newton thrust force.
00:19:58.393 --> 00:20:12.813
In comparison, jet fans used in road tunnels those would have, like I'm using, 950 newton to 1,600 newton, but I've seen on the market that there would be jet fans with 2,800 newton thrusts.
00:20:12.813 --> 00:20:18.188
And if you want a really interesting comparison, the engine of Boeing Dreamliner.
00:20:18.188 --> 00:20:22.315
There's this massive turbojet engine that powers the airplane.
00:20:22.315 --> 00:20:24.548
That one has like 100,000 newton thrust.
00:20:24.548 --> 00:20:30.686
So that's pretty far away from our little jet fans, but the same family nevertheless.
00:20:30.686 --> 00:20:32.807
Anyway, why thrust?
00:20:33.039 --> 00:20:38.592
Thrust is a very good measure because it allows you to calculate how much force you can pass to the air.
00:20:38.592 --> 00:20:43.830
In your carport, a rule of thumb you have 100 square meters of cross-section.
00:20:43.830 --> 00:20:48.349
You want to express one pascal dynamic pressure on that.
00:20:48.349 --> 00:20:49.192
You need 100 newtons.
00:20:49.192 --> 00:20:51.588
Of course that's an extreme simplification.
00:20:51.588 --> 00:20:57.173
You cannot really do engineering calculations like that, but it gives you an idea of how much force you need.
00:20:57.173 --> 00:21:03.292
There will be losses, there will be inefficiencies in how the momentum is transferred to the air.
00:21:03.940 --> 00:21:06.465
Another thing about jet fans is how do they act.
00:21:06.465 --> 00:21:21.192
A lot of people would have the misconception that the jet fan sucks the smoke at one end and releases the smoke on the other end, therefore pushing the smoke further away, and this, like it could look like that when they operate.
00:21:21.192 --> 00:21:25.299
But this is not really the fundamental principle on which they operate.
00:21:25.299 --> 00:21:32.388
The jet fans are more like your hair dryer, hand dryer or those annoying leaf blowers.
00:21:32.388 --> 00:21:53.248
The idea is that you want to push a stream of air at very high velocity into the car park that, through entrainment, exchanges momentum with the surrounding air, with air that surrounds it, and eventually you have a much bigger mass of air but a much lower velocity.
00:21:53.248 --> 00:22:04.583
So you kind of transfer the momentum from the blades in your jet fan into the air, into the jet fan, and that high velocity stream released from the jet fan transfers the momentum through the surrounding air.
00:22:04.583 --> 00:22:09.433
Now it takes a lot of space for this momentum transfer to happen.
00:22:09.433 --> 00:22:16.743
It would take, I would say, 20, 30 meters of space in front of your jet fan for this momentum to fully, fully happen.
00:22:16.743 --> 00:22:29.611
And this means that the jet, if you have a fire at one location in a car park, the jet van that really is acting on that location is not the one above the fire but the one 30 meters before the fire.
00:22:29.611 --> 00:22:35.094
That's the jet van that will create the uniform velocity distribution that you are looking for.
00:22:35.094 --> 00:22:38.567
So the jet vans operate much further than they are.
00:22:38.839 --> 00:22:43.192
It's a very wrong misconception that they operate at the location where they are hanged.
00:22:43.192 --> 00:22:53.963
You would space them so you cover most of the car park with the low velocity flow that you're creating by their operation.
00:22:53.963 --> 00:22:58.534
So they would be horizontally spaced by 8 to 12 meters.
00:22:58.534 --> 00:23:03.468
In the direction of the operation they would be spaced by 32 to 48 meters.
00:23:03.468 --> 00:23:14.588
From my experience, those are the optimal distances and if you can make a nice grid of jet fans in your rectangular car park like this, you're going to have a very good system.
00:23:15.119 --> 00:23:24.606
Well, there obviously are challenges if the geometry of your car park is complicated, especially if you have a central core of the building inside the car park.
00:23:24.606 --> 00:23:27.680
So this is a common way to design buildings.
00:23:27.680 --> 00:23:31.806
You would have a square cut in the ground and you would have a central core.
00:23:31.806 --> 00:23:37.140
So you have a square car park and those are very challenging to ventilate.
00:23:37.140 --> 00:23:38.454
With JetFan systems it takes a lot very challenging to ventilate with jet fan systems.
00:23:38.454 --> 00:23:39.681
It takes a lot of work to optimize them.
00:23:39.681 --> 00:23:40.746
Still possible, though.
00:23:40.746 --> 00:23:44.729
Now another common question that I ask, like how strong they are?
00:00:00.541 --> 00:00:02.208
00:00:02.208 --> 00:00:08.173
00:00:08.173 --> 00:00:18.592
00:00:18.592 --> 00:00:22.731
00:00:22.731 --> 00:00:23.870
00:00:23.870 --> 00:00:24.760
00:00:24.760 --> 00:00:32.070
00:00:32.109 --> 00:00:42.887
00:00:42.887 --> 00:00:45.353
00:00:45.353 --> 00:00:51.250
00:00:51.250 --> 00:00:55.947
00:00:55.947 --> 00:01:02.533
00:01:02.533 --> 00:01:05.254
00:01:05.254 --> 00:01:11.451
00:01:11.451 --> 00:01:13.203
00:01:13.203 --> 00:01:28.087
00:01:28.087 --> 00:01:32.027
00:01:32.027 --> 00:01:36.242
00:01:36.242 --> 00:01:42.284
00:01:42.284 --> 00:01:43.528
00:01:43.528 --> 00:01:45.492
00:01:49.921 --> 00:01:51.466
00:01:51.466 --> 00:01:54.981
00:01:54.981 --> 00:02:18.072
00:02:18.072 --> 00:02:29.734
00:02:29.734 --> 00:02:39.240
00:02:39.240 --> 00:02:43.230
00:02:43.230 --> 00:02:51.110
00:02:51.110 --> 00:02:54.147
00:02:54.147 --> 00:02:55.411
00:02:55.560 --> 00:02:58.729
00:02:58.729 --> 00:03:02.090
00:03:02.090 --> 00:03:13.473
00:03:13.473 --> 00:03:24.550
00:03:24.550 --> 00:03:32.133
00:03:32.133 --> 00:03:55.835
00:03:55.835 --> 00:04:03.293
00:04:03.293 --> 00:04:04.514
00:04:04.514 --> 00:04:06.180
00:04:06.180 --> 00:04:14.507
00:04:15.068 --> 00:04:16.740
00:04:16.740 --> 00:04:19.750
00:04:19.750 --> 00:04:25.569
00:04:25.569 --> 00:04:27.286
00:04:27.286 --> 00:04:29.307
00:04:29.307 --> 00:04:42.353
00:04:42.353 --> 00:04:44.307
00:04:44.920 --> 00:04:47.730
00:04:47.730 --> 00:04:53.449
00:04:53.449 --> 00:05:06.752
00:05:06.752 --> 00:05:09.228
00:05:09.228 --> 00:05:17.952
00:05:17.952 --> 00:05:23.069
00:05:23.069 --> 00:05:25.814
00:05:25.814 --> 00:05:38.086
00:05:38.086 --> 00:05:40.620
00:05:40.620 --> 00:05:46.963
00:05:46.963 --> 00:05:50.607
00:05:50.911 --> 00:05:57.927
00:05:57.927 --> 00:06:05.685
00:06:05.685 --> 00:06:13.983
00:06:13.983 --> 00:06:28.225
00:06:28.725 --> 00:06:29.949
00:06:29.949 --> 00:06:31.940
00:06:31.940 --> 00:06:36.050
00:06:36.050 --> 00:06:42.422
00:06:42.422 --> 00:06:57.567
00:06:58.048 --> 00:07:07.822
00:07:07.822 --> 00:07:14.382
00:07:14.382 --> 00:07:38.942
00:07:38.942 --> 00:07:49.250
00:07:49.250 --> 00:08:00.894
00:08:00.894 --> 00:08:02.480
00:08:03.081 --> 00:08:04.886
00:08:04.886 --> 00:08:07.952
00:08:07.952 --> 00:08:15.689
00:08:15.689 --> 00:08:20.879
00:08:20.879 --> 00:08:24.370
00:08:24.370 --> 00:08:25.685
00:08:25.685 --> 00:08:26.312
00:08:26.312 --> 00:08:28.235
00:08:28.235 --> 00:08:29.817
00:08:29.817 --> 00:08:33.505
00:08:33.505 --> 00:08:37.261
00:08:37.942 --> 00:08:41.450
00:08:41.450 --> 00:08:47.652
00:08:47.652 --> 00:08:51.750
00:08:51.750 --> 00:08:58.369
00:08:58.369 --> 00:09:01.328
00:09:01.328 --> 00:09:05.068
00:09:05.068 --> 00:09:09.149
00:09:09.149 --> 00:09:12.145
00:09:12.145 --> 00:09:16.205
00:09:16.647 --> 00:09:28.975
00:09:28.975 --> 00:09:31.467
00:09:31.467 --> 00:09:35.851
00:09:35.851 --> 00:09:41.230
00:09:41.230 --> 00:09:43.807
00:09:43.807 --> 00:09:48.828
00:09:49.299 --> 00:10:02.586
00:10:02.586 --> 00:10:12.261
00:10:12.261 --> 00:10:13.465
00:10:13.465 --> 00:10:22.804
00:10:22.804 --> 00:10:30.662
00:10:30.662 --> 00:10:32.826
00:10:32.826 --> 00:10:35.852
00:10:35.852 --> 00:10:45.095
00:10:45.095 --> 00:10:47.708
00:10:47.708 --> 00:10:49.386
00:10:49.386 --> 00:10:52.860
00:10:52.980 --> 00:10:59.951
00:10:59.951 --> 00:11:05.773
00:11:05.773 --> 00:11:09.591
00:11:09.591 --> 00:11:14.631
00:11:14.631 --> 00:11:18.890
00:11:18.890 --> 00:11:30.590
00:11:30.590 --> 00:11:34.951
00:11:34.951 --> 00:11:53.988
00:11:54.469 --> 00:12:07.041
00:12:07.041 --> 00:12:15.908
00:12:15.908 --> 00:12:20.085
00:12:20.085 --> 00:12:31.280
00:12:31.280 --> 00:12:32.725
00:12:32.725 --> 00:12:46.090
00:12:46.090 --> 00:12:57.168
00:12:57.168 --> 00:13:00.590
00:13:01.179 --> 00:13:03.386
00:13:03.386 --> 00:13:06.969
00:13:06.969 --> 00:13:10.669
00:13:10.669 --> 00:13:12.828
00:13:12.828 --> 00:13:17.519
00:13:17.519 --> 00:13:23.312
00:13:24.164 --> 00:13:27.306
00:13:27.306 --> 00:13:38.368
00:13:38.368 --> 00:13:39.792
00:13:39.792 --> 00:13:48.408
00:13:48.408 --> 00:13:57.695
00:13:57.774 --> 00:14:11.520
00:14:11.520 --> 00:14:13.004
00:14:13.004 --> 00:14:18.104
00:14:18.104 --> 00:14:21.942
00:14:21.942 --> 00:14:25.312
00:14:26.081 --> 00:14:33.828
00:14:33.828 --> 00:14:38.427
00:14:38.427 --> 00:14:40.307
00:14:40.307 --> 00:14:47.005
00:14:47.005 --> 00:14:50.562
00:14:51.245 --> 00:14:55.173
00:14:55.173 --> 00:15:00.879
00:15:00.879 --> 00:15:04.625
00:15:04.625 --> 00:15:14.788
00:15:14.788 --> 00:15:26.451
00:15:26.451 --> 00:15:33.312
00:15:33.312 --> 00:15:40.289
00:15:40.309 --> 00:15:42.962
00:15:42.962 --> 00:15:45.107
00:15:45.107 --> 00:15:49.342
00:15:49.342 --> 00:15:56.927
00:15:56.927 --> 00:16:06.306
00:16:06.306 --> 00:16:13.730
00:16:13.730 --> 00:16:14.714
00:16:14.714 --> 00:16:21.270
00:16:21.270 --> 00:16:27.471
00:16:27.471 --> 00:16:41.831
00:16:41.831 --> 00:16:47.889
00:16:48.510 --> 00:16:57.836
00:16:57.836 --> 00:17:14.125
00:17:14.125 --> 00:17:15.930
00:17:15.930 --> 00:17:21.530
00:17:21.530 --> 00:17:23.482
00:17:23.482 --> 00:17:31.309
00:17:31.309 --> 00:17:33.844
00:17:33.844 --> 00:17:37.397
00:17:37.397 --> 00:17:43.271
00:17:43.311 --> 00:17:48.509
00:17:48.509 --> 00:17:50.894
00:17:50.894 --> 00:17:53.569
00:17:53.569 --> 00:18:00.946
00:18:00.946 --> 00:18:13.089
00:18:13.089 --> 00:18:17.911
00:18:17.911 --> 00:18:21.166
00:18:21.166 --> 00:18:23.471
00:18:23.471 --> 00:18:30.332
00:18:30.332 --> 00:18:32.520
00:18:32.820 --> 00:18:35.923
00:18:35.923 --> 00:18:38.244
00:18:38.244 --> 00:18:41.548
00:18:41.548 --> 00:18:52.615
00:18:52.615 --> 00:18:54.396
00:18:54.396 --> 00:19:01.269
00:19:01.269 --> 00:19:04.931
00:19:04.931 --> 00:19:07.047
00:19:07.047 --> 00:19:12.465
00:19:12.465 --> 00:19:14.806
00:19:15.327 --> 00:19:20.987
00:19:20.987 --> 00:19:25.125
00:19:25.125 --> 00:19:29.824
00:19:29.824 --> 00:19:32.071
00:19:32.071 --> 00:19:41.648
00:19:41.648 --> 00:19:52.230
00:19:52.230 --> 00:19:58.393
00:19:58.393 --> 00:20:12.813
00:20:12.813 --> 00:20:18.188
00:20:18.188 --> 00:20:22.315
00:20:22.315 --> 00:20:24.548
00:20:24.548 --> 00:20:30.686
00:20:30.686 --> 00:20:32.807
00:20:33.039 --> 00:20:38.592
00:20:38.592 --> 00:20:43.830
00:20:43.830 --> 00:20:48.349
00:20:48.349 --> 00:20:49.192
00:20:49.192 --> 00:20:51.588
00:20:51.588 --> 00:20:57.173
00:20:57.173 --> 00:21:03.292
00:21:03.940 --> 00:21:06.465
00:21:06.465 --> 00:21:21.192
00:21:21.192 --> 00:21:25.299
00:21:25.299 --> 00:21:32.388
00:21:32.388 --> 00:21:53.248
00:21:53.248 --> 00:22:04.583
00:22:04.583 --> 00:22:09.433
00:22:09.433 --> 00:22:16.743
00:22:16.743 --> 00:22:29.611
00:22:29.611 --> 00:22:35.094
00:22:35.094 --> 00:22:38.567
00:22:38.839 --> 00:22:43.192
00:22:43.192 --> 00:22:53.963
00:22:53.963 --> 00:22:58.534
00:22:58.534 --> 00:23:03.468
00:23:03.468 --> 00:23:14.588
00:23:15.119 --> 00:23:24.606
00:23:24.606 --> 00:23:27.680
00:23:27.680 --> 00:23:31.806
00:23:31.806 --> 00:23:37.140
00:23:37.140 --> 00:23:38.454
00:23:38.454 --> 00:23:39.681
00:23:39.681 --> 00:23:40.746
00:23:40.746 --> 00:23:44.729