171 - Exploring Water Mist Systems with Max Lakkonen

Transcript

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Hello everybody, welcome to the Fire Science Show.

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In our everyday job, modeling is one of the main tools Computer modeling or numerical modeling, cfd modeling these are the tools that we are mainly using in our performance-based design, and there are still some topics in the world of modeling fires that I believe are pretty rough, or I just approach with caution and one of such topics is modeling any water-based fixed fire fighting systems, such as sprinklers, dilute systems or water mist.

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In this podcast episode, we will focus on the third one, the water mist systems, no matter how you distinct them high pressure, low pressure, water mist.

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We're just going to talk about the water mist and we're going to talk about the challenges in how to model performance of such systems.

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But you know me, it's not just going to be how.

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The question why will occur many times in the interview, because for me, and the most important thing, is why we need to model, what we get from the modeling, what is the objective that we're trying to achieve and, if we are clear on that, how do we reach that objective?

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For this episode, I have invited Max LekaLnen.

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He's the managing director of IFEB and literally a few weeks ago, or even a few days ago, max has been chosen as the president of the International Water Mist Association, so congratulations, max.

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It's a very good person to talk to.

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I've heard him speak about modeling water mist multiple times and I'm sure you will enjoy him talking as well.

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One more thing IWMA the Water Mist Association has also released a position paper on modeling water mist with CFD, and that position paper is linked in the show notes and is a very good companion to this podcast episode, as it captures most of the stuff that we wanted to convey through the episode in a written form.

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So, without further ado, let's spin the intro and jump into the episode.

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Without further ado, let's spin the intro and jump into the episode.

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Welcome to the Firesize Show.

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My name is Vojtěch Vyjgřínský and I will be your host.

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Hello everybody, I am here joined by Max Lakkonen from IFAB, managing Director of IFAB.

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Hey, max, good to see you in the podcast.

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How about you?

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So I've invited.

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Max Lakkonen, the Head of Scientific Council at the IWMA and who came into the show is the president of the IWMA.

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Congratulations on becoming the next president of the IWMA.

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Thank you very much.

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Any particular goals you have for this presidency?

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Yeah, I'm not sure if we would have enough time for this podcast to go through, but definitely I'm having my own mission and I think we, as a society or industry, we recognize that there are a few things that we want to change.

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We have all the chrono, so definitely some changes are going to happen during the coming season I'm looking forward for that, and also the scientific council.

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You seem to leave it in the good hands of bogdan achenga.

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He was also a guest of the fire science show.

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I'm very happy with the developments in the international water mist association.

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Uh, anyway, let's move, uh to the subject which is, uh, surprise, surprise water mist, and I've seen you talk about modeling water mist in the past.

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I think you had a presentation about modeling in iw may in warsaw, which I even covered in the fire science show.

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I know that you just hadn't talked about modeling water mist in antwerp in the iw may conference that was held literally in the last week.

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So I thought, yeah, you're, you seem like a good guy to talk about modeling, and modeling is something my audience loves, so perhaps let's let's talk a little bit on modeling the water miss.

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How about that?

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yeah, absolutely, I'm.

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I'm fine to to do that, but obviously I think modeling and water miss is a.

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It's a quite complicated topic which we have recognized also as a as a society.

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But I think it's also important to understand the fundamentals and how we have ended up to this moment that we are modeling water mist system.

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But obviously there's many decades of work behind and also experimental tests, and I think that would be a good starting point, starting from not day one, but having the background and then ending up to the modeling which is nowadays too.

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Perfect.

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I actually appreciate this approach of modeling, rather than just dropping your random software obtaining colorful images but referring to experiments.

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And boy, in the world of WaterMist, experiments is what you guys have.

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Plenty of.

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This is the entire industry.

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Okay, let's start with the basics, or the fundamentals of water mist.

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So how about we start with the definition, or where the water mist even came from?

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Yeah, well, actually the definition is quite clear, so it refers to your droplet size.

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So either DV90 or DV99 is less than 1000 micron, one millimeter, which obviously is a very, very broad definition.

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But obviously it has some historical reason that some other technology did not really appreciate too much smaller droplets so they expanded that to quite wide range.

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Is this dropletplet size for any particular reason?

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Was it just a cut of points to distinguish what them is from sprinkle technology?

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Yeah, that was the thing I mean.

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I've been in the industry for 20 years now.

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Depending on the task, sometimes I've been fully employed by that.

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Nowadays I'm doing, let's say, part's say part-time misrelated things.

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Also other technologies, but in the earliest, at the very first standards, there was different categories, also due to droplets, but that was actually cancelled and now it's a flat rate one millimeter.

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But in practice the mis-IS technologies, they are far smaller droplets than that.

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But couldn't you just define it with like K factors or pressures, operating pressures, yeah.

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I mean droplet size.

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That's really what defines whether it's a MIS system or not.

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But then on the MIS system, there are basically low pressure, medium pressure and high pressure systems low pressure, medium pressure and high pressure systems and obviously depending on the technology they have a little bit of pros and cons to different aspects.

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And traditionally high pressure systems they utilize the least water but they are having the highest pressure.

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Can you indicate from a head what would be the average particle diameter for like high pressure or low pressure?

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What the miss?

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And then maybe the pressures for reference.

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That's a too simple question to be made.

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Oh sorry, because uh, and I think people who are doing modeling they would appreciate to get only certain numbers.

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But we have to remember that miss technology is covering actually very different applications.

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Sometimes they are more in the in the gas related applications and obviously there the droplets are very, very small.

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And you can imagine that, regardless what is the pressure level, if you're putting a mist to a data center or inside the electric cabinet, it's a very fine.

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But if you were would put mist.

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Then the road tunnels.

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So obviously there the droplets that they are much larger because they have to have much more momentum to it, the ventilation.

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So that's that, let's say the introduction, but I would say that typically they are the range of between 50 and 250, 300 microns.

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You see, I'm a practical guy.

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If you gave me that number just straight off, I just put my liters per minute, I power my FDS and start earning serious money on modeling this, and I assume what we want to do in this interview is to kind of stop people from doing that without thinking.

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So thanks for a reality check.

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You mentioned in the panel applications you would have to have momentum to penetrate.

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Now, that's also something I didn't always get in WaterMist, because I assumed that this is a distinguishing line between the Sprinkler technology and WaterMist technology.

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Sprinklers would have those large droppers that penetrate.

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They go down to the fuel, whereas in water mist you have something that basically acts in the gas phase itself, like wetting.

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This surface action on the fuel is much more limited in water mist.

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Can such simplification be made?

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Or really, depending on what the most technology you can achieve, like the best of both worlds, the reality is somewhere between.

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So you can't really gather corals.

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Neither let's let's call sprinkler or deluge systems nor water mist systems.

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So, and obviously typically within the tunnels, we are talking about very, very big fires.

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So actually also the larger droplets they influence in the gas fade because they will evaporate no matter where you are pouring the water.

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In same way also mist systems I mean, as I said, they are having relatively large droplets in tunnel applications and they do also wet it in insane sense than deluge system would do.

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So germans would say that the answer is Jain.

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So it's somewhere between.

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But you know that, like 15 years ago, we had a long discussions with some other known people that whether the droplets would fly out from the tunnel with mist systems.

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And obviously I think that the mist concept was not water mist but real mistcept was that the droplet sizes.

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They were considered way too fine.

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What are utilized in internals?

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Can you broadly categorize the effects water mist has on the fire environment?

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So if we want to model that like what kind of phenomena we would be interested in capturing?

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What do they do to the fire environment?

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well, basically, if we would have a kind of generic system so, and if we would say that we are having a generic fuel as well.

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Traditionally mist systems, they're working three-dimensional, so they will fill the protected volume and then obviously the influence in the gas phase is having the major role, but a portion of the water will also collect on the surfaces, so it's also influencing there.

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And then obviously one of the key things is obviously this extended or let's say, the very superior cooling effect by having high number of small droplets, the traditional big surface area evaporation and the way absorbing the heat.

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And that cooling effect is happening in the gas phase.

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It's in the gas phase.

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Yeah, but obviously a part of the water will also go, depending on the application and how the droplets are tuned, will also go on the surface.

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So prevent the re-ignition that will happen.

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And then, the last but not the least, because there are also some applications where this is really tuned and for example, with flammable liquids, it's also the prevention of oxygen by the large evaporation, the local evaporation, so that will block the entrance of the fresh oxygen.

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So, yes, the technology works in different ways and, depending on the applicator, different characteristic are more emphasized than the others.

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Is it possible to even quantify what percentage of the water applied would evaporate?

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Is this measured or perhaps a part of scientific research?

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If zero was and no particles evaporated, 100% would mean that all of them evaporated.

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What would be a ballpark estimation of a good water mist system.

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I wonder how many of those evaporate actually, or again, it depends on the fire.

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Yeah, I think you just said that it really depends on the fire as well.

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It's very difficult to say.

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In some of the test programs there has been also trials trying to measure this.

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So measuring also the water which is collected on the surfaces and trying to evaluate that how much water was consumed, and obviously larger the fire is, more it will then evaporate.

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So it's kind of proportional to the fire size.

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But I would say that if we are having 50%, if we are having 50%, then we are really at the high end and typically you are spraying much larger area than where the fire is.

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You are not very seldom, you are just targeting and it's more than the research where you are utilizing and you keep the things in control that you are trying to measure the evaporation rates that you are trying to measure the evaporation rates.

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Another question the way how the water mist is currently approved to the market is by extensive testing.

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Pretty much that's my observation of the market, compared, for example, with smoke control.

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In smoke control we have barely anything like that.

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In smoke control we have barely anything like that.

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In smoke control it's all you know mathematical equations that tell you how much smoke you produce.

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Or CFD modeling, where you just simulate your smoke control system and you see if it works In the water mist.

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It's all based on experimental insight.

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Is there also any particular reason why the industry is so uh, I wouldn't like I want to use the word obsessed, but it's not the correct word perhaps why it's so based on on physical testing?

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And does, in such a world of such strong emphasis on physical testing, does performance based design or cfdD even have place for?

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I think your question is, let's say, two, Paul.

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One is related to the experimental testing.

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Another one is then to the new, let's say, design methods, 3D and simulation.

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Yeah, let's chop it into two questions.

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I mean, if we are looking, to the history of water mist.

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I mean now I'm starting very far, so something like 35 years ago.

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That was when the commercial use of water mist started after the fire in Scandinavia and star cruise liner Very, very bad fire.

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And obviously then water mist started to conquer the marine business and nowadays, for example, cruise liners, they are having almost 100% market share and also the engine ships or the machinery rooms.

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I mean they are having very, very high portion of this system.

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So that's where it all started.

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But since day one, watermistist was considered something new and it was careful.

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I mean, everybody had to be careful because higher pressures and new approach and then a lot of experimental tests were required.

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Therefore, basically every new application requires some tests and also because the technologies are different.

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You know, in different uh makes they are based on performance base design.

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They are not, let's say, prescriptive than that sprinklers are, for example, that you do a certain application rate and everything is good.

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But obviously two companies might go to a very same protection objective or the performance with the two different nozzle spacing, two different floor rates, two different nozzle types, and that's been the reason why there has been so much testing in the past.

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But nowadays the situation is good.

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There are many test standards and there are many companies and they are now covering a really huge number of approvals to various different kinds of applications.

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You've mentioned different nozzle types and I assume one company could use different pressure, different flow rates etc.

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So these things are really that sensitive.

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You really have to fine tune that in an experimental setting.

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I mean, I know you are doing that because I've seen that firsthand.

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But I'm like really curious, like let me rephrase the question Is there any way you could like talk about generic water mist, you know, and generic flow rates or generic pressures and just don't go through this expensive, you know pathway of testing?

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No, no, unfortunately that's not the case, and obviously all the companies.

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They have really tried to innovate and find, let's say, technically and commercially, the best solutions.

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It's a different approach but on the other hand it's a bit of the PPD-orientated thing.

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But coming now to your technology design, so the objective was given and it was given by the standardization bodies, by the authorities, that, okay, this is the test you need to do, this is accepted criteria, no matter how you get there.

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And after you have passed the test, you have to do that, the component test, and after that you have the approval to install the system, so kind of like pbd, but powered by experimental research for a very narrow spectrum of use, right it's a narrow in that sense that you, for different risk category, you have to do on fire test series following the standard.

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so obviously if you have to do on-fire test series following the standard, so obviously if you have a building, so in the building you might have an office space or accommodation, you might have a car park, you might have some electric room and obviously cable tunnel.

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So all these they are having on their standards and at the companies they have to invest to get an approval for those, and and this even goes beyond, because it's not just office to car park it's like one system for office with three meter tall ceiling, one for correct with five meter tall ceiling, right correct I mean obviously.

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then it might be that if you're doing with a higher than you are, normally you're okay for lower installation, but if you're doing with a higher, then normally you're okay for lower installation.

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But if you're doing it doesn't work the other way around and obviously if you're having the lower test set up, then obviously you can save a lot of water.

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So, based on that, there's a fire safety engineer, like, let's say, someone just finished their fire safety engineering course at the university.

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Just there's basically no way they can figure it out.

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They need a water mist company to help them find the correct nozzle, spacing, pressure, flow rates, etc.

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Right, because, uh, it's so specific I I find it difficult to to give like a you know, hire a new person to my lab and tell them okay, from tomorrow you're designing Watermist.

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Here's like five books you have to read and you'll be good.

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That won't be enough.

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You need experience from lab, right?

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No, no, no, no, I think it's again another misconception.

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So I mean you can look even some of the standards or standardization organization.

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They show, let's say, which companies have approved certain applications and obviously from there you get the main information to design the system.

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But definitely it's different.

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It's not that you would for every building that you would need to do a validation or fire test.

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I mean it's just that these companies they have done for different number of applications that they are good, regardless of what is the building.

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But transferring the information then from the companies, from the industry to the fire engineer, that's the hurdle to make the link, and obviously IWMA is also playing there between trying to spread the knowledge.

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Okay, that's much better, because for a second I was worried that this is so specific to the solution that there would be no way that just a fire engineer could work.

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But yeah, if you're directed towards the suppliers and suppliers are openly sharing their applications and their protocols and the results of their tests, then probably you can work it out.

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Previously you've also mentioned there are different types of water mist that would result on with different water distributions.

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I know there's low pressure water mist.

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I know there's high pressure water mist.

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Would you like to comment on the types of water mist and perhaps how big of a difference does it really make that you have?

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different operating pressures, because that seems to distinguish them.

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Operating pressures because that seems to distinguish them.

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If I would say, as a rule of thumb, the droplets sizes or small droplets, you can do both with the high or low pressure.

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But if you want to combine small droplet sizes together with the momentum, so having the smaller droplets and shooting them into the protective volume with the high momentum, that requires energy, that requires higher pressure and some of the applications you really gain of having both small droplets and then filling very effectively the volume.

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So that's probably one of the fundamental changes.

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And obviously then it correlates to the flow rate that typically, because of this effect, higher pressures they are having lower flow rates.

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But if we are looking to the standardized risks, so there is a test protocol placed by the standards and obviously you can pass this test with low pressure or high pressure.

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It's then up to the manufacturer what they're going to do.

00:23:22.704 --> 00:23:24.357
I think we've covered a lot of fundamentals.

00:23:24.357 --> 00:23:29.509
Perhaps it's time to start moving to the challenges with CFD modeling.

00:23:29.509 --> 00:23:38.692
The second part of my question where do you see modeling water mists as a part of the design?

00:23:38.692 --> 00:23:50.453
I mean, you obviously can't replace the protocol with CFD itself, but where would it be useful for you as an engineer, to put water mists into your modeling?

00:23:51.079 --> 00:23:57.874
Well, obviously I'd say modeling has been typically used in combination with this system.

00:23:57.874 --> 00:24:08.265
Also, it's frankly decided if there would be a fire test to be carried out, and obviously fire testing is not very cheap.

00:24:08.265 --> 00:24:17.335
Pre-studies by modeling will save a lot from manufacturers, let's say time and cost.

00:24:17.335 --> 00:24:20.183
On the experimental side.

00:24:20.183 --> 00:24:23.173
It would apply also to any other technology.

00:24:23.173 --> 00:24:27.501
So that's kind of virtual pre-testing where it's been used.

00:24:27.501 --> 00:24:39.895
And then obviously then we are not there that we would be able to fully justify the designs of any kind just based on pure CFD.

00:24:39.895 --> 00:24:43.028
So that's still difficult.

00:24:43.028 --> 00:25:06.300
But again, if we are having good experimental data, so then we can use in the kind of post-processing assessing that, for example that compared to the file test, if the geometry would have different dimensions, so probably we can mitigate this based on on the cfd works.

00:25:06.300 --> 00:25:09.346
Or we will have a different ventilation conditions.

00:25:09.346 --> 00:25:13.134
So again we can use cfd to assess the influences.

00:25:13.134 --> 00:25:19.250
Or we want to studyD to assess the influences, or we want to study the effect to the structure, or you name it.

00:25:19.661 --> 00:26:03.824
So you mean more, like in structural fire resistance, we had this extrapolation possibilities that were called the EXAPs extended application and basically it meant that if you run tests on your furnace for long enough, you can extend the height of the sample to a little higher one, based on the fact that you have extended your tests or objective results of an experiment into slightly different geometry, slightly different ventilation conditions, by simulating the original experiment and the extension and then working out like what's the difference?

00:26:03.824 --> 00:26:04.987
Like is it still applicable?

00:26:04.987 --> 00:26:05.588
Something like that?

00:26:05.950 --> 00:26:07.121
yeah correct, correct.

00:26:07.121 --> 00:26:19.395
So typically then is is then utilizing, let's say, or doing the validation with the experimental test, and then moving this scenario into the real geometry.

00:26:20.240 --> 00:26:23.900
Yeah, being blessed with collaboration between ITB and the Baltic Fire Lab.

00:26:23.900 --> 00:26:31.013
This is also something that we see an immense future in studying and learning how to do properly.

00:26:31.013 --> 00:26:34.041
And how about building applications Like?

00:26:34.041 --> 00:26:43.025
I won't break any NDAs if I tell you I've been challenged to those simulations a few times in my life and then a few times we had to do them because the client really needed them.

00:26:44.126 --> 00:27:10.251
What I have in mind is simulating what it means in an office layout, to prove that it works, or to give a proof that it doesn't like destroy the operations of ventilation or some other, but basically as a proof that in the building setting it's going to operate how to even say it nicely To give a bunch of nice colorful pictures that it works correctly.

00:27:10.251 --> 00:27:14.069
What's your take on those aspects of PVD?

00:27:14.069 --> 00:27:19.904
Because, if I may, uh, one more sentence that that's what we do with smoke control.

00:27:19.904 --> 00:27:26.107
For smoke control we don't have protocols, we don't have extensive experimental proof for any different occupancy.

00:27:26.107 --> 00:27:32.425
We just do the system as it is on the building and based on that we make conclusions does it work or not?

00:27:33.288 --> 00:27:36.973
yeah, and I I think there is a fundamental difference.

00:27:36.973 --> 00:27:54.906
When we're talking about smoke control, so then we are not really influencing the fire, and obviously when we are having water being involved, so typically that influences the pure loses process and and obviously it's interacting with the fire itself.

00:27:54.906 --> 00:27:58.294
So already the equations are way more difficult.

00:27:58.294 --> 00:28:11.811
So, yes, we also, we are doing a lot of simulation related to smoke control in buildings, in tunnels, in metro stations, and it's standardized there.

00:28:11.811 --> 00:28:21.210
But if we are looking to the office building, so typically in the office building I mean office areas, it's typical or ordinary areas at one.

00:28:21.700 --> 00:28:31.750
Normally there is not even question whether the MIS system or shrinker, with the regular spacing five millimeters per minute, whether they would be accepted or not.

00:28:31.750 --> 00:28:40.049
Typically it has to do then, like you said, with the certain ventilation condition that some people will come with a question.

00:28:40.049 --> 00:28:44.327
They probably don't do a fixed question for sprinklers because they think it's a standard.

00:28:44.327 --> 00:28:55.430
Very few people actually remember where this five millimeters per minute actually came from and probably that time the furniture was different and the building materials were also different.

00:28:55.430 --> 00:29:00.428
But anyway, that's a side topic, but for these special cases.

00:29:00.428 --> 00:29:12.468
So there's something with the ventilation or with the atrium or whatsoever, and it has to do a lot with the experience of the people using the CFDS.

00:29:14.061 --> 00:29:15.888
And I assume, validation well, I assume.

00:29:15.888 --> 00:29:19.451
I know validation for those cases is very, very challenging.

00:29:19.451 --> 00:29:32.660
When we were visiting the Baltic Fire Lab a few weeks ago on the summer school, bogdan was explaining water mist and he mentioned that the water mist experiments are compared to sprinkler experiments.

00:29:32.660 --> 00:29:38.865
And I've asked him are sprinkler experiments expected to be compared with water mist as reference?

00:29:38.865 --> 00:29:41.106
And he made a very sad face.

00:29:41.106 --> 00:29:42.564
So it's kind of weird.

00:29:42.584 --> 00:29:49.819
You know that one technology is given completely different scrutiny as another, even though we are in the same fire safety market.

00:29:49.819 --> 00:30:01.121
And the performance of that, and especially if you compare it to the smoke control, where you have literally no experimental proof and you base everything on on your engineering judgment fueled by numerical modeling.

00:30:01.121 --> 00:30:11.968
You you've said something very important explaining me that that case is that you will have difficulties capturing the influence between the mist and the fire.

00:30:11.968 --> 00:30:22.869
So what if you go another simplified way just reduce the fire size and just model the cooling effects to what the mist has on the smoke and air?

00:30:22.869 --> 00:30:27.507
Would that give you anything, any knowledge you could work with?

00:30:27.507 --> 00:30:30.384
Or it's just too generic to?

00:30:30.443 --> 00:30:31.950
find it useful in engineering.

00:30:32.200 --> 00:30:48.327
Yeah, I think that's the, the, the common way, that's a common practice because we see that the cfd is not major enough to to go 100 modeling, including the combustion in combination with mist.

00:30:48.327 --> 00:30:55.613
So then the the other approach is then using the semi-emperial models, which we actually strongly suggest.

00:30:55.613 --> 00:31:17.392
So we are taking the design fire curve based on the experimental tests, that we use this, and then we can model that how water miss is influenced, the outcome, the output of the fire, how it's cooling and how is, for example, shielding, what are the radiation level or heat transfer to the structure?

00:31:17.392 --> 00:31:27.031
There the question is that, if you don't have the experimental data, so then the question is that where do you cut the design curve?

00:31:27.031 --> 00:31:39.332
So is that when the first sprinkler will activate, you then take the flat If you have the data from the free burn test, and that's where there is, let's say, normally the main discussion.

00:31:40.039 --> 00:31:44.632
So one approach would be just to base it on the nearest protocol you have.

00:31:44.632 --> 00:31:53.689
Let's say you're having an office, so there is this office protocol with these desks and items on the desk, fire, shielded from the water, et cetera, et cetera.

00:31:53.689 --> 00:31:59.807
If you have heat release rate from experiment like that with water mist, you just put that into CFD.

00:31:59.807 --> 00:32:19.846
And if you don't have an access to a good enough experiment with heat release rate measurements, which are not that common actually, you would basically go alpha T squared growth applicable for a specific design situation and then, just based on activation, figure out a reasonable time to cut off the curve and flatten it.

00:32:19.846 --> 00:32:20.347
Do I?

00:32:20.407 --> 00:32:21.231
understand correctly.

00:32:21.231 --> 00:32:23.147
Yeah, that would be.

00:32:23.147 --> 00:32:30.005
Let's say, they're very simplified, I think I rather always would prefer the real measurements of the fuel pack.

00:32:30.759 --> 00:32:32.625
As in referring to experiment.

00:32:33.027 --> 00:32:33.869
Yeah correct.

00:32:35.340 --> 00:32:45.173
And then obviously, depending how conservative the approach you want to do, if you have any crypt, that will be the influence of mist, then to the fire itself.

00:32:45.173 --> 00:32:56.133
I mean, you can do the most conservative, but you don't give any impact, you let it burn as a maximum and then you see what will be the outcome.

00:32:56.133 --> 00:33:03.054
And then obviously there are also some tests where there is a data how it's influencing.

00:33:03.054 --> 00:33:07.071
But then obviously this has to do also a lot with the manufacturers.

00:33:07.071 --> 00:33:11.925
They process this data, so you have to be close to them.

00:33:13.461 --> 00:33:25.708
One that comes to my mind is, if I was doing a car park, I would probably just leave, you know, the car park kit release rate as it is from my normal generic design fire and just model the cooling effects.

00:33:25.708 --> 00:33:37.127
I mean that would probably end in some like worst case scenario where you fail to influence the fire inside the vehicle, but she got the cooling effects which.

00:33:37.127 --> 00:33:40.386
Because, like, what question are we answering with this?

00:33:40.386 --> 00:33:59.375
Like if we cut down the case where we want to showcase a colorful pictures to the firefighter who has to say whether the building is approved or not, if we just cut this use of cfd, which obviously would be like one third or maybe half of the market and you want to study something, you want to understand, what question can you get?

00:33:59.375 --> 00:34:11.871
And the idea that comes to my mind is that, okay, I'm going to have different temperatures, my smoke is going to have different buoyancy, that most likely influences my flows and layers and everything right.

00:34:12.400 --> 00:34:14.568
But let me throw the question back to you.

00:34:14.568 --> 00:34:18.525
If it would be a traditional Spreepio, how would you do that?

00:34:18.925 --> 00:34:24.226
Huh, yeah, I would probably in this case do the same If it's a car park.

00:34:24.226 --> 00:34:31.224
Car park is for me a specific scenario in which the vehicles are generally meant to not let water in.

00:34:31.224 --> 00:34:32.809
You know Exactly.

00:34:33.380 --> 00:34:34.083
That's the point.

00:34:34.083 --> 00:34:41.795
Even you know, know, when you're doing the oh it's fun test arrangement, you you activate or you start the fire under the table.

00:34:41.795 --> 00:34:54.027
Yeah, so obviously sprinkler will not do anything until the fire will go above the table and ignites the things because there's no entrance for water influencing theluenced fire.

00:34:54.027 --> 00:34:58.181
So this very same question remains regardless.

00:34:58.181 --> 00:35:02.092
What is then the technology you are utilizing?

00:35:02.742 --> 00:35:19.233
But if you ask me the question what I would do if I was simulating a high-rec storage building, then I would most likely try to estimate the time to trigger the sprinklers in between four settings.

00:35:19.233 --> 00:35:29.362
So I have the furthest distance to my sprinklers and I would apply some delay because I assume that it takes time to build up the pressure in the pipes.

00:35:29.362 --> 00:35:35.469
You know, trigger the jockey pump, then trigger the main pump and also before all four hats start up.

00:35:35.469 --> 00:35:40.532
So let's say I would have the initial trigger in 100 seconds.

00:35:40.532 --> 00:35:53.253
I would probably add like at least 60 seconds to that and then I would cut my alpha T-square curve in that case, or maybe alpha T-thirds curve if I was doing design for Singapore.

00:35:53.253 --> 00:35:55.547
But yeah, I would probably do that.

00:35:55.547 --> 00:35:58.489
I'm not sure how valid or common that would be.

00:35:59.139 --> 00:36:02.063
But obviously there you need to study a lot that.

00:36:02.063 --> 00:36:03.172
What is your field?

00:36:03.172 --> 00:36:04.099
Absolutely.

00:36:04.420 --> 00:36:06.168
And whether it's the outer surface.

00:36:06.168 --> 00:36:17.927
We are actually doing the work or we've been doing actually for the battery storages, similar to the high rack storages or multiple shelves, but anyway, that's a different topic.

00:36:17.927 --> 00:36:31.226
But we actually, I mean we started with the model, the main input data which is the influence to the heat release rate, and I mean over this whole CFD water mist combination.

00:36:31.226 --> 00:36:46.474
We actually published as an IWMA position paper last week where we as a society, we wanted to give a kind of best practice how to tackle these topics.

00:36:47.440 --> 00:36:54.014
And, on contrary, because it's this practice that really triggers me, annoys me very, very badly.

00:36:54.014 --> 00:36:56.467
And it's your society doing that.

00:36:56.467 --> 00:37:03.300
No, not you personally, perhaps, but no, you have those guys who do tunnels and they would burn the town, the fire.

00:37:03.300 --> 00:37:07.510
Without water mist in the tunnel, the fire would reach like 200 megawatts.

00:37:07.510 --> 00:37:10.304
Then they would run the same test with water mist.

00:37:10.304 --> 00:37:13.842
It reaches whatever 30 megawatts, 50 megawatts, whatever the number.

00:37:14.422 --> 00:37:21.806
And then, uh, they give an impression that the water mist is capable of fighting 200 megawatt fire, and for me it's like such a trigger.

00:37:21.806 --> 00:37:26.711
I mean, what water mist does is preventing the 200 megawatt fire from ever happening.

00:37:26.711 --> 00:37:31.170
But when it is 200 megawatts, there's not much you can do.

00:37:31.170 --> 00:37:33.889
And why I'm annoyed?

00:37:33.889 --> 00:37:35.414
There's not much you can do.

00:37:35.414 --> 00:37:36.920
And why I'm annoyed?

00:37:36.920 --> 00:37:43.188
Because we've been forced to run simulations for cases where someone wanted 200 megawatt fire and the water mist at the same time.

00:37:43.188 --> 00:37:44.525
And prove me it works.

00:37:44.525 --> 00:37:53.106
And I'm like it's just like you're asking me for a Star Trek and Star Wars universes merged together in one space.

00:37:53.106 --> 00:37:54.525
It just will not work.

00:37:54.525 --> 00:37:55.922
It's not how it works.

00:37:55.922 --> 00:37:56.724
It triggers me a lot.

00:37:58.269 --> 00:38:09.887
I think I have to tell you one thing that we are probably the first one who have actually done the test 200 megawatt digger law and then activated the MIS system.

00:38:09.887 --> 00:38:12.568
I'm not sure if you were aware of that.

00:38:12.568 --> 00:38:19.313
There is one occasion when it was done and it was for the channel tunnel.

00:38:19.697 --> 00:38:19.838
Okay.

00:38:21.021 --> 00:38:24.590
And it was 2,000 pallets and I don't know how many pools.

00:38:24.590 --> 00:38:31.570
We did it, but it's a rail tunnel with a piston effect, so we also modeled the ventilation conditions.

00:38:31.570 --> 00:38:46.655
But there is one occasion where it's been done and very, very scary Something like I don't even remember it must be 15 years ago, but it had nothing to do with the road tunnels though, so that's it?

00:38:46.675 --> 00:38:52.079
No, that's cool, but what happened when you released water into 200 megawatt fire?

00:38:52.079 --> 00:38:56.952
Did it still give you significant reduction in temperatures?

00:38:57.942 --> 00:38:58.804
Absolutely.

00:38:58.804 --> 00:39:06.521
We obviously took it control quite quickly and obviously it's also a combination with the ventilation.

00:39:06.521 --> 00:39:10.744
So there also, the ventilation is asked to play an important role.

00:39:10.744 --> 00:39:28.481
And, having said that, our intention was not to go to 200 megawatt, the trigger imposed was 150 megawatts, but the safety valve of the pump unit popped and we had to restart the pump and then very, very nervous people started to be around and then we started to lose.

00:39:28.481 --> 00:39:30.469
Camera here, camera there.

00:39:30.510 --> 00:39:32.318
Nobody was allowed inside the tunnel.

00:39:32.318 --> 00:39:44.128
Yeah, I can imagine that and you could see that how it was in TSD, how the tunnel was leaking also between the joints, but anyways, everything went fine.

00:39:44.128 --> 00:39:46.646
But obviously you don't want to.

00:39:46.646 --> 00:39:58.487
If you are planning a road tunnel, I mean in the channel tunnel, the train can travel quite a long time having the trucks burning on board, so that's why there's a lot of time.

00:39:58.487 --> 00:40:03.382
But in the road terminal you obviously want to activate as quick as possible.

00:40:03.382 --> 00:40:10.025
If you go to that level of the fires, I mean most of the technical equipment is already destroyed.

00:40:10.025 --> 00:40:13.228
So I mean it doesn't make sense.

00:40:14.682 --> 00:40:23.769
Well, that's a very brutal, yet such such a important uh observation that the technical systems will be already destroyed.

00:40:23.769 --> 00:40:47.945
I I don't think people appreciate logic enough in in the fire community and uh, for me that that's, that's a very logical conclusions that if you don't have your pipes and nozzles there, or they bend it or they fell down from the ceiling which is most likely when you have a fire of 200 megawatts that there's not much they can do to reduce the size, perhaps reduce the.

00:40:47.945 --> 00:40:52.820
Of course they would reduce the temperatures a little bit, but yeah, it's going to be challenging.

00:40:52.820 --> 00:40:58.829
You must have used a lot of water in that channel fire test to get that piece under control.

00:41:00.643 --> 00:41:16.646
Yeah, it was probably more than in the road channel, but it was not, let's say, the huge amount and obviously for many kinds of fires, obviously bigger the fire is, more evaporation there is, better the system will be Okay.

00:41:16.786 --> 00:41:27.041
So we've covered a bit the suppressing the fire tricks and tricks of the trade, how you can deal with that.

00:41:27.041 --> 00:41:30.467
I assume modeling the true suppression at the fuel.

00:41:30.467 --> 00:41:37.701
This is only applicable to, maybe, pre burn studies.

00:41:37.701 --> 00:41:49.215
I know guys at FM are really good at doing stuff like that, like modeling before they burn, and perhaps I'll get someone from FM to talk on that one day.

00:41:49.215 --> 00:41:52.184
How about the gas phase?

00:41:52.184 --> 00:41:55.846
So the phenomena that are happening in gas phase, for me two are important.

00:41:55.846 --> 00:41:57.527
One is three are important.

00:41:57.527 --> 00:42:01.610
One is evaporation, that is, how much heat is taken out in the gas phase.

00:42:01.610 --> 00:42:08.969
The second is the change in oxygen concentration with the evaporation, which you've mentioned, important for the pool fires.

00:42:08.969 --> 00:42:26.289
And third one, uh, for me an important, the uh, water induced airflow, like like the momentum pushed onto the air and how it changes, because for me it's important to consider the smoke layer disruption, for example.

00:42:26.289 --> 00:42:32.809
So how confident are you with our capability of modeling those phenomena with our CFD packages?

00:42:32.809 --> 00:42:36.726
And perhaps there's also tricks of the trade that people should be aware of.

00:42:38.960 --> 00:42:39.846
That's a difficult one.

00:42:39.846 --> 00:42:45.492
So I'm looking more from the perspective of, let's say, application.

00:42:45.492 --> 00:42:50.811
So I mean, what is then practical to be used in real life?

00:42:50.811 --> 00:43:02.668
And before going to that we could look then okay, I mean, if we are looking, looking these very same topics from the academic perspective, so I think there is a lot to be improved.

00:43:02.668 --> 00:43:04.510
So I I think these are.

00:43:05.172 --> 00:43:23.043
If we would then combine these, these three things also with the droplets and the interaction of droplets together, droplets together, these would be, I mean, big stickly.

00:43:23.043 --> 00:43:35.329
Then further, but if we are looking from the, the technology as it is I'm now referring cfd technology as it is so what I've seen is that I think we can predict with a fairly good confidence the, the influences when it comes to the cooling.

00:43:35.329 --> 00:43:43.710
Normally we are not so much of interest about the, the air or, let's say, the oxygen, okay, itself.

00:43:43.710 --> 00:43:50.027
I think that that's more the academic research, but we are more interested that what will happen for the fire.

00:43:50.027 --> 00:44:01.054
So, and obviously that's more the, the question and the, the interaction between the, for example, with the stratification, which truly is of your interest.

00:44:01.054 --> 00:44:09.871
So I think that's also quite well known and there's a lot of data, also from experimental data, from the test.

00:44:11.240 --> 00:44:24.668
We're also looking for effects in relation for tunnels, for example, how big resistance the water mist cloud brings to the tunnel as a factor in my pressure equation that drives the design of my smoke control.

00:44:24.668 --> 00:44:32.731
So there are more factors, but I'm also fairly confident in the ability of modern CFD packages to capture this phenomenon and all that.

00:44:32.731 --> 00:44:37.362
One more that we didn't touch modeling the water mist release.

00:44:37.362 --> 00:44:48.436
That I find really challenging, because if you want to model water mist it doesn't magically appear in your model you have to spray it from something right.

00:44:48.436 --> 00:45:08.532
And to model a real nozzle and model the physics that happens at the nozzle itself, that's like nozzle itself, that's a PhD, like that's a simulation on its own right, but I don't want to do a PhD every time I sell my CFD to someone.

00:45:09.001 --> 00:45:10.246
I need a reliable model.

00:45:10.246 --> 00:45:12.742
So there are simplifications In FDS.

00:45:12.742 --> 00:45:17.965
There is this simple model you put some angles, you put the pressures, you put the flows and you get some outcome.

00:45:17.965 --> 00:45:20.030
How you feel about that?

00:45:20.030 --> 00:45:22.516
Where are we heading with this?

00:45:22.516 --> 00:45:31.043
Is it going to be more simple, like I'll get the catalog of nozzles from manufacturer one, two, three, I'll just put them in my model and they will work?

00:45:31.043 --> 00:45:39.371
Or there is a lot of stuff that I should pay attention to when I try to model that no, I don't think so that it would be so complicated.

00:45:39.500 --> 00:45:49.242
I mean we have done multiple times multiple nozzles and no BHD, no BHDs yet Again.

00:45:49.242 --> 00:45:57.391
I mean, obviously you are doing the comparison for sprinklers and sprinklers are default values basically.

00:45:57.391 --> 00:46:04.630
So if you would have more complicated sprinkler head as well, I mean you would need to do exactly the same exercise.

00:46:04.630 --> 00:46:17.581
But typically the mist nozzles, they are having the optimum performance, they are having the multiple orifices, so multiple kind of jets per head, and this is like you said.

00:46:17.581 --> 00:46:28.855
You have the model, the geometry, you need to know the droplet distribution and then you need to know the velocity and that's pretty much all what you need to do.

00:46:28.855 --> 00:46:44.414
So we've been quite at least satisfied with the way we have done and we have done also comparison just with the application rate, experiential versus CFD, and with the results.

00:46:45.260 --> 00:47:03.503
Okay, and for the final, maybe from your experience modeling different types of water mist systems, any particular case which you recollect that gave you the most trouble, or issues like the most challenging one you've done, I mean, I think they all.

00:47:03.523 --> 00:47:06.672
They have had challenges in a certain ways.

00:47:06.672 --> 00:47:16.632
I mean, often it's a combination that, okay, we are having very big volume and then obviously we have to be using very small cell sizes.

00:47:16.632 --> 00:47:25.847
I mean it can do with that kind of difficulties, or it have to do with the difficulties that we don't have a good validation data.

00:47:25.847 --> 00:47:43.333
Then we have to do much more analytical work, we have to look to some application which being close, or it might be also that we have to think about the interaction between water and the fire itself and how it's going to influence.

00:47:43.333 --> 00:47:47.672
We don't want to go with the overly conservative approach.

00:47:47.672 --> 00:48:06.532
So there are give a kind of guidance that what is best practice, the kind of boundaries, what is what is allowed, what is not.

00:48:06.532 --> 00:48:11.349
I think that's the the important message that I would say max, thank you.

00:48:11.411 --> 00:48:21.246
Thank you so much for for this lovely interview and it was great to hear about modeling from the new president of International Water Mist Association.

00:48:21.246 --> 00:48:24.387
Anything you want to add as your final remark?

00:48:24.387 --> 00:48:33.965
Perhaps a word of courage to those who will be faced with modeling water mist when to seek resources and where to find help in this journey.

00:48:35.902 --> 00:48:38.619
I think the very first applicant to start with is obviously this IWMA position paper.

00:48:38.619 --> 00:48:41.547
I think the very first applicant to start with is obviously this IWMA position paper.

00:48:41.547 --> 00:48:44.688
I think that will give a good kickstart.

00:48:45.440 --> 00:48:46.947
Is it available online already?

00:48:46.947 --> 00:48:47.561
It?

00:48:47.581 --> 00:48:48.063
will be.

00:48:48.063 --> 00:48:52.387

171 - Exploring Water Mist Systems with Max Lakkonen

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