Aalto fire research team at IAFSS 2017

 

Aalto fire research group at the IAFSS 2017 symposium banquet.Left to Right: Dr. Kaiyuan Li, Rahul Janardhan, Prof. Simo Hostikka, Topi Sikanen and Deepak Paudel

Aalto fire research group at the IAFSS 2017 symposium banquet.Left to Right: Dr. Kaiyuan Li, Rahul Janardhan, Prof. Simo Hostikka, Topi Sikanen and Deepak Paudel

The 12th edition of the triennial IAFSS Symposium was held at Lund University, Sweden this year. Four members of the Aalto fire research group, headed by Prof. Simo Hostikka, were present at the symposium to share their research with the fire science community.

Prof. Hostikka spoke about “Heat and mass transfer in the condensed phase” in the Condensed phase subgroup of the MacFP workshop.

Dr Kaiyuan Li presented his paper about “Char cracking of MDF due to thermal shock effect induced pyrolysis shrinkage“.

Rahul Janardhan, PhD student, presented the paper from the PAHAHUPA project titled, “Fire induced pressure and smoke spreading in mechanically ventilated buildings with air tight envelopes“.

Deepak Paudel, PhD student, presented the poster “Uncertainties in the prediction of
fire-barrier temperature: Simulation and validation of a fire experiment”. 

Also, Topi Sikanen from VTT Technical Research Centre of Finland presented his paper on “Predicting the heat release rates of liquid pool fires in mechanically ventilated compartments“.

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Will the induction cooktops wipe out kitchen fires?

Cooking or stove -originated fires are a significant group of residential fires. These fires start from a stove or a cooktop if it is left on alone, food is left on a hot pan for a long time or if there are other, flammable materials too close the high-temperature parts. Different technologies are already available to avoid such ignitions, including the stove guards that cut off the voltage when they detect a possible ignition. Although such technologies can be very efficient, I have started to think if the kitchen fires could be reduced with some other means. Could we prevent fires from igniting in the first place? Or could we improve safety without extra investment?

The importance of the stove fires is evident. According to the Finnish fire statistics of 2011-15 [1], the yearly count of building fires was 5760 in average, leading to 73 fire deaths and 124 M EUR direct economic losses annually. About 1000 (17 %) fires originated from cooking and 700 (12 %) from electrical appliances. In fire deaths, the shares of these two origins were  8.2 % and 7.4 %, respectively. On top of these, we have the ‘unknown’ category in each statistics.

So what technological change could make the change? Let’s have an analogy: When I started to work in fire research at the end of 1990’s, televisions were one of the most important ignition sources. A lot of effort was put in developing fire-safe televisions, mainly by using fire retardant polymers. Interestingly, about the time when the fire retardant polymers fully came into market, TV-technology changed from cathode ray tubes to flat screens, and televisions practically disappeared from fire ignition statistics. Natural evolution of the market removed the problem. Could we see similar evolution in stoves?

Based on my personal experience, induction heating -based stoves can make the difference. Instead of first heating the stove and relying on heat conduction to heat up the cooking pans or pots, an alternating magnetic field is used to create magnetic hysteresis and electrical current in the pan, which then heats up due to the resistance. The fire safety benefit is obvious because the amount of high temperature surfaces is reduced.

Kookplaat inductie

The yearly number of sold cooktops and kitchen stoves in Finland is about 168,000. In 2016, about 50,000 (30 %) of them were based on the induction technology [2]. The share of induction -based appliances is much higher in integrated cooktops (65 %) than in floor-standing stoves (10 %), but their shares are gradually increasing in both stove types.

To estimate the potential safety impact, we must compare the rate of stove renewals to the total population. At the end of 2015, there were 2,600,000 occupied dwellings in Finland, 45 % of them being in the blocks of flats [3]. Assuming that the floor-standing stoves are installed in flats, the share of induction stoves in these dwellings will increase only by 1 % each year. Also assuming that the integrated cooktops are installed in the other dwelling types, we can estimate that about 3 % of dwellings will have a new induction cooktop each year. If the share of the induction cooktops and stoves does not increase significantly, the possible safety benefit cannot be reached within the next 30 years. The impact will smallest in the low-investment housing, such as rental buildings. On the other hand, that’s where the cities and municipalities have the greatest power to influence.

I think this topic needs more research to investigate the potential safety improvement. First of all, we should understand the physics of stove ignitions and the difference between thermal conditions typical for different stove technologies. Second, we should estimate the potential for natural and enforced market shares, as well as policy making. When the money is tight, we should utilize the possibility.

References

  1. Pelastustoimen taskutilasto 2011-2015. Pelastusopiston julkaisu, D-sarja: Muut 4/2016. 2. painos. http://info.smedu.fi/kirjasto/Sarja_D/D4_2016.pdf
  2. Elektroniikan Tukkukauppiaat ry (ETK), www.etkry.com and www.gotech.fi. Visited December 2, 2016.
  3. Official Statistics of Finland (OSF): Dwellings and housing conditions [e-publication].
    ISSN=1798-6761. Overview 2015, 1. Dwelling stock 2015 . Helsinki: Statistics Finland [referred: 10.4.2017].

 

 

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Nordic Fire and Safety Days 2017 – remember to submit

Aalto University is one of the organizers of the 2017 Nordic Fire and Safety Days.

There are still few days to submit your abstract. Last year, it was great event.

NFSD2017

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New article highlights the importance of the fire -induced pressure

Our latest article, titled ‘Experiments and Numerical Simulations of Pressure Effects in Apartment Fires‘ is now available at Fire Technology -journal. It is OpenAccess.

In this paper we summarize the experimental findings and numerical simulation validation. The main conclusion of the experimental work was that the pressure in normal apartment fire can become dangerously high if the fire development is as fast as in the experiments. (Simulations later in the project showed that in fact, fast t2-fire is enough to cause problems.)

So what is so dangerous about pressure?

First, we noticed that very soon after the ignition, the pressure exceeds the level of 100-200 Pa, meaning that the inwards opening door cannot be opened from inside. A person trying to leave the apartment in the early stages of the fire would not be able to do so!

Secondly, a bit stronger fire, ignited in the closet of the apartment, was able to break the light-weight external wall of the apartment. This is shown also in the Youtube-video as well.

The sensitivity of the over-pressure to the envelope air-tightness was very clearly demonstrated. This means that the above-mentioned problems will become more and more important when we build modern air-tight buildings for the sake of energy efficiency, or in order to manage the conditions inside very tall buildings.

Now, when the Finnish building code for structural fire safety (E1) is under modification, it is important to take these findings into account, and require that the pressures are taken into account in building design, along with the traditional threats like fire spreading.

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MSc thesis topic in the numerical simulation of passive fire protection systems

We are looking for a MSc student to this paid MSc thesis project.

Background: Passive fire protection systems (e.g. stone wool) are used in building and other industries to protect structures and devices from heat and hazardous conditions, such as fire. Design of such systems has been mainly based standardized testing, but a clear need for simulation-based design tools exists.

Task: You will construct a numerical simulation model for the thermo-chemical behavior of a thermal insulation / fire protection material using existing simulation tools, such as FDS or Comsol. The model development consists of the specification of heat transfer mechanisms and formulation of chemical reaction scheme to describe the exothermic reactions inside the material. You will determine the model parameters using small-scale experiments and an optimization algorithm, and validate the model using large-scale experimental data. The simulation model can be used for the product development, performance assessment, and risk analyses.

Advisor: Thesis advisor will be PhD Hannu-Petteri Mattila, Paroc Oy, Parainen.

Practicalities: Starting time in winter/spring 2017. The work will be made in the premises of Aalto University or at Paroc (Parainen), as agreed later. Grant of 12 000 eur will be applied from the Aalto University’s Science and Technology Foundation.

Expectations: The topic can suit for the students of (applied) mathematics, physics, civil engineering, energy technology and chemistry.  Relevant (non-exclusive) skills: Thermodynamics, heat transfer, numerical analysis, modelling and simulation. Good oral and written English. Group-working skills.

Apply before 9.12.2016 by sending your cover letter, CV and study transcript to simo.hostikka@aalto.fi.

Contact
Prof. Simo Hostikka
Fire Safety Engineering, School of Engineering
simo.hostikka@aalto.fi
050 447 1582

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Welcoming new Building Technology students

It was a pleasure to welcome the new students to the Building Technology Master’s programme. Simo (program director) gave the introductory lecture. After that the students had orientation orienteering around the department, during which Kai told them about FSE, and Rahul and Umar presented their thesis projects.

CIV_new_students_2016

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Visit to Imperial College London

Dr. Kaiyuan Li visited the HazeLab (Fire) group in Imperial College London under the support from COST Action FP1404 and gave a lecture on modeling pyrolysis of charring materials.

IMG_20160714_131042-min13615082_10154172144116071_1872493478010170807_n

 

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Dr. Kaiyuan Li Joined the2nd Conference for Fire Science and protection of Special buildings and structures on 22 to 24th July 2016, in Chongqing, China and the 36th International Symposium on Combustion COEX, Seoul, Korea, July 31 – August 5, 2016

Dr. Kaiyuan Li attended these two conferences and gave a talk on FDS in Chongqing and presented a paper co-authored with Simo on Char cracking in Seoul.

WP_20160723_08_50_17_Pro-minWP_20160731_17_41_37_Pro-min WP_20160731_18_15_18_Pro-min WP_20160802_17_52_33_Pro

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New doctoral student position in computational thermal radiation

We are looking for a new enthusiastic member to our team to develop the computational methods for thermal radiation in fires.

It was year 2000 when I was sent from VTT to work as a guest researcher at NIST/BFRL. Within the next year (2000-2001) we wrote, with Dr. Kevin McGrattan, a Finite Volume Method (FVM) -based solver for the thermal radiation to the Fire Dynamics Simulator. FVM is quite similar to the more commonly used Discrete Ordinates Method (DOM). That piece of code has served the fire safety engineers and researchers pretty well over the fiveteen years. Of course, a number of people have contributed to that code since that, but the main body code and the model formulation are still the same.

Limitations and problems have been observed over the years. For instance, the ray effect is a problem for the long-distance calculation as it makes the radiative heat fluxes very non-uniform due to the numerical issues. And so is the relatively clumsy spectral modelling option, which enforces most of us to do gray gas calculations even in the cases where the spectral band -nature of the gas emission and absorption makes a difference. And the recent experiences indicate that the accurate calculation of radiation penetration into the liquid pool requires spectral resolution.

So, there is work to do. See the announcement at http://www.aalto.fi/en/about/careers/jobs/view/899/.

 

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Nordic Fire and Safety Days in Copenhagen

Simo, Rahul, and Kai-Yuan Li attended the NFSD 2016 conference last week in Copenhagen. Simo and Rahul gave presentations on the PAHAHUPA project (pressure maanagement), and Kai about char cracking experiments and modelling.

The conference was very well organized – thanks to Anne Dederichs of SP and team at Aalborg University. It seemed very valuable to have an opportunity for Nordic networking among fire researchers. The conference has an aim to be a mix of fire and other safety topics, but at least this time, the most of the topics dealt with fire. In coming years, I would hope to see more authorities and people from ministries and funding bodies to attend. I think they should follow the topics popping up in this kind of events.

Aalborg_venue Simo_and_Rahul_at_NFSD2016

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