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- Axelsson, Jesper, et al.
(författare)
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Bus fire safety
- 2008
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Rapport (refereegranskat)
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| 2. |
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| 3. |
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| 4. |
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| 5. |
- Försth, Michael, et al.
(författare)
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In-situ measurements of toxic gases in a tube furnace
- 2009
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Rapport (refereegranskat)abstract
- Infrared Polarization Spectroscopy (IRPS) was used to detect and quantify HCl and HCN in an 800 mm long tube furnace. Pieces of a PVC-carpet or pellets of nylon 6,6 were continuously fed into the furnace producing a heavy smoke. This constitutes a very harsh environment from a diagnostic point of view due to the high smoke density and relatively long length of the furnace. Despite this it was possible to quantify HCl and HCN concentrations in the smoke down to a levels of 50 ppm using IRPS. The explanation for this success is twofold. Firstly the IRPS method is inherently almost noise free due to the use of crossed polarisers, creating a virtually zero background. Secondly the problem with laser beam attenuation due to scattering in the smoke, especially with soot particles, decreases in importance with the fourth power of the laser wavelength. This means that infrared measurements represent a great advantage over measurements in the ultraviolet or visible wavelength range. It is concluded that IRPS shows great promise as a new diagnostics tool in fire technology for small-scale as well as for large scale experiments. Furthermore the in situ nature of the method should be emphasized since this means that valuable information is obtained that can not be extracted from sampling methods such as MS/GC or FTIR for example. This information is important, for example, in egress calculations and analysis of fire chemistry. The method can easily be adapted for other gases such as HF, NO, NO2, HBr, CO and SO2.
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| 6. |
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| 7. |
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| 8. |
- Försth, Michael
(författare)
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Ny laser för att mäta flöden
- 2007
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Ingår i: BrandPosten. ; :37, s. 35-
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 9. |
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| 10. |
- Försth, Michael
(författare)
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On the importance of spectrally resolved absorptivity data in fire technology
- 2009
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Rapport (refereegranskat)abstract
- Radiation is one of the two main heat transfer processes in transporting energy from flames to a surface. The other process is convection and was not considered in this report. The spectral absorptivity of 72 products was measured in the wavelength region 0.3-20 mm. This wavelength region contains virtually all radiation energy from a fire. Based on the measurements, and on the theory for radiative heat transfer, the effective absorptivity for fire induced heat radiation for the different products were calculated. These typically lies in the range 0.75-0.95. It was also found that the effective absorptivity varies significantly with the temperature of the heat source. The reason for this is that the spectrum of the emitted radiation from a heat source, such as a fire, changes with temperature. This has limited effect on the heating of a surface. The dependence of the effective absorptivity on heat source temperature is important when the absorptivity is used as input for calculations of ignition temperature and thermal inertia. Using existing models for predicting ignition temperature and thermal inertia, and correcting these models with the new information on effective absorptivity, it could be shown that the effects were significant but not very large. It was considered that the uncertainties in the model are so high that corrections for the effective absorptivity might be of minor importance compared to the other uncertainties and assumptions. An interesting observation was that the absorptivity of radiation from fires for products exposed to irradiation in the cone calorimeter decreased with increased exposure time, that is, the absorptivity decreased when the products darkened due to heat. This is surprising since, for example, wood that is darkened when exposed to heat obviously has a higher absorptivity in the visual part of the spectrum than fresh non-darkened wood. This is an important observation since it opposes the general view that heat transfer increases with increased thermal exposure due to darkening Finally, it was concluded that none of the studied materials showed a particularly low absorptivity in the infrared region and therefore none of the products stands out as particularly good reflector of radiation from fires. Several ideas were presented for how such spectrally tailored surfaces, with low absorptivity for radiation from fires, can be produced.
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