Multiphysics Modelling of Stone Wool Fire Resistance
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Multiphysics Modelling of Stone Wool Fire Resistance Deepak Paudel and Aleksi Rinta-Paavola, Aalto University, Espoo, Finland Hannu-Petteri Mattila, Owens Corning Paroc, Parainen, Finland Simo Hostikka *, Aalto University, Espoo, Finland Received: 26 June 2020/Accepted: 3 October 2020
Abstract. In fire resistance tests, stone wool’s organic matter undergoes exothermic oxidative reactions sustained by external heat, causing mass transfer in the structure. The previous modelling attempts, lacking the mass transfer physics, fall short in predicting the temperature of high density and high organic content samples. To fill this gap in the fire engineering modelling capability, we include mass transfer in our calculation, and validate the model using experimental fire resistance data. As an alternative, we use a heat conduction -based model lacking the gas transfer but with reaction kinetics coupled to the stone wool’s organic mass %. The results show that the thermal effects of the oxidative degradation can be predicted by introducing the simplified diffusion processes. The oxygen transfer and exothermic reactions depend upon the amount of organic content, and the uncertainty of temperature predictions is 20%. In average, temperatures and critical times are more accurately predicted by the heat conduction model, while, the peak temperature prediction uncertainty is low ( 10%) with the multiphysics model. The uncertainty compensation method reduces the difference between the two model predictions. Nevertheless, further validation study is needed to generalize the uncertainty compensation metrics. Finally, we demonstrate how a gas flow barrier on the cold side (sandwich) can effectively reduce the peak temperature of the high organic content-stone wools.
List of Symbols A c df D D0 Ea e f Dh h k l T
Pre-exponential factor Heat capacity or constant term Fibre diameter Products gas diffusion coefficient Products gas surface diffusion coefficient Activation energy Specific extinction coefficient Factor Enthalpy of combustion Heat transfer coefficient Conductivity or kernel function Stone wool thickness Temperature * Correspondence should be addressed to: Simo Hostikka, E-mail: simo.hostikka@aalto.fi
1
Fire Technology 2020 Th T1
Hot-side temperature Ambient temperature
Greek Letters C h b d q r r rw / x_ l
Emissivity Fibre mean angle Extinction coefficient or power term Systematic bias Error Density Stefan–Boltzmann constant Standard deviation in errors, Standard deviation in outputs, w Porosity Reaction rate Mean
Subscripts and Superscripts 0 1 2 a f o p s xx,s ^ xx
Initial value Hot-side surface Cold-side surface Air Fibre Organic content Product Solid Specific density Observed quantity
1. Introduction Stone wools are widely used in residential buildings and industrial facilities for thermal insulation and fire resistance [1]. Under conventional safety regulation, the design of such passive fire protection is based on the standard fire test carried out according to EN 1363-1. The test procedure for thermal insulation performance co
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