Sauna Simulation

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EXPERIMENTAL AND COMPUTATIONAL FLUID DYNAMICS STUDY OF A FIRE HEATED SAUNA – VALIDATION, DESIGN AND FIRE RISKS ANALYSIS Corentin Macqueron1 and Perttu Leppänen2 Corresponding author, Computational Fluid Dynamics Engineer 11 place de la convention, 78 280, Guyancourt, France +33 6 98 26 43 77 corentin.macqueron@gmail.com 1

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PhD Student, Tampere University of Technology, Department of Civil Engineering Korkeakoulunkatu 10, FI-33720 Tampere, Finland perttu.leppanen@tut.fi

Abstract – An experimental fire heated sauna is built according to the European standard EN 15821, providing results for fire risks analysis and for comparison with a computational fluid dynamics modelling performed with the open source Fire Dynamics Simulator (FDS) software. It is found that the peak flue temperature can reach values well above the temporally averaged temperature which is considered in the EN 15821 testing methodology. This might explain why accidental fires are observed even with chimneys correctly dimensioned according to EN 15821, because this standard is not conservative enough and should hence be modified. It is also found that FDS performs well for flame, air, flue and stones temperatures, as well as for stove mass flow rate and heat fluxes, by comparison to the measurements and other data from the literature. The model performance is less conclusive for stove and wall temperatures, but it is nonetheless shown that FDS can be used for sauna design and fire risks analysis. Keywords – Sauna, Computational Fluid Dynamics, Fire Dynamics Simulator, wood, stove, fire, EN 15821

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comparison basis for numerical simulations performed with FDS (Fire Dynamics Simulator), a fire-dedicated open source CFD (computational fluid dynamics) software [9] [10] [11] [12] [13]. The numerical results from the sauna simulations were then compared to the sauna setup measurements and other data from the literature in order to assess the performance of FDS and thus to what extent this new approach might be effectively reliable.

INTRODUCTION

The traditional sauna, very popular in Finland and Scandinavia, is a fire heated insulated room built for dry bath activities that have numerous beneficial physiological effects [1] [2]. During the 2008-2014 period, ~2000 fires broke out from the sauna buildings in Finland [3] [4] [5], representing ~5% of all the building fires in Finland. At the same time, ~700-900 fires ignited from fireplaces and chimneys every year in Finland. The causes of the fires are amongst other things too small protection distances and too high flue gases temperatures. Investigations are required in order to better understand and suppress these causes. In order to do so, an experimental sauna setup has been built in the Tampere University of Technology [6] [7], following the European standard EN 15821 [8] in order to study flue gas temperatures and accidental fire risks.

2. EXPERIMENTAL SETUP 2.1. Sauna An experimental sauna setup has been built in the Tampere University of Technology [6] [7], following the European standard EN 15821 [8] in order to study flue gas temperatures and accidental fire risks. This setup is used as a basis for wood stove and sauna modelling and is shown on Fig. 1-2-3-4.

Following this experimental investigation, the idea arose that numerical simulation could also be used for further inquiry. The experimental sauna setup built in the Tampere University of Technology hence served as a

The volume of the cabin is 20 m3.

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