Evaluation of localized pool fire models to predict the thermal field in offshore topside structures
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(2020) 42:613
TECHNICAL PAPER
Evaluation of localized pool fire models to predict the thermal field in offshore topside structures Miguel R. Manco1 · Murilo A. Vaz1 · Julio C. R. Cyrino1 · Alexandre Landesmann2 Received: 17 February 2020 / Accepted: 17 October 2020 © The Brazilian Society of Mechanical Sciences and Engineering 2020
Abstract This article presents a comparative study to predict the thermal behavior of an offshore topside structure under localized fire using different fire models. Thermal fields are estimated using models with different approaches. Sophisticated fire models based on computational fluid dynamics (CFD) are often used in the analysis of this type of accident. However, their high complexity and calculation time make it difficult to use in the design stage of the structure. Simple models usually offer lower temperatures than those estimated by the CFD-FEM model, with limited use in structures with complex geometries. Localized fire with ellipsoidal solid flame (LF-ESF) model was developed as an alternative to previous models that are excessively complex (CFD based) or estimate lower temperatures (Simple). LF-ESF model can evaluate in the design stage the thermal behavior of steel structures under localized fires with the appropriate accuracy in acceptable computation time. The thermal analysis is developed with the aid of commercial software of finite elements. Three case studies are analyzed considering localized fire due to the burning of hydrocarbons. The first two develop the thermal analysis in simple structures and show the main differences between each fire model considered. The last case study evaluated the thermal behavior of an offshore topside structure. The results obtained allow to conclude that the LF-ESF model realistically represents the temperature fields generated by the fire with a relatively low computational cost as compared to the CFD models. Keywords Pool fire · Localized fire · Modified solid flame model · FDS · CFD · FEM List of symbols Roman lowercase b Characteristic plume radius (m) cp Specific heat (J/g K) e′′r,abs Radiant energy absorbed (kW/m2) e′′r,emi Radiant energy emitted (kW/m2)
Technical Editor: Celso Kazuyuki Morooka. * Miguel R. Manco [email protected] * Murilo A. Vaz [email protected] Julio C. R. Cyrino [email protected] Alexandre Landesmann [email protected] 1
Ocean Engineering Program, COPPE/UFRJ, Rio de Janeiro, Brazil
Civil Engineering Program, COPPE/UFRJ, Rio de Janeiro, Brazil
2
e′′r,inc Radiant incident energy (kW/m2) e′′r,ref Radiant energy reflected (kW/m2) g Gravitational acceleration (m/s2) 2 hAST tot Net adiabatic heat transfer coefficient (kW/m K) 2 hconv Convective heat transfer coefficient (kW/m K) k Thermal conductivity (W/mK) m′′ Burning rate per unit area (kg/m2 s) q′′conv Convective heat flux (kW/m2) qf Heat release rate per unit area (kW/m2) q′′tot Net heat flux (kW/m2) q′′rad Radiant heat flux (kW/m2) r Radial distance to flame axis (m) r̄ Normalized flame axis distance td
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