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Thermal analysis techniques play a key role to determine and characterize solid phase thermal decomposition. In this sense, Simultaneous Thermal Analysis (STA, i.e. TGA and DSC tests carried out simultaneously) are widely employed, since it provides information about how mass is lost and energy released while the temperature of the sample increases. Fire computer models combined with methods numerical methods are widely used to represent the results from tests and to achieve the values of the kinetic and thermal parameters. Previous works looked forward achieving those parameters using, as unique optimization target, the mass loss curve (TGA) or its derivative (DTGA). As the study of heat release rate is a decisive element to characterize the material properly, most recent works were adding additional measures. These extra measurements concern the heat transfer and the energy required or released during temperature programmed heating, such as heat rate release, heat of gasification, or the surface temperatures of the samples. The information about the energy is provided by the Differential Scanning Calorimetry curve (DSC). Despite of the employment of the information provided by the DSC, this information usually is not used as a target to approach the DSC simulated curve to the experimental one as TGA does. Based on the lack of use of the DSC curve as numerical approaching process to set the kinetic properties, we decide to explore the possibility of adding this as a new target in the process. Therefore, kinetic and thermal properties might be achieved fitting experimental and simulated curves simultaneously, which should allow us to take into account the decomposition process and their energy released. Results obtained in the present work reveal the major challenge of getting a set of parameters, which can fit DSC curve. The level of accuracy reached when only TGA is utilized as target to approach is higher than the level of accuracy of DSC curve. This fact makes increase the value of the errors when both curves are used as targets to approach. In other words, an approach to both curves simultaneously cannot be directly made. With this consideration in mind, this paper proposes an alternative methodology in order to fit TGA curve considering the optimization of the DSC curve. The methodology proposed in the present work is applied to the analysis of poly(methyl methacrylate) (PMMA). The authors would like to express their thanks to the Nuclear Safety Council for the cooperation and cofinancing of the project "Simulation of fires in nuclear power plants" and the Spanish Ministry of Economy and Competitiveness for the PYRODESIGN Project grant, Ref.: BIA2012-37890, financed jointly by ERDF.

Natural venting systems present numerous advantages opposite to the mechanical exhaust for the smoke control – a reduction in both facilities and maintenance costs–. Nevertheless, the influence of numerous factors affects significantly their efficacy: the architectural characteristics of the building, the direction and wind velocity, the proximity of tall buildings, the smoke temperature, the environmental interior and exterior temperatures, the existence of snow or ice on the ceiling, etc. All of them are important, but the influence of the environmental exterior temperature plays a decisive role. The goal of this Investigation Research was to evaluate the influence of the external temperature on the smoke movement and the hot layer descent regarding the efficacy of the natural venting systems installed for the smoke control in large atria. The analysis was developed using the ‘Fire Dynamics Simulator - FDS’ model (1), a computational fluid dynamics (CFD) model of fi re-driven fluid flow for the study of fire. The results demonstrated that a design that does not contemplate this factor can turn out to be inadequate, since it has a decisive influence to guarantee human safety. The obtained results showed very significant differences about the different parameters linked to the smoke movement in an atrium. Entre las diferentes estrategias de Control y Evacuación de los Humos del Incendio, los sistemas de ventilación natural presentan numerosas ventajas frente a la ventilación mecánica – fundamentalmente una menor inversión tanto en equipos como en gastos de mantenimiento –. Sin embargo, su eficacia depende de la influencia ejercida por numerosos factores – características arquitectónicas del edificio, dirección y velocidad del viento, proximidad de edificios de gran altura, temperatura de los humos, temperatura ambiental interior, temperatura en el exterior del recinto, existencia de nieve o hielo en cubierta, etc. –. La influencia de la temperatura exterior al recinto, en especial, ejerce un papel decisivo. El objeto del Estudio fue evaluar la influencia de la temperatura ambiental exterior en el movimiento de los humos y el posible descenso de la capa de gases calientes en relación a la eficiencia de los dispositivos de ventilación natural instalados en la cubierta de Grandes Atrios para el control de los humos, mediante herramientas avanzadas de Modelado y Simulación Computacional. Para los trabajos de investigación se empleó el modelo de simulación computacional de incendios ‘Fire Dynamics Simulator (FDS)’ (1), modelo de dinámica de fluidos computacional (CFD) para reproducir el fenómeno del incendio. Los resultados demostraron que un diseño que no contemple este factor puede resultar inadecuado, al ejercer una influencia decisiva para la consecución de la Seguridad de las personas durante la evacuación. Se mostraron diferencias significativas en los resultados en relación a diferentes parámetros vinculados al movimiento de humos en un atrio.