The last two decades have witnessed the shift of structural fire design from prescriptive approaches to performance-based approaches in order to build more advanced structures while reducing costs. However, it is recognised that the implementation of performance-based approaches requires several key elements that are currently not fully developed or understood. This research set out to address some of these issues by focusing on the development, validation and application of methodologies for accurate predictions of thermal responses of structures in fire using numerical methods. This research firstly proposed a numerical approach with the finite element and the discrete ordinates method to quantify the fire imposed radiative heat fluxes to structural members with cavity geometry. With satisfactory results from the verification and validation tests, it is used to simulate heat transfer to unprotected steel I-sections with symmetrical cavities exposed to post-flashover fires. Results show that the cavity geometry could strongly attenuate the radiative energy, while the presence of hot smoke enhances radiative transfer by emission. Average radiative fluxes for the inner surfaces of the I-sections are seen to increase with smoke opacity. In addition, the net radiative fluxes are observed to decrease faster for I-sections with higher section factors. This work also shows that the self-radiating mechanism of I-sections is important in the optically thin region, and existing methodologies neglecting these physics could significantly underpredict steel temperatures. The next focus of this work is to develop a thermal analysis framework dedicated to structures-in-fire modelling in the OpenSees (Open System for Earthquake Engineering Simulation) platform which has been developed towards a highly robust, extensible and flexible numerical analysis framework for the structural fire engineering community. The thermal analysis framework, which is developed with object-oriented programming paradigm, consists of a fire module which has incorporated a range of conventional empirical models as well as the travelling fire model recently developed elsewhere to quantify the fire imposed boundary conditions, and a heat transfer module which addresses non-linear heat conduction in structural members with the finite element method. The developed work has demonstrated good performance from benchmark problems where analytical solutions are available and from full scale tests with measured data. With the thermal analysis capability developed in this work together with the work by other colleagues to quantify the mechanical response at elevated temperatures, the extended OpenSees framework can be used to predict structural performances subjected to a wide range of re scenarios. This work uses OpenSees for a case study of a generic composite structure subjected to travelling fires. The latest work on travelling fire methodology for structural fire design has been implemented in the OpenSees framework. The work presented in this thesis is the first effort to examine both the thermal and structural responses of a composite tall building in travelling fires using OpenSees. Results from the thermal analysis show that travelling fires of larger sizes (e.g. burning area equal to 50% of the floor area) are more detrimental to steel beams in terms of more rapid heating rate, while those of smaller sizes (e.g. burning area equal to 4% of the floor area) burn for longer duration and thus are more detrimental to concrete slabs in light of higher peak temperatures. The results also show that fires of large sizes tends to produce higher through-depth thermal gradients in the steel beam sections particularly in neighbouring regions with the concrete slab. Due to less rapid heating rates but prolonged burning durations, smaller fires produce lower thermal gradients but with higher temperatures in the concrete slab particularly at locations far from the fire origin. The subsequent structural analysis suggests that travelling fires produce higher deflections and higher plastic deformations in comparison with the uniform parametric fires, particularly with smaller fire sizes producing more onerous results. The results seem to be more physically convincing and they challenge the conventional assumption that the post-flashover fires are always more conservative for structural performance.

Mémoire (M.Sc.A.)--Université du Québec à Chicoutimi, 1991. / Document électronique également accessible en format PDF. CaQCU

<p>The overall aim of this project is to study the heat transfer inside the reaction chamber of the Hot-Wire Chemical Vapor Deposition (HWCVD) system with a commercial software package FLUENT6.3 / it is one of the most popular Computational Fluid Dynamics solvers for complex flows ranging from incompressible to mildly compressible to even highly compressible flows. The wealth of physical models in FLUENT allows us to accurately predict laminar and turbulent flows, various modes of heat transfer, chemical reactions, multiphase flows and other phenomena with complete mesh flexibility and solution-based mesh adaptation. In this study the 3-D HWCVD geometry was measured and created in GAMBIT which then generates a mesh model of the reaction chamber for the calculation in FLUENT. The gas flow in this study was characterized as the steady and incompressible fluid flow due to the small Mach number and assumptions made to simplify the complexity of the physical geometry. This thesis illustrates the setups and solutions of the 3-D geometry and the chemically reacting laminar and turbulent gas flow, wall surface reaction and heat transfer in the HWCVD deposition chamber.</p>

<p>The overall aim of this project is to study the heat transfer inside the reaction chamber of the Hot-Wire Chemical Vapor Deposition (HWCVD) system with a commercial software package FLUENT6.3 / it is one of the most popular Computational Fluid Dynamics solvers for complex flows ranging from incompressible to mildly compressible to even highly compressible flows. The wealth of physical models in FLUENT allows us to accurately predict laminar and turbulent flows, various modes of heat transfer, chemical reactions, multiphase flows and other phenomena with complete mesh flexibility and solution-based mesh adaptation. In this study the 3-D HWCVD geometry was measured and created in GAMBIT which then generates a mesh model of the reaction chamber for the calculation in FLUENT. The gas flow in this study was characterized as the steady and incompressible fluid flow due to the small Mach number and assumptions made to simplify the complexity of the physical geometry. This thesis illustrates the setups and solutions of the 3-D geometry and the chemically reacting laminar and turbulent gas flow, wall surface reaction and heat transfer in the HWCVD deposition chamber.</p>

The different technologies of passive cooling concepts have to rely on a good thermal coupling between a building's thermal mass and indoor air. In many cases, the ceiling is the only surface remaining for a good coupling. Further research is necessary to investigate discrepancies between existing correlations. Therefore, the overall aim of the work described in this thesis is the investigation of heat transfer at a heated ceiling in an experimental chamber. Acoustic baffles obstruct the surface of the ceiling and impede heat transfer. However, there is nearly no published data about the effect of such baffles on heat transfer. Available results from simulations should be verified with an experimental investigation. Consequently, one of the primary aims of this work was to experimentally determine the influence of such acoustic baffles. A suitable experimental chamber has been built at Biberach University of Applied Sciences. The thesis describes the experimental chamber, the experimental programme as well as results from five different test series. With a value of ±0.1Wm⁻²K⁻¹ for larger temperature differences, uncertainty in resulting convective heat transfer coefficients for natural convection is comparable to that of results from an existing recent experimental work often recommended for use. Additionally, total heat transfer (by convection and radiation) results are presented. Results are given for natural, forced and mixed convection conditions at an unobstructed heated ceiling. Furthermore, results for acoustic baffles in both an unventilated and a ventilated chamber are shown. Natural convection results show a very good agreement with existing correlations. Under mixed convection conditions, convective heat transfer at an unobstructed ceiling decreases to the limiting case described by natural convection. Installation of acoustic baffles leads to a reduction in total heat transfer (convection and radiation) between 20% and 30% when compared to the case of an unobstructed ceiling.

The theme of diploma thesis is a design optimization of air distribution in swimming-pool hall with regard to free water surface evaporation. This problem was solved according to determined criterions with the aid of CFD simulation. Experimental measurement part of the thesis deals with evaporation problems where own formula for this physical phenomenon is determined. This formula is compared with already known algorithms. Author suggests that such formula might be integrated in CFD software.