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The reason why the discrete transfer method, often used to compute radiative heat transfer in combustion chambers, is not conservative was investigated. A conservative equation is suggested and evaluated. A simple treatment of isotropic scattering media is also shown. The original and conservative equations of the method are used for two-dimensional and three-dimensional enclosures with a participating medium.

The range of validity of the Rayleigh-Debye-Gans approximation for the optical cross sections of fractal aggregates (RDG-FA) that are formed by uniform small particles was evaluated in comparison with the integral equation formulation for scattering (IEFS), which accounts for the effects of multiple scattering and self-interaction. Numerical simulations were performed to create aggregates that exhibit mass fractallike characteristics with a wide range of particle and aggregate sizes and morphologies, including [x.sub.p] = 0.01-1.0, [absolute value of m - 1] = 0.1-2.0, N = 16-256, and [D.sub.f] = 1.0-3.0. The percent differences between both scattering theories were presented as error contour charts in the [absolute value of m - 1][x.sub.p] domains for various size aggregates, emphasizing fractal properties representative of diffusion-limited cluster-cluster aggregation. These charts conveniently identified the regions in which the differences were less than 10%, between 10% and 30%, and more than 30% for easy to use general guidelines for suitability of the RDG-FA theory in any scattering applications of interest, such as laser-based particulate diagnostics. Various types of aggregate geometry ranging from straight chains ([D.sub.f] [approximately equal to] 1.0) to compact clusters ([D.sub.f] [approximately equal to] 3.0) were also considered for generalization of the findings. For the present computational conditions, the RDG-FA theory yielded accurate predictions to within 10% for [absolute value of m - 1] to approximately 1 or more as long as the primary particles in aggregates were within the Rayleigh scattering limit ([x.sub.p] [less than or equal to] 0.3). Additionally, the effect of fractal dimension on the performance of the RDG-FA was generally found to be insignificant. The results suggested that the RDG-FA theory is a reasonable approximation for optics of a wide range of fractal aggregates, considerably extending its domain of applicability. Key words: Rayleigh-Debye-Gans, optical cross sections, fractal aggregates, laser diagnostics.

A three-dimensional mathematical model based on the numerical solution of the governing equations of mass, momentum, and energy, and transport equations of scalar quantities is presented. The model is applied to a power station boiler of the Portuguese Electricity Utility for which experimental data are available. Predictions of the gas temperature and chemical species concentrations are compared with the measurements. Three different grids were employed to ensure that conclusions are not affected by the grid refinement. It was found that using a combustion model based on the chemical equilibrium assumption, the predicted gas species concentrations are in good agreement with the data and the temperature profiles display the correct trend, although the temperature was underpredicted, especially in the burner region. The influence of the air/fuel ratio and power load were also successfully simulated. The present results reveal the predictive capabilities of the model and its usefulness for design or optimization studies.

The approximate Rayleigh-Debye-Gans (RDG)/fractal-aggregate (FA) theory for the optical properties of soot aggregates is evaluated by using the models developed on the basis of the ICP algorithm. The evaluation emphasizes Guinier regime of the RDG-FA theory. The evaluation reveals that the RDG-FA theory is consistent with the numerical uncertainties model. The scattering properties and refractive indices of the soot are accurately provided by the RDG-FA theory.

The effects of combustion excess-air level, air preheating, and fuel composition on the nitric oxide emissions from an industrial glass furnace are studied through the use of a mathematical model. The mathematical model is based on the solution of the time-averaged form of the governing conservation equations for mass, momentum, energy, and chemical species. The k-epsilon turbulence model is employed for modelling the turbulence fluxes. The flame is modelled as a turbulent diffusion one and the chemical reactions associated with the heat release are assumed to be fast. The fluctuations of scalar properties are accounted for by use of a clipped-Gaussian probability density function. The thermal radiation, playing the dominant role in the heat-transfer process, is modelled using the discrete transfer method. Because of the high temperatures at which industrial glass furnaces operate a considerable amount of thermal NO is formed. The present work presents a model, based on a chemical kinetic approach, to predict the nitric oxide emissions from industrial glass furnaces. The Zeldovich mechanism, retaining the reverse reactions, is incorporated in the model in order to predict the instantaneous NO net formation rate from atmospheric nitrogen. The whole procedure is applied to a cross-fired regenerative furnace. A set of parametric studies is carried out, demonstrating the ability of the model to evaluate the influence of changes in operating conditions on the NO emissions.

Byline: J.E. Ramos, R.A. Pitarma, M.E. Ferreira, M.G. Carvalho Presently, most people are aware that pollution of the external air (atmospheric pollution) is prejudicial to health, but few know that the indoor environment can also have highly noxious effects in human beings. In certain cases indoor pollution even can reach levels higher than about ten times that of external pollution. All over the world there are more and more frequent unpleasant manifestations in relation to indoor Lisboa Codex environment quality. This domain is a new challenge for environmental education, which has a fundamental role in the increment of the quality of life. The main objective of this paper is the relationship among the different environmental parameters, the occupational health and the variety of sensations and states of mind in which satisfaction with the indoor environment is expressed. They are referred to as the several causes of an inadequate indoor environment.