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The problem of smoke spread through elevator shafts in high rise buildings is analyzed theoretically and numerically in this paper. While experiments and computational fluid dynamics (CFD) models have been used for such exercises, there is a need for fast reduced-order models for such scenarios. Towards this goal, a transient network model called High-rise fire smoke transport and opacity reduced-order model (Fire-STORM) was developed to investigate heat and mass transfer through the elevator shaft during fires. The model numerically solves the coupled set of differential equations of the fire floor in conjunction with the steady state conservation equations of the elevator shaft. The model is validated in two stages. First, the stack effect in a non-fire scenario is analyzed. Pressure differences through exterior doors and elevator doors are compared with experimental data available in the literature and results of a computational fluid dynamics tool. Then, a first-floor fire scenario is considered for the same high-rise building in four different cases which are combinations of different building tightness and ambient temperatures. The results are compared with CFD simulations. For the four different building envelope and ambient thermal conditions, the soot mass fractions and optical visibilities were calculated and compared to CFD predictions. Overall, Fire-STORM is a simple and fast tool to model the evolution of heat and mass transfer in a high-rise building affected by fire. While Fire-STORM is excellent in predicting transient smoke transport for buildings with loose envelopes, it should be used with caution for buildings with tight envelopes since the errors for these cases are relatively high. Despite this, the relative computational speed difference between Fire-STORM and the CFD model highlights the utility of a reduced-order model for firefighter decision making and building control system design. [ABSTRACT FROM AUTHOR]

Compartment fire behaviour under ceiling ventilation was experimentally investigated in a reduced-scale compartment. Different fuels, including methane, propane, N-heptane, ethanol and N-butanol, covering both gas and liquid phase fuels were used in the experiments. Measurements included gas fuel flow rate, pool fire Mass Loss Rate, gas temperature, and gas mole fraction. The fire development processes in ceiling vented compartments were described using energy and species balances. The influence of both the vent size and the fire size on energy and species transfer was examined. A ventilation limited extinction boundary was found for ceiling vented compartments and the general self-extinction processes were represented. The experimental results were plotted using a ventilation parameter ( A v 5 / 4 / Q ̇ f ) derived from balance equations. It was found that this parameter can be used to identify the general ventilation condition in ceiling vented compartments. The oxygen concentration and gas temperature were shown to depend on the ventilation parameter. [ABSTRACT FROM AUTHOR]

Accurate prediction of the radiative heat transfer is of great importance in simulations of combustion processes. To compute the total radiative transfer, it is necessary to integrate the radiative transfer equation (RTE) over the entire wavelength spectrum, a highly time consuming task that still demands the use of gas models. In this work, a finite volume code is used to simulate a steady-state methane-air diffusion flame. The code solves the equations for the conservation of mass, momentum, individual species and energy. The solution also includes a chemistry model for the formation of soot, which is of major importance in the computation of the radiation heat transfer. The radiation exchanges am computed by the discrete ordinates method, and using two different approaches: the gray gas model and the spectral-line based weighted-sum-of-grays-gases (SLW) model. The results for the temperature distribution, gas species concentration, and soot formation am examined with the two different radiation gas models used. [ABSTRACT FROM AUTHOR]

Considers the design of thermal systems which considers boundary conditions for transient radiating enclosures. Description of the problem as a transient inverse boundary condition estimation problem; Details of a proposed solution algorithm; Solution of the inverse problem using the conjugate gradient method.

Presents a study which investigated inverse boundary design for radiation, convection and conductions combined-mode heat transfer. Physical and mathematical formulation; Regularization of the system of equations; Results and discussion.

This paper presents a model‐based study of the impact of implementing radiant (radiation‐dominated) concentric‐tube recuperators on fuel use in an indirectly‐fired industrial heat treating (austenitization/quench hardening) furnace. The recuperators recover some of the waste heat from the burner exhaust to preheat the inlet air to the burners, thus reducing the amount of fuel required for combustion. The novelty of this work consists of developing a physics‐based model of a recuperator, which captures local gas‐to‐surface convective heat transfer and long‐range surface‐to‐surface radiation interactions, and using the model to analyze and optimize the energy use of the furnace. An iterative algorithm is proposed to solve the poorly‐conditioned energy balance equations. The steady‐state system operation is optimized using surrogate models. Extensive simulation studies demonstrate that heat integration reduces fuel consumption significantly without affecting product quality. © 2018 American Institute of Chemical Engineers AIChE J, 65: e16414 2019 [ABSTRACT FROM AUTHOR]

In this paper, we develop an energy-focused model of an industrial roller hearth heat treating furnace. The model represents radiation heat transfer with nonparticipating gas and convective heat transfer. The model computes the exit temperature profile of the treated steel parts and the energy consumption and efficiency of the furnace. We propose a dual iterative numerical scheme to solve the conservation equations and validate its efficacy by simulating the dynamics of the furnace during startup, as well as for steady-state operation. A case study investigates energy consumption within the furnace under temperature control. We first consider a heuristic control strategy using simple linear controllers. A response surface approach is then used to find the optimal set points that minimize energy consumption while ensuring desired part temperature properties are met when processing is complete. With optimized set points, 4.8% less energy per part is required versus the heuristic set points. [ABSTRACT FROM AUTHOR]

Abstract: The increase in temperature of some consumer products, especially electronic devices, results in an increase of semivolatile organic compound (SVOC) emissions. Brominated Flame Retardants (BFRs), such as polybrominated diphenyl ethers (PBDEs), are used in many electronic casings and circuit boards to protect consumers from fires. However, the heat from the internal circuitry increases the SVOC vapor pressure and the material–air partition coefficient decreases, driving SVOC transport out of the substrate and into the indoor environment. In the case of a computer tower, the cooling fan also increases the mass transfer coefficient, further increasing emissions. Such enhanced emissions are a concern since recent studies claim adverse health effects of PBDEs on human health. In this study, a simplified heat and mass transfer model is developed to characterize the combined heat and mass transfer problem for a computer tower in an indoor space to determine the levels of PBDE that would be outgassed. As expected, higher temperatures increase the emission rate of the SVOC and explain one of the transport mechanisms for BFRs into the environment. The emission rate of PBDEs was on the order of tens of nanograms per hour. The concentration of PBDEs in the air increases 40–80% for every 5°C increase inside the computer case, depending on the congener. If these emission rates prove to be toxicologically significant, then models such as the one proposed can be used in risk analysis modeling and to develop mitigation strategies. [Copyright &y& Elsevier]