• Fire Science and Engineering
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• v.19 no.4 s.60
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• pp.18-25
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• 2005

In this study, numerical analysis of two-dimensional unsteady natural convection of air in a square enclosure heated from below, was performed as a basic research of fire science. SIMPLE algorithm was used to the pressure term of momentum equations in the numerical analysis. The numerical analysis were studied for the two model cases and two heat conditions, respectively, which are different with insulation of enclosures and position of heat applied. Also, the ceiling temperatures of enclosure were measured to compare the accuracy of numerical analysis, and it is found that the temperature predicted by numerical analysis were agreed well with the measurements. Streamline and isotherm of the each model case were acquired for each time step.

• Fire Science and Engineering
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• v.24 no.6
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• pp.54-60
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• 2010

An experimental study has been carried out to determine the flow rate for a feasible N2 generator to extinguish the fire, and this study analogized the correlations to determine the flow rate for $N_2$ generator considered an Oxygen concentration, protected enclosure, discharging pressure and discharging time. We manufactured simple protected enclosure for analyzing fire-extinguishing performance of the $N_2$ generator. As a $N_2$ gas is exhausted on protected enclosure, a various of Oxygen concentration is measured to analyze fire-extinguishing performance experimentally. The correlations determined as an uncertainty analysis for the Oxygen concentration deviations of the theoretical and experimental value. The analogized correlations is Q = (21 $\times$ V)/($O_2+{\zeta}{\cdot}P$)-V. In case of $300m^3$ protected enclosure, 0.8 MPa discharging pressure and $40m^3$/min $N_2$ flow rate, the Oxygen concentration is decreased below 15% within 3 minutes.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.296-303
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• 2000

Study on natural convection in a rectangular enclosure with a heating point has been studied by numerical and experimental methods. The governing equations were solved by a finite volume method, and for pressure term was used a SIMPLE algorithm. The parameters considered for numerical study are positions and surface temperature of a heating point i.e. Y/H = 0.25. 0.5. 0.75 and $11^{\circ}C{\leq}{\Delta}T{\leq}59^{\circ}C$. The results of isotherms and velocity vectors have been represented for various parameters. Based on the numerical data. the mean Nusselt number in the space can be expressed as a function of Grashof number

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.788-791
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• 2003

Optimal loudspeaker positions are important as much as the control algorithms and hardware performance in the active noise control system. This study is similar to the past researches on the optimal transducer locations but with a far field noise source having a plane wave characteristic and the noise coming through an opening such as a window in the enclosure. An optimization technique called simulated annealing algorithm is used to find a set of optimal loudspeaker positions from a larger possible loudspeaker positions. Loudspeakers are placed on the surface of opening at the wail. Using the measured acoustic transfer impedances and numerical simulations with the optimization technique, optimal positions we identified and compared. When a small number of loudspeakers are used, loudspeaker positions on the opening near the center seems to be the best place, but when a larger number of loudspeakers are used it was difficult to find simple patterns Un the optimal positions.

• Fire Science and Engineering
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• v.11 no.1
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• pp.21-35
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• 1997

The natural convection and combined heat transfer induced by fire in a rectangular enclosure is numerically studied. The model for this numerical analysis is partially opened right wall. The solution procedure includes the standard k-$\varepsilon$ model for turbulent flow and the discrete ordinates method (DOM) is used for the calculation of radiative heat transfer equation. In numerical study, SIMPLE algorithm is applied for fluid flow analysis, and the investigations of combustion gas induced by fire is performed by FAST model of HAZARD I program. In this study, numerical simulation on the combined naturnal convection and radiation is carried out in a partial enclosure filled with absorbed-emitted gray media, but is not considered scattering problem. The streamlines, isothermal lines, average radiation intensity and kinetic energy are compared the results of pure convection with those of the combined convection-radiation, the combined heat transfer. Comparing the results of pure convection with those of the combined convection-radiation, the combined heat transfer analysis shows the stronger circulation than those of the pure convection. Three different locations of heat source are considered to observe the effect of heat source location on the heat transfer phenomena. As the results, the circulation and the heat transfer in the left region from heating block are much more influenced than those in the right region. It is also founded that the radiation effect cannot be neglected in analyzing the building in fire. And as the results of combustion gas analysis from FAST model, it is found that O2 concentration is decreased according to time. While CO and CO2 concentration are rapidly increased in the beginning(about 100sec), but slowly decreased from that time on.

• Solar Energy
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• v.17 no.3
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• pp.67-73
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• 1997

In order to development of a new wall structure type thermal diode for energy saving, the numerical studies have been performed for natural convection across an rectangular enclosure with the various lengthes of the heat source and sink plate. The governing equations for the two-dimensional, laminar, natural convection process in an enclosure are discretized by the control volume approach which insures the conservative characteristics to be satisfied in the calculation domain, and solved by a elliptic SIMPLE algorithm. The momentum and energy equations are coupled through the buoyancy term.

• Architectural research
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• v.15 no.1
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• pp.9-15
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• 2013

Effects of physical attributes of workstation enclosures on the performance of office workers with different difficult levels of office tasks and moods are presented. Performance scores in complex tasks were expected to increase with greater workstation enclosures while those in simple tasks would be the same. Mood ratings were expected to be higher in lower workstation enclosures. Performance of 102 college students on ambient office sounds (45 dBA) with office tasks were measured for 100 minutes under three different workplace enclosures: (1) four foot partitions on two sides; (2) six foot partitions on three sides; and (3) a fully enclosed workstation with eight foot partitions. The tasks were to memorize a paragraph with 130 words (complex task) and to search phone numbers (simple task). The complex task performance in the fully enclosed workstation was increased compared to that in the workstation with four foot partitions (p < 0.001) and to that in the workstation with six foot partitions (p < 0.05). However, occupants in the fully enclosed workstation with office sounds without speech generally gave higher mood ratings. It indicates that closed individual offices may offer important contributions to collaborative work as well as individual productivity. These findings would help design community revise open plan design to increase collaboration among office workers.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.49-55
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• 2009

This paper evaluates performances of a recently developed divergence-free finite element method based on Hermite interpolated stream functions. Velocity bases are derived from Hermite interpolated stream functions to form divergence-free basis functions. These velocity basis functions constitute a solenoidal function space, and the simple gradient of the Hermite functions constitute an irrotational function space. The incompressible Navier-Stokes equation is orthogonally decomposed into a solenoidal and an irrotational parts, and the decoupled Navier-Stokes equations are projected onto their corresponding spaces to form proper variational formulations. To access accuracy and convergence of the present algorithm, three test problems are selected. They are lid-driven cavity flow, flow over a backward-facing step and buoyancy-driven flow within a square enclosure. Hermite interpolation functions from cubic to quintic are chosen to run the test problems. Numerical results are shown. In all cases it has shown that the present method has performed well in accuracies and convergences. Moreover, the present method does not require an upwinding or a stabilized term.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.6
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• pp.653-663
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• 2000

A lot of hazardous wastes are discharged as by-products of working process by industrial development. Hazardous wastes is physical characteristics of difficult destruction at hight temperature. Numerical simulation and combustion experiment performed of dump incinerator for hazardous waste incineration. For the numerical simulation, the SIMPLEST algorithm was used to ensure rapid converge A K-$\varepsilon$ model was incorporate for the enclosure of turbulence flow. Combustion model was used by ESCRS (extended simple chemically reacting system) model available of CHEMKIN thermodynamic data for the source term of species conservation equation or energy equation. Radiation model is used by six flux model. A parametric screening studies was carried out through numerical simulation and experiment. Residence time and concentration in the incinerator was strongly dependent on the parameters of mixture velocity, mixture equilibrium ratio, surrogate velocity and surrogate equilibrium ratio.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.52-57
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• 2007

The control characteristics for radiant panel heating system with automatic thermostatic valves were researched by computer simulation and experiment. The unsteady energy analysis using equivalent R-C circuit method and radiation heat transfer analysis of enclosure analysis method with simple structured rooms was performed. The results of flow rate changes of the simulation study are good fit with the ones of experimental one.