• Fire Science and Engineering
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• v.27 no.3
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• pp.20-29
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• 2013

To investigate numerically the effects of geometry and location of vertical opening on the thermal and chemical fire characteristics in full-scale under-ventilated compartment fires, the ventilation factor ($A\sqrt{h}$) to estimate a theoretical maximum inflow of ambient air and the mass loss rate in a heptane pool fire were fixed for all cases. It was shown that variations in door geometry affected significantly the change in thermal and chemical characteristics inside the compartment. Variations in window location resulted in the complex change in additional fire characteristics including the fire duration time and recirculating flow structure. These results were analyzed in details by the multi-dimensional flow and fire characteristics including the vent flow and fuel/air mixing phenomena.

• Economic and Environmental Geology
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• v.42 no.6
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• pp.609-618
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• 2009

High permeable faults are important geological structures for fluid flow, energy, and solute transport. Therefore, high permeable faults play an important role in the formation of hydrothermal fluid (or hot spring), high heat flow, and hydrothermal ore deposits. We conducted 2-D coupled thermal and hydraulic modeling to examine thermohydraulic behavior in fault zones with various permeabilities and geometric conditions. The results indicate discharge temperature in fault zones increases with increasing fault permeability. In addition, discharge temperature in fault zones is linearly correlated with Peclet number ($R^2=0.98$). If Peclet number is greater than 1, discharge temperature in fault zones can be higher than $32^{\circ}C$. In this case, convection is dominant against conduction for the heat transfer in fault zones.

• Journal of Animal Environmental Science
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• v.18 no.1
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• pp.1-8
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• 2012

The study was conducted to investigate the effects of climate on indoor environment of a swine house with natural. This study was tested in the beef swine stall at Young-in, Kyung-ki do. The test was experimented for the effect of interior environment by the outdoor environment and the interior-pan. The results are as follows. 1. In test 1 ($T_{out}$ : $25.7^{\circ}C$, without fan), an indoor air flow pattern was showed that entered from sidewall winch-curtain to went out of a indoor by the ridge winch-curtain. And the velocity of a section of the center was measured two times as large as the velocity of the floor. It is the acceleration of the velocity by thermal buoyancy. And, the entered air was rapidly dissipated by flow energy. So that in the swain livestock with sidewall winch-curtain is effected by thermal buoyancy. And the air temperature of the indoor was distributed more higher as compared with the outdoor temperature. This result is caused by the sensible heat from swine and the ventilation is restricted. 2. In test 2 (($T_{out}$ : $25.7^{\circ}C$, with fan), the velocity of a section of the center was measured more higher as compared with the test 1. And the variance of air velocity was distributed higher as compared with the test 1. This result is showed dead region of air flow with a fan operation. And, the variance of gas density was distributed lower as compared with the test 1.

• Journal of Energy Engineering
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• v.28 no.4
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• pp.103-110
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• 2019

The domestic innovative power reactor named iPOWER will employ the passive molten corium cooling system(PMCCS) to cool down and stabilize the core melt in the severe accident. The final design concept of the PMCCS is yet to be determined, but the in-vessel retention through external reactor vessel cooling has been also considered as a viable strategy to cope with the severe accident. In this study, the two-phase natural circulation flow established between the reactor vessel and the insulation was simulated using a thermal-hydraulic system code, MARS-KS. The flow path of cooling water was modeled with one-dimensional nodes, and the boundary condition of the heat load from the molten core was defined to estimate the naturally-driven flow rate. The evolution of major thermal-hydraulic parameters were also evaluated, including the temperature and the level of cooling water, the void fraction around the lower head of the reactor vessel, and the heat transfer mode on its external surface.

• Solar Energy
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• v.12 no.3
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• pp.28-36
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• 1992

The performance of a latent heat storage system using a thermosyphon as the heat transfer device between the heat source and the phase change material was investigated experimentally. In order to increase the effective conductivity of the phase change material, layers of copper wire mesh were immersed in the paraffin wax(Sunoco P-116) in such a way that they also may be considered as fins of the thermosyphon. The important results are as follows : (1) The void space of the wire mesh allowed the convection to occur, thus enhanced the performance of the system : (2) The increase of the number of layer of wire mesh increased the conduction heat transfer. However, it also had adverse effect of subduing convective motion of liquid wax : and (3) Overall heat transfer coefficient and thermosyphon conductance increased with the increase of the number of layer of wire mesh, whereas the heat transfer coefficient between the thermosyphon and the wax decreased.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.68-77
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• 2017

High-frequency combustion instability results from a feedback coupling between the unsteady heat release rate and the acoustic waves formed resonantly in the combustion chamber. It can be modeled as thermoacoustic problems with various degrees of the assumptions and simplifications. This paper presents numerical analysis of self-excited combustion instabilities in a variable-length lean-premixed combustor and designs of passive control devices such as baffle and acoustic resonators in a framework of 3-D FEM Helmholtz solver. Nonlinear behaviors such as steep-fronted shock waves and a finite amplitude limit cycle are also investigated with a compressible flow simulation technique.

• Journal of Bio-Environment Control
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• v.9 no.3
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• pp.166-170
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• 2000

Three methods for heat collection, which were the flat solar collector, two fan with radiator, and square pipe method, were studied to sue efficiently solar energy in the three different glasshouses for two years. The flat plate solar collector method was made use of the commercial solar collector with collection area of 24$m^2$, the method of two fans with radiators collected solar energy at the top of the glasshouse. An thermal storage tank was constructed underneath in teach glasshouses. When an area of 1,000$m^2$ was heated to the minimum temperature of 9$^{\circ}C$, the decrease rate of heating fuel for the flat plate solar collector, the fan attached radiator and the square pipe methods were 7%, 19% and 28% respectively. The flat plate solar collector method, which could be heated approximately 40-50$m^2$, was currently used by most of the farmer. Under the condition, the decrease rate of annual heating fuel was 14% which was not better for an economic annual heating fuel. If the fan with radiator method was operated, the use of installation and maintenance were required. So, it could not be good economic efficiency of solar heating. The heating efficiency of the square pipe method was relatively better thant those of the flat plate solar collector or the fan attached radiator. Since the cost of materials and its installation of the use of square pipe method was lower than any other method. However, corrosion of the pipe, greater shade in the greenhouse and strength against the square pipe were problems that should be overcome in the square pipe method.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.1
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• pp.21-29
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• 2002

Hybrid propulsion systems provide many advantages in terms of stable operation and safety. However, classical hybrid rocket motors have lower fuel regression rate and combustion efficiency compared to solid propellant rocket motor. The recent research efforts are focused on the improvement of volume limitation and regression rate in the hybrid rocket engine. The present study has numerically investigated the combustion processes in the hybrid rocket engine. The turbulent combustion is represented by the eddy breakup model and Hiroyasu and Nagle and Strickland-Constable model are used for soot formation and soot oxidation. Radiative heat transfer is modeled by finite volume method. To reduce the uncertainties for convective heat transfer near solid fuel surface having strong blowing effect, the Low Reynolds number $\kappa-\varepsilon$ turbulent model is employed. Based on numerical results, the detailed discussion has been made for the turbulent combustion processes in the vortex hybrid rocket engine.

• Journal of the Korean Institute of Telematics and Electronics
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• v.10 no.3
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• pp.10-22
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• 1973

Recently, nematic and nematic-cholesteric mixtures of substances have been discovered which have stimulated progress in electronics research and industry. In the liquid crystalline state, compounds with nematic mesopheses possess the ability to scatter light, depending on the strength of an applied electric field. The rewaking of interest in this fascinating but long-neglected area has occasioned the introduction of the subjects at the situation of the chemists. Since 1888 year, approximately 2000 compounds have been found to possess the unusual properties of what are commonly referred to as liquid crystals. In this paper, a comprehensive review will not be attempthed here. Nevertheless, some general information necessary to familarize the reader with rather exotic field will facilitate an understanding of the new effect and its application.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.41-42
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• 2006

A study on the combustion characteristics by using Emulsion Fuel in Diesel Engine is performed experimentally. In this paper, the experiments are performed at engine speed 1800rpm, emulsion fuel ratio is 0%, 10%, 20%, and main measured items are specific fuel consumption, pressure, ratio of pressure rise, rate of heat release etc. The obtained conclusions are as follows. 1) Specific fuel consumption increase maximum 19.8% at low load, but is not effected at full load. 2) Ratio of pressure rise and rate of heat release are about the same in the case of 10% and 20% of emulsion fuel ratio. 3) Cylinder Pressure increase 11.7%, ratio of pressure rise increase 60.4% in case of emulsion fuel ratio 20% at full load. 4) Rate of heat release increase 76.9% in case of emulsion fuel ratio 20% at full load.