• Journal of the Korean Society of Safety
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• v.30 no.4
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• pp.64-72
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• 2015

The purpose of this study is to study the safety of a small LPG storage tank with a capacity less than 3 ton when it is exposed to an external fire. First, simulation studies were carried out using ASPEN Plus and PHAST to demonstrate that overpressurization in the tank can be relieved by discharging the LPG through an adequately sized safety valve, but the release may lead to the secondary risk of fire and explosion around the tank. Next, the temporal variations of the temperatures of the lading and tank wall were obtained using AFFTAC, which showed that the tank wall adjacent to the vapor space could be overheated in about 11 min to such a point that the weakened strength might cause a rupture of the tank and subsequent BLEVE. The consequences of the BLEVE were estimated using PHAST. Finally, several practical measures for preventing the hazards of overheating were suggested, including an anti-explosion device, sprinkling system, insulation, heat-proof coating, and enhanced safety factor for tank fabrication. The effectiveness of these measures were examined by simulations using AFFTAC and ASPEN Plus.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.7
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• pp.659-668
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• 2005

The thermal performances of glass evacuated tube solar collectors are numerically investigated. Four different shapes of solar collectors are considered and the performances of these solar collectors are numerically investigated. Dealing with only collecting tube, the effects of not only the shape of the absorber tube but also the incidence angle of solar irradiation on the thermal performance of the collector are studied because the energy obtained by the absorber can be varied according to the incidence angle of solar radiation. However, the solar irradiation consists of the beam radiation as well as the diffuse radiation. Also, in actual system, the interference of solar irradiation and heat transfer interaction between the tubes should be considered. Therefore, this study considered these effects is carried out experimentally and numerically. The accuracy of the numerical model is verified by experiments. The result shows that the thermal performance of the absorber used a plate fin and U-tube is about $25\%$ better than those of the other models.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.71-75
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• 2003

The conduit fer superconducting cable is welded and plastically deformed during the jacketing process to make the CICC (Cable-in-Conduit-Conductors) fer a fusion magnet. The jacketing process of KSTAR (Korea Superconducting Tokamak Advanced Research) conductors is composed of several sequential steps such as rounding, welding, sizing, and square-rolling. Since the welded zone in Incoloy 908 conduit is brittle and easy to have flaws, there may be a possibility of stress corrosion cracking during the heat treatment of coil when both the induced tensile residual stress and the concentration of oxygen in the furnace are sufficiently high. The steps of the jacketing process were simulated using the finite element method of the commercial ABAQUS code, and the stress distribution in the conduit in each step was calculated, respectively. Furthermore, the variations of residual welding stresses through the steps of the jacketing process were calculated and analyzed to anticipate the possibility of the stress corrosion cracking in the conduit. The concentrated high tensile residual welding stresses along the welding bead decrease by the plastic deformation of the following sizing step. The distribution in residual stresses in the conductor for magnet coil is mainly governed by the last step of square-rolling.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.3
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• pp.282-290
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• 2013

A primary air pollutant as an indicator of air quality released from incomplete combustion is Carbon monoxide. A study of the distributions of CO concentration with no heat source in a tunnel model closed at left end side is simulated with a commercial CFD code. The tunnel model is used to investigate the CO concentration distributions at three Reynolds numbers of 990, 1970, and 3290. which are computed by the inlet velocities of 0.3, 0.6 and 1.0 m/s. The CFD predictive approaches can be useful for a better design to analyze the distributions of CO concentrations. In the case of the tunnel model closed at left end side alone, the concentration changes of x/H=-5 and -2.5 have the similar laminar characteristics like the case of the tunnel model closed at both end sides expecially at low values of Reynolds number. Irregular average CO concentration variations at Re=1790 are considered that the transition from laminar to turbulent flow occurs even in three different tunnel models.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.8
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• pp.1073-1082
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• 1998

When thermal diffusivity is measured by laser flash method, the thermal diffusivity call be calculated front the assumption of the uniformly heated whole surface of the specimen. It has been known that the approximate 5% error is made by the non-uniform energy distribution on the specimen surface of laser pulse heat source. In this study, to obtain the highly-uniformed laser beam, which has both the low non-uniform heating error from non-uniform laser beam and the energy loss, research was carried out on no transmitting loss by optical fiber and high repetitions. In addition, heating error and thermal diffusivity were measured as the measuring positions were varied and compared with the results using the uniform and the non-uniform laser beams. In addition, dole to using the uniformalized laser beam, the whole surface of the specimen was heated uniformly and as a result, it was the thought that this was very effective to reduce the variations of the errors of the thermal diffusivity as the measuring positions were varied. It can be obtained that when the thermal diffusivity of POCO-AXM-5Q1 of SRM in NBS was measured with both the uniform and the non-uniform laser beams, the dispersion error of the former was from 2 to 2.5%, which was more improved than that of the latter.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.172-178
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• 1990

To predict the qualitative performance characteristics of Stirling Engines, an analytical approach to the Ideal Adiabatic Model set up by Urieli et al. has been treated. First, volume variations of both the expansion and the compression cylinders are approximated to piecewise linear function of the crank angle, which make it possible to specify the mass flow direction of each cylinder a priori to solve a set of basic equation. In consequences, an engine cycle can be considered as a combination of 4-type fundamental process. For each process, pressure is obtained as a solution of the algebraic equation. Application of the cyclic steady condition to the whole cycle completes the analysis. Further investigations result in analytical expressions for cyclic heat and work in terms of dependent variables determined from the pressure. The results are expected useful in establishing the preliminary design conditions of Stirling Engines.

• Journal of Environmental Science International
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• v.10 no.5
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• pp.337-342
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• 2001

The Rondonia Boundary Layer Experiment (RBLE-II) was conceived to collect data the atmospheric boundary layer over two representative surface in the Amazon region of Brazil; tropical forest and a deforested, pasture area. The present study deals with the observations of atmospheric boundary layer growth and decay. Although the atmospheric boundary layer measurements made in RBLE-II were not made simultaneously over the two different surface types, some insights can be gained from analysing and comparing with their structure. The greater depth of the nocturnal boundary layer at the forest site may be due to influence of mechanical turbulence. The pasture site is aerodynamically smoother and so the downward turbulent diffusion will be much pasture than over the forest. The development of the convective boundary layer is stronger over the pasture than over the forest. The influence of the sensible heat flux is important but may be not enough to explain the difference completely. It seems that energy advection may occur from the wet and colder(forest) to the dry and warmer area(pasture), rapidly breaking up the nocturnal inversion. Such advection can explain the abrupt growth of the convective boundary layer at the pasture site during the early morning.

• Journal of Microbiology and Biotechnology
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• v.10 no.4
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• pp.507-513
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• 2000

A bacteriocin-producing organism, Enterococcus sp. T7, was isolated from human fecal samples. Bacteriocin T7, named tentatively as the bacteriocin, was produced by Enterococcus sp. T7 and it inhibited some strains of Lactobacillus. Staphylococcus, Enterococcus, and Streptococcus, but not all the lactococci and gram-negative bacteria tested. Bacteriocin T7 inhibited the growth of Listeria monocytogenes Scott A, but the degree of inhibition was less than those for other sensitive gram-positive vacteria. Bacteriocin T7 in MRS broth started to produce at the middle of the exponential growth phase and the inhibitory activity reached its maximum level during the stationary growth phase. Bacteriocin T7 was stable against heat treatments, pH variations (pH 2-10), and exposure to organic solvents. The molecular weight of bacteriocin T7 was estimated to be 6.500 Da by SDS-PAGe. All these facts, including physico-chemical stabilities, small molecular size, and inhibition of Kisteria monocytogenes, indicate that bacteriocin T7 is likely to be a member of the class IIa bacteriocins.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.4
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• pp.70-83
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• 1997

We made a selection of engine operating conditions in the natural aspiration type diesel engine as load and speed. The effects on the power, smoke emission and cylinder pressure characteristics of these variations in operating conditions were observed experimentally. Also, the smoke emission was predicted by using the Arrhenius equation and empirical equation of the smoke emission was made. At the same time, the correlations, between the combustion and smoke emission characteristic were examined. From the above results, it is clear that to prevent power dropping and to decrease exhaust fume whin the conditions are changed, one should improve the intake system. To do this, the best way is to lower the air-fuel mixing ratio. We found that the parameters of the indicated mean effective pressure, maximum pressure and its location and combustion duration, etc. change the motion in accordance with the conditions described above. Also, we found that the variation of the pressure cycle comes from an amplified variation of the early part of process. From the analysis of comparing combustion and exhaust fume, the exhaust fume is produced at the latter time of combustion and decreased when the combustion ratio is higher. Also, we developed a special formula which can predict the exhaust fume value according to the engine load and speed.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.3
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• pp.358-364
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• 2016

The combustion and exhaust emission characteristics in a spark ignition (SI) engine with various test fuels (bioethanol - gasoline blends) and air-fuel ratio were investigated in this research. To investigate the influence of the excess air ratio and ethanol blends on the combustion characteristics such as the cylinder pressure, rate of heat release (ROHR), and fuel consumption rate were analyzed. In addition, the reduction effects of exhaust emissions such as carbon monoxide (CO), unburned hydrocarbon (HC), and oxides of nitrogen (NOx) were compared with those of neat gasoline fuel under the various excess-air ratios. The results showed that the peak combustion pressures and the ROHR of bioethanol fuel cases were slightly higher than those of gasoline fuel at all test ranges and fuel ratio. As compared with gasoline fuel (G100) at each given excess air ratio, BSFC of bio-ethanol was increased. The CO, HC, NOx emissions of bio-ethanol blends were lower than those of gasoline fuel under overall experimental conditions.