• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.2
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• pp.144-150
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• 2006

The purpose of this study is to predict outlet temperature and humidity through underground pit for the reduction of cooling load and heating load. Commonly, the underground temperature is lower than outdoor in summer but the reverse happens in winter. When the outdoor average air temperature is $25.7^{\circ}C$ during cooling periods, the average outlet air temperature through underground pit is $23.6^{\circ}C$ with 3 m-depth and 60m-length and is $22.2^{\circ}C$ with 3 m-depth and 150 m-length. When the outdoor average air temperature is $4.9^{\circ}C$ during heating periods, the average outlet air temperature through underground pit is $7.7^{\circ}C$ with 3m-depth and 60 m-length and is $10.8^{\circ}C$ with 3 m-depth and 150 m-length. The outlet air temperature is affected by more length than depth of underground pit. The diffusion ratio of outdoor humidity is $-7.7\times10^{-8}kg/s$ in cooling periods and $9.29\times10^{-7}kg/s$ in heating periods.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.281-288
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• 2004

Combustion using oxygen enriched air is an energy saving technology that can increase thermal efficiency by improving the burning rate and by increasing the flame temperature. Flame figures, OH radical intensities, temperature distributions and emissions concentration were examined according to oxygen enriched concentration(OEC) in a turbulent diffusion flat flame. As long as the oxygen enriched concentration was increased, the length and volume of the flat flame was decreased while OH radical intensity was raised and the flame temperature was increased. However, RMS of the fluctuating temperature was decreased, and more homogeneous temperature field was formed. Thermal NO also was increased with increase of oxygen enriched concentration, but CO was decreased due to the increase of chemical reaction rate.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.1
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• pp.29-38
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• 1994

Particle contamination into and out of a cavity-cylindrical cavities with aspect ratios(width/depth) less than, equal to 1 and langer than 1, and also three dianensional T's attached to a cylindrical flow tube was studied numerically, using a finite difference method. In the process of unsteady particle diffusion, the particles contained in a concentration boundary layer near the tube wall plays an important role in the initial stage, after which a quasi-steady concentration profile is developed inside the cavity, resulting in an exponential change of concentration with time. Average concentration and its rate of change are observed to be closely correlated by a power law function in terms of Reynolds number and the logarithm of Schmidt number. Effects of the three parameters-Re, Sc, and aspect ratio-are analysed and well explained.

• Journal of Mechanical Science and Technology
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• v.18 no.2
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• pp.325-334
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• 2004

Computational experiments on fundamental un stretched laminar burning velocities and flame response to stretch (represented by the Markstein number) of hydrogen-air flames at high temperatures and pressures were conducted in order to understand the dynamics of the flames including hydrogen as an attractive energy carrier in conditions encountered in practical applications such as internal combustion engines. Outwardly propagating spherical premixed flames were considered for a fuel-equivalence ratio of 0.6, pressures of 5 to 50 atm, and temperatures of 298 to 1000 K. For these conditions, ratios of unstretched-to-stretched laminar burning velocities varied linearly with flame stretch (represented by the Karlovitz number), similar to the flames at normal temperature and normal to moderately elevated pressures, implying that the "local conditions" hypothesis can be extended to the practical conditions. Increasing temperatures tended to reduce tendencies toward preferential-diffusion instability behavior (increasing the Markstein number) whereas increasing pressures tended to increase tendencies toward preferential-diffusion instability behavior (decreasing the Markstein number).

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.267-268
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• 2012

Soot formation and oxidation characteristics of air-diluted propane diffusion flames have been experimentally investigated under the elevated pressure conditions. PAH concentrations showed more pressure sensitive behavior comparing to soot volume fractions. The flame/soot temperatures in soot oxidation region were obtained using the MOLLIP technique. Under the complete soot oxidation environment, the flame/soot temperature is increased with pressure. The increased temperature could accelerate the soot oxidation process and then exothermic oxidation reaction, in turn, could further raise the flame/soot temperature, which would result in the enhancement of soot oxidation process.

• Journal of the Korean Society of Combustion
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• v.7 no.2
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• pp.24-33
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• 2002

The morphology of deposits on $15-{\mu}m$ thin SiC filaments has been investigated with SEM in a co-flowing, propane/air laminar diffusion flame. The average size of mature soot particles deposited in the luminous flame edge is strongly dependent on their axial position in a typical heavily sooting flame. The surface growth of liquid-phase PAHs molecules and the transition to soots from fully-developed precursors could be observed in the radial deposition of the flame. Two sooting regimes were found: one is the transition from the condensed-phase precursors; the other is the aggregation of smaller soot particles (or chains of them) to be carried along particle path lines. In the high temperature flame edge outside the soot luminous flame surface, the very thin fiber-like structures, which are about 10 nm thick, were found.

• Journal of the Korean Society of Combustion
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• v.8 no.3
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• pp.1-7
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• 2003

Combustion using oxygen enriched air is an energy saving technology that can increase thermal efficiency by the improvement of burning rate and by the high temperature flame. Flame figures, OH radical intensities, temperature distributions and emission concentrations were measured according to oxygen enriched concentration and swirl number in a turbulent diffusion flat flame. It appeared that flame figure became flat and NO concentration decreased with increase of swirl number, and that the flame temperature increased high with increase of oxygen enriched concentration. In particular, it was most significant between oxygen concentration $40{\sim}60%$.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.149-155
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• 2002

A promising new approach to achieve low pollutants emission and improvement of flame stabilities is tested experimentally using a hybrid cyclone jet combustor employing both premixed and diffusion combustion mode, Three kind of nozzles are used for LNG(Liquified Natural Gas) as a fuel. The combustor is operated by two method, One is ATI(Air Tangential Injection) mode, generated swirl flow by air as general swirl combustor, and the other is PTI(Premixed gas Tangential Injection) mode, The PTI mode consists of diffusion flame of axial direction and premixed cyclone flame of tangential direction in order to stabilized the diffusion flame. The results showed that the stable region of the PTI mode is more larger than the ATI mode. In addition, the reduction of NOx emission in PTI mode, as compared with that for the ATI mode is at least 50% in stable region. Also, even using the low calorific fuel as $CO_2$-blended gas, the cyclone jet combustor has high performance of flame stability.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.9-14
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• 2005

The purpose of this study is to predict VOCs emission rates from multi-layers materials, which are composed of single-layer materials having various VOCs emission rates, by using effective diffusion coefficients of the single-layer materials. The study was consisted of two parts; the one is the prediction of VOCs emission rates from multi-layer materials through numerical methods. The other is the measurement of VOCs emissions rates of wall composite and floor composite in Mock-up rooms for comparing the prediction and the experiments' values. The results of the study show that the short-term VOCs emission rates of multi-layers materials can be predicted from the effective diffusion coefficients of single materials in odor accuracy.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.9
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• pp.878-887
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• 2001

Experimental investigation has been carried out to examine the operating characteristics of a bubble pump for diffusion absorption refrigerator. The effects of heat input and delivery height on generation rate of refrigerant vapor and circulation rate of solution have been investigated. as a result heat input and delivery height increase, circulation rate of solution increases. And the smaller the tube diameter, the larger the circulation rate of solution. Pumping ratio increases to a critical point and then decrease with the increase of heat input, and it increases with the increase in delivery height. In this paper, Marcus's analytical theory was also examined. It was found that the Marcus\`s analytical theory of a bubble pump was not appropriate for a bubble pump using ammonia aqueous solution as a working fluid.