• 한국가스학회지
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• 제19권1호
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• pp.51-56
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• 2015

To assess downward positions of water spray for the small-scale release of chlorine gas, dispersion coefficients for the Gaussian dispersion model were validated at the small-scale release experiment. And the downwind distances of water spray were assessed with the simulated results. As results, the Gaussian plume model using the Briggs' dispersion coefficient well estimated the dispersed characteristics for small-scale release of chlorine gas. The best adequate downwind position of water spray is the position of the maximum concentration of chlorine at the ground level. And the adequate vertical and horizontal dimensions of water spray consider the maximum width and height of cloud.

• Journal of Advanced Marine Engineering and Technology
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• 제35권7호
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• pp.946-956
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• 2011

The main objectives of this study are to analyze the leaked gas dispersion and quantify the potential overpressures due to vapor cloud explosions in order to identify the most significant contributors to risk by using Computational Fluid Dynamics (CFX & FLACS) for gas fuelled ships. A series of CFD simulations and analyses have been performed for the various gas release scenarios in a closed module, covering different release rates and ventilating methods. This study is specially focused on the LNG FGS (Fuel Gas Supply) system recently developed for the propulsion of VLCC crude oil carriers by shipyards. Most of work presented is discussed on the gas dispersion from leaks in the FGS room, and shows some blast prediction validation examples.

• 한국대기환경학회지
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• 제21권5호
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• pp.537-545
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• 2005

A new dispersion model for dense gas is constructed in the Lagrangian framework. Prediction of concentration by the proposed model is compared with measure data obtained in the experiment conducted in Thorney Island in 1984. Two major effects of dense gas dispersion, gravity slumping and stratification effect, are successfully incorporated into LDM (Lagrangian dense gas model). Entrainment effect is naturally modelled by introducing stochastic dispersion model with the effect of turbulence suppression by stratification. Not only various releasing conditions but also complex terrain can be extended to, although proposed model is appropriate for flat terrain.

• 한국가스학회지
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• 제8권1호
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• pp.13-17
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• 2004

무거운 독성가스의 소규모 누출에 대한 가우시안 연속모델의 적용성을 평가하기 위하여 염소가스의 소규모 누출에서 염소농도의 실험값과 여러 가지 분산계수를 사용한 가우시안 연속모델에 의해 산출한 이론값을 비교하였다. 그 결과, 염소가스 분산은 분산계수와 대기안정도에 따라 상당히 차이가 있었으며, 염소농도는 Briggs의 분산계수와 유효 누출높이를 사용한 가우시안 연속모델에 의해 비교적 정확하게 산출할 수 있었다.

• 한국가스학회지
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• 제8권2호
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• pp.8-14
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• 2004

본 연구는 염소가스의 소규모 연속누출에서 분산특성과 독성영향을 해석하였다. 염소 농도의 실험값과 이론값을 비교한 결과, Briggs의 분산계수와 유효누출높이를 사용한 가우시안 모델이 BM 모델보다 적용성이 우수하였다. 또한 가우시안 모델에 의해 염소농도를 산출하고 해석한 결과, 염소분산은 누출속도 보다 대기안정도와 바람속도에 크게 영향을 받으며, 독성영향은 염소분산에 미치는 매개변수의 영향과 유사한 경향을 나타내었다. 이때, 여러 독성기준에 의해 산출된 피해범위로부터 인명을 보호하기 위한 위험지역을 파악할 수 있었다.

• 에너지공학
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• 제24권4호
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• pp.117-123
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• 2015

최근 산업체에서는 성분을 알 수 없거나, 데이터베이스를 보유하지 않는 가스들의 사용이 증가하고 있는 추세이다. 가스들의 사용양이 증가함에 따라 확산범위와 속도를 예측 할 수 있는 소프트웨어들이 사용의 중요성이 증가하고 있는데, 이들 소프트웨어들은 기존에 보유하고 있는 가스들의 자료에 의존하여 확산거리 및 속도를 예측하기 때문에 새로운 가스들이 확산거리(속도)를 예측하기는 매우 어려운 실정이다. 따라서 본 연구에서는 가스의 확산 및 폭발을 예측할 수 있는 FLACS S/W 및 등가가스를 이용하여 불특정한 가스들의 확산을 예측할 수 있는 방법을 제시하고자 한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.899-904
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• 2003

A new model for dense gas dispersion is formulated within the Lagrangian framework. In several accidental released situations, denser-than-air vapour clouds are formed which exhibit dispersion behavior markedly different from that observed for passive atmospheric pollutants. For relevant prediction of dense gas dispersion, the gravity and entrainment effects need to implemented. The model deals with negative buoyancy which is affected by gravity. Also, the model is subjected to entrainment. The mean downward motion of each particle was accounted for by considering the Langevin equation with buoyancy correction term.

• 한국전기전자재료학회논문지
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• 제30권9호
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• pp.589-595
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• 2017

MOS-FET structured gas sensors were manufactured using MWCNTs for application as NOx gas sensors. As the gas sensors need to be heated to facilitate desorption of the gas molecules, heat dispersion plays a key role in boosting the degree of uniformity of molecular desorption. We report the desorption of gas molecules from the sensor at $150^{\circ}C$ for different sensor electrode gaps (30, 60, and $90{\mu}m$). The COMSOL analysis program was used to verify the process of heat dispersion. For heat analysis, structure of FET gas sensor modeling was proceeded. In addition, a property value of the material was used for two-dimensional modeling. To ascertain the degree of heat dispersion by FEM, the governing equations were presented as partial differential equations. The heat analysis revealed that although a large electrode gap is advantageous for effective gas adsorption, consideration of the heat dispersion gradient indicated that the optimal electrode gap for the sensor is $60{\mu}m$.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.353-363
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• 2019

This paper presents a comprehensive simulation and assessment of gas dispersion above sea from a subsea release using a Computational Fluid Dynamics (CFD) approach. A 3D CFD model is established to evaluate the behavior of flammable gas above sea, and a jack-up drilling platform is included to illustrate the effect of flammable gas cloud on surface vessels. The simulations include a matrix of scenarios for different surface release rates, distances between surface gas pool and offshore platform, and wind speeds. Based on the established model, the development process of flammable gas cloud above sea is predicted, and the dangerous area generated on offshore platform is assessed. Additionally, the effect of some critical factors on flammable gas dispersion behavior is analyzed. The simulations produce some useful outputs including the detailed parameters of flammable gas cloud and the dangerous area on offshore platform, which are expected to give an educational reference for conducting a prior risk assessment and contingency planning.

• Safety and Health at Work
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• 제1권1호
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• pp.98-101
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• 2010

This study explored the health hazard of those exposed to methylene chloride by assessing its atmospheric concentration when a tear gas mixture was aerially dispersed. The concentration of methylene chloride ranged from 311.1-980.3 ppm (geometric mean, 555.8 ppm), 30 seconds after the dispersion started. However, the concentration fell rapidly to below 10 ppm after dispersion was completed. The concentration during the dispersion did not surpass the National Institute for Occupational Safety and Health 'immediately dangerous to life or health' value of 2,300 ppm, but did exceed the American Conference of Governmental Industrial Hygienists excursion limit of 250 ppm. Since methylene chloride is highly volatile (vapor pressure, 349 mmHg at $20^{\circ}C$), the post-dispersion atmospheric concentration can rise instantaneously. Moreover, the o-chlorobenzylidenemalononitrile formulation of tear gas (CS gas) is an acute upper respiratory tract irritant. Therefore, tear gas mixtures should be handled with delicate care.