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화재시뮬레이션에 의한 보 인접 스프링클러헤드의 동작시간 분석에 관한 연구
최대현(Choi, Daehyun),이재문(Lee, Jaemoon),민세홍(Min, Sehong) 한국방재학회 2020 한국방재학회논문집 Vol.20 No.1
본 연구에서는 국가화재정보시스템의 화재통계 분석을 통해 차량화재의 위험성에 대하여 파악하였으며, 화재발생시 초기소화의가장 중요한 역할을 하는 스프링클러 소화설비의 동작에 대한 분석을 수행했다. 시뮬레이션은 NFSC 103에서 보와 가까운스프링클러헤드 설치기준에 대하여 현행기준과 개정지침을 구분하여 시나리오를 구성하였으며, 추가적으로 주차장 화재발생시FAN을 기동할 경우 스프링클러헤드의 동작시간에 대해 분석했다. 시뮬레이션 프로그램으로 FDS를 사용하였으며, 시뮬레이션결과 개정지침을 적용할 경우 화원 직상부의 스프링클러헤드가 현행기준에 대한 결과와 비교하여 약 1분 먼저 동작하여개정지침의 적용이 적절함을 확인하였다. 화재발생시 감지기에 의해 FAN을 동작시킬 경우 직상부 스프링클러헤드는 FAN이동작하지 않았을 때의 시뮬레이션 결과와 비교하여 2분 이상 동작이 지연됨을 확인하였다. If the revised guidelines were applied to thesimulation, the sprinkler head located directly above the fire source was activated approximately 1 minin advance compared to the sprinkler head operating under current standards. Therefore, it was found that the revised guidelines were suitable and aided in early fire extinguishing attempts. In the case where a fan was operated along with the detector, during the outbreak of a fire, it was found that the operation of the sprinkler head located directly above the fire was delayed by two or more minutes compared to the simulated case where no fan was operated.
최대현(Daehyun Choi),박형민(Hyungmin Park) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
In this study, flow around an in-line array of spheres has been investigated, focusing on the interaction between the sphere wakes. In a circulating water tunnel, 12.7 mm-diameter steel balls have been aligned along the direction of flow, with each sphere held by a thin steel wire. Considered Reynolds number for a single sphere is 1,000 and the number of spheres is increased up to five with varying the distance between them, as well. PIV and dye visualization has been used in order to measure the velocity fields and vortex shedding frequency. It is found that hairpin vortices are periodically detached from each sphere, move to downstream and undergo active interaction with other sphere’s wake. For the case of an array with two spheres, three distinctive flow structures have been identified depending on the distance between spheres. When the number of the spheres added, we find that there exists a specific trend on the Strouhal number. Also, the time-averaged velocity field and turbulence intensity in the wake will be discussed depending on the considered conditions.
듀얼노즐에서 나오는 기체 제트유동과 물줄기와의 상호작용
최대현(Daehyun Choi),이주호(Juho Lee),박은수(Eunsoo Park),변정원(Jungwon Byun),박형민(Hyungmin Park) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
The liquid atomization through a gas-phase jet has various applications of coating, cooling, and material processing. Previously, most studies used a single-nozzle, but multi-stage configuration is considered to overcome its limitations. In this study, we experimentally study jet flows through two annular nozzles (upper and lower). To optimize the jet flow, we vary parameters like the pressure of each nozzle, the angle of the lower nozzle, distance between upper and lower nozzles, and so on. For each configuration, the single-phase gas jet flow is measured with a particle image velocimetry, which is classified depending on the turbulent kinetic energy, and the mean streamwise momentum. Also, we perform the tests of water-glycerin mixture atomization and measure the size distribution of atomized droplets, while varying the mass flow rate and the viscosity of liquid. It is found that the higher upper nozzle pressure is required to suppress the back flow, and the atomized droplet size can be controlled. Finally, we try to propose a model for predicting the size of atomized particles according to dual-nozzle configurations.
이수재(Lee, Soojae),최대현(Choi, Daehyun),전희권(Jun, Heekwon) 한국신재생에너지학회 2010 한국신재생에너지학회 학술대회논문집 Vol.2010 No.06
Fuel Cell cogeneration system is a promising technology for generating electricity and heat with high efficiency of low pollutant emission. We have been developed 5kW class fuel cell cogeneration system for commercial and residential application. The fuel processor is a crucial part of producing hydrogen from the fossil fuels such as LNG and LPG. The 5kW class high efficiency fuel processor consists of steam reformer, CO shift converter, CO preferential oxidation(PrOx) reactor, burner and heat exchanger. The one-stage CO shift converter process using a metal oxide catalyst was adopted. The efficiency of 5 kW class fuel processor shows 75% based on LHV. In addition, for the purpose of continuous operation with load fluctuations in the commercial system for residential use, load change of fuel processor was tested. Efficiency of 30%, 50%, 70% and 100% load shows 75%, 75%, 73% and 72%(LHV), respectively. Also, during the load change conditions, the product gas composition was stable and the outlet CO concentration was below 5 ppm. The Fuel processor operation was carried out in residential fuel cell cogeneration system with fuel cell stack under dynamic conditions. The 5kW class fuel processor have been evaluated for long-term durability and reliability test including with improvement in optimal operation logic.