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김태형 ( Tae Hyeung Kim ),하현철 ( Hyun Chul Ha ),정춘화 ( Chun Hwa Jeoung ),서정윤 ( Jeoung Yoon Seo ),박승욱 ( Cheng Xu Piao ),양준호 ( Jun Ho Yang ),이효우 ( Xiao Yu Li ) 한국산업위생학회 2007 한국산업보건학회지 Vol.17 No.3
18 Local exhaust ventilation systems in 10 melting companies located in an industrial complex were tested to know the status of maintenance. Test items were fan flowrates, fan static pressures, rotational speeds and differential pressures of bag filters. Only 22% of the tested fans has more than 80% flowrate efficiency. 44% of the fans has lower than 60% efficiency. The performance of the fans are not in a good status. For the fans with lower than 60% efficiency, the analysis shows that the lower flowrate might be caused by the degradation of fan performance. On the other hand, for the fan s with higher than 60% efficiency, the main cause of flowrate reduction might be too much pressure losses due to clogging of filter bags. The degradation of fans usually lead the reduction of hood capture efficiency, resulting in the increase of contaminant concentrations in workplace. To keep fans in good status, self inspections should be periodically conducted. This inspection should include the measurements of flowrate and pressures. The most important thing to be performed is the initial test of local exhaust ventilation system because the initial test data should be used to know the level of system degradation.
방해기류 존재시 추적자 가스법을 이용한 푸쉬풀 후드 효율 평가
김태형 ( Tae Hyeung Kim ),하현철 ( Hyun Chul Ha ),강호경 ( Ho Gyung Kang ) 한국산업위생학회 2006 한국산업보건학회지 Vol.16 No.3
A push pull hood system is frequently applied to control contaminants evaporated from an open surface tank. Efficiency of push pull hood system is affected by various parameters, such as, cross draft, vessel shapes, tank surface area, liquid temperature. A previous work assisted by flow visualization technique qualitatively showed that a strong cross draft blown from the pull hood to push slot could destroy a stable wall-jet on the surface of tank, resulting in the abrupt escape of smoke from the surface. In this study, the tracer gas method was applied to determine the effect of cross-draft on the capture efficiency qualitatively. A new concept of capture efficiency was introduced, that is, linear efficiency. This can be determined by measuring the mass of tracer gas in the duct of pull hood while the linear tracer source is in between push slot and pull hood. By traversing the linear tracer source from the push slot to the pull hood, it can be found where the contaminant is escaped from the tank. Total capture efficiency can be determined by averaging the linear efficiencies. Under the condition of cross-draft velocities of 0, 0.4, 0.75, 1.05 and 1.47m/s, total capture efficiencies were measured as 97.6, 95.4, 94.6, 92.7 and 70.5% respectively. The abrupt reduction of efficiency with cross-draft velocity of 1.47m/s was due to the destruction of tank surface wall-jet by the countercurrent cross-draft. The same phenomenon was observed in the previous flow visualization study. As an alternative to overcome this abrupt efficiency drop, the 20% increase of hood flow rates was tested, resulting in 20% efficiency increase.
카트리지 필터 여과집진기 충격기류시스템의 최적탈진조건에 관한 실험적 연구
박승욱 ( Cheng Xu Piao ),하현철 ( Hyun Chul Ha ),김성준 ( Sung Joon Kim ) 한국산업보건학회 2015 한국산업보건학회지 Vol.25 No.4
Objectives: Many types of dust collector are used for industrial ventilation, with the most common types being the cylinder bag filter system, rectangular bag filter system and cylinder type cartridge filter system. The cylinder type cartridge bag filter, which has more filtering area than other types of bag filter, can increase the pulse time and extend the useful lifeof the filter. This can save operational costs and installation area. Materials: This study used cylinder type cartridge bag filter equipment and tested the impact of vibration level and filter pressure with different pulse jet cleaning conditions. The final, cleaning efficiency was calculated through input dust mass and cleaning dust mass Conclusions: Two optimum cleaning condition groups were found. The first condition group was 3 kgf/cm2 pulse pressure, 15 cm pulse distance, 0.2 s pulse time with an H-10 type nozzle. The second condition group was 3 kgf/cm2 pulse pressure, 15 cm pulse distance, 0.3 s pulse time with an H-10 type nozzle.
전산유체역학을 이용한 용접흄농도 간접적 예측가능성 연구
박승욱,김태형,서정윤,허영빈,임정호,강대웅,하현철,Piao, Cheng Xu,Kim, Tae Hyeung,Seo, Jeoung Yoon,He, Rong Bin,Lim, Jung Ho,Kang, Dae Woong,Ha, Hyun Chul 한국산업보건학회 2009 한국산업보건학회지 Vol.19 No.4
There are various methods for welding fume control. These methods can be divided into local exhaust system, general ventilation system and integrated control system. With the general ventilation system, we should have a good prediction tool for testing various appropriate control options. But, until now there are not many studies about how to predict the welding fume concentrations. Especially, the prediction of welding fume concentration is not a very easy task because welding fume is the particulate matters. In this study, we tried to measure $CO_2$ concentrations and welding fume concentrations in a small single room with a small ventilation opening. Using commercially available CFD (Computational Fluid Dynamics) software, we tried to predict $CO_2$ concentrations under the exactly same conditions. Then, we tried to compare the numerical $CO_2concentrations$ with the experimental results to know whether we could predict $CO_2$ concentrations. Then we tried to compare $CO_2$ concentrations with experimental welding fume concentrations to know whether we can use the numerical $CO_2concentrations$ to predict the welding fume concentration indirectly.