• 대한기계학회논문집B
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• 제20권9호
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• pp.2924-2932
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• 1996

As the environmental pollution can be greatly reduced and the waste heat can be also recovered through a combustion of municipal solid waste, the incineration begins to be highlighted recently in our country. But it is very difficult to be operated with constant combustion conditions for a long time as the domestic waste is composed of various components, contains a large percentage of water, and has a low heating value. Therefore, the cold flow test and partial hot flow test were conducted in the incinerator by use of injection angles of a secondary air affecting fluid flow as the first action to maintain the optimum combustion conditions. A model to a scale of 1:10 was designed and manufactured through the similarity of model and prototype flows. Velocities and temperatures were measured through the experiment. From the results, fluid flows of secondary air obtained from partial hot flow test correspond almost well with those of main flow obtained from cold flow test. Consequently, injection angles of secondary air are proved to affect main flow decisively.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권11호
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• pp.519-526
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• 2005

This paper presents computer simulation results for developing new type of SF$_{6}$ Circuit Breaker in terms of cold gas flow after small current interruption. This cold gas flows down a nozzle into the chamber of a circuit breaker. There are many difficult problems in analyzing the gas flow due to complex geometry, moving boundary, shock wave and so on. When predicting the dielectric capability of a gas circuit breaker after interruption, the gas pressure and density distributions due to the cold gas must be considered in addition to the electrical field imposed across the gas. A self-coded computational fluid dynamics (CFD) program is used for the simulation of cold gas flow in order to evaluate the electrical field characteristic across open contacts and transient characteristics of insulations after small current interruption.

• 대한핵의학회지
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• 제21권2호
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• pp.183-190
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• 1987

In Raynaud's phenomenon, the authors measured finger blood flow after ice water exposure by analyzing the time activity curve of radionuclide angiography on both hands. The results were as follows: 1) The digital blood flow did not decrease after ice water exposure in normal subjects. 2) In the patients with Raynaud's phenomenon, there were two groups: the one had decreased digital blood flow after cold exposure, and the other had paradoxically increased digital blood flow after cold exposure. 3) There was no difference in the digital blood flow of hand in room temperature between the normal and the patients with reduced digital blood flow after cold exposure, but the digital blood flow of the hand in room temperature was markedly reduced in the patients with paradoxically increased flow after cold exposure. 4) In the static image the difference was not significant in comparision with the dynamic study, because it represents pooling of the blood in the vein rather than flow. 5) After the treatment with nifedipine, the digital blood flow increased. In conclusion, the radionuclide angiography was useful in measuring the digital blood flow in Raynaud's phenomenon, and further studies with various drugs is expected.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.181-185
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• 2010

고체로켓모터 추진제 그레인의 핀-슬롯 표면에서의 연소로 인해 생성된 고온, 고압의 연소가스는 그레인 핀-슬롯 및 내삽노즐을 통해 외부로 방출되면서 형성되는 유동은 매우 복잡하고 다양한 형태를 가진다. 핀-슬롯형 그레인 및 내삽노즐을 가지는 고체로켓모터의 2D, 3D 스케일모델에 대한 공기유동 모사시험을 수행하였으며, 회전력 발생 등과 같은 내부유동발생 메커니즘을 규명할 수 있는 효과적인 연기-유동장 가시화 기법의 적용방법에 대한 검토가 이루어 졌다. 실험모델의 투영부를 통해 다양한 광원 및 촬영장치 방향을 이용하여, 축류 실험모델 노즐 선단부에서의 비대칭 와류튜브에 의한 선회류를 가시화하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.637-642
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• 2017

본 연구에서는 우주발사체의 터빈배기구 열교환기의 입구조건을 모사하는 고온고압 증기 발생장치의 개발을 위해 설계/제작한 엔진 헤드와 구축한 설비를 검증하는 내용을 담고 있다. 단일 분사기를 설계/제작하여 수류시험을 진행했으며, 이를 통해 각 단일 분사기당 설계유량이 공급되는 차압을 확인하고, 분무형태를 patternator를 통해 확인했다. 이를 바탕으로 선정한 분사기로 엔진 헤드를 제작했으며 수류시험과 실추진제 분무시험이 진행됐다. 연소시험을 통해 유량, 압력, 연소효율 등에 대해 분석했으며 이를 통해 고온고압 증기 발생장치 개발을 위한 엔진 헤드 검증을 마쳤다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 C
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• pp.1512-1516
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• 1994

FLIC(Fluid in cell) method has been used for analyzing a cold gas flow field in an interrupter of a circuit treater since 1970s. In this paper FLIC method is applied to calculation of a cold gas flow and then combined with the simple are analysis method in order to investigate the flow field characteristics in a puffer type interrupter rated at 145kV 40kA. The results for a cold gas flow agree with the experimental measurement well. The other results such as pressure rise, arc temperature, post-arc current and so forth am also reasonable and show the possibility that the combined program can be applied to the design of UHV interrupters.

• 한국기계가공학회지
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• 제21권3호
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• pp.110-117
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• 2022

A chiller cooler absorbs the thermal energy of water to generate cold water and supplies the generated cold water to a cold water pipe buried in the wall of a small mobile modular house to greatly increase the cooling area. An attempt was made to reduce the required cooling time significantly. A small chiller cooler suitable for the cooling load of a small mobile modular house with an area less than 3.3 m² was employed. When cooling is done during summer using a chiller cooler installed outdoors, heat absorption energy loss occurs in the cold water pipe owing to the high temperature. To address this, a study was conducted to reduce the endothermic energy loss significantly. As the mass flow rate of the cold water flowing inside the cold water pipe increased, the temperature decrease gradient of the cold water increased. From the start of the cooling operation, the air temperature of the small mobile modular house decreased linearly in proportion to the operation time. Furthermore, the temperature of the air inside the small mobile modular house decreased in proportion to the increase in the flow of water inside the cold water pipe.

• 한국지리정보학회지
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• 제22권2호
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• pp.133-151
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• 2019

본 연구는 찬공기 특성을 유역단위로 분석하고, 유역 내 생성되는 찬공기를 도시 바람길 계획에서 활용하는 방안을 제안하는 것을 목적으로 한다. 이를 위해, 경기도 지역의 북쪽에 위치한 중랑천 유역의 의정부시, 남쪽에 위치한 안양천 유역 및 양재천 탄천 유역의 과천시를 연구 대상지로 선정하였다. 찬공기 특성 분석을 위해 독일에서 개발된 모형인 KALM(Kaltluftabflussmodell)을 활용하였으며, 야간 6시간 동안 생성되는 찬공기 흐름 및 찬공기층 높이를 파악하였다. 중랑천 유역의 주요 바람길이 흐르는 곳에 위치해 있는 의정부시는 남쪽 외곽에서부터 유입된 찬공기가 의정부시 전체 바람길 계획의 중요한 부분을 차지하고 있다. 또한, 서쪽의 사패산 일대에서 생성된 찬공기는 시청 인근의 중심상업지구까지 유입되고 있어 도심의 열환경을 조절하는 주요한 역할을 수행하는 것으로 판단된다. 반면, 의정부시 동쪽지역은 바람길 이용이 원활하지 않는 것으로 파악되었다. 동쪽의 관악산과 서쪽의 청계산 등에서 생성된 찬공기 흐름은 과천시의 북쪽 지역에서 가장 활발하였는데, 이 흐름은 안양천 및 양재천 탄천 유역 전체에서도 주요한 바람길이다. 이에 비해, 찬공기 흐름이 원활하지 않은 남쪽지역에 '과천지식정보타운 공공주택지구' 조성이 계획되어 있어 향후 이 지역의 주거환경이 저하될 가능성이 크다. 향후, 이 지역을 개발할 경우 상세한 바람길 분석을 통한 바람길 활용 계획을 추가적으로 수립할 것을 제안하였다.

• Journal of Biosystems Engineering
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• 제33권6호
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• pp.396-403
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• 2008

Because thermal non-uniformity of transported agricultural products is mainly affected by cooling air flow pattern in the cold transport equipment, the analysis and control of flowfield is key to optimization of cold transport equipment. The objectives of this study were to estimate the effects of geometric and operating parameters of cold container on the air flow and heat transfer, and find the optimum design parameters for the low temperature level and its uniformity in given cold container with CFD simulations. Existences of ducts, gaps between pallets and geometries of exit as geometric parameters and fan blowing velocity as operating parameter were investigated. CFD simulations were carried out with the FLUENT 6.2 code. The result showed that optimum design condition was bulk loading with no duct, wall exit and 8.0 m/s of fan blowing velocity.

• 동력기계공학회지
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• 제7권2호
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• pp.17-22
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• 2003

As side-by-side refrigerators came into existence, there has been a growing concern about the free%ins-up of the vital equipment in a walk-in freezer. Due to a bad performance, customers are experiencing too much frustration. In order to minimize the freezing phenomena, the numerical simulation has been performed on the characteristics of cold air flow in a side-by-side refrigerator. The flow field has been simulated with a standard $k-\varepsilon$ turbulent model and a SIMPLE algorithm based on the finite volume method. Through the results of the analysis of the pattern of cold air flow, finally the shape of outlet for cold air flow was modified. The present model was compared with the modified model. The latter was better than the former in minimizing the freezing phenomena.