연료전지용 딤플형 이중관열교환기의 열전달 성능에 관한 연구

조동현(Dong-Hyun CHO) 한국수산해양교육학회 2015 水産海洋敎育硏究 Vol.27 No.6

In the present study, the heat transfer performance of dimpled double-pipe heat exchangers for fuel cells that are utilized as cooling systems of fuel cells was studied. In addition, to comparatively analyze the heat transfer performance of dimpled double-pipe heat exchanger for fuel cells, plain double-pipe heat exchangers were also studied. Experimental results were derived on changes in the Reynolds numbers of the cooling water flowing in dimpled and plain double-pipe heat exchangers and changes in the heat flux of the air. Thereafter, to verify the reliability of the experimental results, the theoretical overall heat transfer coefficients and the experimental overall heat transfer coefficients were comparatively analyzed and the following results were derived. The heat transfer rate lost by the hot air and that of the heat transfer rate obtained by the cooling water were well balanced. The experiments of plain double-pipe heat exchangers and dimpled double-pipe heat exchangers were conducted under normal conditions and the theoretical overall heat transfer coefficient and the experimental overall heat transfer coefficient coincided well with each other. In both plain double-pipe heat exchangers and dimpled double-pipe heat exchangers, heat transfer rates increased as the cooling water flow velocity increased. Under the same experimental conditions, the heat transfer performance of dimpled double-pipe heat exchangers was shown to be higher by 1.2 times than that of plain double-pipe heat exchangers.

해수취수시설에서 이중관 구조를 갖는 취수관 연구(I): 수리모형실험

박영진,김지호,임인규,김태원 한국방재학회 2015 한국방재학회논문집 Vol.15 No.2

The current small and medium seawater intake facilities have significant problems due to suspended solids, unstable intake and maintenance, etc. A double pipe structure and underground type seawater intake system is being developed to overcome the existing weaknesses and an experimental model test was conducted to verify the proper intake discharge for the double pipe type intake pipe. In order to examine the design parameter of the intake pipe, we have examined the intake discharge according to the length of intake pipe, perforated ratio and water depth change using the experimental modeling test with/without the intake pump. From the result of experiment for the forced water intake with the intake pump, the intake discharge was not sensitive to with/without filtered sand layer and length of intake pipe. The double type intake pipe did not decrease the intake efficiency. Therefore, when the length of the double pipe type intake pipe model was about 1m(prototype 10m), it was possible to take the intake discharge supply without degradation in the water intake efficiency. In the pressure head without the intake pump, the intake discharge was affected by water depth as the length of intake pipe is short and the perforated ratio is low. From the results, the length of intake pipe must be design more than minimum of 1 m(prototype 10 m). In order to secure stable intake discharge, the perforated ratio must be established more than 359%. 기존 중·소규모 해수취수시설의 경우 부유물질, 취수의 불안정 및 유지관리의 어려움으로 인해 해수취수의 어려움이 발생하고 있었다. 이와 같은 단점을 극복하고자 이중관 구조를 갖는 매설식 해수취수시스템이 개발 중이며, 이중관 구조의 취수관에 대한 적정 취수량을검증하기 위해 수리모형실험을 수행하였다. 취수관 설계인자를 검토하기 위해 펌프에 의한 강제취수와 펌프흡입이 없는 압력수두 조건에서 취수관의 길이, 유공율, 조위 변화에 따른 취수량을 검토하였다. 펌프에 의한 강제취수 실험결과 취수량은 여과사 포설 유·무및 취수관 길이에 민감하지 않았다. 또한, 이중관 구조의 취수관이 취수효율을 저하시키기 않았다. 이에 펌프 강제취수에서는 이중관길이 1m (실제 10 m)의 경우에도 충분한 유량공급이 가능할 것으로 판단된다. 펌프흡입이 없는 압력수두 조건의 경우 취수량은 관길이가 짧고 유공율이 낮은 관의 경우에는 조위의 영향을 크게 받으므로 취수관의 길이는 최소 1.0 m이상 (원형10 m) 설계되어야 적당한것으로 나타났다. 안정적인 취수량 확보를 위해서는 유공율은 최소 359% 이상이 확보되어야 한다.

도시가스 매설이중배관 건전성 향상에 관한 실험적 연구

임형덕 한국산업융합학회 2020 한국산업융합학회 논문집 Vol.23 No.5

City gas buried pipes are managed by corrosion protection to prevent corrosion. In the case of the press-in section, the double pipe and the main pipe may cause corrosion under the influence of stray current, which can shorten the life of the pipes. In addition, if the insulator is filled in the press-in section, the press-in section itself is a single structure, and can be directly affected by external impact, and when the surrounding ground subsidence occurs, the stress may be concentrated, resulting in serious consequences. In this study, a serration-type shock absorber in the form of a sliding support was proposed as a new buried double piping construction method using EPS. The serration-type shock absorber can contribute to the improvement of the integrity of the buried double piping, as it can utilize the gas piping's own ductility and stress distribution characteristics with proper anti-corrosion management and shock-absorbing material properties by preventing contact inside the buried double pipe. However, for application to ground piping, there remains a task to supplement the vulnerability against fire due to the characteristics of EPS materials.

LNG 연료공급장치 적용을 위한 이중배관 시스템의 다물리 CAE 기반 설계 검증에 관한 연구

오재원(J.W. Oh),성기영(K.Y. Sung),이정희(J.H. Lee),배상은(S.E. Bae),조수길(S.G. Cho),김형우(H.W. Kim) 한국전산유체공학회 2019 한국전산유체공학회지 Vol.24 No.3

This study was carried out for design verification based on CAE of double piping system used in LNG fuel supply system. The double pipe is composed of an inner pipe through which LNG flows, an outer pipe through which air flows, and support for supporting between the inner pipe and the outer pipe. In order to apply the developed double piping system to the fuel supply system, it is necessary to secure air circulation characteristics, heat stability, structure stability, and vibration safety against gas leakage. Therefore, the verification of multiphysics research is required. The double piping used for LNG fuel supply system is an important equipment used in the engine room of LNG propulsion ships and safety design is very important because of the risk of secondary damage caused by LNG leakage. Therefore, in this study, multiphysics CAE technology is applied to review the safety while satisfying the design requirements of the developed double pipe. Considering the pressure loss of the fan, machine engine and pipeline, the predicted actual flow condition was predicted within the allowable flow range. In addition, the structural and dynamic stability analysis showed that the support operates in the safe area.

강제 역세척 모듈을 이용한 해수취수시설 흐름특성 분석

박영진(Young-Jin Park),조진규(Jin-Kyu Cho),김지호(Ji-Ho Kim) 한국환경관리학회 2014 環境管理學會誌 Vol.20 No.3

본 연구에서는 여과사를 이용하여 부유물질을 저감시킨 해수를 2중관 구조의 취수관을 통해 직접 취수하는 매립형 해수취수시설에 대해 수리모형실험과 수치모의를 하고 이를 비교 분석하였다. 수리모형실험에서 여과사가 포설되지 않은 상태에서 단일관과 이중관의 취수량을 변화시켜가며 흡입압력과 토출압력을 분석한 결과 압력과 유량 모두 유사하게 나타나 이중관의 효율이 저하되지 않은 것으로 나타났다. 또한, 사용된 수치모의를 통해 외부관이 없는 경우 취수관 하류 구간의 유속이 불안정하게 모의되었으나 외부관이 있는 이중관의 경우 취수관 하류 구간의 유속이 안정적으로 나타났다. This paper presents the analyzation and experimentation of the hydraulic model and numerical model of the underground-type seawater intake system; directly intaking the seawater with reduced floating material using sand filter through double structured intake pipe. In the hydraulic model experiment we analyzed the suction pressure and discharge pressure while changing the intake amount of single pipe and double pipe, based on the similar result of both the pressure and flux. Also it turned out that the efficiency of the double pipe was not reduced in a state which sand filter was not laid underground. In addition, using the numerical model, double pipes with external pipes showed stable velocity of the downstream section of intake pipe while the velocity of double pipes with no external pipe turned out to be unstable.

배수설비 시스템에서 PVC 관의 소음 특성

안창환(Chang-Hwan Ahn),공성훈(Sung-Hoon Kong) 한국생활환경학회 2007 한국생활환경학회지 Vol.14 No.3

The purpose of this study is to suggest the fundamental data for noise control design and standard criteria for PVC pipe by theoretical simulation and experimental research. To predict decibel noise pressure, the actual and theoretical test results by using PVC single pipe, PVC double pipe and PVC threefold-jointed, are carefully examined for the drainage facilities' nise in this study. Also, this study would presents fundamental informations and date on the reduction of the drainage facilities' noise by analyzing vibration modes of pipes. The major results are as follows; 1) The noise protect performance of double PVC pipe are prefer then single PVC pipe 10 ㏈ condition. 2) Theoretical noise reduction effects for double PVC pope and threefold-jointed pipe are have similar effects in 2 KHz~4 KHz band and some differences are shown in low level ㎐ band.

이중송수관로를 이용한 안정적인 송수를 위한 설계인자에 관한 연구

현인환,홍준의,김두일 대한상하수도학회 2013 상하수도학회지 Vol.27 No.1

Water interruption is often caused by a rupture in the branch-like singular pipeline. This will cause critical complaints from household and may decrease public service quality. As an alternative of singular pipeline, additional parallel pipeline could be installed for sustainable water supply. This system is called double pipeline system and able to be utilized for water transmission line between treatment plant and distribution reservoir. Construction of double pipeline was thought to increase capital cost, which can be an issue to waterworks authorities. Reducing capital cost was possible by means of installing connectors between two parallel pipelines because of reduced diameter of each pipe. To obtain optimal design condition for connectors, it was necessary to compare water pressure according to accident location, to investigate flow according to connection pipe spacing, connection pipe diameter, and aging of pipe. Reliable and economical connection layouts were determined based on these results. The cost estimation for each design condition was carried out. Cost was approximately reduced by 20 ~ 30 % compared to the double pipeline without connections. In addition to this, connection between double pipelines could expect extra benefits for maintenance since the pipe could be repaired and rehabilitated without interruption

RNG k-ε 알고리즘을 이용한 해수취수시스템 분석

김지호(Kim, Ji-Ho),김태원(Kim, Tae-Won),이승오(Lee, Seung-Oh),박영진(Park, Young-Jin) 한국산학기술학회 2013 한국산학기술학회논문지 Vol.14 No.12

기존 해수취수시스템의 경우 해수오염, 부유물질, 취수의 불안정 및 유지관리의 어려움 등으로 인해 해수취 수의 어려움이 발생하곤 하였다. 이와 같은 단점을 극복하고자 매설식 해수취수시스템을 개발하여 격포항에 설치하였 다. 본 연구에서는 새로운 시스템의 거동을 검토하고자, 수질관측 및 3차원 수치모의 실험을 수행하였다. 이 취수시스 템에 대하여 총 5회에 걸쳐 COD, 총질소, 총인, PH 그리고 부유물질에 대하여 수질분석을 수행한 결과, COD, 총질 소, 총인, PH의 경우 취수 전 ? 후 저감 효과는 미미하였다. 그러나 부유물질의 경우 수산용수 1급 5 mg/L 이하로 정 화되는 효과가 나타났다. 수치모형은 유한체적법 기반의 CFX 모형과 RNG k-ε 알고리즘을 선정하였으며, 여과사, 외 부관 지름 및 두께를 재현하기 위해서 다공성 알고리즘을 적용하였다. 수치모의 실험을 수행한 결과, 2중관 구조가 내외부 관 사이의 공간에 의해 압력의 분포를 균등하게 하여, 흐름 상태나 안정적인 취수측면에서 유리한 것으로 분 석되었으며, 취수관을 다열 배치하였을 때 중앙 취수관과 비교하여 양쪽 취수관에서 유량이 0.98배로 감소하였지만 유동의 간섭현상은 발생하지 않았다. Seawater intake systems have significant problems due to seawater pollution, suspended solids, unstable intake and maintenance etc. An underground type seawater intake system was newly developed to overcome the existing weaknesses and was facilitated in Gyukpo port. In this study, to check the performance of the new system, the samples for water quality and the 3-D numerical modeling test were conducted. The five times test included the COD, total nitrogen, total phosphorus, pH, and suspended solid for the intake system. The analyses show that the COD, total nitrogen, total phosphorus, PH showedminor changes before and after. On the other hand, the change in suspended solids was significant and water was purified below 5 mg/l, first level fisheries water, after. The numerical model adopted the RNG k-ε algorithm and the CFX model based on the finite volume method. The porosity algorithm was used to reproduce filtered-sand, outer diameter, and thickness. The numerical results showed that the double pipe is advantageous in that it provides a uniform pressure between the inner and outer pipe for the flow to be stable. In addition, the use of multiple intake pipes did not interfere with the discharge reduction of 0.98 at the both intake pipes compared with the central intake pipe."

LFLP와 DBLP 자연채광시스템의 성능평가 비교 연구

최용전(Jeon Yong Choi),강은철(Eun Chul Kang),이의준(Euy Joon Lee) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.8

본 논문에서는 자연채광 시스템 LFLP(Linear Fresnel Light Pipe)와 DBLP(Double Blind Light Pipe)시스템을 비교하였다. LFLP시스템은 평행한 빛을 선형프레넬렌즈를 이용하여 선형 형태로 빛으로 집광하여 자연채 광에 이용하는 시스템이며, DBLP시스템은 베네시안 형태의 블라인드를 이용하여 빛을 반사시켜 자연채광에 이용하는 시스템이다. DBLP시스템은 LFLP시스템을 개선한 것으로 시스템 앞쪽에 위치한 블라인드는 태양의 고도에 따른 빛을, 뒤쪽에 위치한 블라인드는 태양의 방위각에 따른 빛을 변광부로 반사시키도록 설계 되었다. DBLP시스템의 변광부는 콘모양으로 이루어 져 있으며 블라인드에 의해 반사된 빛을 산광부로 보내주는 역할을 하며, 산광부로 들어온 빛은 실내조명에 사용된다. 따라서 맑은 날(clear sky)을 기준으로 두 시스템의 효율을 비교하면 DBLP시스템이 LFLP시스템보다 세배 높게 나오는 것으로 나타났다. The LFLP (Linear Fresnel Light Pipe) system uses a linear Fresnel lens to follow the sun and concentrates the parallel sunlight into a line. A LFLP daylighting system has been developed and updated to a DBLP (Double Blind Light Pipe) daylighting system to improve the overall system efficiency in the morning and afternoon. The new design consists of a double-blind style with a cone-shaped light transformer. The blinds are used to collect the sun’s altitude and azimuth movements through the day. Behind the two sets of blinds is the light transformer, which is based on a parabolic-shaped light concentrator. The light transformer is designed to efficiently deliver light within a thirty-degree radial spread so that the light pipe can internally reflect the light. The results of scale-model tests are encouraging, and the efficiency is three times higher than that of the previous LFLP system.

자연채광시스템 LFLP와 DBLP의 성능평가 비교 연구

최용전(Yong-Jeon Choi),강은철(Eun-chul Kang),이의준(Euy-Joon Lee) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

The LFLP(Linear Fresnel Light Pipe) system used the linear Fresnel lens would follow the sun and concentrated the parallel sunlight into a line. A LFLP daylighting system has been developed and updated to a DBLP(Double Blind Light Pipe) daylighting system to improve the overall system efficiency in the morning and afternoon. The new design consists of Double Blind style with a cone shaped light transformer. The blinds are used to collect the sun's altitude and azimuth movements throughout the day. Behind both sets of blinds is the light transformer, which is based on a parabolic shaped light concentrator. The light transformer was designed to efficiently deliver the light within a 30 degree radial spread so the light pipe could total internally reflect the light. This system was designed to have two light transformers output into a single light pipe. One quarter scale models were made of the new system and both light transformers with blinds had a maximum efficiency greater than fifty percent. This allowed 24,000 to 30,000 lumens to be inputted into a single light pipe. The results of the scale model tests look encouraging and the efficiencies are three times higher than the previous LFLP system.