• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.42-47
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• 2008

This paper reports the system performance of a hybrid plant, which combines a renewable energy plant of GSHP(Ground Source Heat Pump) with a conventional plant (screw water chiller). To find out operational cost and operating characteristics, the performance of the hybrid system was measured in a building located in Jeju island. Based on the measured data, the operating characteristics were analyzed and the operational cost was estimated by using payment table, which was provided by the Korea Electric Power Cooperation. Operating methods to save energy were recommended.

• 에너지공학
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• 제10권4호
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• pp.318-326
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• 2001

중저온 배열회수를 통해 열설비의 열효율을 향상시키기 위하여 1 MW급 유기랭킨사이클시스템을 설계, 개발하였다. 포항제철소에 있는 두 대의 100 MW급 기력발전소에서 발생하는 175$^{\circ}C$의 배가스를 산업체에서 발생하는 대표적인 중저온배열원으로 선정하고, 환경오염을 최소화할 수 있는 신냉매인 HCFC-123을 시스템의 작동유체로 선정하였다. 유기냉킨사이클시스템의 시험운전을 통하여 유기랭킨사이클시스템이 산업체의 중저온배열을 회수하는데 유용함을 확인하였다. 열수의 가열, 터빈기동 및 전기투입방법 등의 운전방법을 최적화하였다. 그러나 HCFC-123 공급펌프의 능력부족으로 작동유체의 공급이 부족하여 정격출력보다 낮은 670kW의 전력을 생산할 수 있었다. HCFC-123의 공급유량을 증가시키기 위하여 파이프의 압력손실저하 및 펌프의 성능 향상을 위한 펌프교체 등이 고려되어야 함을 알 수 있었다.

• 설비공학논문집
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• 제28권1호
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• pp.29-34
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• 2016

The friction factor unit was studied to find a more economic alternative compared to the conventional 30 mmAq/m. The pipe and pump for cooling water piping used in a failing were selected, and the friction factor unit was changed to calculate the pipe diameter and the brake shaft power. Based on current electric charges, After the brake shaft power was converted into operational costs based on current electric charges, then an economic analysis was conducted considering that incorporated the initial installation costs and operational costs for the pump. We found that the friction factor unit when using 20 mmAq/m is more economical than that with 30 mmAq/m, if the piping is used for more than 4 years. The small friction factor unit is desirable when the piping is used for quite a long period of time, and the selection of a more economic friction factor unit should considering the period of usage will be important.

• 상하수도학회지
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• 제25권4호
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• pp.581-589
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• 2011

Generally, treated water or raw water is transported into storage reservoirs which are receiving facilities of local governments from multi-regional water supply systems. A water supply control and operation center is operated not only to manage the water facilities more economically and efficiently but also to mitigate the shortage of water resources due to the increase in water consumption. To achieve the goal, important information such as the flow-rate in the systems, water levels of storage reservoirs or tanks, and pump-operation schedule should be considered based on the resonable water demand forecasting. However, it is difficult to acquire the pattern of water demand used in local government, since the operating information is not shared between multi-regional and local water systems. The pattern of water demand is irregular and unpredictable. Also, additional changes such as an abrupt accident and frequent changes of electric power rates could occur. Consequently, it is not easy to forecast accurate water demands. Therefore, it is necessary to introduce a short-term water demands forecasting and to develop an application of the forecasting models. In this study, the forecasting simulator for water demand is developed based on mathematical and neural network methods as linear and non-linear models to implement the optimal water demands forecasting. It is shown that MLP(Multi-Layered Perceptron) and ANFIS(Adaptive Neuro-Fuzzy Inference System) can be applied to obtain better forecasting results in multi-regional water supply systems with a large scale and local water supply systems with small or medium scale than conventional methods, respectively.

• 한국해안·해양공학회논문집
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• 제22권2호
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• pp.67-72
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• 2010

본 연구에서는 조류발전용 헬리컬 수차를 발전소 냉각수 배수로에서의 수력 개발에 이용하기 위하여 수차구조물의 설치로 인한 수위 증가가 냉각수 순환 계통에 미치는 영향을 파악하였다. 배수로 암거 출구부에 가로 3.6 m $\times$ 세로 1.5 m의 헬리컬 수차 1 set(2기 일체형)를 설치하는 경우에 대하여 배수로의 수위변화 및 압력변화를 수치해석을 통해 분석한 결과, 평균해수위시에는 seal well 하류의 수위 변화 영향이 seal well의 weir에 의해 차단되어 상류로 전파되지 않았다. 그러나 고조시에는 weir의 월류 흐름형태가 잠김 월류가 되고 seal well 전 후단이 모두 만관흐름상태가 되어 하류의 압력변화가 상류로 전파되었다. 방류 개시 후 약 10분간 불안정한 압력변화가 발생하나 이후 안정되며, 약 0.2 m 내외의 수두 증가로 냉각수 순환펌프 소요 동력이 증가할 수 있으나 안전성에는 영향을 주지 않을 것으로 판단되었다. 따라서, 수력 개발 타당성 평가시 냉각수 순환펌프의 소요전력 증가를 고려할 필요가 있다.

• 물과 미래
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• 제12권2호
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• pp.36-42
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• 1979

This study has been conducted to find out the location and amount of the subterrain water body developed in the alluvial stratum in Paho-Dong, Sungsee-Myo-n, Dalsung-Kun are. An earlier test drilling was done in this area by R.O.K. Agricultural Promotion Corporation. The area consists of a small river basin and surrounding low hills developed around the junction of the Nakdong and Kumho Rivers. The strata of this area are made of Paldal gravel, Bokhyundong and Banyawol layers which were formed in the cretaceous period of the Meso-saicera or acid dikes and covered with-irregular alluvial layers. The alluvial layer in this area is composed of rather minute particles and proportional electric resistance tests on this layer show $10^2\;-\;10^3\;\Omega/cm$. The drillings up to 12meters deep showed only the sand layer (Form 3 to 26meters in thickness) contains water. The sand layers can not be considered a good water trapping one. Applying the data from the drillings to A.Hazen's equation, $K\;=\;{cd_e}^2\;(0.7\;+0.03t)$ to get the theoretical value of the water infilterated, I calculated it as K=13.92m/day. And again the value was set to Dupuit equation, (equation omitted) to acquire the pumping water amount the result was $Q_1\;=\;77.20\;\textrm{m}^3/day$. When the data-applied to the equation for pumping water amount, (equation omitted), the results were $Q_2\;=\;122.39\;\textrm{m}^3/day$ and K = 38m/day $Q_1\;and;Q_2$ (tow types of pumping water amount) represent proper value decrease and maximum value decrease respectively. Therefore, $Q_2$ is the least amount of water we can pump. The area covers about $1,555,000\;\textrm{m}^2$ and the maximum water needed in this area amounts to $155,000\textrm{m}^3$. That means we have to drill 1,406 pumping wells. It is concluded that undertaking the project in this area is irrational or even desperate and surface water should be developed more favorably.

• 한국태양에너지학회 논문집
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• 제28권3호
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• pp.7-14
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• 2008

400RT geothermal system which is the biggest capacity among on-operations at present in Korea is measured and evaluated on 23rd${\sim}$26th Jan. 2008 during those days building is not allowed owners and/or tenants to move in. The geothermal system is consist with vertical-typed 112 geothermal heat exchangers which are installed circle-like 1 row with 4m interval, and has 16 units of 25USRT geothermal-source heat pump(GSHP)s. And each 5 units of circulation pump are running for geothermal heat exchangers and hot water supplies. The followings are the results. The temperatures at G.L. -70m of 2 boreholes are varied quite similarly. The average temperature difference between inlet and outlet of geothermal pipes is $4.1^{\circ}C$, and that of hot water supply is $3.2^{\circ}C$, of Zone 3's each 4 GSHPs when being operated. Despite temperature fluctuations by heating loads, the average temperature difference between main pipes of inlet and outlet of geothermal heat exchangers is measured as $4.1^{\circ}C$. This study propose "Geothermal System COP" which includes not only consumed electric power by compressor but also circulation pumps and auxiliary utilities. By comparing the geothermal system COP with GSHP's performance specification, it is clear that the performances of GHSPs of this site are satisfied with the specification.

• 한국자동차공학회논문집
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• 제25권2호
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• pp.236-241
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• 2017

Electrohydraulic forming is a high-speed forming process that deforms a blank using electric discharge in liquid. When high voltage is discharged in the water, a shock wave is propagated from the tip of the electrodes to the blank, causing the blank to be deformed into the die. Electrohydraulic forming has many advantages including improved formability and reduced bouncing effect and springback. The objective of this paper was to conduct a feasibility study to identify the electrohydraulic effect. An electrohydraulic forming apparatus was developed and experiments were carried out. The results of the experiment showed that the developed apparatus had sufficient energy to deform the blank into the die. Using the hole to emit residual air in the die was more effective than using the vacuum pump in terms of saving on experiment time.

• 한국분무공학회지
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• 제27권1호
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• pp.42-49
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• 2022

Flash boiling occurs in a couple of modern engineering systems and understanding its mechanism is important. In this experimental study, discharge coefficient of flash boiling spray from simple orifice nozzle was measured, and backlight imaging was acquired at injection pressure to 6.0 bar and temperature to 163℃ for the purpose. Pressurized water by pump was used for working fluid and was heated by electric heater and ejected through simple orifice nozzle diameter of 0.5 mm. High speed camera with long distance microscope was used for backlight imaging in two FoV having magnification of 3.3 and 0.64. The decrease of discharge coefficient according to degree of superheating and evolution of flash boiling spray imaged at various pressure and temperature were explained by the pressure field inside the injector.

• 한국항해항만학회지
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• 제36권1호
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• pp.35-41
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• 2012

본 논문은 수중체용 냉각 시스템에 관하여 분석하고, 수중체에 최적화된 냉각 제어 알고리즘에 관하여 연구하였다. 수중체용 대용량 추진 전동기는 동손 및 철손으로 인해 발생하는 고열로부터 전동기를 안정적으로 보호하기 위해 청수를 이용한 냉각 시스템이 사용된다. 이 냉각 시스템은 전동기의 온도를 유지하기 위해 외부 환경 및 전동기의 회전수 유지시간에 따라 해수 및 청수 펌프 RPM을 조절한다. 본 논문에서는 제안하는 냉각 시스템의 검증을 위한 시뮬레이션 프로그램을 구성하였으며, 다양한 제어 기법을 적용하여 냉각 수행 능력을 검증하였다. 그 결과 제안하는 냉각 알고리즘은 열적 안정성과 효율이 기존 냉각 알고리즘에 비해 높음을 확인하였다.