• Journal of Biosystems Engineering
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• 제29권6호
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• pp.521-530
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• 2004

The solar powered water pump is very ideal equipment because solar power is more intensive when the water is more needed in summer and it is very helpful in the rural area, in which electrical power is not available. The average solar radiation power is $3.488\;kWh/(m^2{\cdot}day)$ in Korea. In this study, the experimental system of the water pump driven by the radiation energy were designed, assembled, tested and analyzed fur realizing the solar powered water pump. Energy conversion ken radiation energy to mechanical energy by using n-pentane as operating material was done and the water pumping cycles were able to be continued. The quantity of the water pumped per cycle ranged from 2 L to 10 L depending on the level of the valve open area far the vapour supply. The average quantity was about 4,366 cc. The thermal efficiency was about $0.018\%$. The pressure level of the n-pentane vapour in flash tank was about $110\~150\;kPa$ and that in the water tank was $93\~130\;kPa$. The pressure in the condenser during cycles was maintained as about 70 kPa. The condensation of the n-pentane vapour in the water tank was increased with the cycles even though the internal and external insulation were done. Air tank performance was better with increasing of the water piston displacement and the water could be pumped with the water piston displacement becoming higher than 6,500 cc.

• 한국BIM학회 논문집
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• 제4권2호
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• pp.25-32
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• 2014

Today, there is a growing need of environment-friendly buildings, so-called 'green', facilities, and energy saving buildings to decrease environmental pollutants released into cities by construction activities. Green-Building Information Modeling (Green-BIM) is a purpose-built solution which supports to forecast energy consumption of 3-D model of a building by augmenting its primary 3-D measurements (width, height and depth) with many more dimensions (e.g. time, costs, social impacts and environmental consequences) throughout a series of sequential phases in the lifecycle of a building. The current study was carried out in order to integrate vegetation systems (particularly green roof and green wall systems) and investigate thermal performance of the new Sainsbury's building which will be built on Melton road, Leicester, United Kingdom. Within this scope, a 3-D building model of the news Sainsbury's building was first developed in $Autodesk^{(R)}$ $Revit^{(R)}$ and this model was then simulated in $Autodesk^{(R)}$ $Ecotect^{(R)}$once weather data of the construction site was obtained from $Autodesk^{(R)}$ Green Building $Studio^{(R)}$. This study primarily analyzed data from (1) solar radiation, (2) heat gains and losses, and (3) heating and cooling loads simulation to evaluate thermal performance of the building integrated with vegetation system or conventionally available envelops. The results showed that building integrated vegetation system can potentially reduce internal solar gains on the building rooftops by creating a 'bioshade'. Heat gains and losses through roofs and walls were markedly diminished by offering greater insulation on the building. Annual energy loads for heating and cooling were significantly reduced by vegetation more significantly through the green roof system in comparison to green wall system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1988-1989
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• 2007

Polyethylene is widely used as the insulator for power cable. To investigate the conduction mechanism for power cable insulation under ac high field, it is very important to acquire the dissipation current under actual running field. Recently, we have developed the unique system, which make possible to observe the nonlinear dissipation current waveform. In this system, to observe the nonlinear properties with high accuracy, capacitive current component is canceled by using inverse capacitive current signal instead of using the bridge circuit for canceling it. We have already reported that the dissipation currents of $40\;{\mu}m$ thick LDPE film at 10 kV/mm and over 140 Hz, it starts to show nonlinearity and odd number's harmonics were getting large. To investigate the conduction mechanis ms in this region, especially space charge effect, various kinds of estimation, such as time variations of instantaneous resistivity for one cycle, FFT spectra of dissipation current waveforms and so on, has been examined. As the results of these estimations, it was found that the dissipation current will depend on not only the instantaneous value of electric field but also the time differential of applied electric field due to taking a balance between applied field and internal field. Furthermore, two large peaks of dissipation current for each half cycle were observed under certain condition. In this paper, to clarify the reason why it shows two peaks for each half cycle, the film thickness dependences of dissipation current waveforms were observed by using the three different thickness LDPE films.

• Journal of the Korean Wood Science and Technology
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• 제45권2호
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• pp.147-158
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• 2017

Among the energy consumption in building, the heating energy takes the largest part. Therefore, it is important to minimize the heat energy loss in building for the reduction of overall energy use in construction. The most important points for the minimization of energy loss in building are insulation and airtightness. Especially, in wood houses, airtightness is very important for energy saving as well as increase of durability. However, the researches on airtightness of wood buildings have been started recently and are very deficient especially in Korea. In this study, air leakage properties and airtightness performance were evaluated for light-frame wood houses built in Daejeon and Chungnam area. Total 7 houses were evaluated, among which four houses (Case 1 to Case 4) were in the construction stage before interior finish and the other three houses (Case 5 to Case 7) were after completion of construction work. The tests for airtightness were conducted by pressurization-depressurization method, and the factors included in the measurements includes air leakage rate at 50 Pa (CMH50), air change rate at 50 Pa (ACH50), equivalent leakage area (EqLA) and EqLA per floor area. As a result of this study, key air leakage points in wood houses were found to be the gaps between floor and wall, the holes for wiring and plumbing, the double glasses windows and the entrance doors. The average value of ACH50 for the houses after completion of construction work was $3.5h^{-1}$ that was similar to Europe standard ($3.0h^{-1}$). ACH50 was proportional to EqLA per floor area but inversely proportional to the internal volume, the net floor area and the area of window.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.291-291
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• 2013

The interior vehicle noise due to the exterior aerodynamic field is an important topic in the acoustic design of a car. The air flow detached from the A-pillar and impacting the side windows are of particular interest as they are located close to the driver / passenger and provides a lower insulation index than the trimmed car body parts. HMC is interested in the numerical prediction of this aerodynamic noise generated by the car windows with the final objective of improving the products design and reducing this noise. The methodology proposed in this paper relies on two steps: the first step involves the computation of the exterior flow and turbulence induced non-linear acoustic field using the CAA(Computational aeroacoustics) solver CAA++. The second step consists in the computation of the vibro-acoustic transmission through the side window using the finite element vibro-acoustic solver Actran. The internal air cavity including trim component are included in the simulation. In order to validate the numerical process, an experimental set-up has been created based on a generic car shape. The car body includes the windshield and two side windows. The body is made of aluminum and trimmed with porous layers. First, this paper describes the method including the CAA and the vibro-acoustic models, from the boundary conditions to the different components involved, like the windows, the trims and the car cavity is detailed. In a second step, the experimental set-up is described. In the last part, the vibration of the windshield and windows, the total wind noise level results and the relative contributions of the different windows are then presented and compared to measurements. The influence of the flow yaw angle (different wind orientation) is also assessed.

• 한국건축친환경설비학회 논문집
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• 제12권6호
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• pp.531-542
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• 2018

Building energy demands have highly risen in modern society; thus, It is necessary to reduce building energy demands especially commercial buildings adopting a curtain wall architecture. Curtain wall architectures have a high ratio of windows which is a vulnerable in heat insulations as cladding. In order to complement insulation performance of windows in these buildings, there are various methods adopted often such as installing blinds, wing wall and films. There are two suggestions of this paper. 1) WWR (Window-to-Wall Ratio) makes a impaction of energy demands in buildings. 2) Another one is an efficiency of blind systems which are installed in buildings in order to reduce cooling demands. It is also critical to make fundamental model for low-energy building construction by processing a lot of simulation As a result by this study, 1) an external blind system is more useful for reducing cooling energy demands rather than an internal blind system. 2) Buildings which have a large window require more amount of cooling demands. In case of WWR 45%, it needs more cooling energy rather than WWR 15% model's 3) Adopting blind system would reduce energy demands. WWR 45% model with external blind systems reduces about 4% of cooling energy demands compared to same model without any blind systems.4) it is necessary to study an efficiency of blind systems combined with renewable energy and it will be possible to reduce more energy demand in building significantly.

• 한국추진공학회지
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• 제25권3호
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• pp.42-55
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• 2021

본 연구에서는 중심선 방정식 선정에 따른 노즐 성능 영향성을 확인하고자 하였다. 곡선 방정식과 설계 형상 파라미터를 활용하여 S-형 노즐 3조와 Double S-형 노즐 3조를 설계하였고 노즐 차폐 성능은 차폐율 정의를 이용하여 평가하였다. 그리고 내부 유동을 분석하기 위해 속도 분포도와 압력분포도로 특성을 연구하였고, 노즐 성능 계수로는 총 추력 비(f)와 노즐 단열 효율계수(η)를 통해 노즐의 성능을 평가하였다. 중심선에 따른 S-형 노즐의 성능 영향성을 분석한 결과 출구에서 급격한 곡률 변화가 있는 중심선은 노즐 성능이 우수한 반면 차폐율이 낮은 특징이 있다. 반면에 입구에서 급격한 곡률 변화가 있는 중심선은 노즐 성능이 낮아지고 차폐율이 높은 특징이 있다. Double S-형 노즐은 첫 번째 곡률에서 완만한 특징을 보이는 중심선을 사용하는 것이 노즐 성능과 차폐율이 우수하였다.

• 한국압력기기공학회 논문집
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• 제17권2호
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• pp.119-125
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• 2021

Subsea pipelines are widely used to transport hydrocarbons from ultra-deep seawater to facilities on the coast. A sandwich pipe is a pipe-in-pipe system in which the annulus between the two concentric steel pipes is filled with polymer cores and fillers for insulation and structural reinforcement. Sandwich pipeline is always exposed to complex loading such as bending moment, bulking, internal and external pressures caused by installation, operation and environmental factors. This research provides insights into the structural integrity of sandwich pipeline exposed to complex loading conditions using a linear matching method (LMM). The finite element model of the sandwich pipeline has been generated from previous research, and the model validation is performed by comparing the results of the linear analysis between the two models. The temperature dependent material properties are used to simulate the behavior of real pipeline, and the elastic-perfectly plastic (EPP) model has been taken into account for the material non-linearity. Numerical results provide comprehensive insights into the structural response of the sandwich pipeline under monotonic and cyclic loading and provide notable points about the evaluation of the plastic collapse limit and the elastic shakedown limit of the sandwich pipeline.

• 생물환경조절학회지
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• 제29권4호
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• pp.320-325
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• 2020

본 연구는 최근 신소재 단열재로 주목받고 있는 실리카 에어로겔을 이용하여 현재 사용되고 있는 다겹보온커튼의 단점을 보완하고 보온성을 유지 및 향상시킬 수 있는 새로운 조합의 다겹보온커튼을 제작 하여 현장에 설치함으로써 보온성과 경제성을 분석하고자 한다. 실험에 사용된 다겹보온커튼은 실리카 에어로겔이 함유된 부직포를 사용하여 2가지의 조합으로 제작하였으며 시중에 판매, 사용되고 있는 관행 다겹보온 커튼과의 차이에 따른 온습도변화와 연료소비량을 측정하여 비교분석하였다. 실험결과 단동온실과 연동온실에서 다겹보온커튼 차이에 따른 온습도변화는 미세하게 나타났으나, 거의 비슷한 온습도 값을 유지하였다. 이는 실리카 에어로겔을 이용한 다겹보온커튼이 관행 다겹보온커튼에 비해 온습도 제어 측면에서 문제가 없음을 나타냈다. 난방에너지 비교분석 결과, 실리카 에어로겔을 이용한 다겹보온커튼이 관행 다겹보온커튼에 비해 연료소비량은 단동온실에서 약 15%, 연동온실에서 약 20%의 연료소비량을 절감한 것으로 나타나 온실의 규모와 사용기간이 증가함에 따라 난방에너지는 절감될 것으로 판단된다. 실리카 에어로겔 이용 다겹보온커튼이 관행 다겹보온커튼에 비해 통기성과 보온성이 증가되는 것이 확인되었다. 그러나, 연동온실에서 사용된 다겹보온커튼은 관행 다겹보온커튼에 비해 무게가 증가하고 뻣뻣하여 시공성과 작동성이 떨어지는 것을 확인할 수 있었다. 이에 단동온실에서 사용된 다겹보온 커튼에서는 개선사항을 적용하였다. 내부단열재의 교체를 통해 두께를 감소시키고 뻣뻣함을 개선함으로써 농가가 사용하기에 충분한 가능성이 있다는 것을 확인하였다.

• 생물환경조절학회지
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• 제27권3호
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• pp.253-259
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• 2018

본 연구에서는 딸기의 생육 및 환경관련 데이터를 활용하여 딸기 재배 온실의 최적 환경 구현을 위한 시스템을 선정하고 생산성 향상에 대한 연구를 위한 기초자료로 활용할 목적으로 서부 경남 지역 중 딸기 재배로 유명한 지역의 온실을 대상으로 현장조사를 실시하였다. 이 결과를 바탕으로 경상대학교 내에 딸기 재배용 테스트 베드 온실을 설치하여 연구를 실시하고자 본 연구를 수행하였다. 그 결과 재배농가의 연령대를 보면, 상대적으로 50대 및 60대가 가장 많았지만, 50대 이하가 27개 농가로서 전체의 약 67.5%정도이었고, 60대 이상은 32.5%정도인 것으로 나타났다. 재배경력의 경우, 10년 이하가 주류를 이루고 있지만 30년 이상인 경우도 있었다. 대상농가 모두가 단동온실로서 대부분이 아치 형태인 것으로 나타났으며, 양액재배 농가가 약 75%정도로 토경재배보다 많은 것으로 나타났다. 양액재배의 경우, 전체 농가가 고설재배를 하고 있었다. 단동온실의 폭, 측고 및 동고는 조사지역에 관계없이 각각 7.5~8.5m, 1.3~1.8m 및 2.5~3.5m정도 이었다. 서까래 간격도 0.7~0.8m정도인 것으로 나타났다. 고설재배의 경우, 고설재배 베드의 폭, 높이 및 간격은 각각 0.25m전후, 1.2m전후 및 1.0m전후인 것으로 조사되었다. 딸기 품종의 경우, 국산이 약 97.5%를 차지하고 있었고, 이 중 설향이 약 65.0%로서 가장 선호하고 있는 것으로 나타났다. 온실 내부 환경요인으로 38개 농가가 온도와 상대습도만 계측하였다. 2개 농가는 최근에 국산 제품인 스마트 팜 시스템을 도입한 농가도 있었다. 양액재배의 경우는 양액제어 시스템을 이용하고 있었다. 이 외에도 관비기를 사용하거나 환기 및 유동 팬을 사용하고 있는 농가도 있었다. 온습도 조절은 스마트 팜 시스템을 도입한 농가를 제외하고 약 85%인 34개 농가에서 측창이나 환기팬을 작동시키는 제어패널만을 이용하여 조절하였고, 수동으로 측창을 개폐하고 있는 농가도 10%정도인 4개 농가가 있었다. 보온 및 난방의 경우, 전체 대상 농가가 수막을 이용하고 있었다. 이 외에 필요에 따라 기름 및 전기보일러, 방열 램프 및 부직포 등을 병행하여 이용하는 농가도 다수 있었다.