• International journal of advanced smart convergence
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• 제6권4호
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• pp.1-8
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• 2017

In this work, the effects of fairly influential factors on performance of vacuum system, such as constant pressure and outgassing effect were simulated to propose the optimum design factors. Outgassing effects of selected vacuum materials on the vacuum characteristics were simulated by the $VacSim^{Multi}$ simulation tool. This investigation examined the feasibility of reliably simulating the outgassing characteristics of common vacuum chamber materials (aluminum, copper, stainless steel, nickel plated steel, Viton A). The optimum design factors for vacuum systems were suggested based on the simulation results. And, the effects of throttle valve applications on vacuum characteristics were also simulated to obtain the optimum design model of variable conductance on high vacuum system. Simulated vacuum characteristics of the proposed modelling were agreed with the observed experimental behaviour of real systems. Pressure limit valve and normally on-off control valve were schematized as the modelling of throttle valve for the constant process-pressure. Simulation results were plotted as pump-down curve of chamber and variable conductance of throttle valve. Simulated behaviors showed the applications of throttle valve sustained the process-pressure constantly, stably, and reliably.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.7-12
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• 2003

heat pipe with screen meshed wick. The heat pipe was designed in 200 screen meshs, 500 mm length and 12mm O.D tube of copper, water as working fluid and nitrogen as non-condensible gas. Heat pipe used in this study has evaporator, condenser and adiabatic section, respectively. Experimental data of wall temperature distribution along axial length is presented for heat transport capacity, condensor cooling water temperature change, degrees of an inclination angle, and operating temperature.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2010년도 하계학술대회 논문집
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• pp.565-567
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• 2010

This paper proposes a new Maximum Power Point Tracking (MPPT) control algorithm for PV-Cell (Photo voltaic) based on Incremental Conductance MPPT algorithm. The ICN (Incremental Conductance method) algorithm is widely used due to the high tracking accuracy and adaptability to the rapidly changing isolation condition. In this paper, a modified ICN MPPT algorithm is proposed. This method adjusts automatically the step-size of reference to track the PV-Cell maximum power point, thus it improves the maximum power point tracking speed and accuracy.

• 설비공학논문집
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• 제18권4호
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• pp.320-327
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• 2006

Numerical analysis and experimental study are performed to investigate the effect of heat load and operating temperature on the thermal performance of several variable conductance heat pipe (VCHP) with screen meshed wick. The heat pipe is designed in 200 screen meshes, 500 mm length and 12.7 mm outer diameter tube of copper, water (4.8 g) is used as working fluid and nitrogen as non-condensible gas (NCG). Heat pipe used in this study has evaporator, condenser and adiabatic section, respectively. Analysis values and experimental data of wall temperature distribution along axial length are presented for heat transport capacity, condenser cooling water temperature change, degrees of an inclination angle and operating temperature. These analysis and experiment give the follow findings: For the same charging mass of working fluid, the operating temperature of heat pipe becomes to be high with the increasing of charging mass of NCG. When the heat flux at the evaporator section increases, the vapor pressure in the pipe rises and consequently compresses the NCG to the condenser end part and increases the active length of the condenser. From previous process, it is found out we can control the operating temperature effectively and also the analysis and experimental results are relatively coincided well.

• Journal of Power Electronics
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• 제15권2호
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• pp.487-496
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• 2015

In order to ensure that photovoltaic (PV) systems work at the maximum power point (MPP) and maximize the economic benefits, maximum power point tracking (MPPT) techniques are normally applied to these systems. One of the most widely applied MPPT methods is the incremental conductance (INC) method. However, the choice of the step size still remains controversial. This paper presents an improved variable step size INC MPPT algorithm that uses four different step sizes. This method has the advantages of INC but with the ability to validly adjust the step size to adapt to changes of the PV's power curve. The presented algorithm also simultaneously achieves increased rapidity and accuracy when compared with the conventional fixed step size INC MPPT algorithm. In addition, the theoretical derivation and specific applications of the proposed algorithm are presented here. This method is validated by simulation and experimental results.

• 한국안광학회지
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• 제4권2호
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• pp.105-111
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• 1999

PECVD 방법에 의하여 제작된 수소화된 비정질 탄소박막에서 측정 전압에 따른 전기전도도의 급격한 변화와 시간에 따른 전류의 이완 현상을 관측하였다. 이 현상은 Hammer 등에 의해 four-probe 측정과 샌드위치형 전극 시료에 대해서 측정한 것과 동일하였다. 본 연구에서는 "높은 전압에서 전자가 트랩에 포획될 확률이 작아진다"는 가정 하에서 정성적이지만 전기전도도의 측정 전압 의존에 관한 세 가지 현상이 비교적 잘 설명됨을 제시하였다.

• 대한기계학회논문집A
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• 제38권2호
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• pp.157-166
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• 2014

경수로 핵연료가 원자로내에서 연소되는 동안 핵연료 펠릿에서부터 피복관까지 온도해석은 핵연료 안전 해석에 있어 중요한 요소이며, 경수로 핵연료 온도 해석을 하기 위해서는 간극 모델 개발이 필수적이다. 간극 열전도도는 특성상 간극 두께값에 의존적이게 되며 이러한 특성으로 인해 다차원 간극 열전도도 모델이 비선형적 거동을 보인다. 본 연구에서는 선형화된 다차원 간극 열전도도 모델 개발을 위해 가상 연결 간극 요소를 제안하였다. 제안된 간극 연결 요소에 간극 열전도도를 적용하기 위해 등가 열전달 계수를 정의하였다. 제안된 모듈을 평가하기 위해 상용코드 ANSYS APDL 을 이용하여 열-구조 연계 해석 모듈을 구현하였으며, 다양한 예제를 통해 정확성과 수렴성을 평가하였다.

• 조명전기설비학회논문지
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• 제26권8호
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• pp.27-34
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• 2012

This paper proposes variable incremental conductance(IC) algorithm for maximum power point tracking(MPPT) control of photovoltaic. The conventional perturbation & observation(PO) and IC MPPT control algorithm generally uses fixed step size. A small step size reduces a tracking error in the steady state but slows a tracking speed in the transient state. Also, a large step size is fast a tracking speed but increases a tracking error. Therefore, this paper proposes variable IC MPPT algorithm that adjust automatically step size according to operating conditions. To improve a tracking speed and accuracy, when operating point is far from the maximum power point(MPP), the step size uses maximum value and when a operating point is near from the MPP, the step size uses variable step size that adjust according to slope of P-V curve. The validity of MPPT algorithm proposed in this paper prove through compare with conventional PO and IC MPPT algorithm.

• 한국진공학회지
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• 제6권4호
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• pp.298-307
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• 1997

CRT부품 탈가스(outgassing)를 온도를 변화 시켜가며 측정할 수 있고 시료의 열탈착 특성을 측정할 수 있는 TDS(Thermal Desorption Spectroscopy) 측정 장치를 설계 제작하였다. 제작된 시스템은 유효 배기속도를 조절할 수 있는 진공 장치와 시료의 온도조절 장치, 탈가스 측정 가치로 구성되어 있다. 제작된 시스템의 최저 도달 진공도는 $1{\times}10^{-7}$Pa 이하였고 가변 콘덕탄스(conductance)를 채택하여 유효 배기 속도를 조절 할 수 있도록 제작되었다. 가변 콘덕탄스 조절에 따른 시료위치에서의 유효 배기 속도 변화를 측정하였다. 텅스텐 히터와 온도조절기를 이용하여 시료의 온도는 600℃까지 ±1℃ 이내 오차로 조절 할 수 있었으며 온도 상승률도 조절할 수 있었다. 측정계기로 사용한 이온 진공계(ion gauge)와 사중극 질량분석기(quadrupole mass spectrometer)의 감도를 측정하여 정량적인 측정을 할 수 있도록 하였다. 제작된 시스템을 이용하여 CRT 공정에서의 부품별 온도별 측정 예와 공정분석에의 적용 예를 보였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1651-1656
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• 2003

The present study has been conducted to analytically investigate the thermal control performance of variable conductance heat pipe(YCHP) with axial grooves. The condenser port of the YCHP is occupied by a inert gas in which the concentration of gas is varied with the operation temperature and the heat transport capacity is thus varied with the operating temperature due to the variation of inert gas concentration. In this study, numerical evaluation for the thermal control of the YCHP with axial grooves is made from the 1st order diffusion model that considers the diffusive expansion of inert gas by concentration gradient. Ammonia is used as a working fluid and Nitrogen as a control gas in the Aluminum tube. As a result, the thermal performance of YCHP based on diffusion model has been compared with that of YCHP from flat front model. Additionally, it is found that the concentration of inert gas is distributed in the condenser region of YCHP with axial grooves.