마이크로 미러 구동기의 디자인 및 해석에 대한 수치적 연구

권기남 (權起楠) 弘益大學校 大學院 2006 국내석사

MEMS는 기존의 반도체 공정을 이용하여 수 ㎛ 크기의 기계부품을 제작 하는 분야이다. 화학공학이나 전기 분야에서 반도체 공정 기술이 발전하였기 때문에 공정 등 많은 부분에서 기계 분야 외적의 지식이 많이 필요하다. 하지만 반도체 공정의 부과 물로 여겨졌던 MEMS가 새로운 분야로 재탄생하게 됨으로써 반도체공정과는 다르게 기계 분야의 기술이 많이 필요 하게 되었다. 이중 마이크로 구동기는 직접적인 기계적 특성을 지니고 있기 때문에 기계분야에서 크게 다룰 수 있는 연구 분야가 될 것이다. 또한 이 마이크로 구동기로 작동되는 마이크로 미러는 기계적 동작 특성 연구가 매우 필요하므로 기계분야에서 적합한 분야로 평가된다. 마이크로 미러는 광신호를 바로 광신호로 바꾸는 OXC(Optical Cross Optical)방식의 광스위치의 핵심 부품이다. 인터넷 트래픽의 폭발적인 증가 등을 배경으로 최근 전 세계적으로 광 네트워크 인프라에 대한 투자가 적극적으로 이루어지고 있고 WDM(Wavelength Division Multiplexing)을 이용한 광 백본망이 폭 넓게 보급되고 있는데, 그러한 네트워크에 없어서는 안 될 존재가 광 스위치이다. 마이크로 미러를 이용한 광 스위치기술이 앞으로의 광통신 시장을 좌우하게 될 것이다. 하지만 아직 까지 마이크로 미러의 제작과 제어등의 부분에서 광 스위치로 사용 될 만한 수준에 이르지 못했다. 따라서 본 연구에서는 좀 더 나은 구동기를 설계하고 이것을 마이크로 미러에 접목하여 광 스위치에 알맞은 미러 제작을 목표로 하였다. 정전기력 구동기를 이용한 광스위치는 판과 판 사이에 발생하는 정전기력을 이용하여 발생되는 변위를 이용한 마이크로 미러 이다. 기존의 구동기는 캔틸레버 (Cantilever) 형태의 단순한 구조지만 토션바 (Torsion Bar) 형태의 지지대를 만들어 접촉각을 크게 만들어 주었고, 또한 디자인을 변경하여 최적의 설계조건을 찾아내었다. 열팽창 구동기의 구동형태에는 차동저항방식과 바이메탈방식이 있다. 차동저항 방식의 열팽창 구동기는 구동기의 면적차에 따른 저항 차이에 발생되는 열팽창 변위의 차이에 따라 구동 변위가 발생한다. 차동저항의 구동기가 최대 효율을 얻을 수 있도록 최적 설계를 한 후 최대허용온도로 제한된 변위를 늘려주기 위해서 바이메탈 방식과 차동저항방식을 결합한 형태인 Metal/Poly-Silicon 구동기를 설계하였다. 본 구동기는 최대 항복응력과 최대허용온도의 한계점까지 최대 구동변위로 작동 되도록 제작 되었다. 바이메탈 방식의 열팽창 구동기는 서로 다른 열팽창률을 갖는 두 물질이 발생하는 변위차를 이용하여 구동하는 변위이다. 기존의 구동기는 한 가지 움직임을 갖는데 비하여 서로 다른 방향의 변위를 갖도록 2개의 구동기를 설계하여 미러 지지대가 굽힘이 아닌 비틀림 변형하도록 설계하였다. 본 연구에 의한 마이크로 미러는 폭 20㎛, 길이 100㎛밖에 안되는 크기의 구동기, 폭 100㎛, 길이 100㎛밖에 안되는 크기의 마이크로 미러의 경우에도, 11V DC에서 28㎛의 변위, 28°의 구동각을 얻을 수 있었고, 이는 구동각 약 5°의 종래기술에 비하여 엄청난 향상이다. MEMS (Micro Electro mechanical systems) technology has generated a significant a mount of interest in the business sectors. This interest is focused on the potential performance and cost advantages with micro scale device fabricated based on silicon processing technology. It is a technique to fabricate micro scaled devices which is often mechanically actuated. Our micro mirrors are fabricated MEMS technique. Micro mirrors are used optical switch for optical communication system. Micro mirrors for a new optical communication method like WDM (Wavelength Division Multiplexing) and OXC (Opticl Cross Connect), which be needed to study the switching speed and large deflection for using the MEMS optical switching device. The goal of this study is to demonstrate micro actuators having a large deflection and rotating angles for requiring micro mirrors. Micro actuators are essential for micro electromechanical systems of movable components. Optimization of their dynamic properties is conducted using the Intellisuite. Actuators for driving micro mirrors are classified into those using electrostatic forces and using thermal expansion effects. Electro mechanical actuators are actuated the electrostatic force to create motion. Thermomechanical actuators use the physical expansion or contractionthat occurs in materials as they undergo temperature changes. Electrostatic actuators are designed adapting torsional springs to avoid plastic deformation during the actuation with large tilting angles. If externally imposed voltages increases greater than 550V, a local plastic deformation occurs. Thermal actuators of length, 200μm and thickness, 2μm, with a 40μm long flexure and a 15μm wide cold arm deflect up to 13μm at the tip around 10V We also design thermal expansion type actuators for driving micro mirrors. Actuation mechanisms of the thermal expansion type are classified into different-resist and bi-metal ones. For obtaining larger deflections, metal/poly-silicon actuators combining both methods are devised. Numerical simulations using the commercial software show that metal/poly-silicon actuators can result in deflections twice as large as the conventional poly-silicon actuators can. We also design thermal bimetal type actuators for driving micro mirrors. It reports the design and simulation of thermal double-cantilever beam bimorph(TDCB) actuators that can be used to drive micromirrors. TDCB actuators combine two paralleled bimorph actuators acting in opposite directions for rotational control of micromirrors. Each actuator is structured by nickel and silicon dioxide thin film with an embedded polysilicon line as a heat source. With a size of only 20μm width and 100μm length, TDCB actuators result in vertical displacement of 20μm at 20V DC which is a significant improvement, comparing to the conventional thermal bimorph actuators.

有限要素法에 의한 流體素子 內部 流動解析 및 熱特性에 關한 硏究

노헌영 弘益大學校 1986 국내석사

사각채널내에 배열된 반원 리브의 열·유동특성에 관한 연구

이경환 경상대학교 대학원 2011 국내박사

The various shapes of artificial attachments like fin or rib, dimple are fitted in the flow channel to create flow separation and reattachment; vortices and recirculation near the wall and these effects are the main reasons for heat transfer enhancement in such channels. The rib geometry and arrangement in the channel also alter the flow field resulting in different the convective heat transfer coefficient and the overall thermal performance. When the spacing of artificial attachments is too dense to yield enough reattachment, it affects inversely to increase heat transfer. on the other hand if the spacing is too large between periodically arranged ribs, heat transfer efficiency does not improve significantly. because boundary layer was developed from the reattachment point. Therefore, heat transfer efficiency can be increased by moderately using the rib shapes, sizes and spacing. The point is to be noted not only to the enhanced heat transfer but also perspective of huge pressure drop because of artificial flow interruptions in the flow channel. So the heat transfer enhancement and pressure drop both factors should be chosen as a fact of overall performance. The turbulent flow characteristics and heat transfer augmentation on the periodically arranged semi-circular ribs in a rectangular channel have been investigated. The aspect ratio of the rectangular channel was AR=5, the rib height-to-hydraulic diameter rate was 0.07. The rib height-to-channel height rate was set as e/H=0.117 for various PR(rib picth-to-rib height rate) between 8~14, respectively. The SST k-ω turbulence model and v2 - f model were used to find out the heat transfer and flow characteristics of near the wall which are suited to obtain realistic phenomena. The numerical analysis results show turbulent flow characteristics, heat transfer enhancement and friction factor as observed experimentally. The results predict that turbulent kinetic energy(k) is closely relative to the diffusion of recirculation flow. and v2 - f model simulation results have a good agreement with experimental values.

Experimental Study on Effects of Carbon Dioxide to the Thermal Desalination System : 열 담수화 장치에서 이산화탄소의 배출에 관한 실험적 연구

바야라 나산 경상대학교 대학원 2012 국내석사

열 담수화 시스템에서 용해된 비 응결 가스(NGC)의 발생은 응축 열 전달 저하, 에너지 소비량은 증가하는 심각한 문제이다. NGC는 주로 질소 (N2), 산소 (O2), 아르곤 (Ar)와 이산화탄소 (CO2) 등 다른 가스로 구성되어 있다. 그러나 이산화탄소는 해수에 화학적으로 용해되고, 스케일형성에 밀접하게 관련 되어있다. 그러므로 스케일 형성을 예측할 수 있는 적절한 과정의 이해와 적절한 방출시스템을 사용하는 것이 필요하다. 이 연구의 목적은 열 담수 시스템에서 발생하는 NGC의 복잡함을 밝혀내는 것 이다. 특히 그 중에서도 해수에 화학적으로 반응하는 이산화탄소와 그것이 어떻게 스케일 형성에 영향을 미치는 대한 복잡함을 밝히는 것이다. 본 논문에서는 열 담수 시스템의 성능, 이산화탄소의 발생, 염수와 담수에 영향 등이 실험실 규모로 조사되어 졌다. 단일 효용 증발관는 산업에 적용하기에 제한되어 있고, 선박과 다중효용법를 개발하는데 주로 사용되고 있다. 이 논문에서는 단일 효용 증발관를 선택하여 사용 했다. 증발기 세포의 10개의 티타늄 가열 튜브는 해수증발을 위해 수평으로 설치 되었고, 물이 가열튜브를 가열시키는 증기로 사용되었다. 그리고 그것은 온도를 제어하기 위한 전열기에 연결되어 있다. 끓는 온도는 증발 셀의 압력에 의해 제어 되어진다. 실험연구는 단계로 나누어져 있다. 첫째로 시스템 성능을 분석하고 둘째로 이산화탄소의 발생을 조사하기 위해 해수를 분석하고, 증발 온도와 예열기의 온도가 실험 진행의 매개 변수로 사용하였다. 성능 테스트 분석은 증발기 압력에 의해 제어되는 다양한 끓는 온도 범위에서 실시 하였다. 해수 분석에 관해서는 염분와 PH가 매개 변수로 사용되었고, 그것은 휴대용 염분측정기와 PH측정기로 측정 하였다. 마지막 결과는 이산화탄소 배출비율이 끓는 온도에 직접적인 영향을 미치는 것을 확인 할 수 있었다. 또 다른 문제는 이산화탄소가 응결수에 쉽게 흡착되는 것 이다. In the thermal desalination system release of dissolved non-condensable gases (NCG) are serious problem with reducing heat transfer for condensation, energy consumption and more. NCG mainly contains few different gases which are the nitrogen (N2), oxygen (O2), argon (Ar) and carbon dioxide (CO2). However only carbon dioxide (CO2) chemically dissolves in seawater, reacts with concentration component of seawater and closely related to scale formation. Therefore it’s necessary to understand proper progress to predict scale formation and use proper venting system. The aim of the study is reveal the complication of the non-condensable gases release from the thermal desalination system, especially the carbon dioxide which reacts with chemically to the concentration components of the seawater and how it is related to scale formation. In this thesis, performance of thermal desalination system, release of carbon dioxide and effects to brine and distillate are investigated in laboratory scale. Single-effect distillers have very limited industrial application and mainly used in marine vessels, development to the multi-effect distillers. Single-effect distiller is chosen as thermal desalination system in this study. In the evaporation cell 10 titanium heating tubes are placed in horizontal directions to evaporate the seawater. General water is used as steam to heat the heating tubes and is connected to the electric heater to control temperature. Boiling temperature is controlled by pressure of the evaporation cell. The experimental study has divided into stages, firstly analyse system performance and secondly analyse the seawater to investigate the release of carbon dioxide. The evaporation temperature and preheater temperature are chosen as parameters of the experimental progress. The performance test analyse has been conducted in various boiling temperature ranges which controlled by evaporator pressure. As for the seawater analyse, salinity and pH are used as main parameters and it is tested by portable salt meter and pH meter. Finally the results were showed that release of carbon dioxide rate has directly influenced by boiling temperature. Another matter is released carbon dioxide has easily adsorbed to condensed water.

리튬브로마이드 수용액막의 흡수특성에 대한 실험적 연구

이준규 弘益大學校 大學院 2001 국내석사

흡수식 열펌프에서 유하액막에 의한 가스나 증기의 흡수과정은 난방 및 냉방 성능을 결정하는 중요한 열 및 물질전달과정이다. 본 연구에서는 농도 60%의 리튬브로마이드 수용액이 관외측을 따라 유하액막으로 흘러내릴 때 수증기 흡수과정에 대하여 수용액막의 레이놀즈수(80-200)와 비흡수가스의 체적농도 (O%-lO%)가 흡수과정의 열 및 물질전달에 미치는 영향을 실험적으로 연구하였다. 수용액막 레이놀즈수 100 이상의 영역에서 6열의 수평관 외측에 액막이 완전하게 형성됨을 확인하였다. 수용액의 농도가 증가함에 따라 열전달특성과 물질전달특성이 감소하였다. 흡수과정중 레이놀즈수 150에서 비흡수가스의 체적농도가 증가함에 따라 유하액막의 열 및 물질전달율은 감소하였다. 특히 열 및 물질전달 특성은 순수 수증기에 소량의 비흡수가스가 유입되었을 때 그 저하율이 심각하였다. In the present study, the effects of film Reynolds number (80~200) and volumetric content of non-absorbable gases (0~10%) in water vapor on the absorption process of aqueous LiBr solution were investigated experimentally. The formation of solution film on the horizontal tubes of six rows were observed to be complete for Re>100. The heat and mass transfer coefficients were measured as a function of film Reynolds number at different volumetric concentration of non-absorbable gases. Increase of solution concentration resulted in the decrease of heat transfer and mass transfer characteristics. As the concentration of non-absorbable gases increased at Reynolds number 150, mass transfer rate decreased. The degradation effects of non-absorbable gases seemed to be significant especially when small amount of non-absorbable gases were introduced to the pure water vapor.

열간 단조 공정의 폐열을 이용한 온수 획득에 관한 연구

김철표 경상대학교 대학원 2009 국내석사

Nowadays, the world is facing environmental crisis and shortage of resource problem at the same time. In particular, climate changes not only induce weather disasters but also cause the subsequent destruction of the ecosystem essentially and this threatening the survival of mankind. It was predicted that the annual economic loss due to the climate change will be reach 5~20% of whole world GDP, if overconsumption of energy system continues as recent state. (2006, Stern report). The economic development of developing countries and continuous increasing of the world's population will be instigating the shortage of energy resources and accelerating price increases of energy. Hence, reduce the primary energy consumption in other hand development and introduction of application technology with environment-friendly energy are needed. Recently, since the energy problem, application of renewable energy was highlighted such as solar energy, wind power energy and so on. Many researches focus on develop alternative energy and energy conservation technologies and these research are actively under going. Among these include numerous on energy conservation technologies through waste heat recovery. However, most of the technology is limited to industrial facilities and large capacity boiler device so that broad expansion on applications technologies is required. In this research, investigate the hot water acquisition through waste heat recovery in small capacity of boiler. Furthermore, validate efficiency of waste heat recovery respect to various capacities of boiler use commercial software and finally intent to contribute to design optimal heat exchange system. Therefore, in this study conduct both experimental and numerical analysis and the results can be summarized as follow: 1. The temperature of water heated by exhaust gas from furnace and maintain steady state after 8 hours experiment running. 2. It shows that the obtained heat of cooling water is tending upwards with the change of times. 3. During experiment cooling water can be obtain maximum difference of temperature by 25 ℃. 4. Total amount of recovered heat with the steady state reach around 40,000 kJ/h. 5. Comparison results show that experiments and numerical simulation have a good agreement within the range of 10% on temperature distribution. 6. Based on the verified numerical model, the feasibility of hot water acquisition according to flow rate of the cooling water and the effluence of different season condition were investigated. As the results, the flow rate of cooling water and season condition has no significant effect on of acquisition of the hot water. 7. According to experiments and numerical analysis results it can be consider that in case of recycling the waste heat(temperature range: 300 ~ 400℃) from small capacity of furnace have high benefits to supply necessary hot water used for heating and throughout industrial field.

나노 구리 입자를 이용한 히트파이프의 열전달 향상에 관한 연구

정현권 경상대학교 대학원 2012 국내박사

The paper focuses on the pressure characteristics inside single loop oscillating heat pipe (OHP) which have 8.0 mm inner diameter copper tube with loop height of 725 mm. Piezoresistive absolute pressure sensor (Model-Kistler 4045A5) has been used to get data. Distilled water is used as working fluid inside the OHP with different filling ratios of 40%, 60%, 80% of total inside volume. Experimental results show that the thermal characteristics are significantly inter-related with pressure fluctuations as well as pressure frequency. And the pressure frequency also depends upon the evaporator temperature maintained in the range of 60℃ to 90℃. The investigation shows that 60% filling ratio gives the highest inside pressure magnitude and highest number pressure frequency at any of setting evaporator temperature and the filling ratio of 60% filling shows the lowest thermal resistance. The main purpose of this research is the investigation of thermal performance of water based copper nanofluids charged into single loop oscillating heat pipe (OHP). The effects of filling ratios and copper particle concentration over thermal resistance and pressure fluctuation inside oscillating heat pipe have been investigated. Experimental results show that the thermal characteristics are significantly inter-related with pressure fluctuations as well as pressure frequency with different nanofluid concentration. The pressure frequency also depends upon the evaporator temperature which has been maintained from 60℃ to 90℃. The experimental results show the 60% filling ratio gives the highest inside pressure magnitude of highest number pressure frequency at any of setting of evaporator temperature and 5wt% results had the lowest thermal resistance.

유동상에서 산기부의 영향에 대한 실험적 연구

이기수 홍익대학교 1998 국내석사

A Study on the Heat Transfer Characteristic of Open-cell Metal Foam : 오픈셀 발포금속의 열전달 특성에 관한 연구

김미화 경상대학교 대학원 2009 국내석사

The use of metal foams has been widely increasing by virtue of its novel properties in various areas. They are relative new materials with characteristics of low density, high surface area to unite volume ratio, varieties of possible materials. The applications include compact heat exchangers for airborne equipment, air-cooled condenser towers, and compact heat sink for electronics. Due to the character of metal foam, applying metal foam into these applications would result in these merits including high efficient, compact and light weight. It is an approach to characterization on the thermal transfer behavior of fluid through metal foam. In the chapter one, basic introduction on metal foam was done including metal foam categorization, and application area. Typically, there are two groups, closed cell and open-cell metal foam. This paper is restricted to the study on open-cell metal foam. Chapter two summarized the main open literatures on the properties of open-cell metal foam. The geometry of foam, including fiber and pore diameter, the surface area density was introduced. Two concerns during the design process, heat transfer and hydraulic performances are mainly depended on permeability, inertial coefficient and effective conductivity, so these factors evaluation method is also included in this chapter. There are mainly three mechanisms of heat transfer inside of metal foam, heat transfer between heat source and fluid, between heat source and metal fiber, inertial heat transfer between metal fiber and fluid. This arises one question whether the difference is negligible. Chapter three discusses the acceptance of one thermal equation heat transfer model, and then provides a typical optimization process of choosing material. This paper discusses two application cases with metal foam, heat sink and compact heat exchanger. Heat sink is used to dissipate excess heat from electronic device in order to keep the device under maximum temperature. Metal foam is one possible material for heat sink design for the higher efficiency and lighter weight. Simplified simulation on fin tube heat exchanger is done. However, due to the complex geometry of foam structure, undirected simulation is done by implying thermal equilibrium heat transfer model which is verified in previous chapter discussion.

Panel method를 이용한 임의의 형상에 대한 외부 유동장 해석

송수형 홍익대학교 1993 국내박사