• Title/Summary/Keyword: Vacuum condition

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A Flow Analysis of a Solution Pump for an Absorption Chiller (흡수식 냉동기용 용액펌프의 유동특성 해석)

  • Bae Wonyoung;Lee Kichoon;Hur Nahmkeon;Jeong Siyoung
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.569-572
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    • 2002
  • In the present study, flow simulations of a solution pump fer an absorption chiller are performed. The results are compared to the experimental data. Since the cavitation is more likely to occur in a solution pump due to Its operation under vacuum condition, and the cavitation was not considered in the present computations, the computed and experimental results show large discrepancies. For more accurate performance prediction of a solution pump, a cavitation model is required in the flow simulation. Flows through an inducer are also studied to see the effect of design parameters on performance characteristics. It is shown from the results that, if not properly designed, recirculation legion may exist near the hub region of the Inducer, and the suction surface may experience higher pressure than the pressure surface of the inducer, which may deteriorate the performance.

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Experimental Study on Fresh Water Generation System with Low Pressure Evaporation (저압 증발기를 갖는 청수제조 장치에 관한 실험적 연구)

  • Chung, Han-Shik;Wibowo, Supriyanto;Lee, Gyeong-Hwan;Shin, Yong-Han;Jeong, Hyo-Min
    • Journal of Power System Engineering
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    • v.15 no.2
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    • pp.25-30
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    • 2011
  • A fresh water generation system is designed for converting brackish water or seawater into fresh water. In this paper fresh water generation by distillation process that evaporates feed water and subsequently condenses vapor as evaporation product to get fresh water was studied and city water was employed as feed water. The system uses the ejector to create a vacuum, under which liquid can be evaporated at lower temperature than it at normal or atmospheric condition, hence less energy consumption. The effect of various operating conditions i.e. temperature of feed water and different orifice diameters were studied experimentally to investigate the characteristic of the system. It was found that these parameters have significant effect in the performance of fresh water generation system with low pressure evaporation.

The development of high wear resistant tappet in diesel engine (Diesel Engine용 내마모 초경 Tappet 개발)

  • 송근철;심동섭;김경운;조정환
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1998.10a
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    • pp.313-322
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    • 1998
  • Tappet has wear problems like scuffing or pitting because of high Hertzian contact stress by line contact type between cam and tappet. To overcome this wear problems, we developed the high wear resistant tappet. Developed tappet consists of WC base alloyed tip and steel body. These two parts were directly bonded each other at high temperature under vacuum condition. To estimate the wear resistance of tungsten carbide tappet, we perform the scuffing test and engine dynamo test. As the result, tungsten carbide tappet has better wear resistance than conventionally chilled iron tappet.

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Growing and Luminous Characterization of ZnGa2O4:Mn Thin Film Deposited by RF Magnetron Sputtering (RF 스퍼터링 방법에 의한 ZnGa2O4:Mn 박막의 성장거동과 발광특성)

  • 정승묵;김영진
    • Journal of the Korean Ceramic Society
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    • v.40 no.7
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    • pp.652-656
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    • 2003
  • The green emitting phosphor, BnGa$_2$O$_4$:Mn thin films with spinel structure were deposited by rf magnetron sputtering at various Ar/O$_2$ ratios. Thin film phosphors were heat-treated in air and $N_2$+vacuum atmosphere, respectively. Effects of Ar/O$_2$ ratios and annealing conditions on the structural and photoluminescence (PL) and cathodeluminescence (CL) properties were investigated. Luminous properties were more improved by inhibiting the films from contacting with oxygen during heat treatment.

Fabrication and Characteristics of $CuInS_2$ Thin Film ($CuInS_2$ 박막 제조 및 그 특성)

  • Park, Gye-Choon;Jeong, Woon-Jo;Kim, Seong-Ku;Ryu, Yong-Tek;Chung, Hae-Duck;Lee, Jean
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1992.11a
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    • pp.84-89
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    • 1992
  • The polycrystalline $CuInS_2$ thin films are prepared by vacuum heat treatment of layer, which is deposited by vaccum evaporation in order. The electrical and optical properties of the films are investigated at various sulfur deposition mole rate, substrate temperature, heat treatment temperature and time. From data, n type-$CuInS_2$ exhibits resistivity, transmittance and energy band gap with 142[${\Omega}{\cdot}cm$], 73[%], and 1.5[eV] respectively at optimum fabrication condition. Finally, the films are fabricated with chalcoprite structure.

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Development of Magnetic Abrasive Jet Machining System for Precision Internal Polishing of Circular Tubes (원형관의 내면정밀가공용 순환식 자기입자분사가공 시스템 개발)

  • 강윤희
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 1995.10a
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    • pp.24-29
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    • 1995
  • A recently developed finishing process using rotating magnetic field is known to be very efficient for the finishing of parts such as vacuum tube, sanitary tube, etc., which are difficult to be finished by the conventional finishing methods as they are generally curbed tubes. But, the finishing system using rotating magnetic field have the defect that is the cross section of workpiece only circle because of internal rotating tool. Therefore, new finishing process of the workpieces which cross section are not circle is important and required. magnetic abrasive jet machining is a new concept finishing process. It is the precision internal finishing method using working fluid mixed with magnetic abrasives, which is jetted into the internal surface of tube. And magnetic poles are equipped on external surface of tube. In this study new concept finishing process or, magnetic abrasive jet machining system was developed. machining condition was predicted using simulation and some characteristics of the finishing process was analyzed.

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Analysis of a Hot Rolling Roller and Spring-back of Electrode Materials for Secondary Batteries (이차전지 전극제조용 열간압연롤러와 전극재료의 열 변형 및 스프링백 해석)

  • Kim, Kyung-Sik;Kim, Cheol
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.538-543
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    • 2008
  • A roller with a shaft and hot oil paths for pressing electrodes of polymer batteries were modeled and analyzed by FEM. There are many hot oil tubes in the roller and shaft, through which $72^{\circ}C$ hot oil flows for heating the surface of a roller and shaft. Thermal deformations and temperatures distributions of the roller and shaft were calculated and a convection boundary condition on surfaces was used. The influence of existence of a groove in the shaft on the flatness of a roller surface caused by thermal deformation was investigated. In addition, the amount of spring-back of electrodes under vacuum pressure and heating was calculated after the hot rolling process. It was shown from this study that the groove in one shaft had a favorable effect on the surface flatness.

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Controllable Growth of Single Layer MoS2 and Resistance Switching Effect in Polymer/MoS2 Structure

  • Park, Sung Jae;Chu, Dongil;Kim, Eun Kyu
    • Applied Science and Convergence Technology
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    • v.26 no.5
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    • pp.129-132
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    • 2017
  • We report a chemical vapor deposition approach and optimized growth condition to the synthesis of single layer molybdenum disulfide ($MoS_2$). Obtaining large grain size with continuous $MoS_2$ atomically thin films is highly responsible to the growth distance between molybdenum trioxide source and receiving silicon substrate. Experimental results indicate that triangular shape $MoS_2$ grain size could be enlarged up to > 80um with the precisely controlled the source-to-substrate distance under 7.5 mm. Furthermore, we demonstrate fabrication of a memory device by employing poly(methyl methacrylate) (PMMA) as insulating layer. The fabricated devices have a PMMA-$MoS_2$/metal configuration and exhibit a bistable resistance switching behavior with high/low-current ratio around $10^3$.

Magnetic Interference on the Infrastructure for a Super-speed Tube Train

  • Lee, Hyung-Woo;Jang, Seung-Yup;Kang, Bu-Byoung;Cho, Su-Yeon;Lee, Ju
    • Journal of Electrical Engineering and Technology
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    • v.6 no.3
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    • pp.364-368
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    • 2011
  • The super-speed tube train was introduced to increase the speed of ground transportation. It levitates magnetically and runs in a partial vacuum tube, which significantly reduces air resistance. However, strong magnetic force sufficient to propel the massive train can affect the infrastructure. The induced eddy current produces joule heat, and raises the inside temperature of the girder, which might lead to electrochemical corrosion on the girder, thereby weakening its durability. In this paper, the authors analyzed the magnetic flux and induced eddy current in the reinforced concrete girder by using three-dimensional FEM, particularly by varying the number of reinforcing steels of the upper flange of the girder to the condition of almost the same flexural strength and reinforcing steel amount.

Physical and Electrical Characteristics of Varnish and Varnish Treated Insulating Paper for Pole Transformers

  • Jung, Jong-Wook;Song, Il-Keun;Koo, Kyo-Sun;Song, Hyun-Seok;Kwak, Hee-Ro;Han, Yong-Huei
    • KIEE International Transactions on Electrophysics and Applications
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    • v.2C no.6
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    • pp.321-326
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    • 2002
  • This paper describes the mechanical and electrical characteristics of insulating paper impregnated with diluted varnish(W-128), according to Korean Standards. The varnish was diluted with a solvent of 6 different wt%. Kraft paper and Nomex paper were impregnated with the diluted varnish in a vacuum condition, and then completely dried. As the mechanical characteristics, the thickness of the completely dried varnish, the drying time and the tensile strength of the specimens were measured, and as the electrical characteristics, the permittivity, the tan $\delta$ and the specific resistance were evaluated as well.