• Title/Summary/Keyword: flux guide

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Study on Single-Phase Thermal and Hydrodynamic Characteristics in the Entry Region of a Mini-Channel Heat Sink (히트싱크 미세채널 내의 입구유동 영역에서의 단상 열유동 특성에 관한 연구)

  • Jang, Yong-Hee;Kim, Yong-Chan;Lee, Kyu-Jeong
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.12
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    • pp.1007-1016
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    • 2006
  • Although the advance in electronic technology enables a large number of circuity to be packed in a small volume, it is simultaneously required to remove the high heat load produced by them. In this study, the heat transfer and pressure drop characteristics of a mini-channel heat exchanger, which is designed for liquid cooling of electronic components, are investigated by varying operating conditions. Water and FC-72 were used as working fluids. The mini-channel heat exchanger was made with circular shape channels having din-meters of 2, 3, and 4 mm in regular intervals, and the channel length was 100 mm. The header and inlet guide pathway to provide uniform inflow were attached at the inlet of the test section. Copper block including the heaters was attached at the sidewall of the test section as a heat source, which provided the heat flux from 5 to $15W/cm^2$. The entrance effects enhanced the heat transfer coefficient in the mini-channel significantly. In addition, the single-phase pressure drop in the mini-channel was very similar to that predicted by the laminar flow correlation except that the transition Re decreased due to flow instability in the entrance region.

A Study on Mechanical Properties of SM490-TMC Back Plate(40 mm) Steel by SAW Welding (SM490-TMC 후판(40 mm) 강재의 SAW 용접을 통한 기계적 특성 연구)

  • Lee, Soung-Jun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.22 no.3
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    • pp.88-93
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    • 2021
  • SAW (Submerged Arc Welding) is often used for ship construction or welding pressure vessels and involves spraying a flux in a powder form to a welding site to a certain thickness and continuously supplying electrode wires therein. This welding method enables high current welding up to 1,500 to 3,000 A. Arc efficiency is higher than 95% and the technique allows clean work as it creates less welding fume, which is composed of fine metal oxide particles, and the arc beam is not exposed. In this study, SM490C-TMC thick plates were heterogeneously welded by SAW. Mechanical properties of welds were measured, and welds were assessed macroscopically and for adhering magnetic particles. The following conclusions were drawn. Bending tests showed no spots exploded on sample surfaces or any other defect, and plastic deformation testing confirmed sufficient weld toughness. These results showed the 1F welding method has no shortcomings in terms of bending performance.

Water film covering characteristic on horizontal fuel rod under impinging cooling condition

  • Penghui Zhang;Bowei Wang;Ronghua Chen;G.H. Su;Wenxi Tian;Suizheng Qiu
    • Nuclear Engineering and Technology
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    • v.54 no.11
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    • pp.4329-4337
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    • 2022
  • Jet impinging device is designed for decay heat removal on horizontal fuel rods in a low temperature heating reactor. An experimental system with a fuel rod simulator is established and experiments are performed to evaluate water film covering capacity, within 0.0287-0.0444 kg/ms mass flow rate, 0-164.1 kW/m2 heating flux and 13.8-91.4℃ feeding water temperature. An effective method to obtain the film coverage rate by infrared equipment is proposed. Water film flowing patterns are recoded and the film coverage rates at different circumference angles are measured. It is found the film coverage rate decreases with heating flux during single-phase convection, while increases after onset of nucleate boiling. Besides, film coverage rate is found affected by Marangoni effect and film accelerating effect, and surface wetting is significantly facilitated by bubble behavior. Based on the observed phenomenon and physical mechanism, dry-out depth and initial dry-out rate are proposed to evaluate film covering potential on a heating surface. A model to predict film coverage rate is proposed based on the data. The findings would have reliable guide and important implications for further evaluation and design of decay heat removal system of new reactors, and could be helpful for passive containment cooling research.

An Overview of the Pretreatment Processes in Seawater Desalination Plants using Reverse Osmosis Membranes (역삼투막을 이용한 해수담수화 플랜트에서 전처리 공정 기술)

  • Ahn, Chang Hoon;Lee, Wonil;Yoon, Jeyong
    • Journal of Korean Society of Water and Wastewater
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    • v.23 no.6
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    • pp.811-823
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    • 2009
  • Seawater desalination process using a reverse osmosis (RO) membrane has been considered as one of the most promising technologies in solving the water scarcity problems in many arid regions around the world. To protect RO membrane in the process, a thorough understanding of the pretreatment process is particularly needed. Seawater organic matters (SWOMs) may form a gel layer on the membrane surface, which will increase a concentration polarization. As the SWOMs can be utilized as a substrate, membrane biofouling will be progressed on the RO membrane surface, resulting in the flux decline and increase of trans-membrane pressure drop and salt passage. In the middle of disinfection, an optimal chlorine dosage and neutralizer (sodium bisulfite, SBS) should be practiced to prevent oxidizing the surface of RO membranes. Additional fundamental research including novel non-susceptible biofouling membranes would be necessary to provide a guide line for the proper pretreatment process.

Improvement of Dynamic Characteristic of Large-Areal Planar Stage Using Induction Principle (인덕션 방식을 이용한 평면 스테이지의 동특성 개선)

  • Jung, Kwang-Suk;Park, Jun-Kyu;Kim, Hyo-Jun
    • Journal of Institute of Control, Robotics and Systems
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    • v.15 no.7
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    • pp.675-682
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    • 2009
  • Instead of direct driving like BLDC, the induction principle is adopted as a driving one for planar stage. The stage composed of four linear induction motors put in square type is activated by two-axial forces; low-frequency attractive force and thrust force of the linear induction motors. Here, the modified vector control whose new inputs are q-axis current and dc current biased to three phase current instead of d-axis current or flux current is applied extensively to overall motion of the stage. For the developed system, the precision step test and the constant velocity test are tried to guarantee its feasibility for TFT-LCD pattern inspection. However, to exclude a discontinuity due to phase shift and minimize a force ripple synchronized with the command frequency, the initial system is revised to the antagonistic structure over the full degree of freedom. Concretely describing, the porous air bearings guide an air-gapping of the stage up and down and a pair of liner induction motors instead of single motor are activated in the opposite direction each other. The performances of the above systems are compared from trapezoid tracking test and sinusoidal test.

Design of Linear XY Stage using Planar Configuration and Linear Motors with Halbach Magnet Array (평면형 구조와 Halbach 자석배열 선형모터를 이용한 리니어 XY 스테이지의 설계)

  • Kim, Ki-Hyun;Lee, Moon-G.
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.19 no.4
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    • pp.553-561
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    • 2010
  • In flat panel display or semiconductor industries, they install the equipments with fine line width and high throughput for fabrication and inspection. The equipments are required to have the linear stage which can position the work-piece with high speed, fine resolution on wide range of motion. In this paper, a precision planar linear XY stage is proposed. The stage has a symmetric planar window configuration and is guided by air-bearings on granite plate. The symmetric planar window configuration makes the stage has robustness against dynamic and thermal disturbances. The air-bearings let the stage move smooth on straight guide bar and flat granite surface. The stage is actuated by linear motor with Halbach magnet array (HMA). HMA generates more confined magnetic flux than conventional array. The linear motors are optimized by using sequential quadratic programming (SQP) with the several constraints that are thermal dissipation, required power, force ripple and so on. The planar linear XY stage with the symmetric planar configuration and the linear motors is implemented and then the performance such as force ripple, resolution and stroke are evaluated.

The Effect of Lateral Displacement on the Performance in the Controlled-PM LSM (횡변위가 제어-영구자석형 선형동기전동기의 특성에 미치는 영향)

  • Lee, Ju
    • Journal of the Korean Magnetics Society
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    • v.8 no.5
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    • pp.308-316
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    • 1998
  • In this paper, the effects of lateral displacement on the thrust, lift force and (guide force) are investigated by 3-D Finite Element Analysis (FEA) in controlled-PM LSM which has some strong points that electrical power can be minimized and the thrust and lift force can be simultaneously obtained. The variations of airgap flux density and the forces concerning lateral displacement have been analyzed and the effect of lateral displacement and airgap length on the motor performance have been investigated in detail by analysis and experiment results. As the result of this study, the characteristics of PM-LSM concerning with the change of lateral placement and airgap have been made clear quantitatively.

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Dynamic response of linear actuator with the thrust force of transverse flux linear motor (횡자속 선형전동기의 추력특성에 따른 선형액추에이터의 동특성)

  • Woo, B.C.;Hong, D.K.;Kang, D.H.;Jang, J.H.;Kim, J.M.
    • Proceedings of the KIEE Conference
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    • 2005.07b
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    • pp.1192-1194
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    • 2005
  • 선형전동기는 일반적으로 회전형 전동기를 잘라 평면에 펼친 다음 회전형 전동기와 같이 구동할 경우 직선운동을 하는 전동기이다. 회전형 전동기에 비해서 효율특성을 다소 떨어지지만 직선운동을 위한 전동기가 필요할 경우에는 많이 사용하고 있는 실정이며 회전형의 경우 고정자와 회전자의 극간격을 유지하기 위해서 축을 중심으로 구동할 수 있게 제작하고 있는 실정이다. 그러나 선형전동기의 경우 정확한 극간경의 유지를 위해서 LM guide를 사용하는 것이 일반적이며 이로 인해서 고정자회 이동자 사이의 정확한 간격을 유지할 수 있게 된다. 또한 자속의 흐름과 이동자의 이동방향에 따라 일반적으로 선형전동기를 구분하는데 자속의 흐름으로 인해 만들어지는 평면과 이동자가 움직이는 방향이 같은 면 상에 있으면 종자속이라고 하고 횡방향으로 놓여질 경우 횡자속 선형전동기라고 부른다. 본 연구에서는 횡자속 선형전동기에서 발생되는 추력특성을 고려하여 선형액추에이터를 설계할 경우 발생되는 추력읜 불균일성에 대한 내용으로 전동기의 추력 특성 파형에 따른 성형 액추에이터의 동특성을 알아보았다. 특히 액추에이터에서 발생되는 공진특성을 기준으로 불때 같은 에너지로 약 2배의 동특성을 얻을 수 있었고 반력은 거의 같은 특성을 얻을 수 있었다.

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Study on Determination of Boron using the PGAA Facility at HANARO Research Reactor (하나로의 즉발감마선 방사화분석 장치를 이용한 붕소의 정량에 대한 연구)

  • Chung, Young-Sam;Cho, Hyun-Jae;Moon, Jong-Hwa;Kim, Sun-Ha;Kim, Young-Jin
    • Analytical Science and Technology
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    • v.16 no.5
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    • pp.391-398
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    • 2003
  • Basic research for the determination of boron content in biological sample has been carried out using the PGAA facility of the 24MW research reactor(HANARO). For investigation of characteristics for the measurement condition, neutron flux and its homogeneity were measured at irradiating geometry. The size of thermal neutron beam collimated from beam guide is $2{\times}2cm^2$ at the sample position. The neutron flux measured was the range of $1.0{\sim}6.5{\times}10^7n{\cdot}cm^{-2}{\cdot}s^{-1}$, and flux distribution from center within the radius of 4.5 mm and 9.0 mm was $5.77{\pm}0.71{\times}10^7n{\cdot}cm^{-2}{\cdot}s^{-1}$ and $4.68{\pm}1.64{\times}10^7n{\cdot}cm^{-2}{\cdot}s^{-1}$, respectively. Accordingly, sample size is adjusted within 10 mm for a homogeneous irradiation of high quality. Measurement system is designed to reduce the background source by Compton scattering and to improve the analytical sensitivity. To investigate the energy calibration and Compton suppression effect of gamma-ray counting system, the background conditions on both of Compton and single-mode were measured using NaCl standard. On the other hand, degree of spectral interference for sodium 472 keV peak as a matrix effect in the sample is established for an accurate boron analysis, and then boron content in three certified reference materials (NIST SRM 1570a, 1547, 1573a) was measured by using two modes and the results were compared with each other.

Design and Control of Ultra-precision Dual Stage with Air bearings and Voice coil motor for nm scanning system (나노 정밀도 스캐닝 용 공기베어링과 보이스 코일 모터의 초정밀 이중 스테이지 설계 및 제어)

  • Kim K.H.;Choi Y.M.;Kim J.J.;Lee M.G.;Lee S.W.;Gweon D.G.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.06a
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    • pp.1883-1886
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    • 2005
  • In this paper, a decoupled dual servo (DDS) stage for ultra-precision scanning system with large working range is introduced. In general, dual servo systems consist of a fine stage for short range and a coarse stage for long range. The proposed DDS also consists of a $XY\theta$ fine stage for handling and carrying workpieces and one axis coarse stage. Its coarse stage consists of air bearing guide system and a coreless linear motor with force ripple. The fine has four voice coil motors(VCM) as its actuator. According to a VCM's nature, there are no mechanical connections between coils and magnetic circuits. Moreover, VCM doesn't have force ripples due to imperfections of commutation components of linear motor systems - currents and flux densities. However, due to the VCM's mechanical constraints the working range of the fine is about $25mm^2$. To break that hurdle, the coarse stage with linear motors is used to move the fine about 500mm. Because of the above reasons, the proposed DDS can achieve higher precision scanning than other stages with only one servo. With MATLAB's Sequential Quadratic Programming (SQP), the VCMs are optimally designed for the highest force under conditions and constraints such as thermal dissipations due to its coil, its size, and so on. And for their movements without any frictions, guide systems of the DDS are composed of air bearings. To get precisely their positions, a linear scale with 5nm resolution are used for the coarse stage's motion and three plane mirror laser interferometers with 5nm for the fine's $XY\theta$ motions. With them, on scanning the two stages have same trajectories. The control algorithm is named Parallel method. The embodied ultra-precision scanning system has sub 100nm following error and in-positioning stability.

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