• Title/Summary/Keyword: Coil tube

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Evaluation of Heat Transfer performance of Wire-coil Inserted Tube (와이어코일 삽입법을 이용한 열전달 촉진기술 성능평가)

  • 이주동;박종호;이상천
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.5
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    • pp.457-465
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    • 2000
  • An experiment was carried out to evaluate the thermal performance of the wire-coil inserts method. Tested were the smooth tubes with the wire-nil inserts of various pitch and helix angle combinations. Test fluids were the 50%-solution of the ethylene glycol and the Hue water. Heat transfer coefficient and friction factors were deduced from the measured values of temperatures, flowrates and pressure drops. A unified dimensionless correlation for the heat transfer coefficients was developed as a function of the pitch to diameter ratio, the Reynolds number and the Prandtl number. An exergy analysis was performed to evaluate an optimal operating condition with the wire-coil inserts.

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Compact Anode Design with the Heat Capacity Performance in Rotating Anode X-ray Tube for Digital Radiography

  • Lee, Seok Moon
    • Applied Science and Convergence Technology
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    • v.24 no.5
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    • pp.136-141
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    • 2015
  • We studied the compact anode design to develop 100 kW rotating anode X-ray tube with large focal spot 1.2 mm, small focal spot 0.6 mm and tube voltage 150 kV for large hospital digital radiography using computer thermal simulation. The larger thermal radiation effect in a high vacuum can reduce the temperature of anode so the method to increase the surface area of anode is investigated. The anode has the multi-tier shape at the back side of TZM body of anode and also bigger diameter of anode. The number of multi-tiers was varied from 6 to 15 and the diameter of anode was also varied from ${\Phi}74$ to ${\Phi}82$. From ANSYS transient thermal simulation result, we could obtain $1056.4^{\circ}C$ anode maximum temperature when applying 100 kW input power at 0.1 second on target focal track which is less than $1091^{\circ}C$ of the conventional 75 kW X-ray tube with reduced anode weight by 15.5% than the conventional anode. The compact anode of reduced anode weight is able to improve the unwanted noise when the rotor is rotating at high-speed and also reduce the rotational torque which the cost effective stator-coil is possible. It is believed that the anode with 15 ea multi-tiers using ${\Phi}82$ can satisfy with the specification of the anode heat capacity. From the results of this paper, it has been confirmed that the proposed compact anode can be used as the anode of 100 kW rotating anode X-ray tube for digital radiography.

Study of Heat Transfer and Safety Evaluation for Heating Coils in the Fuel Tank of a Ship (선박 연료탱크 내 가온기의 열유동 및 안전성 평가에 관한 해석)

  • Moon, Jin-Gwon;Park, Jong-Chun;Kwon, Yoo-Hong;Yoo, Won-Seok;Ahn, Soo-Whan
    • Journal of Ocean Engineering and Technology
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    • v.24 no.5
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    • pp.22-30
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    • 2010
  • The fuel tank of a ship is filled with heavy fuel oil (HFO) that has a very high viscosity. In order to inject the HFO into the engine easily, heating coils are usually installed inside the fuel tank to heat the HFO and lower its viscosity. Currently, several different types of heating coils are used, e.g., fin-type, bare-type, drum-type, and shell-and-tube-type. It is well known that the shell-and-tube-type heating coil has good performance and high efficiency. In this study, experiments were conducted to determine the heat transfer efficiencies of three different shell-and-tube-type heating coils. Heat transfer efficiency was evaluated by using FLUENT 6.3.26 software. Also, structural safety was assessed by using ANSYS.simulation software.

A Study of Eddy Current Test for fin Tube in Different Fin Height (Fin 높이가 다른 Fin Tube의 와전류탐상에 관한 연구)

  • 이동진
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2003.10a
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    • pp.118-124
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    • 2003
  • 응축기, 증발기, 전열관에 사용되는 Fin Tube는 열전달효율 향상을 위하여 Fin의 높이 를 증가시키고, Tube의 최소두께를 얇게 가공하는 경향으로 발전하고 있다. 따라서, Fin Tube의 와전류탐상(ECT; Eddy Current Testing)에 의한 결함검출에 더욱 어려움이 예상된다. 본 연구에서는 Fin Tube의 Fin 높이를 3단계로 변화시켜 Tube를 제작하고, Tube에 축 방향결함, 원주방향결함, 원형결함을 각각 Fin Tube의 안쪽에 최소두께의 20%, 40%, 60% 의 동일결함율을 갖는 인공결함 시험편을 제작하였다. 제작한 원형결함시험편에 와전류탐상을 수행하여 Fin 높이에 따른 최적주파수의 변화를 연구하였다. Fin높이가 다른 원형결함 시험편에 1~20KHz 주파수를 적용한 결과 최적주파수는 12KHz로 Fin높이에 크게 영향을 받지 않음을 밝혔다 또한 Fin높이에 따른 최적주파수변화는 크지 않으나 Fin 높이가 높을수록 100%관통결함의 위상각(40')에 근접하여 나타났다. 축방향결함, 원주방향결함, 원형결함을 갖는 시험편에 와전류탐상을 수행한 결과 원형결함을 갖는 시험편의 신호 감도가 축방향결함, 원주방향결함보다 좋게 나타났다.

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An experimental study on heat transfer characteristics in the ice storage system of ice-on-coil type with rectangular finned tube during freezing process (직사각형 휜이 부착된 관외착빙형 빙축열조에서 응고과정시 열전달 특성에 관한 연구)

  • Kwon, H.Y.;Koh, J.Y.;Jeong, B.Y.;Yim, C.S.
    • Solar Energy
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    • v.20 no.4
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    • pp.61-67
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    • 2000
  • The purpose of this study is to improve heat transfer by attaching rectangular fins to tube. Experiments were carried out under the following conditions - Aspect ratio$(W_f/R_f)$ is 0.7, 1.2 and 1.8. Temperature conversion between high and low positions of water in the thermal storage appeared because maximum density point of water is about $4^{\circ}C$ and inlet direction of working fluid influenced conductive heat transfer Compared with the unfinned tube(bare tube), the rectangular tube increased the ice thermal storage energy and the ice thermal storage energy was increased as aspect ratio was increased.

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Endovaginal and Endorectal Surface Coils for in-ViVo Human MR Imaging and Spectroscopy (자궁경부암 진단용 MR 질내표면코일과 전립선암 진단용 MR 경직장표면코일의 제작 : 인체에서의 MR 영상과 MR 분광)

  • 문치웅;조경식
    • Journal of Biomedical Engineering Research
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    • v.16 no.4
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    • pp.481-491
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    • 1995
  • Endovaginal and endorectal receiver only surface coils were designed for MR imaging (MRI) and $^1H$ MR spectroscopy (MRS) for the uterine cervix and the prostate. The shape of endovaginal coil wire was rectangular with round corner. Size of the coil wire was empirically determined for 7cm and 4cm along the long and short axis, respectively. The coil wire loop was supported by acryl handle and bent about $150^{\circ}$ at one side of the loop considering the average angle of the cervix to the vagina. We called this as a "spoon-type endovaginal coil". The wire of the endorectal coil was made of the flexible materials so that the wire loop became long elliptic shape by pushing the acryl handle into the plastic tube for the comfort of patients when the coil was inserted into the cervix. Then, the shape was maintained to be circle by popping out handle. Conventional spin echo (SE) and fast spin echo (FSE) sequences were used as 71 and 72 weighted imaging sequences, respectively. Matrix size was 128~$256{\times}256$. FOVs for surface coil and body coil were 14cm and 24cm, respectively. 3D volume localized in vivo $^1H$ MR spectroscopy of the human cervix and prostate was performed using PRESS or STEAM localization method with the following parameters . TR=3 sec, TE=135 msec for PRESS or 30 msec for STEAM, NEX=2, NS=48, Sl=2048, and SW=2500 Hz. Using home-built endovaginal and endorectal coils, excellent T1- and T2-images were obtained to visualize early cervical and prostate tumors. 3D volume localized in vivo IH MRS was useful to differentiate the cancerous tissue from the normal tissue.

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Fouling Characteristics of Washable Shell and Coil Heat Exchanger (세척이 가능한 원통 코일형 열교환기의 파울링 특성에 관한 연구)

  • Hwang, Jun Hyeon;Na, Byung Chul;Oh, Sai Kee;Koo, Kyoung Min;Lee, Jae Keun;Ahn, Young Chull
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.27 no.2
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    • pp.69-74
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    • 2015
  • In this work, we studied the shell and helically coiled tube heat exchangers. Shell and coil heat exchangers with different rate of water flow and plate heat exchanger with same capacity were tested for condensing conditions. We proposed design guide using modified Wilson plot method. We compared fouling characteristics between shell and coil heat exchanger and plate heat exchanger, when they were washed and were not washed. The shell and coil heat exchanger showed 120% of higher saturated fouling resistance value and 4% of better heat transfer ratio than the plate heat exchanger.

Preliminaly Result of Whole-body Slotted Tube Resonator for 3.0T MRI

  • Kim, Kyoung-Nam;Park, Bu-Sick;Chung, Sung-Taek
    • Proceedings of the KSMRM Conference
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    • 2001.11a
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    • pp.151-151
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    • 2001
  • Purpose: 3.0 Tesla whole-body resonator provides a potential to have significant increase in imag quality and resolution in high resolution application such as cardiac, spine and extremit imaging. The aim of this study is to design an optimized 3.0T whole-body coil to produce high sensitivity and quality using slotted tube resonator.

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The Performance Analysis of the Fin-Tube Heat Exchanger Using CFC Alternative Refrigerant (CFC 대체냉매를 사용한 핀-관 열교환기의 성능해석)

  • 박희용;박경우;차재병
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.9
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    • pp.2358-2372
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    • 1993
  • In this study, the computer modeling for prediction of the performance of fin-tube heat exchanger using alternative refrigerant, HFC-134a was developed and the computer program for calculating the various properties of HFC-134a and the existing refrigerant CFC-12 and HCFC-22 was made. The heat exchanger modeling is based on a tube-by-tube approach, which is capable of analysis for the complex coil array. Performance of each tube is analyzed separately by considering the cross-flow heat transfer with external airstream and the appropriate heat and mass transfer relationships. A performance comparison according to the different refrigerants is provided using this developed model. As the result of this study, total heat transfer rate of evaporator and condenser using HFC-134a were found higher than that of using CFC-12 for the same operating conditions. When the mass flow rate of HFC-134a was less than CFC-12 about 18. 16%, the cooling capacities of evaporator were found to be the same.

A PHOTOELASTIC STUDY ON THE INITIAL STRESS DISTRIBUTION OF THE MOLAR ANCHORING SPRING(MAS) DURING RETRACTION OF THE MAXILLARY CANINE (상악견치 후방견인시 저항원 조절을 위한 MAS(Molar Anchoring Spring)의 초기 응력분포에 관한 광탄성학적 연구)

  • Chun, Youn-Sic
    • The korean journal of orthodontics
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    • v.26 no.4
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    • pp.341-348
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    • 1996
  • The efficiency of maxillary canine retraction by means of sliding mechanics along an 0.016 continuous labial arch and an 0.009 inch in diameter with a lumen of 0.030 inch NiTi closed coil spring was compared with that using the same NiTi closed coil spring and Molar Anchoring Spring(MAS) which was designed by author. MAS was made of .017" X .025" TMA wire and was given 60 degree tip-back bend on the wire close to the molar tube. This study was designed to investigate molar and canine root control during retraction into an extraction site with continuous arch wire system. Two techniques were tested with a continuous arch model embedded in a photoelastic resin. A photoelastic model was employed to visualize the effects of forces applied to canine and molar by two retraction mechanics. With the aid of polarized light, stresses were viewed as colored fringes. The photoelastic overview of the upper right quadrant showed that stress concentrations were observed in its photoelastic model. The obtained results were as follows. 1. Higher concentration of compression can be seen clearly at the distal curvature of the canine and mesial curvature of the molar and premolar when NiTi closed coil spring was applied only, which means severe anchorage loss of the molar and uncontrolled tipping of the canine. 2. The least level compression was presented at the mesial root area of the molar and premolar, and mesial root area of the canine when NiTi closed coil spring and MAS were used simultaneously. Especially mesial alveolar crest region of the canine was shown moderate level of compression that means MAS can be used as a appliance for anchorage control and prevention of canine extrusion and uncontrolled tipping during canine retraction.

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