• Title/Summary/Keyword: spiral

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Lubrication Performance Analyses of Spiral Groove Dry Gas Seals - Part II: Detailed Performance Evaluation of Groove Design Parameters (스파이럴 그루브 드라이 가스 시일의 윤활 성능해석 - Part II: 그루브 설계 파라미터의 상세 성능평가)

  • Lee An Sung;Yang Jae-Hun;Choi Dong-Hoon
    • Tribology and Lubricants
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    • v.20 no.2
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    • pp.68-76
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    • 2004
  • Applying a general Galerkin FE lubrication analysis method to spiral groove dry gas seals, this study intends to analyze in detail the effects of groove design parameters, such as a spiral angle, groove width ratio, groove radius ratio, groove depth ratio, and groove taper ratio, on the lubrication performances of an opening force, leakage, axial stiffness and damping, and angular stiffness and damping at low and high rotating speeds: 3,600 and 15,000 nm. Results show that, for the primary design consideration performances such as the opening force and axial and angular stiffnesses, a spiral angle of $25^{\circ}$, a groove width ratio of 0.46, a groove radius ratio of 1.1, a groove depth ratio of 1.0, and a groove taper ratio of 0.0 are preferred. Where the recommended relatively low values of groove depth and taper ratios are to keep the axial and angular dampings positive or higher than 0 particularly at the high rotating speed.

Experimental Study on In-Tube Condensation Heat Transfer Characteristics of Helically Coiled Spiral Tubes (코일형 나선 전열관의 내부 응축열전달 특성에 관한 실험 적 연구)

  • Park, Jong-Un;Gwon, Yeong-Cheol;Han, Gyu-Il
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.12
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    • pp.1676-1683
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    • 2001
  • An experimental study on condensation heat transfer characteristics of helically coiled spiral tubes was performed. The refrigerant is R-113. A refrigerant loop was established to measure the condensation heat transfer coefficients. Experiments were carried out uniform heat flux of 15 kw/m$^2$, refrigerant quality of 0.1∼0.9, curvature ratio of 0.016, 0.025 and 0.045. The curvature of a coil was defined as the ratio of the inside diameter of the tube to the diameter of the bending circle. To compare the condensation heat transfer coefficients of coiled spiral tubes, the previous results on coiled plain tubes and straight plain tubes were used. The results shows that the condensation heat transfer coefficients of coiled spiral tubes largely increase, as increasing Re and quality, compared to those of coiled plain tubes and straight plain tubes. As increasing degree of subcooling, however, the condensation heat transfer coefficients on coiled spiral tubes decrease. It is found that the heat transfer enhancement is more better than coiled plain tubes and straight plain tubes, as increasing curvature ratio.

Microparticle Separator based on Dean Vortex in Spiral Microchannel (나선형 미세채널 내부에 형성되는 딘와류 이용한 미세입자 분리소자)

  • Byun, Kang Il;Kim, Hyung Jin;Kim, Byeong Hee;Seo, Young Ho
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.23 no.6
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    • pp.555-560
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    • 2014
  • This paper presents a microparticle separator using a spiral microchannel. A particle separator based on the dean vortex was designed, fabricated, and characterized. Two different spiral microchannels were fabricated. Width and initial radius of rotation in the spiral microchannel were fixed to $300{\mu}m$ and 1.75 mm, respectively. Two different depths of the microchannels were designed at $50{\mu}m$ and $80{\mu}m$. In this experimental study, the equilibrium position of microparticles was monitored by using fluorescent microbeads. In the case of a low dean number (<1.0), lift force and dean drag force were similar, indicating that microbeads were distributed to almost all areas across microchannels. However, in the case of a high dean number (>1.0), dean drag force rather than lift force was dominant, indicating that microbeads moved toward the inner wall of the spiral microchannel.

Improved Reconstruction Algorithm for Spiral Scan Fast MR Imaging with DC offset Correction (DC offset을 보정한 나선 주사 초고속 자기공명영상의 재구성 알고리즘)

  • 안창범;김휴정
    • Journal of Biomedical Engineering Research
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    • v.19 no.3
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    • pp.243-250
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    • 1998
  • Reconstruction aspects of spiral scan imaging for ultra fast magnetic resonance imagine(MRI) have been investigated with polar and rectangular coordinates-based reconstruction. For the reconstruction of the spiral scan imaging, acquired data in spiral trjectory should be converted to polar or rectangular grids, where interpolation techniques are used. Various reconstruction algorithms for spiral scan imaging are tested, and reconstructed image qualities are compared with computed phantom. An improved reconstruction algorithm with dc-offset correction in projection domain is proposed, which provides the best reconstructed image quality from the simulation. Image artifact with existing algorithms is completely removed with the proposed method.

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Design of a 0.5~2 GHz Cavity-Backed Spiral Antenna (0.5~2 GHz 캐비티 백 스파이럴 안테나 설계)

  • Jeon, Nam-Du;Shin, Dong-Hoon;Park, Dong-Chul
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.21 no.3
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    • pp.269-277
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    • 2010
  • In this paper, the design of a 0.5~2 GHz cavity-backed spiral antenna is described. Combined arm pattern with a log spiral in the inner region and an Archimedean spiral in the outer region, a backing cavity, and a Marchand coaxial balun for feeding are designed. Termination resistors are used to improve antenna characteristics at the lower frequency of the operation frequency. VSWR, axial ratio, gain and HPBW(Half Power Beam Width) characteristics are simulated using CST's MWS. Finally, the validity of these approaches is verified by comparing the simulated results with the measured ones. Also, the measurement results are compared with the performance of a commercial spiral antenna.

Thermal Performance of a Spirally Coiled Finned Tube Heat Exchanger Under Wet-Surface Conditions

  • Wongwises Somchai;Naphon Paisarn
    • Journal of Mechanical Science and Technology
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    • v.20 no.2
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    • pp.212-226
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    • 2006
  • This paper is a continuation of the authors' previous work on spiral coil heat exchangers. In the present study, the heat transfer characteristics and the performance of a spirally coiled finned tube heat exchanger under wet-surface conditions are theoretically and experimentally investigated. The test section is a spiral-coil heat exchanger which consists of a steel shell and a spirally coiled tube unit. The spiral-coil unit consists of six layers of concentric spirally coiled finned tubes. Each tube is fabricated by bending a 9.6 mm diameter straight copper tube into a spiral-coil of four turns. The innermost and outermost diameters of each spiral-coil are 145.0 and 350.4 mm, respectively. Aluminium crimped spiral fins with thickness of 0.6 mm and outer diameter of 28.4 mm are placed around the tube. The edge of fin at the inner diameter is corrugated. Air and water are used as working fluids in shell side and tube side, respectively. The experiments are done under dehumidifying conditions. A mathematical model based on the conservation of mass and energy is developed to simulate the flow and heat transfer characteristics of working fluids flowing through the heat exchanger. The results obtained from the present model show reasonable agreement with the experimental data.

CFD Analysis for Spiral-Jacketed Thermal Storage Tank in Solar Heating Systems (태양열 시스템에 적용된 나선재킷형 축열조의 CFD 해석)

  • Nam, Jin-Hyun;Kim, Min-Cheol;Kim, Charn-Jung;Hong, Hi-Ki
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.20 no.10
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    • pp.645-653
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    • 2008
  • Spiral-jacketed thermal storage tanks can greatly simplify solar heating systems while maintaining the thermal performance at a similar level as conventional systems with an external heat exchanger. Proper design of the spiral-jacket flow path is essential to make the most of solar energy, and thus to maximize the thermal performance. In the present work, computational fluid dynamics (CFD) analysis was carried out for a spiral-jacketed storage tank installed in a solar heating demonstration system. The results of the CFD analysis showed a good agreement with experimentally determined thermal performance indices such as the acquired heat, collector efficiency, and mixed temperature in the storage tank. This verified CFD modelling approach can be a useful design tool in optimizing the shape of spiral-jacket flow path and the flow rate of circulating fluid for better performance.

Study on Frequency Characteristics for Double-Layer Symmetric Spiral Inductor (2층 대칭 나선형 인덕터에 대한 주파수 특성 연구)

  • Kim, Jae-Wook
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.15 no.5
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    • pp.315-320
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    • 2022
  • In the case of a general spiral inductor, the orientation of the port is affected as it has an asymmetric structure. In this paper, double-layer spiral inductor that can have a symmetrical structure is proposed, and the simulation and frequency characteristics are analyzed. Compared to the conventional single-layer symmetrical inductor having an inductance of 3.9~4.2nH, the proposed double-layer symmetric spiral inductor has an inductance of 11~12nH in 0.3~1.2GHz frequency range, a quality factor of about 4.4 in 800MHz, and a self-resonant frequency of about 2.7~2.8GHz without changing the port. Compared to the general spiral inductor having a large difference depending on the port, it was confirmed that the influence on the port direction was small.

Case Studies of Penetration Characteristics of DCM Wall Using Spiral Mixing Blades in Soil Layers (특수교반날개를 사용한 DCM 공법의 지반 관입 특성에 대한 사례연구)

  • Jung, Doo-Hoi;Jeong, Gyung-Hwan;Yang, Tae-Seon
    • Journal of the Korean Geotechnical Society
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    • v.23 no.3
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    • pp.133-140
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    • 2007
  • DCM (Deep Cement Mixing Method) has been applied to build structures such as self-supported earth retaining walls. DCM columns should be penetrability into the stiff layer to assure the self-supporting ability. On the penetration increase of blade attached to the DCM mixing tools, a spiral mixing blade has been revised. Penetration characteristics of spiral blades in the stiff soil layer were evaluated through Gimhae and Incheon areas. The spiral mixing blades could penetrate into the stiff soil layers which have the N-value of greater than 30 although the penetration rate is somewhat slow. Penetration characteristics and economical efficiency should be discussed to determine the critical depth of the spiral mixing blade because the penetration efficiency can decrease in the stiff layer in this paper.

Support Characteristics of Rock Bolt and Spiral Bolt (록 볼트 및 스파이럴 볼트의 지보특성)

  • Cho, Young-Dong;Song, Myung-Kyu;Lee, Chung-Shin;Kang, Choo-Won;Ko, Jin-Seok;Kang, Seong-Seung
    • Tunnel and Underground Space
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    • v.19 no.3
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    • pp.181-189
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    • 2009
  • This study is to evaluate an effect of supports with respect to these supports after comparing the characteristic of support between rock bolt of a widely used type and spiral bolt of a new type. For these purposes, we performed pull-out test in laboratory about rock and spiral bolts in the case of cement-mortar grout curing periods, 7 and 28 days, then calculated pull-out load, displacement, external pressure, inner pressure and shear stress using data obtained from the results of pull-out test, respectively. In relation between pull-out load and displacement, displacement of spiral bolt is larger than one of rock bolt. It is considered that mechanical property of rock bolt is due to larger than one of spiral bolt. In addition, displacement of supports shows nearly same or decreasing with curing periods. We found that because adhesive force between supports and cement-mortar grout is increasing with compressive strength of grout according to curing periods. The inner pressure of spiral bolt is represented larger than one of rock bolt at a step of same pull-out load. It is suggested that spiral bolt is more stable than rock bolt, maintaining stability of ground or rock mass, when supports are installed in a ground or rock mass under the same condition. Putting together with above results, we can consider that spiral bolt as a new support on an aspect of pull-out load and inner pressure is larger than rock bolt in a ground or rock mass under the same condition. Moreover, spiral bolt is more effective support than rock bolt, considering an economical and constructive aspects of supports, as well as ground or rock stability before or after installing supports.