• Title/Summary/Keyword: Coil pitch

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Study on the Vibration Analysis of Damper Clutch Spring (댐퍼 클러치 스프링의 진동 해석에 관한 연구)

  • Cho, Jae-Ung;Han, Moon-Sik
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.10 no.4
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    • pp.22-30
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    • 2011
  • This study analyzes harmonic vibration with natural frequency according to the configuration of damper clutch. In the case of double spring, equivalent stress at same direction of the revolution at inner and outer coil spring is over 30% as compared with at its opposite direction. Natural frequency or harmonic response with maximum deformation in case of the less coil pitch is below 3Hz as compared with in case of the more coil pitch. As the coil pitch of damper spring as the case 2 or 4 becomes smaller, its mass and deformation can be large. In these cases, spring constant and natural frequency become smaller. In the case 5 or 6 of double spring at natural vibration or harmonic response, the frequency becomes over 300Hz. As the result of this study is applied by the design of damper spring, the damage at its connected part is prevented and the durability can be predicted.

Fluidization and Heat Transfer Characteristics in the Fluidized Bed(II) (기일고류동층내류동화(氣一固流動層內流動化) 및 전열특성(傳熱特性)에 관한 연구(硏究)(II))

  • Park, Jong-Suen;Baek, Ko-Kil;Kim, Yeun-Young;Jeon, Sung-Taek
    • Solar Energy
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    • v.14 no.2
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    • pp.51-60
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    • 1994
  • The fluidization characteristics of the furan foundry sand fluidized bed and the heat transfer characteristics on a single spiral coil tube in the bed have been investigated. In the paper, the heat transfer coefficients for a single spiral coil tube are measured in the furan foundry sand bed as a function of the ratio of heated coil tube pitch to diameter(p/Do) and the ratio of heated coil tube pitch to particle size(p/dp). The experimental results are as follows. 1) Mean heat transfer coefficients increases according to the increasing ratio of heated coil tube pitch to diameter(p/Do). 2) The Increasing rates of mean Nusselt numbers are more greater in the case of p/Do=1.58 than p/Do=4.75. 3) Mean Nusselt number can be expressed by the following equation, $Nu_{mean}=C\;Re^m\;Pr_g^{0.4}(p/dp)^n$.

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Cooling characteristics of a Liquid cooler Using Thermoeletric Module (열전소자를 이용한 액체 냉각기의 냉각열전달 특성)

  • Park, Min-Young;Lee, Geun-Sik
    • Proceedings of the SAREK Conference
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    • 2007.11a
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    • pp.197-202
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    • 2007
  • In this study, the cooling characteristics of a liquid cooler using thermoelectric module was experimentally investigated. The experiment was conducted for various inner structures of liquid cooler (4 cases), hot fluid flow rates (0.15-0.25 L/min), number of T.E module (2, 4, 6 set), and the cooling water flow rates (200-600 cc/min) for both parallel and counter flow types. Among the results, better cooling performance geometry was selected. And experiment was also carried out to examine further enhancement of cooling performance by inserting coils (pitches: 0.2, 3, 6 mm) into the hot-fluid channel. Present results showed that the short serpentine type(case2) indicated the best cooling performance. In the case of coil pitch of 3 mm, the best cooling performance was shown, more than 10% increase of the inlet and outlet temperature difference, compared with the case of the cooler without coil. Consequently, the inserted coil pitch should be properly selected to improve cooling performance.

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Cooling Heat Transfer Characteristics of $CO_2$ on Tube Geometry of Inclined Helical Coil Type Gas Coolers (경사진 헬리컬 코일형 가스냉각기의 관형상에 따른 $CO_2$ 냉각 열전달 특성)

  • Son, Chang-Hyo;Oh, Hoo-Kyu
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.19 no.9
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    • pp.640-646
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    • 2007
  • The cooling heat transfer coefficient of $CO_2$ (R-744) for tube and coil diameter (CD), inclined angle of tube and coil pitch of inclined helical coil type copper tubes were investigated experimentally. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and a inclined helical coil type gas cooler (test section). The test section consists of a smooth copper tube of 2.45 and 4.55 mm inner diameter (ID). The refrigerant mass flukes were varied from 200 to 800 [$kg/m^2s$] and the inlet pressures of gas cooler were 7.5 to 10.0 [MPa]. The heat transfer coefficients of $CO_2$ in inclined helical coil tube with 2.45 mm ID are $5{\sim}10.3%$ higher than those of 4.55 mm. The heat transfer coefficients of 41.35 mm CD are $8{\sim}32.4%$ higher than those of 26.75 mm CD. Comparison between $45^{\circ}\;and\;90^{\circ}$ of coil angle, the heat transfer coefficients of $45^{\circ}$ are higher than those of $90^{\circ}$. For coil pitch of gas cooler, the heat transfer coefficients of inclined helical coil gas cooler with coil pitch of 5 mm are similar to those of 10 and 15 mm.

Optimization of Coil Design for Helical Magneto-Cumulative Generators (나선형 자장압축발전기의 코일설계 최적화)

  • 국정현;이흥호
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.53 no.8
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    • pp.477-487
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    • 2004
  • Helical magneto-cumulative generators(MCGs) are devices which convert explosive energy into electromagnetic energy. The electromagnetic energy supplied from an external circuit is amplified by an explosively driven metal conductor mounted at the center of a helical coil compressing magnetic flux between the conductor and the coil. To optimize the coil design, output properties of small-size helical MCGs were measured while varying design parameters; the number of coil sections, length of the sections, pitch in the sections, and type of copper wire. Dimensions of the coil were kept constant, 50 mm in diameter and 200 mm in length. The coil was fabricated by using enamel-coated copper wire of 1 mm in diameter. The highest energy amplification ratio and figure of merit were 52.5 and 0.81, respectively. from an helical MCG with initial inductance of 63.7 $\mu$H at initial energy of 0.152 kJ Based on the experimental and calculated results, empirical formulas capable of optimizing coil designs were derived. By using these formulas, pitch in each coil section can be obtained at an arbitrary inductive load for high energy amplification ratio and figure of merit.

Evaluation of Heat Exchange Rate in Horizontal Slinky and Coil Type Ground Heat Exchangers Considering Pitch Interval (피치 간격에 따른 수평 슬링키형과 코일형 지중 열교환기의 열효율 평가)

  • Yoon, Seok;Lee, Seung-Rae;Kim, Min-Jun;Kim, Woo-Jin;Go, Gyu-Hyun;Jeon, Jun-Seo
    • Journal of the Korean Geotechnical Society
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    • v.30 no.7
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    • pp.55-61
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    • 2014
  • The need of geothermal energy is constantly increasing for economical and environmental utilization. Horizontal ground heat exchangers (GHEs) can reduce installation cost and increase efficiency. There are many kinds of GHEs, and it is known that slinky and spiral coil type GHEs show high thermal performance. Therefore, this paper presents experimental results of heat exchange rates in horizontal slinky and spiral coil type GHEs installed in a steel box whose size is $5m{\times}1m{\times}1m$. Dried Joomunjin standard sand was filled in a steel box, and thermal response tests (TRTs) were conducted for 30 hours to evaluate heat exchange rates by changing different pitch spaces of horizontal slinky and spiral coil type GHEs. As a result, spiral coil type GHE showed 30~40% higher heat exchange rates per pipe length than horizontal slinky type GHEs. Furthermore, long pitch interval (Pitch/Diameter=1) showed 200~250% higher heat exchange rates per pipe length than short pitch interval (Pitch/Diameter=0.2) in both spiral coil and horizontal slinky type GHEs, respectively.

Analysis of Half-coiled Short-pitch Windings with Different Phase Belt for Multiphase Bearingless Motor

  • Li, Bingnan;Huang, Jin;Kong, Wubin;Zhao, Lihang
    • Journal of Electrical Engineering and Technology
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    • v.9 no.1
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    • pp.162-169
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    • 2014
  • The analysis and comparation of the half-coiled short-pitch windings with different phase belt are presented in the paper. The half-coiled short-pitch windings can supply the odd and even harmonics simultaneously, which can be applied in multiphase bearingless motor (MBLM). The space harmonic distribution of the half-coiled short-pitch windings with two kinds of phase belt is studied wi th respect to different coil pitch, and the suitable coil pitch can be selected from the analysis results to reduce the additional radial force and torque pulse. The two kinds of half-coiled short-pitch windings are applied to the five- and six-phase bearingless motor, and the comparation from the Finite Element Method (FEM) results shows that the winding with $2{\pi}/m$ phase belt is fit for the five phase bearingless motor and the winding with ${\pi}/m$ phase belt is suitable for the six phase bearingless motor. Finally, a five phase surface-mounted permanent magnet (PM) bearingless motor is built and the experimental results are presented to verify the validity and feasibility of the analysis. The results presented in this paper will give useful guidelines for design optimization of the MBLM.

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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A Study on the Drag Reduction Effect and Heat Transfer Enhancement of Non ionized Surfactant and Water Mixture in a Circular Pipe Flow (비이온계 계면활성제 첨가수에 대한 관내 유동저항 감소 및 열전달 촉진에 관한 연구)

  • Kim, Myoung-Jun
    • Journal of Advanced Marine Engineering and Technology
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    • v.31 no.5
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    • pp.552-557
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    • 2007
  • This paper has dealt with the effect of non ionized surfactant and water mixture on drag reduction and heat transfer enhancement in a circular pipe flow with experimentally. The test section was consisted of stainless steel pipe with inside diameter of 16mm. The wire coil was used to increase heat transfer in a pipe and the on ionized surfactant(Oleyl Dihydroxyethyl Amino Oxide, ODEAO) was used to reduce the drag force of water mixture with surfactant. The main parameters of this experiment were diameter and pitch of wire coil and the ratio of test section length and horizontal wire coil length. In this experiment, the acquired results were 1) Drag reduction effect existed in this ODEAO-water mixture, 2) Friction factor and heat transfer were increased with insertion the heat transfer enhancement coil, 3) With increasing of pitch ratio, heat transfer was decreased, and 4) Heat transfer was decreased by the decreasing of inserting coil diameter.

Experimental study on the correlation between measurement length and winding or twist pitch for magnetization loss occurring in CORC and TSTC

  • Ji-Kwang Lee;Jinwoo Han;Kyeongdal Choi;Woo-Seok Kim
    • Progress in Superconductivity and Cryogenics
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    • v.25 no.4
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    • pp.40-44
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    • 2023
  • For high-temperature superconducting power applications that need large current capacity, a large current conductor manufactured using multiple superconducting tape is required. Conductors being studied for large currents capacity such as CORC, TSTC, and RACC have advantages and disadvantages, and in order to use these conductors in coil form and apply them to AC power devices, research on magnetization loss occurring in superconductors due to external magnetic fields is essential. To accurately measure magnetization loss in a conductor that is twisted by stacking straight conductors like TSTC, the correlation between the measuring system and the shape of the sample must be clearly known to accurately measure the loss. In this paper, we will confirm the difference in magnetization loss measurement values according to the correlation between the length of the pickup coil and the twist pitch of the sample in CORC and TSTC shapes, and review considerations for accurate magnetization loss measurement from the results.