• Title/Summary/Keyword: inner tube

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Analysis of the Stress Characteristics of Double Layered Tube at Elevated Temperature (고온에서 이중튜브의 열응력특성해석)

  • Kim, E.H.;Jang, J.H.;Park, S.P.;Moon, Y.H.
    • Transactions of Materials Processing
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    • v.19 no.7
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    • pp.405-410
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    • 2010
  • Double layered tube that has been used for transportation and oil piping system is occasionally exposed to elevated temperature. The change in stress state at elevated temperature is important for the safe design of double layered tube. In this study, the variation of stress state for hydroformed double layered tube of which inner tube is stainless steel and outer tube is mild steel has been analytically analyzed. To characterize the thermal stress at elevated temperature, analytical model to provide thermal stresses between outer tube and inner tube was developed by using theories of elasticity and Lame equation. The feasibility of analytical model is verified by finite element analysis using ANSYS $CLASSIC^{TM}$, commercially available code. The variation of thermal stress at various thickness combination of inner and outer tube has also been investigated by proposed analytical model.

Effects of Fin Configuration on the Evaporator Performance (휜 형상에 따른 증발기의 전열 성능)

  • Lee, Jin Ho;Kwon, O Kap
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.2 no.1
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    • pp.27-36
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    • 1990
  • An experimental investigation was made to study the performance characteristics of evaporator having different fin configurations and tube inner grooves. Three different types of fin such as super slitted fin, slitted fin, plain fin, and two types of tube such as inner grooved tube, and bare tube, are tested varying the air velocity, evaporation temperature and superheat of refrigerant. Results show that in the range of air side Reynolds number $3{\times}10^3\;-\;1.5{\times}10^4$ evaporator with super slitted fin and inner grooved tube shows best performance. It is 80% higher in overall heat transfer coefficient and 2.6 times higher in pressure loss compared to that with plain fin inner grooved tube. Friction factor is found to be almost independent of evaporating temperature and degree of superheat, while Colburn j factor varies with evaporating temperature.

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Bifurcation Behaviours of Composite Tubes With Two Different Materials Subjected To Uniform Radial Shrinkage At The External Surface (외주에 균일한 압축을 받는 두꺼운 복합원관의 분지거동)

  • ;;Tomita,Y.
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.2
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    • pp.269-275
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    • 1990
  • Nonaxisymmetric bifurcation behaviours of composite tubes two different materials subjected to uniform radial shrinkage at the external surface have been investigated and compared with those of single tube. The effect of material parameters normalized with respect to those of outer tube upon the bifurcation point and corresponding mode has been clarified. The parameters substantially affect the bifurcation mode with long-wavelength so that the composite tube with low hardening exponent or with high yield stress of inner tube destabilizes the overall deformation of the tube. However surface type bifurcation, short-wavelength mode, shown on the traction-free inner surface is hardly affected by the material parameters. The surface type bifurcation completely depends on the material characteristics of inner tube and the bifurcation point of composite tube almost coincides with the of single tube.

A study about shape processing for the bend of the Copper-Tube that use Hair Pin Bending Machine (Hair Pin Bending Machine을 이용한 동 튜브 굽힘 성형가공에 관한 연구)

  • Kang, Heung-Sik;Kim, Dong-Sung;Heo, Sin;Hong, Sung-In
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.1705-1708
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    • 2003
  • The purpose of this study is to investigate the manufacturing technique on the U type Draw-Bending of inner grooved tube. This bending process make the U shape tube by Hair Pin Bending machine. The U type tube requires the quality of product that satisfy sufficient conditions for a heat exchanger. The mandrel components act the important roles that prevent wrinkles and keep the shape of cross section of bended tube at bending process. We performed the FEM simulation using LS-DYNA software and the bending test of inner groove tube and then, compared bending simulation with bending test results about mandrel ball diameter, mandrel position and optimal clearance between mandrel and tube.

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Behavior of CFST columns with inner CFRP tubeunder biaxial eccentric loading

  • Li, Guochang;Yang, Zhijain;Lang, Yan;Fang, Chen
    • Steel and Composite Structures
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    • v.22 no.6
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    • pp.1487-1505
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    • 2016
  • This paper presents the results of an experimental study on the behavior of a new type of composite FRP-concrete-steel member subjected to bi-axial eccentric loading. This new type of composite member is in the form of concrete-filled square steel tube slender columns with inner CFRP (carbon fiber-reinforced polymer) circular tube, composed of an inner CFRP tube and an outer steel tube with concrete filled in the two tubes. Tests on twenty-six specimens of high strength concrete-filled square steel tube columns with inner CFRP circular tube columns (HCFST-CFRP) were carried out. The parameters changed in the experiments include the slenderness ratio, eccentric ratio, concrete strength, steel ratio and CFRP ratio. The experimental results showed that the failure mode of HCFST-CFRP was similar to that of HCFST, and the specimens failed by local buckling because of the increase of lateral deflection. The steel tube and the CFRP worked together well before failure under bi-axial eccentric loading. Ductility of HCFST-CFRP was better than that of HCFST. The ultimate bearing capacity of test specimen was calculated with simplified formula, which agreed well with test results, and the simplified formula can be used to calculate the bearing capacity of HCFSTF within the parameters of this test.

A Study on the Fluid Flow of Vortex Nozzle for Generating Micro-bubble (미세버블 발생용 보텍스 노즐의 유체유동에 대한 연구)

  • Yu, Seong-Hun;Park, Sang-Hee;Kang, Woo-Jin;Han, Seung-Wook
    • Journal of the Korean Society of Industry Convergence
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    • v.25 no.4_2
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    • pp.637-644
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    • 2022
  • In this study, the flow characteristics according to the shape of the vortex nozzle was studied by numerical analysis and the amount of microbubble generation was measured experimentally. The shape of the vortex nozzle is cylindrical, diffuser, and conical type. The axial fluid velocity in the induced tube gradually increased from the inlet to the outlet. In particular, the fluid velocity in the nozzle part increased rapidly. The velocity distribution of the fluid at the inlet of the induced tube showed that the flow rotates counterclockwise in the outer region and the inner center of the induced tube. At the outlet of the induced tube, the cylindrical and conical type showed rotational flow, and the diffuser type showed irregular turbulent flow. The dimensionless pressure ratio 𝜂 of the inner region of the induced tube was lower than that of the outer region. Also, 𝜂 near the outlet of the induced tube in cylindrical and conical type showed a similar tendency to the inlet area. At the outer region of inlet of induced tube, intense vorticity was observed on the wall and in lower region. At the inner region of inlet of induced tube, intense vorticity was observed on the inner wall of the induced tube and in the central region of the inlet of the induced tube. At the outlet of induced tube, in the case of the cylindrical and conical type, intense vorticity was observed near the inner wall, the diffuser type showed irregular strong vorticity inside the tube. The total number of bubbles measured was the most in the cylindrical type, and the microbubbles less than 50mm occurred the most in the conical type.

Heat Transfer Characteristics of Fin-Tube Heat Exchanger using Two-Port Tube of Small Inner Diameter by Mechanical Expansion (연결세경관을 이용한 휜관형 열교환기의 기계확관에 의한 전열특성)

  • Lee, Sangmu;Park, Byung-Duck
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.28 no.11
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    • pp.428-433
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    • 2016
  • The fin and tube heat exchanger using a two-port tube has in air-conditioner heat exchanger because heat transfer performance. This study investigates the feasibility of a fin and tube heat exchanger using two-port copper tube by mechanical expansion. The optimum size of the tube-expanding bullet for the heat exchanger using two-port tube was through numerical calculation. The heat exchanger using a two-port tube was fabricated by mechanical expansion, and the heat exchanger performance was evaluated condensation and evaporation experiments. Compared to the heat exchanger of a conventional circular tube, the pressure drop per unit length of the heat exchanger with a two-port tube decreased. Compared to the heat exchanger using a conventional circular tube, the overall heat transfer coefficient of heat exchanger with a two-port tube increased up to 13% in the case of condensation, and up to 25% in the case of evaporation. The two-port tube heat exchanger outperforms conventional heat exchanger for air conditioner with a inner grooved circular tube.

A study on the single-phase heat transfer in a counter-flow double-pipe heat exchanger by Wilson plot technique (Wilson plot기법을 이용한 2중관식 대향류 열교환기의 단상 열전달에 관한 연구)

  • Ohm, Ki-Chan
    • Journal of the Korean Solar Energy Society
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    • v.26 no.4
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    • pp.93-100
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    • 2006
  • An experimental study of a counterflow heat exchanger was performed. The heat exchanger had an effective heat transfer length of 1000mm and was operated in a counterflow arrangement with hot water($30{\pm}0.5^{\circ}C$, $Re_i=3500{\sim}20000$) in the inner tube(copper tube, $d_0=9.52mm$) and cold water($15{\pm}0.5^{\circ}C$, $Re_{DH}=10700{\sim}39000$) in the annulus(copper tube, $D_0=19.05mm$). Overall heat transfer coefficients were calculated and heat transfer coefficients in the inner tube and the annulus were determined using Wilson plots. The inner Nusselt number was compared with that of Gnielinski's correlation and they agreed within ${\pm}10%$ error. The trends were typical for a fluid-to-fluid heat exchanger with the overall heat transfer coefficient increasing with both inner and annulus flow rates. In the range of this experiment, Nusselt numbers for the inner tube flow were almost identical with those of the annulus flow at the same Reynolds number.

Characteristic of Heat and Mass Transfer on Inner Ribbed Notched Fin Tube Absorber (내면가공 핀튜브 흡수기의 열 및 물질전달특성)

  • 설원실;권오경;문춘근;정용옥;윤정인
    • Journal of Advanced Marine Engineering and Technology
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    • v.24 no.4
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    • pp.478-485
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    • 2000
  • An experimental study of the absorption process of water vapor into lithium bromide solution was performed. For the purpose of development of high performance absorption chiller-heater utilizing Lithium Bromide solution as working fluid, the absorber is the most effective to improve the performance of an absorber because it requires the largest heat transfer area in an absorption chiller-heater system. This paper introduces bare tube and inner ribbed notched fin tube for the absorber of absorption chiller-heaters. Inner ribbed notched fin tube has about 10∼20% higher heat and mass transfer performance than bare tube conventionally used in absorbers and the it is expected to perform high heat and mass transfer. This paper will provide important information on the selection of absorber tubes in commercial absorption chill-heaters.

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Eccentric performance of CFST columns jacketed with steel tube and sandwiched concrete

  • Weijie Li;Yiyan Lu;Yue Huang;Shan Li
    • Steel and Composite Structures
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    • v.48 no.1
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    • pp.89-102
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    • 2023
  • This study investigates the eccentric performance of concrete-filled steel tubular (CFST) stub columns strengthened with steel tube and sandwiched concrete (STSC) jackets. It was revealed that the STSC jacketing method effectively weakened the cracking of concrete in CFST columns on the convex side and the crash on the concave side. Substantial increases in the eccentric bearing capacities were demonstrated after strengthening. A numerical study was further conducted. The decrease in diameter-to-thickness ratio and increase in strength of outer tube contributed to increase in peak load of all components, whereas the increase in sandwiched concrete strength resulted in load increase on itself and had negligible effects on other components. The parametric study showed the effect of inner concrete strength on columns' bearing capacity was magnified after strengthening, whereas that of inner tube thickness was reduced. Within the parameters investigated, high-strength concrete and high-strength steel can be applied without the concern of early abrupt failure of inner low-strength concrete or steel tube.