• Title/Summary/Keyword: Outer tube

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Fabrication Development of Stainless Steel - cast Iron Dual Tube (스테인리스강-주철 이중복합관의 제조개발에 관한 연구)

  • Choi, Sang-Ho;Kang, Choon-Sik
    • Journal of Korea Foundry Society
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    • v.8 no.4
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    • pp.429-436
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    • 1988
  • The influences of some casting conditions on bonding ratio and state at bonding zone of stainless steel-cast iron dual tube produced by centrifugal casting process were investigated to estimate fabrication technics. 1) Bonding ratio is increasing such as increasing of inner surface temperature of outer metal(stainless steel STS 304), if pouring temperature of inner metal (cast iron) is constant. 2) The more pouring temperature of inner metal (cast iron) increase, the more bonding ratio increase when inner surface temperature of outer metal (cast iron) is constant. 3) As the mold rotary speed is increase, the hatching area of bonding map (perfect bonding area) goes down to the low pouring temperature of inner metal. 4) In order to predict bonding state of two different metal, we are able to make and use the bonding map about casting conditions such as inner surface temperature of outer metal, pouring temperature of inner metal and mold rotary speed.

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Thermal Performance Characteristics of Closed-Wet Cooling Tower (밀폐형 냉각탑의 열성능 특성에 관한 실험적 연구)

  • Sarker, M.M.A.;Kim, E.P.;Moon, C.G.;Yoon, J.I.
    • Journal of Power System Engineering
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    • v.9 no.2
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    • pp.88-92
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    • 2005
  • The experiment of thermal performance about closed-wet cooling tower was conducted in this study. A closed cooling tower is a device similar to a general cooling tower, but with cooling tower replaced by a heat exchanger. The test section for this experiment has the process that the cooling water flows from the top of the heat exchanger to the bottom side in the inner part of the tube, and spray water flows in the gravitational direction in the outer side. Air comes in direct contact with the spray water at the outer side of the tube while passing from the lower the upper part having a counterflow to the spray water. The heat transfer pipe used in this experiment is a bare-type tube having an outer diameter of 15.88mm. The heat exchanger is consisted of seven rows and fifteen columns. In this experiment, thermal performance of the cooling tower is derived from overall heat transfer coefficients between the process fluid and sprayed water and volumetric overall mass transfer coefficient between sprayed water and air.

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Optimal Design of Ultracentrifuge Composite Rotor by Structral Analysis (초고속 원심분리기 복합재 로터의 해석 및 최적설계)

  • 박종권;김영호;하성규
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.1
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    • pp.130-136
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    • 1998
  • A procedure of stress and strength analysis has been proposed for the centrifuge rotor of composite materials of quasi-isotropic laminates. The goal in this study is to maximize the allowable rotating speed, that is, to minimize maximum strength ratio with the given path length by changing the geometric parameter-outer radius and ply angles in quasi-isotropic laminates. Optimum values of the geometric parameter-outer radius and ply angles are obtained by multilevel optimization. All the geometric dimensions and stresses are normalized such that the result can be extended to a general case. Two dimensional analysis at each cross section with an elliptic tube hole subjected to internal hydrostatic pressures by samples as well as the centrifugal body forces has been performed along the height to calculate the stress distribution with the plane stress assumption, and Tsai-Wu failure criterion is used to calculate the strength ratio. The maximum allowable rotating speed can be increased by changing the radii of the outer surface along the height with the maximum strength ratio under the unit value : The optimal number of ply angles maximizing the allowable rotating speed in quasi-isotropic laminates is found to be the half number of tube hole, and the optimal laminate rotation angle is the half of $[{\pi}/m]$. A $[{\pi}/3]$ laminate, for instance, is stronger than a $[{\pi}/4]$ laminate for the centrifuge rotor of 6 tube hole number even though they have the same stiffness.

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Finite Element Analysis on the Displacement Behavior Safety of Hollow Shafts with Equivalent Volume (동등체적을 갖는 중공축의 변위거동 안전성에 관한 유한요소해석)

  • Kim, Chung Kyun
    • Journal of the Korean Institute of Gas
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    • v.20 no.3
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    • pp.73-77
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    • 2016
  • This paper presents the displacement behavior safety of hollow shafts with an equivalent volume for various cross sectional area using a finite element method. The FEM results indicate that the hollow shafts with X-type or Y-type columns between outer tube, middle tube and inner tube may reduce a maximum displacement at the middle length of hollow shafts. Especially, the load-bearing column of X-type or Y-type hollow shaft is directly connected between outer tube and inner tube without a shift for reducing the vertical displacement. And increased thickness of a load-bearing column is recommended for reducing the vertical displacement and increasing the displacement behavior safety for an equivalent volume of a hollow shaft.

A Study on the Characteristics of Evaporative Heat Transfer for Carbon Dioxide in a Horizontal Tube (수평원관 내 이산화탄소의 증발열전달 특성 연구)

  • Cho, E.S.;Yoon, S.H.;Kim, M.S.
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.104-107
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    • 2000
  • Evaporative heat transfer characteristics of carbon dioxide has been investigated. Experiment has been carried out for seamless stainless steel tube with outer diameter of 9.55 mm and inner diameter of 7.75 mm. Direct heating method is used for supplying heat to the refrigerant was uniformly heated by electric current which was applied to the tube wall. The saturation temperature of refrigerant is calculated from the measured saturation pressure by using an equation of state. Inner wall temperature was calculated from measured outer wall temperature, accounting for heat generation in the tube and heat conduction through the tube wall. Mass Quality of refrigerant was calculated by considering energy balance in the preheater and the test section. Heat fluxes were set at 12, 16, 20, 23, and $27kW/m^2$, mass fluxes were controlled at 212, 318, 424, and $530 kg/m^2s$, and saturation temperature of refrigerant were adjusted at 0, 3.4, 6.7 and $10.5^{\circ}C$. From this study, heat transfer coefficients of carbon dioxide have been provided with respect to quality for several mass fluxes, heat fluxes. Finally, the experimental results in this study are compared with the correaltion by Gungor and Winterton(1987).

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Experimental Study on Condensation Heat Transfer Characteristics of Special Heat Transfer Tubes (응축용 특수 전열관의 열전달 특성에 관한 연구)

  • 한규일;박종운;권영철;조동현
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.9
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    • pp.827-835
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    • 2001
  • In this study, condensation heat transfer characteristics were conducted with special heat transfer tubes of SH-C type. Experiments were carried out the saturated vapor temperature of 334K and the wall subcooling of 1.5-4.5K. The refrigerant was R-113 and the enhanced tubes used in the present study were SH-CDR, SH-CYR and SH-CHR. The experimental results showed that the condensation heat transfer coefficients of SH-C type tubes were about 23-66% higher than those of a low integral-fin tube. It was visualized that the condensed liquid on the outer surface of SH-C type tubes flowed continuously down unlike a low integral-fin tube and a plain tube, due to a 3-D extending fin on the outer surface of SH-C type tubes. As a result, the thermal resistance of the condensed liquid decreased and the heat transfer coefficient increased. Also, the enhancement ratio of SH-CDR tube was the highest, and it was about 9-11 times as compared to that of a plain tube.

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An Experimental Study on Natural Convection from a Conducting Tube with Two Axial Fins to a Surrounding Cylinder (두개의 축방향핀을 가진 전도관과 원통사이의 자연대류에 관한 실험적 연구)

  • Ahn, C.R.;Chung, T.H;Kwon, S.S.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.3 no.1
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    • pp.26-33
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    • 1991
  • An experimental study has been performed on the heat transfer by the natural convection from a conducting tube with two axial fins to a surrounding cylinder. In case of vertical fins, the maximum local Nusselt number of conducting tube appears at ${\theta}{\fallingdotseq}145^{\circ}$ and that of outer cylinder appears at ${\theta}=0^{\circ}$, for $l_F=0.3$. In case of horizontal fins, the maximum local Nusselt number of conducting tube appears at ${\theta}=180^{\circ}$ and that of outer cylinder appears at ${\theta}=0^{\circ}$. The local Nusselt number of the upper fin and the downward fin shows negative values for $l_F=1.0$. The local Nusselt number of the lower fin and the downward fin shows higher values than that of the upper fin and the upward fin. The mean Nusselt number of conducting tube in case of vertical fins are increased in order of $l_F=0.6$, 0.3, 1.0 and 0.0, but in case of horizontal fins, in order of $l_F=1.0$, 0.6, 0.3, and 0.0. The mean Nusselt number of outer cylinder in case of vertical fins are increased in order of $l_F=1.0$, 0.0, 0.3 and 0.6, but in case of horizontal fins, in order of $l_F=0.6$, 1.0, 0.3, and 0.0.

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Analysis of the Vibration Transmitting Characteristics of the Insulation-foam for Reducing Refrigerant-induced Noise of a Refrigerator (냉장고 냉매소음 저감을 위한 단열 발포재의 진동 전달특성 분석)

  • Han, Hyung-Suk;Kim, Min-Sung;Jeong, Weui-Bong;Seo, Min-Young;Lee, Soo-Young
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.20 no.1
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    • pp.45-50
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    • 2010
  • In the refrigerator, the two-phase refrigerant-induced noise of the capillary tube in an evaporator-inlet pipe has been a great concern. The capillary tube is usually covered with insulation-foam packed in the space between inner and outer cabinets without any vibration isolation. Therefore, the refrigerant-induced vibration of the capillary tube can be easily transferred to the outer cabinet, which may increase the radiated noise. In this paper, the characteristics of transferred vibration through the insulation-foam are investigated experimentally by using the refrigerantsupplying equipment. The frequency characteristics, such as dynamic Young's modulus and loss factor, of the insulation-foam are also discussed.

An Experimental Study on tee Heat Transfer Enhancement Effect of the Coil Fins for Ice Storage System (빙축열 시스템에서의 코일 휜의 열전달 촉진 효과에 관한 실험적 연구)

  • 성병호;이분희;임광빈;김철주
    • Proceedings of the Korea Society for Energy Engineering kosee Conference
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    • 2004.05a
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    • pp.219-224
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    • 2004
  • The present study was to investigate the heat transfer enhancement effect of coil wire fins in an ice storage system. For the two cases of tubes with internal brine flows, a finned tube with coil wires on its outer surface and a smooth tube, the rates of ice layer were tested and compared for both the icing processes. The coil fins were made of a stainless steel wire with a dia. of 2.0(mm), and the coil had an outer dia. of 10(mm) and a helix angle of 60($^{\circ}$). The experimental results showed that the coil fins could substantially reduce the thermal resistance of the ice layer, and enhance the heat flow rates between the water in the storage tank and the brine. The ice storing time was found to be shortened by 13(%) for the coil fins to get the same amount of ice layer that was built on the smooth tube wall for 10 hours of operation when the same thermal conditions were provided.

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Thermal analysis on triple-passage heat exchangers for a hot tube cooling system (고온의 강관 냉각용 삼중 열교환기에 대한 열해석)

  • 고봉환;박승호;신동신
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.11 no.5
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    • pp.615-623
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    • 1999
  • The objective of present study is to analyze a hot steel-tube cooling system as a kind of concentric triple-passage heat exchanger, whose inner tube is moving with a constant speed. Velocities and temperatures of an antioxidant gas flowing between inner and outer tubes are calculated theoretically for both laminar and turbulent flow regimes and used to give Nusselt numbers and friction factors with respect to various radius ratios and velocity ratios. In addition, it is shown that heat transfer coefficients based on ratios of average heat fluxes from inner and outer tubes might result in great errors for the temperature distributions of the flows, since the local heat transfer coefficients are dependent on the local heat flux ratios.

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