• Title/Summary/Keyword: Effective Diameter

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An Experimental Study on the Thermal Performance Measurement of Large Diameter Borehole Heat Exchanger(LD-BHE) for Tripe-U Pipes Spacer Apply (3중관용 스페이서를 적용한 대구경 지중열교환기의 성능측정에 관한 연구)

  • Lee, Sang-Hoon;Park, Jong-Woo;Lim, Kyoung-Bin
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.11a
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    • pp.581-586
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    • 2009
  • Knowledge of ground thermal properties is most important for the proper design of large scale BHE(borehole heat exchanger) systems. The type, pipe size and thermal performance of the BHE is highly dependent on the ground source heatpump system-efficiency and instruction cost. Thermal response tests with mobile measurement devices were developed primarily for insitu determination of design data for large diameter BHE for triple-U spacer apply. The main purpose has been to determine insitu values of effective ground thermal conductivity and thermal resistance, including the effect of ground-water flow and natural convection in the boreholes. The test rig is set up on a some trailer, and contains a circulation pump, a inline heater, temperature sensors, flow meter, power analysis meter and a data logger for recording the temperature, fluid flow data. A constant heat power is injected into the borehole through the tripl-U pipes system of test rig and the resulting temperature change in the borehole is recorded. The recorded temperature data are analysed with a line-source model, which gives the effective insitu values of rock thermal conductivity and borehole thermal resistance of large diameter BHE for spacer apply.

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Characteristics Evaluation of Process Parameters for Improvement the Precision of Thread ]tolling in Lead Screw (Lead Screw 전조 정밀도 향상을 위한 성형인자의 특성평가)

  • 김광호;김동환;고대철;김병민
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.10a
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    • pp.312-315
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    • 2002
  • This paper summarizes the results of a numerical study conducted to analyze the effect of selected process parameters on material flow and thread profile in thread rolling of large diameter blanks. Based on the previous work where a plane strain mode was found to provide a reasonable approximation of the thread rolling process, the effect of varying thread form, friction factor, flow stress, and blank diameter on effective strain and thread height was analyzed using the finite element code DEFORM. This study show that effective strain for flank angle, that blank diameter had important effect on the as-rolled thread while flow stress, friction factor, and crest round of dies had significant impact on effective strain at the thread root and crest and load of thread rolling. While the rate of strain harding was found to have an effect on the crest profile, the results indicate that it is the primary factor responsible for seam formation in rolled threads.

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Design of the Prestressed Cold Extrusion Die with Two Stress Rings (이중 보강링으로 예압된 냉간압출 금형 설계)

  • Heo, Gwan-Do;Yeo, Hong-Tae;Ye, Sang-Don
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.10
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    • pp.77-82
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    • 2000
  • The design of the prestressed cold extrusion die with two stress rings has been performed in this study. The cold extrusion has been simulated by the rigid-plastic FEM. The stress analysis of die has been performed for both after shrink fitting and during extrusion by using the elastic FEM and the Lame's equation. According to the variation of interferences and diameter ratios, the maximum effective stress has been evaluated. As results, interferences and diameters were determined by the minimization of the maximum effective stress of die insert. The comparison of the maximum effective stress between the proposed design and the conventional design has been discussed. It was found that the maximum effective stress in the die insert is considerably affected by the stiffness of the first stress ring.

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Fluid Flow Characteristics of Al2O3 Nanoparticles Suspended in Water (알루미나 나노유체의 유동 특성에 관한 연구)

  • Jang Seok-Pil;Lee Ji-Hwan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.6 s.249
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    • pp.546-552
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    • 2006
  • In this paper we report fluid flow characteristics of $Al_2O_3$ nanoparicles suspended in water. Especially, the effects of volume fraction with the range of 0.01% to 0.3% and tube diameter with $310{\mu}m$ to 1.735mm on the pressure drop and the effective viscosity of $Al_2O_3$ nanoparicles suspended in water are experimentally investigated. It is shown that the effective viscosity of water-based $Al_2O_3$ nanofluids with 0.1 Vol.% through a circular tube of 1.024mm diameter is increased to about 6%. The effective viscosity from experimental results is compared with that from Einstein model. With the comparison, we show that Einstein model for determining the effective viscosity of nanofluids is not applicable to water-based $Al_2O_3$ nanofluids.

Analysis of Spray Mode Using Modified Pinch Instability Theory (핀치이론의 수정 모델을 이용한 스프레이 모드의 해석)

  • Park, Ah-Young;Hammad, Muhammad A.;Kim, Sun-Rak;Yoo, Choong-D.
    • Journal of Welding and Joining
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    • v.27 no.5
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    • pp.88-93
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    • 2009
  • While the pinch instability theory (PIT) has been widely employed to analyze the spray transfer mode in the gas metal arc welding (GMAW), it cannot predict the detaching drop size accurately. The PIT is modified in this work to increase the accuracy of prediction and to simulate the molten tip geometry to be more physically acceptable. Since the molten tip becomes a cone shape in the spray mode, the effective wire diameter is formulated that the effective diameter is inversely proportional to current square. Modifications are also made to consider the finite length of the liquid column and current leakage through the arc. While the effective diameter influences drop transfer significantly, the current leakage has negligible effects. The effects of modifications on drop transfer are analyzed, and the predicted drop diameters show good agreements with the experimental data of the steel wire.

Analysis of Spray Mode Using Modified Pinch Instability Theory (핀치이론의 수정 모델을 이용한 스프레이 모드의 해석)

  • Park, Ah-Young;Hammad, Muhammad A.;Kim, Sun-Rak;Yoo, Choong-D.
    • Proceedings of the KWS Conference
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    • 2009.11a
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    • pp.44-44
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    • 2009
  • While the pinch instability theory (PIT) has been widely employed to analyze the spray transfer mode in the gas metal arc welding (GMAW), it cannot predict the detaching drop size accurately. The PIT is modified in this work to increase the accuracy of prediction and to simulate the molten tip geometry to be more physically acceptable. Since the molten tip becomes a cone shape in the spray mode, the effective wire diameter is formulated that the effective diameter is inversely proportional to current square. Modifications are also made to consider the finite length of the liquid column and current leakage through the arc. While the effective diameter influences drop transfer significantly, the current leakage has negligible effects. The effects of modifications on drop transfer are analyzed, and the predicted drop diameters show good agreements with the experimental data of the steel wire.

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Reduction of Noise and Input Power in Fuel Cell Blower by Controlling Flow Path (연료전지 블로워의 유로 크기에 따른 소비전력과 소음저감 방법)

  • Tak, Bong-Yeol;Kim, Chan-Kyu;Lee, So-A;Jang, Choon-Man
    • 한국신재생에너지학회:학술대회논문집
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    • 2011.11a
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    • pp.90.2-90.2
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    • 2011
  • This paper describes performance enhancement of a fuel cell's blower by controlling flow path. Different duct diameter at the inlet and outlet of the blower is selected for reducing blower noise level and input power. Hole diameter and the number of hole at the check valve are tested to reduce the input power of the blower. Two types of blower, fuel pressurized blower and cathode blower, are considered in the present study. Throughout experimental measurements of the test blowers, it is found that duct diameter is effective to reduce noise level and input power in the fuel cell blower. Noise reduction due to the optimal duct diameter at the outlet is more effective when flow rate is relatively large. That is, cathode blower has larger noise reduction compared to fuel pressurized blower because of larger flower rate. Input power of the blower can be reduced by controlling the hole diameter and the number of hole at the check valve.

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A Study on the Wide Reach Nozzle of Sprayer(IV) (Characteristics of cap hole diameter and pressure for the medium range nozzle) (휴반용 분무기의 Nozzle에 관한 연구(IV) (중거리용 Nozzle예 있어서 구경과 압력의 특성))

  • 옹장우;이상우
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.17 no.3
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    • pp.3872-3877
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    • 1975
  • This study was conducted to examine the effects of the change of cap hole diameter and pressure on the travelling distance and the sprayed particle size for the medium range nozzle. The results of this study are summarized as follows; 1) The effective travelling distance was about from 1 meter to 8 meters and centro-position of the travelling distance was about 3 or 5 meters. 2) Main effect of change of cap hole diameter for the travelling distance was a slight convex quadratic curve. 3) Main effect of change of pressure increased linearly, its increasing rate about 1.6 was large. 4) Sizes of sprayed particles were less than 250${\mu}$ generally and the sizes decreased according to the increasing of travelling distance. 5) Changes of diameter of sprayed particles by cap hole diameter increased in accordance with increasing of cap hole diameter. 6) Changes of diameter of sprayed particles by the groove depth of swirl plate was very slight.

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A Study on Shear Capacity and Behavior of Large Sized Concrete Anchorage System (대형 콘크리트 앵커시스템의 전단성능 및 거동특성에 관한 연구)

  • Kim, Kang Sik;Shin, Sung Woo;Lee, Kwang Soo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.15 no.5
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    • pp.82-91
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    • 2011
  • In this study, 24 prototype specimens were tested to find out the shear behavior and strength of large anchorage system exceeding 50mm(2") in anchor bolt diameter($d_0$) and 635mm(25") in effective embedment depth($h_{ef}$) not addressed by ACI349-06 Appendix B. Test variables are anchor bolt diameter($d_0$ = 63.5, 76.2, 88.9mm), effective embedment depth($h_{ef}$=635, 762mm), and edge distance($c_1$=381, 508, 762mm). Concrete compressive strength is constant($f_{ck}$=38MPa). Test results ($V_{test}$) were overestimated by $V_{aci06}$(shear strength by ACI 349-06) and $V_{ccd}$(shear strength by CCD method). In large anchorage system exceeding 50mm(2") of anchor bolt diameter($d_0$) and 635mm(25") of anchor bolt effective embedment depth($h_{ef}$), the bolt diameter variation and effective embedment depth($h_{ef}$) has no influence on the shear strenth, But, according to the analysis results of the feature ratio on edge distance($c_1$) and anchor bolt diameter, the feature ratio become smaller, which means anchor bolt diameter is bigger, predicted ratio of test results and predicted equation is larger. It was found that anchor bolt diameter is immediate cause of deterioration in the shear capacity of large anchorage system. To improve and extend the validity of current design recommendations further theoretical and numerical work is needed.

INFLUENCE OF IMPLANT-ABUTMENT INTERFACE DESIGN, IMPLANT DIAMETER AND PROSTHETIC TABLE WIDTH ON STRENGTH OF IMPLANT-ABUTMENT INTERFACE : THREE-DIMENSIONAL FINITE ELEMENT ANALYSIS (임플랜트의 지대주 연결방식, 임플랜트의 직경 및 지대주 연결부위의 직경 차이에 따른 응력분포에 관한 삼차원 유한요소분석)

  • Oh Se-Woong;Yang Jae-Ho;Lee Sun-Hyung;Han Jung-Suk
    • The Journal of Korean Academy of Prosthodontics
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    • v.41 no.4
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    • pp.393-404
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    • 2003
  • Statement of problem. Higher incidence of prosthetic complications such as screw loosening, screw fracture has been reported for posterior single tooth implant. So, there is ongoing research regarding stability of implant-abutment interface. One of those research is increasing the implant diameter and prosthetic table width to improve joint stability. In another part of this research, internal conical type implant-abutment interface was developed and reported joint strength is higher than traditional external hex interface. Purpose. The purpose of this study is to compare stress distribution in single molar implant between external hex butt joint implant and internal conical joint implant when increasing the implant diameter and prosthetic table width : 4mm diameter, 5mm diameter, 5mm diameter/6mm prosthetic table width. Material and method. Non-linear finite element models were created and the 3-dimensional finite element analysis was performed to see the distribution of stress when 300N static loading was applied to model at $0^{\circ},\;15^{\circ},\;30^{\circ}$ off-axis angle. Results. The following results were obtained : 1. Internal conical joint showed lower tensile stress value than that of external hex butt joint. 2. When off-axis loading was applied, internal conical joint showed more effective stress distribution than external hex butt joint. 3. External hex butt joint showed lower tensile stress value when the implant diameter was increased. 4. Internal conical joint showed lower tensile stress value than external hex butt joint when the implant diameter was increased. 5. Both of these joint mechanism showed lower tensile stress value when the prosthetic table width was increased. Conclusion. Internal conical joint showed more effective stress distribution than external hex joint. Increasing implant diameter showed more effective stress distribution than increasing prosthetic table width.