• Title/Summary/Keyword: internal flow

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The Clinical Study on Bell's Palsy Patients with TCD Measurement (TCD를 이용한 말초성(末梢性) 구안괘사환자에 대(對)한 임상적(臨床的) 고찰(考察))

  • Lee, Byung-Ryul;Ann, Taek-Won;Lee, Hyun
    • Journal of Pharmacopuncture
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    • v.6 no.2
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    • pp.91-104
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    • 2003
  • Objective : This study was carried to make out the connection between cerebral artery blood flow velocity and ischemic theory that presumed the cause of Bell's palsy. Method : We measured cerebral artery blood flow velocity each external carotid artery, internal carotid artery, common carotid artery, siphon, superficial temporal artery by TCD to 20 patients who diagnosed as facial nerve palsy from march 2001 to July 2001 and all objectives devided two groups as palsy side. A group is right side facial nerve palsy and B group is left facial nerve palsy. Results : 1. There is no effective change of blood flow in external carotid artery either A, B group. 2. There is no effective change of blood flow in internal carotid artery either A, B group. 3. There is no effective change of blood flow in common carotid artery either A, B group. 4. There is no effective change of blood flow in siphon artery either A, B group. 5. There is no effective change of blood flow in superficial temporal artery either A, B group.

An experimental study on the effects of an inserted coil on flow patterns and heat transport performances for a horizontal rotating heat pipe (수평 회전 히트파이프에서 내부 삽입 코일이 유동 형태 및 열전달 성능에 미치는 영향에 대한 실험 연구)

  • 이진성;김철주;김선주;문석환
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.10 no.6
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    • pp.763-772
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    • 1998
  • The effects of an inserted coil on flow patterns and heat transport performance for a horizontal rotating heat pipe have been studied experimentally. Especially, the present study is to see an internally inserted helical coil inside a RHP would lead to the same kind of results as internal fins. Visualization test conducted for an acryl tube, charged water with at a volumetric rate of 20%. When the flow kept pool regime at a low RPM(less than 1,000 RPM), the movement of coil forced the water to flow in axial direction. But this pumping effect of coil disappeared, when the pool regime changed to annular one which could be created by increasing RPM. The pumping effects for RHP with an inserted coil resulted enhancement both in condensation heat transfer coefficient and heat transport limitation, as obtained in case of using internal fins. But all these effects became negligible in the range of higher RPM(above 1,000∼1,200) with the transition of flow regime to annular flow.

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Direct Numerical Simulation of Strongly-Heated Internal Gas Flows with Large Variations of Fluid Properties (유체의 물성치변화를 고려한 수직원형관내 고온기체유동에 관한 직접수치모사)

  • Bae, Joong-Hun;Yoo, Jung-Yul;Choi, Hae-Cheon;You, Jong-Woo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.11
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    • pp.1289-1301
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    • 2004
  • Direct numerical simulation (DNS) of strongly-heated air flows moving upward in a vertical tube has been conducted to investigate the effect of gas property variations on turbulence modification. Three heating conditions(q$_1$$^{+}$=0.0045, 0.0035 and 0.0018) are selected to reflect the experiment of Shehata and McEligot (1998) at the inlet bulk Reynolds numbers of 4300 and 6000. At these conditions, the flow inside the heated tube remains turbululent or undergoes a transition to subturbulent or laminarizing flow. Consequently, a significant impairment of heat transfer occurs due to the reduction of flow turbulence. The predictions of integral parameters and mean profiles such as velocity and temperature distributions are in excellent agreement with the experiment. The computed turbulence data indicate that a reduction of flow turbulence occurs mainly due to strong flow acceleration effects for strongly-heated internal gas flows. Thus, buoyancy influences are secondary but not negligible especially for turbulent flow at low heating condition. Digital flow visualization also shows that vortical structures rapidly decay as the heating increases.s.

An Experimental Study on the Effects of ...an Inserted Coil on Flow Patterns pd. Beat Transport Performances for a Horizontal Rotating Heat Pipe

  • Lee, Jin-Sung;Kim, Chul-Ju;Kim, Bong-Hun
    • International Journal of Air-Conditioning and Refrigeration
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    • v.8 no.1
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    • pp.50-61
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    • 2000
  • The effects of an inserted coil on flow . patterns and heat transfer performance for a horizontal rotating heat pipe have been studied experimentally. Especially, the present study is to see an internally inserted helical coil inside a RHP would lead to the same kind of results as internal fins. Visualization test conducted for an acryl tube, charged water with at a volumetric rate of 20%. When the flow kept pool regime at a low rpm(less than 1,000rpm), the movement of coil forced the water to flow in axial direction. But this pumping effect of coil disappeared, when the pool regime changed to annular one which could be created by increasing rpm. The pumping effects for RHP with an inserted coil resulted in the enhancement in both condensation heat transfer coefficient and heat transport limitation, as obtained in case of using internal fins. But all these effects became negligible in the range of higher rpm(above 1,000-1,200) with the transition of flow regime to annular flow.

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Study on Flow Interaction between Bubble and Phase Change Material according to Injection Location (주입 위치에 따른 기포와 상변화물질의 유동 상호 작용에 관한 연구)

  • Min Hyeok Kim;Yun Young Ji;Dong Kee Sohn;Han Seo Ko
    • Journal of the Korean Society of Visualization
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    • v.21 no.3
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    • pp.75-84
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    • 2023
  • In this study, we conducted analysis of bubble dynamics and flow of liquid phase change material(PCM) using shadowgraphy and particle image velocimetry(PIV). Characteristics of internal flow varied depending on locations of injection when solid PCM was liquefied from heated vertical wall. When bubbles rose immediately, they exhibited elliptical shape and zigzag trajectory. In contrast, when bubbles rose after merging at the bottom of solid PCM, with equivalent diameter for the inter-wall distance of 0.64 or greater, they showed a jellyfish shape and strong rocking behavior. It was observed by the PIV that the small ellipse bubbles made most strong flow inside the liquid PCM. Furthermore, the flow velocity was highest in the case of front injection, as the directions of temperature gradients and bubble-driven flow were aligned. The results underscore the significant influence of injection location on various characteristics, including bubble size, shape, rising path of bubbles, and internal flow.

Prediction of Internal Broadband Noise of a Centrifugal Fan Using Stochastic Turbulent Synthetic Model (통계적 난류합성 모델을 이용한 원심홴 내부 광대역 소음 예측)

  • Heo, Seung;Kim, Dae-Hwan;Cheong, Cheol-Ung;Kim, Tae-Hoon
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.12
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    • pp.1138-1145
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    • 2011
  • The internal broadband noise of a centrifugal fan in a household refrigerator is predicted using hybrid CAA techniques based on stochastic turbulent synthetic model. First, the unsteady flow field around the centrifugal fan is predicted using computational fluid dynamics(CFD) method. Then, the turbulent flow field is synthesized by applying the stochastic turbulent synthetic technique to the predicted flow field. The aerodynamic noise sources of the centrifugal fan are modeled on a basis of the synthesized turbulent field. Finally, the internal broadband noise of the centrifugal fan is predicted using the boundary element method(BEM) and the modeled sources. The predicted noise spectrum is compared with the experimental data. It is found that the predicted result closely follows the experimental data. The proposed method can be used as an effective tool for designing low-noise fans without expensive computational cost required generally for the LES and DNS simulations to resolve the turbulence flow field responsible for the broadband noise.

Development of an Automated Design System for Oil Pumps with Multiple Profiles(Circle, Ellipse and Involute) (원, 타원 및 인벌루트 조합된 치형형상을 갖는 로터 개발)

  • Jung, Sung-Yuen;Kim, Moon-Saeng;Cho, Hae-Yong;Kim, Chul
    • Journal of the Korean Society for Precision Engineering
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    • v.26 no.3
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    • pp.103-112
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    • 2009
  • A internal lobe pump is suitable for oil hydraulics of machine tools, automotive engines, compressors, constructions and other various applications. In particular, the pump is an essential machine element of an automotive engine to feed lubricant oil. The subject of this paper is the theoretical analysis of internal lobe pump whose the main components are the rotors: usually the outer one is characterized by lobe with elliptical and involute shapes, while the inner rotor profile is determined as conjugate to the other. And the integrated system which is composed of three main modules has been developed through AutoLISP under AutoCAD circumstance. It generates new lobe profile and calculates automatically the flow rate and flow rate irregularity according to the lobe profile generated. Results obtained from the analysis enable the designer and manufacturer of oil pump to be more efficient in this field.

Performance Analysis of Cascade Refrigeration System with Respect to Refrigerants Appling to High Temperature Cycle (고온측 냉매에 따른 이원 냉동시스템의 성능 분석)

  • Yoon, Jung-In;Jeon, Min-Ju;Son, Chang-Hyo
    • Journal of Power System Engineering
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    • v.21 no.3
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    • pp.45-50
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    • 2017
  • This paper presents the Coefficient of performance(COP) and mass flow ratio of cascade refrigeration system with respect to refrigerants appling to high temperature cycle. The operating parameters considered in this study include degree of superheating and subcooling, compressor efficiency, evaporating temperature, condensing temperature and internal heat exchanger effectiveness in high temperature cycle. The result of this study is as follows : The COP of cascade system increases with increasing degree of superheating and subcooling, compressor efficiency and internal heat exchanger effectiveness except increasing condensing temperature. The mass flow ratio of low and high temperature cycle increases with increasing evaporating temperature and condensing temperature, but decreases with increasing internal heat exchanger effectiveness, degree of superheating and subcooling. Also, the mass flow ratio has no correlation with compressor efficiency at high temperature cycle.

Internal Flow Aerodynamic Test of a Mach 5 Scramjet Engine (마하 5 스크램젯 엔진의 내부 유동 공력 시험)

  • Yang, In-Young;Lee, Yang-Ji;Kim, Young-Moon;Lee, Kyung-Jae;Kang, Sang-Hoon;Yang, Soo-Seok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.11a
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    • pp.584-587
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    • 2011
  • An internal flow aerodynamic test was performed for a Mach 5 scramjet engine. The test was done without fuel injection, as a preliminary test for the combustion test. Test engine is an engineering model with intake cross-section of $70mm{\times}200mm$ and total length of 1.7m. Test facility is a blowdown-type, high enthalpy, hypersonic facility. 19 pressures were measured through the holes on the model surface along the engine internal flow passage. It was found that the facility start is possible, and also supersonic flow is maintained inside the engine.

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Internal Flow Characteristics for Tangential Entry Conditions in a Swirl Injector (스월 인젝터에서 접선방향 유입구 조건에 따른 내부유동의 특성 연구)

  • Kim, Sung-Hyuk;Khil, Tae-Ock;Cho, Seong-Ho;Yoon, Young-Bin
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.05a
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    • pp.115-118
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    • 2008
  • Many theoretical and experimental studies have been conducted to investigate elements of the hydrodynamic process, such as variations in liquid film thickness or air core diameter. From these studies, some theoretical relationships have been established through an approximated analytical solution of flow hydrodynamics in a swirl nozzle. However, experimental studies on elements such as internal flow have not produced conclusive results. In this study, the variations and stability of the internal flow were examined by visualizing the air core and measuring the liquid film thickness.

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