• 제목/요약/키워드: Square Cross-sectioned Duct

검색결과 4건 처리시간 0.015초

Turbulence Enhancement by Ultrasonically Induced Gaseous Cavitation in the $CO_2$Saturated Water

  • Lee, Seung-Youp;Park, Young-Don
    • Journal of Mechanical Science and Technology
    • /
    • 제16권2호
    • /
    • pp.246-254
    • /
    • 2002
  • Recent primary concern for the design of high performance heat exchanger and highly integrated electronic equipments is to develop an active and creative technologies which enhance the heat transfer without obstructing the coolant flows. In this study, we found through the LDV measurement that the gaseous cavitation induced by ultrasonic vibration applied to the CO$_2$saturated water in the square cross-sectioned straight duct flow enhances the turbulence much more than the case of non-ultrasonic or normal ultrasonic conditions without gaseous cavitation does. We also found that gaseous cavitation can enhance effectively the turbulent heat transfer between the heating surfaces and coolants by destructing the viscous sublayer.

열선 유속계에 의한 정사각형 단면의 270도 곡관에서의 난류유동 특성에 관한 연구 (Measurement of Turbulent Flows in a Square Sectioned $270^{\circ}$ Bend)

  • 조석휴;최영돈;이건휘
    • 대한기계학회:학술대회논문집
    • /
    • 대한기계학회 2000년도 추계학술대회논문집B
    • /
    • pp.467-472
    • /
    • 2000
  • Most of the past experimental or analytical studies were performed for the curved bend with a square cross-section. Velocity profiles and Reynolds stresses of the turbulence flow in the 270 degree bend with circular cross-section were measured by a hot-wire anemometer. The mean velocity of primary flowing direction effected by the downstream of bend in the entry region of the bend. The flow in the inner part of the bend slowed the distribution velocity relatively large and unsymmetric phenomenon. In the strong secondary flow occurred when the flow passed in the region of 45 degree to 90 degree. The secondary flow appeared very large value in the neighbor region of inner wall.

  • PDF

열선유속계에 의한 180.deg.곡관을 갖는 직사각 단면덕트에서의 난류유동 특성의 측정 (Measurement of turbulent flow characteristics of a rectangular duct with a 180.deg. bend by hot wire anemometer)

  • 박호영;유석재;최영돈
    • 대한기계학회논문집
    • /
    • 제14권3호
    • /
    • pp.734-746
    • /
    • 1990
  • 본 연구에서는 문등이 제안한 방법에 의하여 직사각형 단면의 180˚곡관유동 에서 속도분포와 난류성분을 측정하여 단면의 종횡비 변화에 따른 유동특성과 난류특 성의 변화를 고찰하였다.

타원혼합모형을 이용한 초임계상태 이산화탄소의 압축성계수에 의한 난류열전달 특성 (Compressibility Factor Effect on the Turbulence Heat Transfer of Super-critical Carbon Dioxide by an Elliptic-blending Second Moment Closure)

  • 한성호;서정식;신종근;최영돈
    • 대한기계학회논문집B
    • /
    • 제31권1호
    • /
    • pp.40-50
    • /
    • 2007
  • The present contribution describes the application of elliptic-blending second moment closure to predict the gas cooling process of turbulent super-critical carbon dioxide flow in a square cross-sectioned duct. The gas cooling process under super-critical state experiences a drastic change in thermodynamic and transport properties. Redistributive terms in the Reynolds stress and turbulent heat flux equations are modeled by an elliptic-blending second moment closure in order to represent strongly non-homogeneous effects produced by the presence of walls. The main feature of Durbin's elliptic relaxation second moment closure that accounts for the nonlocal character of pressure-velocity gradient correlation and the near-wall inhomogeneity guaranteed by the elliptic blending second moment closure.