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A variable heat flux model of heat transfer in grinding : model development

Convective heat transfer in rotating isothermal ducts

Dry-out CHF correlation for R134a flow boiling in a horizontal helically-coiled tube

  • Authors: Chen, C.-N. , Han, J.-T. , Jen, T.-C. , Shao, L.
  • Date: 2011
  • Subjects: Critical heat flux , Helically coiled tubes , Heat transfer
  • Type: Article
  • Identifier: uj:5286 , http://hdl.handle.net/10210/14955
  • Description: An experimental study was carried out to investigate the R134a dry-out critical heat flux (CHF) characteristics in a horizontal helically-coiled tube. The test section was heated uniformly by DC high-power source, and its geometrical parameters are the outer diameter of 10 mm, inner diameter of 8.4 mm, coil diameter of 300 mm, helical pitch of 75 mm and valid heated length of 1.89 m. The experimental parameters are the outlet pressures of 0.30–0.95 MPa, mass fluxes of 60–500 kg m 2 s 1, inlet qualities of 0.36–0.35 and heat fluxes of 7.0 103–5.0 104 Wm 2. A method based on Agilent BenchLink Data Logger Pro was developed to determine the occurrence of CHF with a total of 68 T-type thermocouples (0.2 mm) set along the tube for accurate temperature measurement. The characteristics of wall temperatures and the parametric effect on dry-out CHF showed that temperature would jump abruptly at the point of CHF, which usually started to form at the front and offside (270 and 90 ) of the outlet crosssection. The CHF values decrease nearly linearly with increasing inlet qualities, while they decrease more acutely with increasing critical qualities, especially under larger mass flux conditions. The mass flux has a positive effect on CHF enhancement, but the pressure has negative one. A new dimensionless correlation was developed to estimate dry-out CHF of R134a flow boiling in horizontal helically-coiled tubes under current experimental conditions and compared to calculated results from Bowring and Shah correlations.
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Laminar heat transfer and fluid flow in the entrance region of a rotating duct with rectangular cross section : the effect of aspect ratio

Numerical simulation of fluid flow and heat transfer in a curved square duct by using the Lattice Boltzmann method

  • Authors: Liao, Quan , Jen, T.-C.
  • Date: 2008
  • Subjects: Fluid flow , Heat transfer
  • Type: Article
  • Identifier: uj:5274 , ISSN 1040-7782 , http://hdl.handle.net/10210/14943
  • Description: The study of viscous flow in curved ducts is of fundamental interest in fluid mechanics due to the numerous applications such as flows through turbomachinery blade passages, aircraft intakes, diffusers, heat exchangers, and so on [1–6]. The major effect of curved ducts on the fluid flow involves the strong secondary flow due to the longitudinal curvature in the geometry [7–9]. The presence of longitudinal curvature generates centrifugal force (which is perpendicular to the main flow along the axis) and produces so-called secondary flow on the cross sections of ducts.
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Thermal aspect of grinding : heat transfer to workpiece, wheel, and fluid

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