Semi-empirical pressure loss model for viscous flow through high aspect ratio rectangular orifices

An experimental and numerical investigation of the pressure loss and the heat transfer in the bend region of a smooth two-pass cooling channel with a 180°-turn has been performed. The channels have a rectangular cross-section with a high aspect ratio of H/W = 4. The heat transfer has been measured using the transient liquid crystal method. For the investigations the Reynolds-number as well as the distance between the tip and the divider wall (tip distance) are varied. While the Reynolds number varies from 50’000 to 200’000 and its influence on the normalized pressure loss and heat transfer is found to be small, the variations of the tip distance from 0.5 up to 3.65 W produce quite different flow structures in the bend. The pressure loss over the bend thus shows a strong dependency on these variations.

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EFFECT OF ASPECT RATIO ON PRESSURE LOSS AND CHARACTERISTICS OF LOW REYNOLDS NUMBER FLOW THROUGH NARROW SLOTS

10.1615/tfec2017.fne.018387 ◽

2017 ◽

Cited By ~ 1

Author(s):

Yishak Abdulhafiz Yusuf ◽

Aleksey Baldygin ◽

Reza Sabbagh ◽

Michael Leitch ◽

Prashant R. Waghmare ◽

...

Keyword(s):

Reynolds Number ◽

Aspect Ratio ◽

Pressure Loss ◽

Low Reynolds Number ◽

Low Reynolds Number Flow ◽

Reynolds Number Flow ◽

Number Flow ◽

Flow Through ◽

Low Reynolds

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Turbulent flow through a high aspect ratio cooling duct with asymmetric wall heating

Journal of Fluid Mechanics ◽

10.1017/jfm.2018.836 ◽

2018 ◽

Vol 860 ◽

pp. 258-299 ◽

Cited By ~ 3

Author(s):

Thomas Kaller ◽

Vito Pasquariello ◽

Stefan Hickel ◽

Nikolaus A. Adams

Keyword(s):

Heat Transfer ◽

Aspect Ratio ◽

Turbulent Flow ◽

Secondary Flow ◽

High Aspect Ratio ◽

Heated Wall ◽

Turbulent Heat Transfer ◽

Turbulent Heat ◽

Wall Heating ◽

Flow Through

We present well-resolved large-eddy simulations of turbulent flow through a straight, high aspect ratio cooling duct operated with water at a bulk Reynolds number of $Re_{b}=110\times 10^{3}$ and an average Nusselt number of $Nu_{xz}=371$. The geometry and boundary conditions follow an experimental reference case and good agreement with the experimental results is achieved. The current investigation focuses on the influence of asymmetric wall heating on the duct flow field, specifically on the interaction of turbulence-induced secondary flow and turbulent heat transfer, and the associated spatial development of the thermal boundary layer and the inferred viscosity variation. The viscosity reduction towards the heated wall causes a decrease in turbulent mixing, turbulent length scales and turbulence anisotropy as well as a weakening of turbulent ejections. Overall, the secondary flow strength becomes increasingly less intense along the length of the spatially resolved heated duct as compared to an adiabatic duct. Furthermore, we show that the assumption of a constant turbulent Prandtl number is invalid for turbulent heat transfer in an asymmetrically heated duct.

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Facile Fabrication of Open-Ended High Aspect-Ratio Anodic TiO2 Nanotube Films and their Applications

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.512-515.1659 ◽

2012 ◽

Vol 512-515 ◽

pp. 1659-1662 ◽

Cited By ~ 1

Author(s):

Jian Jun Liao ◽

Shi Wei Lin ◽

Neng Qian Pan ◽

Xian Kun Cao ◽

Jian Bao Li

Keyword(s):

Aspect Ratio ◽

High Aspect Ratio ◽

Chemical Etching ◽

Physical Separation ◽

Photocatalytic Reactor ◽

Facile Fabrication ◽

Pore Opening ◽

Flow Through ◽

Photocatalytic Reactions ◽

Nanotube Films

In the present work, we demonstrated a facile process to prepare an open-ended high aspect-ratio TiO2 nanotube films through separating the anodic TNT array from the Ti substrate by a small reverse bias and opening the tube bottom by a chemical etching. The possible mechanisms of film detachment and pore opening processes have been briefly discussed. Such a process allows controlling the open-ended morphology by the straightforward chemical etching, which shows great potential in many applications, such as flow-through photocatalytic reactions, biofiltration, and diffusion controlling, and so on. An example using the open-ended TNT films is finally given as a flow-through photocatalytic reactor. The photocatalytic film has been shown to have multiple functions such as physical separation of contaminants, filtration, and decomposition of organic pollutants during diffusion.

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