A Numerical Study of Flow and Heat Transfer in a Smooth and Ribbed U-Duct With and Without Rotation

Lin, Yanli; Shih, Tsan‐Hsing; Stephens, Mark; Chyu, Minking K.

doi:10.1115/1.1345888

Cited by 98 publications

(36 citation statements)

References 49 publications

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“…Lin et al [9] performed a numerical analysis to study the three-dimensional flow and heat transfer in a U-shaped duct of square cross-section under rotating and non-rotating conditions. The computations are based on the ensemble-averaged conservation equations of mass, momentum, and energy.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of turbulent flow separation in a rectangular duct with a sharp 180‐degree turn by algebraic Reynolds stress model

Sugiyama

Tanaka

Mukai

2007

Numerical Methods in Fluids

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SUMMARYTurbulent flow in a rectangular duct with a sharp 180-degree turn is difficult to predict numerically because the flow behavior is influenced by several types of forces, including centrifugal force, pressure-driven force, and shear stress generated by anisotropic turbulence. In particular, this type of flow is characterized by a large-scale separated flow, and it is difficult to predict the reattachment point of a separated flow. Numerical analysis has been performed for a turbulent flow in a rectangular duct with a sharp 180-degree turn using the algebraic Reynolds stress model. A boundary-fitted coordinate system is introduced as a method for coordinate transformation to set the boundary conditions next to complicated shapes. The calculated results are compared with the experimental data, as measured by a laser-Doppler anemometer, in order to examine the validity of the proposed numerical method and turbulent model. In addition, the possibility of improving the wall function method in the separated flow region is examined by replacing the log-law velocity profile for a smooth wall with that for a rough wall. The analysis results indicated that the proposed algebraic Reynolds stress model can be used to reasonably predict the turbulent flow in a rectangular duct with a sharp 180-degree turn. In particular, the calculated reattachment point of a separated flow, which is difficult to predict in a turbulent flow, agrees well with the experimental results. In addition, the calculation results suggest that the wall function method using the log-law velocity profile for a rough wall over a separated flow region has some potential for improving the prediction accuracy.

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Section: Introductionmentioning

confidence: 99%

Numerical analysis of turbulent flow separation in a rectangular duct with a sharp 180‐degree turn by algebraic Reynolds stress model

Sugiyama

Tanaka

Mukai

2007

Numerical Methods in Fluids

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“…Gupta and Nag (2000) developed an empirical model to predict the heat transfer coefficient in the cyclone of a re-circulating fluidized bed, and obtained good agreement with experimental results. CFD has been used to predict the air flow inside a cyclone by using suitable turbulent models to capture the geometry Lin et al (2001) studied heat transfer in a U-shaped duct of square cross section at a Reynolds number 25,000 using numerical techniques based on finite volume method and showed how the nature of the flow affected the surface heat transfer. However, there is a lack of information on the effectiveness of numerical simulation of turbulent heat transfer as related to the need for keeping liquid from freezing on the internal walls of a wetted wall cyclone.…”

Section: Introductionmentioning

confidence: 99%

Heat Transfer Study on A Bioaerosol Sampling Cyclone

Seo

McFarland

et al. 2008

Engineering Applications of Computational Fluid Mechanics

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ABSTRACT:Computational fluid dynamics, supplemented by theoretical analyses, is used to study turbulent heat transfer in a wetted wall bioaerosol sampling cyclone. The cyclone is designed to operate at temperatures as low as -20ºC so heat must be applied to prevent the liquid (water) from freezing. For the particular application of interest, which is a cyclone with a flow rate of 1250 L/min, the electrical power for heating is limited to 350 W and the local temperature of the heated wall must be properly controlled. The inner wall of the cyclone has a liquid film, which is formed from impact of droplets that are created from atomization of the liquid upstream of the cyclone body. Calculations showed that the mean diameter of the droplets was about 42 µm and they would not freeze in air at temperatures as low as -40ºC. A commercially available CFD package, Fluent, was used in the numerical simulations to predict the turbulent heat transfer coefficients at the cyclone surface, to design heaters, and to study the temperature response of the cyclone wall. A skimmer, which is used to separate the collection liquid from the air stream, was re-designed based on CFD findings. Compared with an earlier cyclone, the power consumption for heating is significantly reduced, yet the new system can be operated at lower temperatures with higher air flow rates. CFD predictions were experimentally tested and good agreement was obtained.

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“…A vast number of numerical investigations have been performed to investigate the ability of numerical models, in particular turbulence models, to predict the heat transfer. Early research has mostly been conducted with the use of the Reynolds-averaged Navier-Stokes (RANS) method with a variety of turbulence models ranging from two-equation eddy-viscosity models such as the k-ε, k-ω SST, v 2 -f model and algebraic stress models, to full Reynolds stress closure with varying degrees of success [3][4][5][6][7][8][9][10][11][12]. In the last two decades, with increasing computational power and capacity, these efforts have transitioned to more advanced time-dependent methods such as large eddy simulations (LES) [13][14][15][16][17][18][19][20][21][22][23][24] and hybrid methods using unsteady RANS (URANS)-LES or detached eddy simulations (DES) [25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

Large eddy simulation for predicting turbulent heat transfer in gas turbines

Tafti

Nagendra

2014

Phil. Trans. R. Soc. A.

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Blade cooling technology will play a critical role in the next generation of propulsion and power generation gas turbines. Accurate prediction of blade metal temperature can avoid the use of excessive compressed bypass air and allow higher turbine inlet temperature, increasing fuel efficiency and decreasing emissions. Large eddy simulation (LES) has been established to predict heat transfer coefficients with good accuracy under various non-canonical flows, but is still limited to relatively simple geometries and low Reynolds numbers. It is envisioned that the projected increase in computational power combined with a drop in price-to-performance ratio will make system-level simulations using LES in complex blade geometries at engine conditions accessible to the design process in the coming one to two decades. In making this possible, two key challenges are addressed in this paper: working with complex intricate blade geometries and simulating high-Reynolds-number ( Re ) flows. It is proposed to use the immersed boundary method (IBM) combined with LES wall functions. A ribbed duct at Re =20 000 is simulated using the IBM, and a two-pass ribbed duct is simulated at Re =100 000 with and without rotation (rotation number Ro =0.2) using LES with wall functions. The results validate that the IBM is a viable alternative to body-conforming grids and that LES with wall functions reproduces experimental results at a much lower computational cost.

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A Numerical Study of Flow and Heat Transfer in a Smooth and Ribbed U-Duct With and Without Rotation

Cited by 98 publications

References 49 publications

Numerical analysis of turbulent flow separation in a rectangular duct with a sharp 180‐degree turn by algebraic Reynolds stress model

Numerical analysis of turbulent flow separation in a rectangular duct with a sharp 180‐degree turn by algebraic Reynolds stress model

Heat Transfer Study on A Bioaerosol Sampling Cyclone

Large eddy simulation for predicting turbulent heat transfer in gas turbines

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