scholarly journals Heat transfer and flow structure through a backward-and forward-facing step micro-channels equipped with obstacles

2020 ◽  
pp. 219-219 ◽  
Author(s):  
Hassnia Hajji ◽  
Lioua Kolsi ◽  
Faouzi Askri ◽  
Chemseddine Maatki ◽  
Walid Hassen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Considerable Effect ◽  
Sudden Expansion ◽  
The Finite Element Method ◽  
Enhancement Of Heat Transfer ◽  
Low Reynolds Numbers ◽  
Micro Channels ◽  
Vortex Separation ◽  
Flow Through

This study presents two-dimensional simulations of a flow-through a sudden expansion/contraction micro-channel with the existence of obstacles. The bottom wall is maintained at constant flux, while the other walls are adiabatic. Rectangular adiabatic obstacles are mounted before the expansion region on the upper and lower wall of the channel used. The finite element method was used to discretize the equations that govern the physical model. Results indicate the apparition of a separate vortex, situated in the corner after the sudden expansion of the microchannel for low Reynolds numbers. For higher values and expansion ratios, the vortex separation length increases. The obtained results show that the obstacles have a considerable effect on the dynamics of the flow and enhancement of heat transfer.

Fluid Flow Bifurcation in Micro-Channels

2003 ◽  
Author(s):  
S. Patel ◽  
D. Drikakis
Keyword(s):  
Fluid Flow ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Flow Transition ◽  
Incompressible Fluid Flow ◽  
Low Reynolds Numbers ◽  
Multigrid Algorithm ◽  
Micro Channels ◽  
Micro Flows ◽  
Flow Through

The paper presents a numerical study of incompressible fluid flow through micro-channels. Using a high-resolution numerical method (second-order accurate) in conjunction with a non-linear multigrid algorithm and the pseudo-compressibility approach, we have investigated micro-flows through straight channels, as well as through a sudden contraction-expansion geometry. For the straight channel geometry, the computational results are in reasonable agreement with the experimental data for various low Reynolds numbers. For the contraction-expansion geometry, the results reveal the flow transition to instability. This is manifested in the form of asymmetric separation downstream of the expansion.

The plane Symmetric sudden-expansion flow at low Reynolds numbers

1993 ◽  
Vol 248 ◽  
pp. 567-581 ◽  
Author(s):  
F. Durst ◽  
J. C. F. Pereira ◽  
C. Tropea
Keyword(s):  
Maximum Flow ◽  
Reynolds Numbers ◽  
Sudden Expansion ◽  
Channel Height ◽  
Low Reynolds Numbers ◽  
Plane Symmetric ◽  
Numerical Predictions ◽  
Flow Through ◽  
Volume Method ◽  
Good Agreement

Detailed velocity measurements and numerical predictions are presented for the flow through a plane nominally two-dimensional duct with a Symmetric sudden expansion of area ratio 1:2. Both the experiments and the predictions confirm a symmetry-breaking bifurcation of the flow leading to one long and one short Separation zone for channel Reynolds numbers above 125, based on the upstream channel height and the maximum flow velocity upstream. With increasing Reynolds numbers above this value, the short separated region remains approximately constant in length whereas the long region increases in length.The experimental data were obtained using a one-component laser-Doppler anemometer at many Reynolds number values, with more extensive measurements being performed for the three Reynolds numbers 70, 300 and 610. Predictions were made using a finite volume method and an explicit quadratic Leith type of temporal discretization. In general, good agreement was found between measured and predicted velocity profiles for all Reynolds numbers investigated.

Thermal Performance of Pin Fins at Low Reynolds Numbers in Mini-Micro-Channels

2007 ◽  
Author(s):  
A. Rozati ◽  
D. K. Tafti ◽  
N. E. Blackwell
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Thermal Performance ◽  
Low Reynolds Number ◽  
Reynolds Numbers ◽  
High Density ◽  
Low Reynolds Numbers ◽  
Micro Channels ◽  
Low Reynolds

The computational study investigates different pin fin arrangements at low Reynolds numbers, which would typically be prevalent in mini-micro-channels used in enhancing heat as well as mass transfer. The effect of pin density, span-wise pitch, and stream-wise pitch is investigated on friction and heat transfer over a range 5<ReD<400. High density pins with small span-wise pitches were found to provide the highest augmentation in heat transfer capacity (conductance), whereas low density pins with or without a large stream-wise pitch were found to provide the least heat transfer benefits in the low Reynolds number range studied. Friction factor decreases considerably as the pin density decreases. The effect of decreasing span-wise pitch increases the friction factor in the low Reynolds number regime (ReD<200) but decreases it beyond ReD = 200 by delaying wake instabilities and the associated increase in form drag. Increasing the stream-wise pitch decreases the friction factor at low ReD<200, but increases it at ReD>200 due to the formation of larger recirculating wakes. Overall it is concluded that a high density arrangement with a small span-wise pitch provides the best thermal performance.

Heat transfer and drag for transverse flow past bundles of finned tubes at low reynolds numbers

1978 ◽  
Vol 14 (10) ◽  
pp. 905-907
Author(s):  
A. S. Lyshevskii ◽  
V. G. Sokolov ◽  
V. M. Sychev ◽  
L. Ya. Shkret
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Transverse Flow ◽  
Low Reynolds Numbers ◽  
Finned Tubes ◽  
Flow Past ◽  
Low Reynolds
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