scholarly journals Flow and heat transfer characteristics downstream of a porous sudden expansion: A numerical study

2011 ◽  
Vol 15 (2) ◽  
pp. 389-396 ◽  
Author(s):  
Khalid Alammar
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Darcy Number ◽  
Sudden Expansion ◽  
Heat Transfer Characteristics ◽  
Maximum Heat ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Maximum Heat Transfer ◽  
Inertia Coefficient

Incompressible, axisymmetric laminar flow downstream of a porous expansion is simulated. Effect of the Darcy number and inertia coefficient on flow and heat transfer characteristics downstream of the expansion is investigated. The simulation revealed circulation downstream of the expansion. Decreasing the Darcy number is shown to decrease the circulation region. The Nusselt number, friction coefficient, and pressure drop are shown to increase, while reattachment and location of maximum heat transfer move upstream with decreasing Darcy number. Similar effects are observed with increasing inertia coefficient.

Parametric Analysis of a Bayonet Tube With a Special Type of Extended Surface

2010 ◽  
Author(s):  
L. Almanza-Huerta ◽  
A. Hernandez-Guerrero ◽  
M. Krarti ◽  
J. M. Luna
Keyword(s):  
Heat Transfer ◽  
Parametric Analysis ◽  
Numerical Study ◽  
Systematic Investigation ◽  
Heat Transfer Characteristics ◽  
Maximum Heat ◽  
Turbulent Transition ◽  
Maximum Heat Transfer ◽  
Internal Fluid ◽  
Extended Surface

The present paper provides a numerical study of a parametric analysis of a bayonet tube with a special type of extended surface during the laminar-turbulent transition. The working internal fluid is air. Attention is focused on the heat transfer characteristics of the tube. The results constitute a systematic investigation of the effect of the extended surface located along the annulus of the bayonet on the overall heat transfer rate. The effects of the variation of some parameters related to the extended surface aiming to attain the maximum heat transfer with the minimum pressure drop are discussed. Comparisons between designs with and without extended surface are also made.

scholarly journals Effect of Prandtl number on heat transfer characteristics in an axisymmetric sudden expansion: A numerical study

2007 ◽  
Vol 11 (4) ◽  
pp. 171-178
Author(s):  
Khalid Alammar
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Prandtl Number ◽  
Turbulent Flow ◽  
Turbulence Model ◽  
Numerical Study ◽  
Sudden Expansion ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Simulated Effect

Using the standard k-e turbulence model, an incompressible, axisymmetric turbulent flow with a sudden expansion was simulated. Effect of Prandtl number on heat transfer characteristics downstream of the expansion was investigated. The simulation revealed circulation downstream of the expansion. A secondary circulation (corner eddy) was also predicted. Reattachment was predicted at approximately 10 step heights. Corresponding to Prandtl number of 7.0, a peak Nusselt number 13 times the fully-developed value was predicted. The ratio of peak to fully-developed Nusselt number was shown to decrease with decreasing Prandtl number. Location of maximum Nusselt number was insensitive to Prandtl number.

scholarly journals Numerical Study on Flow and Heat Transfer Mechanisms in the Heat Exchanger Channel with V-Orifice at Various Blockage Ratios, Gap Spacing Ratios, and Flow Directions

2019 ◽  
Vol 2019 ◽  
pp. 1-21 ◽  
Author(s):  
Amnart Boonloi ◽  
Withada Jedsadaratanachai
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Numerical Study ◽  
Numerical Results ◽  
Blockage Ratio ◽  
Maximum Heat ◽  
Flow And Heat Transfer ◽  
Maximum Heat Transfer ◽  
Smooth Channel ◽  
Gap Spacing

Numerical assessments in the square channel heat exchanger installed with various parameters of V-orifices are presented. The V-orifice is installed in the heat exchanger channel with gap spacing between the upper-lower edges of the orifice and the channel wall. The purposes of the design are to reduce the pressure loss, increase the vortex strength, and increase the turbulent mixing of the flow. The influence of the blockage ratio and V-orifice arrangement is investigated. The blockage ratio, b/H, of the V-orifice is varied in the range 0.05–0.30. The V-tip of the V-orifice pointing downstream (V-downstream) is compared with the V-tip pointing upstream (V-upstream) by both flow and heat transfer. The numerical results are reported in terms of flow visualization and heat transfer pattern in the test section. The thermal performance assessments in terms of Nusselt number, friction factor, and thermal enhancement factor are also concluded. The numerical results reveal that the maximum heat transfer enhancement is found to be around 26.13 times higher than the smooth channel, while the optimum TEF is around 3.2. The suggested gap spacing for the present configuration of the V-orifice channel is around 5–10%.

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