DEVELOPMENT OF LAMINAR MIXED CONVECTION IN VERTICAL SEMICIRCULAR DUCTS

2008 ◽  
Author(s):  
N. A. Elsharif ◽  
A. A. Busedra ◽  
Y. El Hasadi
Keyword(s):  
Mixed Convection ◽  
Laminar Mixed Convection ◽  
Semicircular Ducts

Combined Buoyancy Effects of Thermal and Mass Diffusion on Laminar Mixed Convection in Vertical and Horizontal Semicircular Ducts

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
A. Budabous ◽  
A. A. Busedra
Keyword(s):  
Mass Transfer ◽  
Mixed Convection ◽  
Heat And Mass Transfer ◽  
Convection Boundary Layer ◽  
Input Concentration ◽  
Transfer Rates ◽  
Thermal Boundary Conditions ◽  
Laminar Mixed Convection ◽  
Boundary Layer Development ◽  
Semicircular Ducts

The development of laminar mixed convection with heat and mass transfer in vertical and horizontal semicircular ducts has been investigated for the case of thermal boundary conditions of uniform heat input, concentration at the fluid–solid interface axially, and uniform peripheral wall temperature at any axial station. The governing equations were solved numerically over the following conditions: Pr = 0.7, Le = 1, Re = 500, Grt = 1.66 × 105, and Grc = 1.66 × 105. The combined effects of solutal and thermal Grashof numbers on the flow and thermal fields were observed in terms of the axial velocity, temperature, and concentration distributions, as well as, friction factor, Nusselt number, and Sherwood number. Further, the development of velocity, temperature, and concentration at different axial stations was found to be influenced by the solutal and thermal Grashof numbers. The results also showed that the forced-convection boundary layer development dominates very close to the duct inlet, while further downstream, the heat and mass transfer rates are enhanced due to the effect of solutal buoyancy.

Laminar Mixed Convection in the Entrance Region of Horizontal Semicircular Ducts With the Flat Wall at the Top

2006 ◽  
Vol 129 (9) ◽  
pp. 1203-1211 ◽  
Author(s):  
Y. M. F. El. Hasadi ◽  
A. A. Busedra ◽  
I. M. Rustum
Keyword(s):  
Nusselt Number ◽  
Mixed Convection ◽  
Friction Factor ◽  
Entrance Region ◽  
Wall Friction ◽  
Flat Wall ◽  
Simpler Algorithm ◽  
Laminar Mixed Convection ◽  
Wide Range ◽  
Semicircular Ducts

Laminar mixed convection in the entrance region for horizontal semicircular ducts with the flat wall on top is investigated theoretically. The governing momentum and energy equations are solved numerically using a marching technique with the finite control volume approach following the SIMPLER algorithm. Results are obtained for the thermal boundary conditions of uniform heat input axially with uniform wall temperature circumferentially at any cross section (H1 boundary condition) with Pr=0.7 and a wide range of Grashof numbers. These results include the velocity and temperature distributions at different axial locations, axial distribution of local Nusselt number, and local average wall friction factor. It is found that Nusselt number values are close to the forced convection values near the entrance region and then decrease to a minimum as the distance from the entrance increases and then rise due to the effect of free convection before reaching constant value (fully developed). As the Grashof number increases the Nusselt number and the average wall friction factor increase in both developing and fully developed regions and the location of the onset of the secondary flow moves upstream.

Combined gas radiation and laminar mixed convection in vertical concentric annuli

2002 ◽  
Author(s):  
Ezeddine Sediki ◽  
Anouar Soufiani ◽  
Mohamed Salah Sifaoui
Keyword(s):  
Mixed Convection ◽  
Gas Radiation ◽  
Laminar Mixed Convection

Coupled Thermal Radiation and Mixed Convection Step Flow of Nongray Gas

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
M. Atashafrooz ◽  
S. A. Gandjalikhan Nassab ◽  
K. Lari
Keyword(s):  
Mixed Convection ◽  
Radiative Transfer Equation ◽  
Convection Flow ◽  
Mixed Convection Flow ◽  
Discrete Ordinate ◽  
Full Spectrum ◽  
Step Flow ◽  
Laminar Mixed Convection ◽  
Gray Medium ◽  
Hydrodynamic Behaviors

The main goal of this paper is to analyze the thermal and hydrodynamic behaviors of laminar mixed convection flow of a nongray radiating gas over an inclined step in an inclined duct. The fluid is considered an air mixture with 10% CO2 and 20% H2O mole fractions, which is treated as homogeneous, absorbing, emitting, and nonscattering medium. The full-spectrum k-distribution (FSK) method is used to handle the nongray part of the problem, while the radiative transfer equation (RTE) is solved using the discrete ordinate method (DOM). In addition, the results are obtained for different medium assumptions such as pure mixed convection and gray medium to compare with the nongray calculations as a real case. The results show that in many cases, neglecting the radiation part in computations and also use of gray simulations are not acceptable and lead to considerable errors, especially at high values of the Grashof number in mixed convection flow.

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