Effect of free stream turbulence on the thermal entrance region of a circular duct

1975 ◽  
Vol 2 (2) ◽  
pp. 141-149
Author(s):  
K Goel
Keyword(s):  
Free Stream ◽  
Entrance Region ◽  
Circular Duct ◽  
Free Stream Turbulence ◽  
Thermal Entrance Region ◽  
Thermal Entrance

Heating and Cooling Air and Carbon Dioxide in the Thermal Entrance Region of a Circular Duct With Large Gas to Wall Temperature Differences

1959 ◽  
Vol 81 (4) ◽  
pp. 267-277 ◽  
Author(s):  
Helmut Wolf
Keyword(s):  
Carbon Dioxide ◽  
Wall Temperature ◽  
Entrance Region ◽  
Large Temperature ◽  
Uniform Heat Flux ◽  
Axial Distance ◽  
Number Range ◽  
Circular Duct ◽  
Thermal Entrance Region ◽  
Thermal Entrance

The local heat-transfer characteristics for air and carbon dioxide in the thermal entrance region have been determined experimentally and are compared with predicted values computed from an extension of the theoretical analysis due to Deissler. The experiments were conducted in smooth round tubes having a fully developed turbulent velocity profile and a uniform temperature distribution at the entrance. The boundary conditions of uniform heat flux for heating the gas, and wall temperature constant and variable with axial distance for cooling the gas, were investigated with large temperature differences between the gas and the tube wall. For heating, the experimental results yielded one per cent thermal entrance lengths ranging from 11 to 27 diameters over the bulk Reynolds number range from 50,000 to 246,000. For cooling, one per cent thermal entrance lengths ranging from 12 to 26 diameters were obtained for bulk Reynolds numbers ranging from 17,000 to 218,000. The agreement between theory and experiment was favorable in most cases.

Periodic Forced Convection in a Darcy Metallic Foam: The LTNE Model

2012 ◽  
Author(s):  
Eugenia Rossi di Schio ◽  
Antonio Barletta
Keyword(s):  
Forced Convection ◽  
Outer Boundary ◽  
Method Of Lines ◽  
Mean Value ◽  
Entrance Region ◽  
Solid Matrix ◽  
Metallic Foam ◽  
The Method Of Lines ◽  
Thermal Entrance Region ◽  
Thermal Entrance

The present paper studies the thermal entrance region in a concentric annular duct filled by a fluid saturated porous metallic foam, with reference to steady forced convection and to a thermal boundary condition given by a wall temperature longitudinally varying with a sinusoidal law. The effect of viscous dissipation in the fluid is taken into account, and a two-temperature model is employed in order to evaluate separately the local fluid and solid matrix temperatures. The governing equations in the thermal entrance region are solved numerically by the method of lines. The Nusselt numer and its mean value in an axial period is evaluated, with reference both to the inner and the outer boundary.

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