scholarly journals A Numerical Analysis on Nanofluid Mixed Convection in Triangular Cross-Sectioned Ducts Heated by a Uniform Heat Flux

2015 ◽  
Vol 7 (1) ◽  
pp. 292973 ◽  
Author(s):  
Oronzio Manca ◽  
Sergio Nardini ◽  
Daniele Ricci ◽  
Salvatore Tamburrino
Keyword(s):  
Heat Flux ◽  
Numerical Analysis ◽  
Mixed Convection ◽  
Uniform Heat Flux ◽  
Uniform Heat

Applicability of Uniform Heat Flux Nusselt Number Correlations to Thermosyphon Heat Exchangers for Solar Water Heaters

1999 ◽  
Vol 121 (2) ◽  
pp. 85-90 ◽  
Author(s):  
S. Dahl ◽  
J. Davidson
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Mixed Convection ◽  
Heat Exchangers ◽  
Convection Heat Transfer ◽  
Uniform Heat Flux ◽  
Convection Heat ◽  
Solar Water ◽  
Nusselt Numbers ◽  
Uniform Heat

Nusselt numbers are measured in three counterflow tube-in-shell heat exchangers with flow rates and temperatures representative of thermosyphon operation in solar water heating systems. Mixed convection heat transfer correlations for these tube-in-shell heat exchangers were previously developed in Dahl and Davidson (1998) from data obtained in carefully controlled experiments with uniform heat flux at the tube walls. The data presented in this paper confirm that the uniform heat flux correlations apply under morerealistic conditions. Water flows in the shell and 50 percent ethylene glycol circulates in the tubes. Actual Nusselt numbers are within 15 percent of the values predicted for a constant heat flux boundary condition. The data reconfirm the importance of mixed convection in determining heat transfer rates. Under most operating conditions, natural convection heat transfer accounts for more than half of the total heat transfer rate.

Local Thermal Non-Equilibrium in Mixed Convection in Channels Partially Heated at Uniform Heat Flux Filled With a Porous Medium

2014 ◽  
Author(s):  
Bernardo Buonomo ◽  
Oronzio Manca ◽  
Paolo Mesolella ◽  
Sergio Nardini
Keyword(s):  
Heat Flux ◽  
Mixed Convection ◽  
Metal Foam ◽  
Vertical Channel ◽  
Boussinesq Approximation ◽  
Uniform Heat Flux ◽  
Aspect Ratios ◽  
Uniform Heat ◽  
Lower Temperature ◽  
Non Equilibrium

A numerical analysis of mixed convection in a vertical channel filled with metal foam partially heated at uniform heat flux is studied numerically. Local thermal non-equilibrium and Brinkman-Forchheimer-extended Darcy model are assumed. Boussinesq approximation with constant thermophysical proprieties are considered. Results are carried out for an aluminium foam with 10 pore per inch (PPI) and ε=0.909, the fluid is air. Results, for different Reynolds numbers and geometrical aspect ratios, are given in terms of solid and fluid temperatures, at heated walls and inside the channel at several heights, velocity profile along the channel, local and average Nusselt numbers. Results show that diffusive effect resulted lower temperature values inside the solid and the fluid temperatures are higher in all considered cases. For heated channel with smaller aspect ratios, an average Nusselt number increase is found for solid and fluid phases.

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