A theoretical study of natural convection heat transfer from downward-facing horizontal surfaces with uniform heat flux

1973 ◽  
Vol 16 (3) ◽  
pp. 611-627 ◽  
Author(s):  
Fujii Tetsu ◽  
Honda Hiroshi ◽  
Morioka Itsuki
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Natural Convection ◽  
Theoretical Study ◽  
Convection Heat Transfer ◽  
Uniform Heat Flux ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
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.

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