Modelling of combined forced- and natural-convection heat transfer over upward-facing horizontal heated flat plates

2003 ◽  
Vol 27 (4) ◽  
pp. 327-335 ◽  
Author(s):  
K. Kudo ◽  
T. Kato ◽  
H. Chida ◽  
S. Takagi ◽  
N. Tsui
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Flat Plates

Optimum Plate Spacings for Laminar Natural Convection Heat Transfer From Parallel Vertical Isothermal Flat Plates

1971 ◽  
Vol 93 (4) ◽  
pp. 463-465 ◽  
Author(s):  
E. K. Levy
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Temperature Difference ◽  
Maximum Rate ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Flat Plates ◽  
Plate Spacing ◽  
Laminar Natural Convection

The problem of determining the optimum spacings between parallel vertical isothermal flat plates which are dissipating heat by natural convection to the environment is discussed. One optimum, first suggested by experimental data of Elenbaas with air and later derived theoretically by Bodoia, corresponds to the spacing between parallel vertical plates attached to a surface which will permit the maximum rate of heat transfer from that surface. A different optimum is derived in this paper which for a given heat flux gives the minimum plate spacing required to minimize the temperature difference between the plates and the fluid. The minimum temperature difference is shown to occur when the plate spacing is made sufficiently large that the wall boundary layers do not merge. It is shown that Elenbaas’ optimum, although requiring a plate spacing only 54 percent of that for minimum ΔT, produces a temperature difference which is 38 percent higher than the minimum.

Numerical Investigation of Natural Convection Heat Transfer From an Array of Horizontal Fins in Non-Newtonian Power-Law Fluids

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Jacob K. Mulamootil ◽  
Sukanta K. Dash
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Power Law ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Flat Plates ◽  
Power Law Fluids ◽  
Power Law Index ◽  
Fin Length

Natural convection heat transfer from an array of horizontal rectangular fins on a vertical flat plate in non-Newtonian power-law fluids has been studied. The underlying physical principles affecting heat transfer were studied using comprehensive solutions obtained from numerical investigations. Heat transfer to the power-law fluid was found to depend on the fluid rheology (power-law index) and significantly on the geometric parameters (interfin spacing, fin length) as well. The dependence was quantified using the Nusselt number (Nu) and fin effectiveness (Q/Q0). The present study shows that compared to a fin analyzed in isolation, the spatial arrangement of multiple fins relative to one another in an array does have a significant effect on the flow field around subsequent fins in power-law fluids. Therefore, the average heat transfer coefficient of the natural convection system is affected significantly. The variation of Nu with the dimensionless fin length (l/L), dimensionless interfin spacing (S/L), and fluid power-law index (n) was plotted. The dependence was found to be counter intuitive to expectations based on studies for natural convection from vertical flat plates to power-law fluids. In the present study involving fins, shear-thinning fluids (n < 1) show a decrease in heat transfer and shear-thickening fluids (n > 1) show an enhancement in heat transfer for higher l/L values. The results of the study may be useful in the design of natural convection systems that employ power-law fluids to enhance or control heat transfer.

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