Asymmetrical Non-Uniform Heat Flux Distributions For Laminar Flow Heat Transfer With Mixed Convection In a Horizontal Circular Tube

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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Forced convection heat transfer in a circular tube with non-uniform heat flux around the circumference

International Journal of Heat and Mass Transfer ◽

10.1016/0017-9310(72)90215-3 ◽

1972 ◽

Vol 15 (3) ◽

pp. 527-537 ◽

Cited By ~ 10

Author(s):

A.C Rapier

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Forced Convection ◽

Circular Tube ◽

Convection Heat Transfer ◽

Uniform Heat Flux ◽

Convection Heat ◽

Forced Convection Heat Transfer ◽

Uniform Heat

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Mixed Convection Heat Transfer and Pressure Drop Correlations for Tube-ln-Shell Thermosyphon Heat Exchangers With Uniform Heat Flux

Journal of Solar Energy Engineering ◽

10.1115/1.2888129 ◽

1998 ◽

Vol 120 (4) ◽

pp. 260-269 ◽

Cited By ~ 8

Author(s):

S. D. Dahl ◽

J. H. Davidson

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Pressure Drop ◽

Mixed Convection ◽

Heat Exchangers ◽

Convection Heat Transfer ◽

Uniform Heat Flux ◽

Convection Heat ◽

Uniform Heat ◽

Laminar Mixed Convection

An important issue arising from prior studies of thermosyphon heat exchangers for use in solar water heaters is the need for heat transfer and pressure drop correlations for the laminar, mixed-convection regime in which these many of these heat exchangers operate. In this paper, we present empirical correlations for tube-in-shell heat exchangers with the thermosyphon flow on the shell side. The correlations are determined for uniform heat flux on the tube walls. Ranges of Reynolds and Grashof numbers are 130 to 2,000 and 4 × 105 to 8 × 107, respectively. Nusselt number correlations are presented in a form that combines the contributions of forced and natural convection. Mixed convection dominates forced convection heat transfer in these geometries. Pressure drop is not significantly affected by mixed convection.

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Heat Transfer to Air in a Circular Tube Having Uniform Heat Flux

Journal of Heat Transfer ◽

10.1115/1.3684329 ◽

1962 ◽

Vol 84 (2) ◽

pp. 186-187 ◽

Cited By ~ 7

Author(s):

C. A. Depew

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Circular Tube ◽

Uniform Heat Flux ◽

Uniform Heat

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Mixed Convection Heat Transfer With Longitudinal Fins in a Horizontal Parallel Plate Channel: Part I—Numerical Results

Journal of Heat Transfer ◽

10.1115/1.2910431 ◽

1990 ◽

Vol 112 (3) ◽

pp. 612-618 ◽

Cited By ~ 15

Author(s):

J. R. Maughan ◽

F. P. Incropera

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Mixed Convection ◽

Secondary Flow ◽

Heated Surface ◽

Bottom Plate ◽

Bottom Surface ◽

Uniform Heat Flux ◽

Uniform Heat ◽

Fin Spacing

Numerical calculations for laminar, fully developed mixed convection in a longitudinally finned horizontal channel have been performed for two sets of boundary conditions: (i) an isothermal, heated bottom plate with an isothermal, cooled top plate, and (ii) a uniform heat flux at the bottom surface with an adiabatic upper surface. Heat transfer and the strength of the buoyancy-driven secondary flow increase with increasing Rayleigh number and fin height. Fin spacing affects heat transfer through changes in the axial velocity distribution, the strength of the secondary flow, and the heated surface area, with decreased spacing acting to inhibit secondary flow. For the uniform heat flux condition and a small available pressure drop, close fin spacing can significantly reduce the channel flow rate and increase maximum plate temperatures.

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