Buoyancy effects on laminar heat transfer in the thermal entrance region of horizontal rectangular channels with uniform wall heat flux for large prandtl number fluid

1972 ◽  
Vol 15 (10) ◽  
pp. 1819-1836 ◽  
Author(s):  
K.C Cheng ◽  
S.W Hong ◽  
G.J Hwang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Prandtl Number ◽  
Wall Heat Flux ◽  
Entrance Region ◽  
Rectangular Channels ◽  
Thermal Entrance Region ◽  
Uniform Wall ◽  
Thermal Entrance ◽  
Uniform Wall Heat Flux

Vorticity-Velocity Method for the Graetz Problem and the Effect of Natural Convection in a Horizontal Rectangular Channel With Uniform Wall Heat Flux

1987 ◽  
Vol 109 (3) ◽  
pp. 704-710 ◽  
Author(s):  
F. C. Chou ◽  
G. J. Hwang
Keyword(s):  
Heat Flux ◽  
Prandtl Number ◽  
Numerical Solutions ◽  
Rectangular Channel ◽  
Wall Heat Flux ◽  
Entrance Region ◽  
Grashof Number ◽  
Uniform Wall ◽  
Laminar Convection ◽  
Uniform Wall Heat Flux

Numerical solutions given by a vorticity-velocity method are presented for combined free and forced laminar convection in the thermal entrance region of a horizontal rectangular channel without the assumptions of large Prandtl number and small Grashof number. The channel wall is heated with a uniform wall heat flux. Typical developments of temperature profile, secondary flow, and axial velocity at various axial positions in the entrance region are presented. Local friction factor and Nusselt number variations are shown for Rayleigh numbers Ra = 104, 3×104, 6×104, and 105 with the Prandtl number as a parameter. The solution for the limiting case of large Prandtl number and small Grashof number obtained from the present study confirms the data of existing literature. It is observed that the large Prandtl number assumption is valid for Pr = 10 when Ra ≤ 3×104 but for a larger Prandtl number when the Rayleigh number is higher.

Transient Heat Transfer for Laminar Forced Convection in the Thermal Entrance Region of Flat Ducts

1959 ◽  
Vol 81 (1) ◽  
pp. 29-36 ◽  
Author(s):  
R. Siegel ◽  
E. M. Sparrow
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Steady State ◽  
Thermal Response ◽  
Step Function ◽  
Entrance Region ◽  
Arbitrary Time ◽  
Unit Step ◽  
Thermal Entrance Region ◽  
Thermal Entrance

An analysis is made for transient laminar heat transfer in the thermal entrance region of a flat duct (parallel plate channel) whose bounding surfaces are subjected to an arbitrary time variation of temperature or of heat flux. Initially, the system may be either in an already established steady-state heat-transfer situation, or else, the fluid and duct walls may be at the same uniform temperature. The velocity distribution in the flow is taken to be fully developed and unchanging with time. The solution for arbitrary time-dependent conditions is obtained by generalizing the thermal response to a unit step change in wall temperature or in wall heat flux. This step-function response is found by using the method of characteristics. Heat-transfer results are presented as simple analytical expressions. The time required to achieve steady state after a unit step is also given. Working formulas are summarized at the end of the paper.

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