On the Performance of Ag/Oil Nanofluids in Heat Transfer Enhancement in a Sinusoidal Tube: Constant Heat Flux Boundary Condition

2017 ◽  
Vol 46 (7) ◽  
pp. 913-923 ◽  
Author(s):  
Amin Jafarimoghaddam ◽  
Sadegh Aberoumand
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Heat Transfer Enhancement ◽  
Constant Heat Flux ◽  
Transfer Enhancement ◽  
Constant Heat ◽  
Flux Boundary Condition ◽  
Heat Flux Boundary Condition

On Effects of Temperature Boundary Conditions on Heat Transfer in Turbulent Low-Prandtl-Number Flows

2020 ◽  
Author(s):  
Ivan Otic
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Boundary Conditions ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Flux Boundary Condition ◽  
Large Eddy ◽  
Heat Flux Boundary Condition ◽  
Effects Of Temperature

Abstract One important issue in understanding and modeling of turbulent heat transfer is the behavior of fluctuating temperature close to the wall. Common engineering computational approach assumes constant heat flux boundary condition on heated walls. In the present paper constant heat flux boundary condition was assumed and effects of temperature fluctuations are investigated using large eddy simulations (LES) approach. A series of large eddy simulations for two geometries is performed: First, forced convection in channels and second, forced convection over a backward facing step. LES simulation data is statistically analyzed and compared with results of direct numerical simulations (DNS) from the literature which apply three cases of heat flux boundary conditions: 1. ideal heat flux boundary condition, 2. non-ideal heat flux boundary condition, 3. conjugate heat transfer boundary condition. For low Prandtl number flows LES results show that, despite very good agreement for velocities and mean temperature, predictions of temperature fluctuations may have strong deficiencies if simplified boundary conditions are applied.

Melting Around a Horizontal Heated Cylinder: Part I—Perturbation and Numerical Solutions for Constant Heat Flux Boundary Condition

1984 ◽  
Vol 106 (2) ◽  
pp. 376-384 ◽  
Author(s):  
J. Prusa ◽  
L. S. Yao
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Perturbation Method ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Flux Boundary Condition ◽  
Heated Cylinder ◽  
Heat Flux Boundary Condition ◽  
Rayleigh Numbers

The melting of a solid about a heated cylinder presents an irregularly shaped, moving boundary problem. A transformation is used to immobilize this boundary—replacing the problem of variable geometry by one of constant geometry. A constant heat flux boundary condition is used along the cylinder surface. Using perturbation and numerical methods, several solutions for this transient problem are generated for Stefan, Rayleigh, and Prandtl numbers of Stq = 0.374, Ra = 5000, and Pr = 54. Stq is the ratio of heat transfer rate to the thermal energy needed to melt the solid. Ra • B3 is the measure of the magnitude of the natural convection effect, where B is a dimensionless measure of the size of the melt region called the gap function. Ra itself can be thought of as a dimensionless heat flux, since it does not take the size of the melt region into account. The dimensionless groups Stq and Ra (based upon the surface heat flux) are used to determine two parameter expansions of the dependent variables for the regular perturbation method. The first three terms of the series solutions are determined. They provide accurate solutions for short times after the start of melting, for small values of Stefan and Rayleigh numbers. The accuracy of the perturbation method is verified using a numerical method, which is not limited to short initial time intervals or to small values of Stefan and Rayleigh numbers. Detailed predictions of the melt volume, shape, temperature field, global and local heat transfer rates are given for representative cases. Comparisons with earlier experimental results are made.

scholarly journals Laminar mixing and heat transfer for constant heat flux boundary condition

2012 ◽  
Vol 48 (8) ◽  
pp. 1285-1296 ◽  
Author(s):  
Kamal El Omari ◽  
Yves Le Guer
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Flux Boundary Condition ◽  
Laminar Mixing ◽  
Heat Flux Boundary Condition
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