TURBULENT FORCED CONVECTION IN THE THERMAL ENTRANCE OF RECTANGULAR DUCTS: ANALYSIS FOR DIFFERENT MODELS OF VELOCITY DISTRIBUTION AND MOMENTUM EDDY DIFFUSIVITY

2020 ◽  
Author(s):  
dhiego veloso ◽  
Carlos Antonio Cabral Santos ◽  
Fábio Lima
Keyword(s):  
Velocity Distribution ◽  
Forced Convection ◽  
Eddy Diffusivity ◽  
Thermal Entrance

Periodic Forced Convection in a Darcy Metallic Foam: The LTNE Model

2012 ◽  
Author(s):  
Eugenia Rossi di Schio ◽  
Antonio Barletta
Keyword(s):  
Forced Convection ◽  
Outer Boundary ◽  
Method Of Lines ◽  
Mean Value ◽  
Entrance Region ◽  
Solid Matrix ◽  
Metallic Foam ◽  
The Method Of Lines ◽  
Thermal Entrance Region ◽  
Thermal Entrance

The present paper studies the thermal entrance region in a concentric annular duct filled by a fluid saturated porous metallic foam, with reference to steady forced convection and to a thermal boundary condition given by a wall temperature longitudinally varying with a sinusoidal law. The effect of viscous dissipation in the fluid is taken into account, and a two-temperature model is employed in order to evaluate separately the local fluid and solid matrix temperatures. The governing equations in the thermal entrance region are solved numerically by the method of lines. The Nusselt numer and its mean value in an axial period is evaluated, with reference both to the inner and the outer boundary.

Entropy generation analysis for microscale forced convection with radiation in thermal entrance region

2014 ◽  
Vol 51 (3) ◽  
pp. 307-312 ◽  
Author(s):  
Cyrus Aghanajafi ◽  
Maziar Alasvand Bakhtiarpoor ◽  
Mehran Taghipour ◽  
Farid Mohamadi
Keyword(s):  
Forced Convection ◽  
Entropy Generation ◽  
Entrance Region ◽  
Thermal Entrance Region ◽  
Thermal Entrance

Entropy Generation in Thermally Developing Laminar Forced Convection Through a Slit Microchannel

2010 ◽  
Author(s):  
Arman Sadeghi ◽  
Mostafa Baghani ◽  
Mohammad Hassan Saidi
Keyword(s):  
Forced Convection ◽  
Entropy Generation ◽  
Energy Equation ◽  
Integral Transform ◽  
Axial Coordinate ◽  
Entropy Generation Number ◽  
Group Parameter ◽  
Laminar Forced Convection ◽  
Thermal Entrance ◽  
Increasing Function

The issue of entropy generation in laminar forced convection of a Newtonian fluid through a slit microchannel is analytically investigated by taking the viscous dissipation effect, the slip velocity and the temperature jump at the wall into account. Flow is considered to be hydrodynamically fully developed but thermally developing. The energy equation is solved by means of integral transform. The results demonstrate that to increase Knudsen number is to decrease entropy generation, while the effect of increasing values of Brinkman number and the group parameter is to increase entropy generation. Also it is disclosed that in the thermal entrance region the average entropy generation number over the cross section of channel is an increasing function of axial coordinate.

On The Correlation and Presentation of Information on Turbulent Variable Property Heat Transfer in Tubes

1962 ◽  
Vol 66 (618) ◽  
pp. 397-400 ◽  
Author(s):  
A. J. Ward Smith
Keyword(s):  
Heat Transfer ◽  
Flow Velocity ◽  
Forced Convection ◽  
Subject Matter ◽  
Variable Property ◽  
General Terms ◽  
The Subject ◽  
Thermal Entrance ◽  
Compressibility Effects

This note is concerned with the correlation and presentation of information on heat transfer under conditions of turbulent forced convection for the flow of gases in tubes. Discussion will be confined to the region where thermal entrance effects are absent and, furthermore, it will be assumed that the flow velocity is sufficiently low for compressibility effects to be neglected.The subject matter will be discussed in general terms only and it is not intended to produce quantitative conclusions, which may, however, be found in reference 11.

Effects of Brownian Diffusion and Thermophoresis on the Laminar Forced Convection of a Nanofluid in a Channel

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Eugenia Rossi di Schio ◽  
Michele Celli ◽  
Antonio Barletta
Keyword(s):  
Forced Convection ◽  
Wall Temperature ◽  
Homogeneous Model ◽  
Entrance Region ◽  
Brownian Diffusion ◽  
Boundary Temperature ◽  
Coupled Equations ◽  
Thermal Entrance Region ◽  
Laminar Forced Convection ◽  
Thermal Entrance

A steady laminar forced convection in a parallel–plane channel using nanofluids is studied. The flow is assumed to be fully developed, and described through the Hagen–Poiseuille profile. A boundary temperature varying with the longitudinal coordinate in the thermal entrance region is prescribed. Two sample cases are investigated in detail: a linearly changing wall temperature, and a sinusoidally changing wall temperature. A study of the thermal behavior of the nanofluid is performed by solving numerically the fully–elliptic coupled equations. The numerical solution is obtained by a Galerkin finite element method implemented through the software package Comsol Multiphysics (© Comsol, Inc.). With reference to both the wall temperature distributions prescribed along the thermal entrance region, the governing equations have been solved separately both for the fully developed region and for the thermal entrance region. The analysis shows that if a linearly varying boundary temperature is assumed, for physically interesting values of the Péclet number the concentration field depends very weakly on the temperature distribution. On the other hand, in case of a longitudinally periodic boundary temperature, nonhomogeneities in the nanoparticle concentration distribution arise, which are wrongly neglected whenever the homogeneous model is employed.

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