Heat transfer and entropy generation for laminar forced convection flow of graphene nanoplatelets nanofluids in a horizontal tube

Author(s):  
Mohammad Mehrali ◽  
Emad Sadeghinezhad ◽  
Marc A. Rosen ◽  
Amir Reza Akhiani ◽  
Sara Tahan Latibari ◽  
...  
2014 ◽  
Vol 18 (2) ◽  
pp. 479-492 ◽  
Author(s):  
Meysam Atashafrooz ◽  
Nassab Gandjalikhan ◽  
Babak Ansari

A numerical investigation of entropy generation in laminar forced convection of gas flow over a recess including two inclined backward and forward facing steps in a horizontal duct under bleeding condition is presented. For calculation of entropy generation from the second law of thermodynamics in a forced convection flow, the velocity and temperature distributions are primary needed. For this purpose, the two-dimensional Cartesian coordinate system is used to solve the governing equations which are conservations of mass, momentum and energy. These equations are solved numerically using the computational fluid dynamic techniques to obtain the temperature and velocity fields, while the blocked region method is employed to simulate the inclined surface. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. The numerical results are presented graphically and the effects of bleeding coefficient and recess length as the main parameters on the distributions of entropy generation number and Bejan number are investigated. Also, the effect of Reynolds number and bleeding coefficient on total entropy generation which shows the amount of flow irreversibilities is presented for two recess length. The use of present results in the design process of such thermal system would help the system attain the high performance during exploitation. Comparison of numerical results with the available data published in open literature shows a good consistency.


RSC Advances ◽  
2017 ◽  
Vol 7 (49) ◽  
pp. 30673-30686
Author(s):  
Raja Rabhi ◽  
Abir Yahya ◽  
Bayssain Amami ◽  
Hacen Dhahri

In this work entropy generation and heat transfer for magnetohydrodynamic (MHD) forced convection flow in a micro duct filled with a porous medium are investigated using a modified axisymmetric Lattice Boltzmann Method.


Author(s):  
M Atashafrooz ◽  
SA Gandjalikhan Nassab

This study presents a numerical analysis of three-dimensional laminar forced convection flow of a radiating gas over an inclined backward-facing step in a rectangular duct under bleeding condition. The fluid is treated as a gray, absorbing, emitting, and scattering medium. The three-dimensional Cartesian coordinate system is used to solve the governing equations which are the conservations of mass, momentum, and energy. These equations are solved numerically using the computational fluid dynamic techniques to obtain the temperature and velocity fields, while the blocked-off method is employed to simulate the incline surface. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. Since the gas is considered as a radiating medium, besides the convective and conductive terms in the energy equation, the radiative term also presented. For computation of this term, the radiative transfer equation is solved numerically by the discrete ordinates method to find the divergence of radiative heat flux distribution inside the radiating medium. By this numerical procedure, the role of radiation heat transfer on convection flow of a radiating gas which has many engineering applications (for example in heat exchangers and combustion chambers) is studied in detail. Beside, the effects of bleeding coefficient, albedo coefficient, optical thickness, and the radiation–conduction parameter on heat transfer behavior of the system are investigated. Comparison of numerical results with the available data published in the open literature shows a good agreement.


2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Esam M. Alawadhi

Laminar forced convection flow past an in-line elliptical cylinder array with inclination is simulated using the finite element method. The inclination of the elliptical cylinders is increased with the number of the cylinder in the array, 0 deg for the first cylinder and 90 deg for the last cylinder. The global objective of this research is to enhance the heat transfer out of the cylinders. A parametric study of heat exchanges between the cylinders and flow (expressed by the Nusselt number) is reported for Reynolds numbers between 125 and 1000, while the Prandtl number is fixed at 0.71. The results are compared with an elliptical cylinder array without inclination to assess the heat transfer enhancement. The problem is solved as transient, and a vortex shedding phenomenon is reported. The results indicated that the Reynolds number has a significant effect on the heat transfer out of the cylinders, and the inclination of the elliptical cylinders enhances heat transfer rate up to 238.59%, but pressure drop is increased as high as 700%. Also, skin-friction coefficient along the five cylinders’ perimeter, plots of the velocity flow field, and temperature contours are presented.


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