Effects of a Thick Plate on the Excess Temperature of Iso-Heat Flux Heat Sources Cooled by Laminar Forced Convection Flow: Conjugate Analysis

2014 ◽  
Vol 66 (2) ◽  
pp. 205-216 ◽  
Author(s):  
M. R. Hajmohammadi ◽  
M. Moulod ◽  
O. Joneydi Shariatzadeh ◽  
A. Campo
2013 ◽  
Vol 135 (12) ◽  
Author(s):  
Mohammad Reza Hajmohammadi ◽  
Antonio Campo ◽  
S. Salman Nourazar ◽  
Amir Masood Ostad

It is proposed that a conductive thick plate is placed between a heat source and a cold flowing fluid to improve the forced convection cooling performance. Detailed numerical work is carried out to determine the optimal thickness of the conductive thick plate which minimizes the peak temperature. It is shown that the thick plate significantly reduces the excess temperature of heat sources, by way of conducting the heat current in an optimal manner. It is shown that the reduction in the excess temperature of heat sources depends upon the Reynolds number of the fluid flow and the material thermal conductivity. Correlations for the optimum plate thickness and reduction in excess temperature of heat sources are presented, which could be useful for the practitioners.


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.


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.


2006 ◽  
Vol 129 (9) ◽  
pp. 1295-1299 ◽  
Author(s):  
Y. T. Chen ◽  
J. H. Nie ◽  
B. F. Armaly ◽  
H. T. Hsieh ◽  
R. F. Boehm

Developing turbulent forced convection flow in a two-dimensional duct is simulated for Reynolds numbers ranging from 4560 to 12,000. Simultaneously developing velocity and temperature distributions are reported by treating the inlet flow as isothermal with uniform velocity profile. The walls are supplied with uniform heat flux. Distributions of the streamwise and the transverse velocity components exhibit a maximum near the walls, but not at the center of the duct, in the developing region of the flow. The friction coefficient and the Nusselt number do not reach the fully developed values monotonously, and a minimum in their distributions appears in the developing region. Some results are compared with the available data, and very favorable comparisons are obtained.


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