scholarly journals Entropy Generation Analysis of Laminar Flows of Water-Based Nanofluids in Horizontal Minitubes under Constant Heat Flux Conditions

Entropy ◽  
2018 ◽  
Vol 20 (4) ◽  
pp. 242 ◽  
Author(s):  
Mehrdad Karimzadehkhouei ◽  
Mostafa Shojaeian ◽  
Abdolali Sadaghiani ◽  
Kürşat Şendur ◽  
M. Mengüç ◽  
...  
Keyword(s):  
Heat Flux ◽  
Entropy Generation ◽  
Constant Heat Flux ◽  
Laminar Flows ◽  
Constant Heat ◽  
Water Based

Entropy Generation Minimization of Fully Developed Internal Convective Flows With Constant Heat Flux

2003 ◽  
Author(s):  
Eric B. Ratts ◽  
Atul G. Raut
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Entropy Generation ◽  
Cross Sections ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Entropy Generation Minimization

This paper addresses the thermodynamic optimum of single-phase convective heat transfer in fully developed flow for uniform and constant heat flux. The optimal Reynolds number is obtained using the entropy generation minimization (EGM) method. Entropy generation due to viscous dissipation and heat transfer dissipation in the flow passage are summed, and then minimized with respect to Reynolds number based on hydraulic diameter. For fixed mass flow rate and fixed total heat transfer rate, and the assumption of uniform heat flux, an optimal Reynolds number for laminar as well as turbulent flow is obtained. In addition, the method quantifies the flow irreversibilities. It was shown that the ratio of heat transfer dissipation to viscous dissipation at minimum entropy generation was 5:1 for laminar flow and 29:9 for turbulent flow. For laminar flow, the study compared non-circular cross-sections to the circular cross-section. The optimal Reynolds number was determined for the following cross-sections: square, equilateral triangle, and rectangle with aspect ratios of two and eight. It was shown that the rectangle with the higher aspect ratio had the smallest optimal Reynolds number, the smallest entropy generation number, and the smallest flow length.

scholarly journals Entropy Generation during Turbulent Flow of Zirconia-water and Other Nanofluids in a Square Cross Section Tube with a Constant Heat Flux

Entropy ◽  
2014 ◽  
Vol 16 (11) ◽  
pp. 6116-6132 ◽  
Author(s):  
Hooman Yarmand ◽  
Goodarz Ahmadi ◽  
Samira Gharehkhani ◽  
Salim Kazi ◽  
Mohammad Safaei ◽  
...  
Keyword(s):  
Heat Flux ◽  
Turbulent Flow ◽  
Cross Section ◽  
Entropy Generation ◽  
Constant Heat Flux ◽  
Constant Heat

Laminar Entropy Generation Over a Flat Plate With Isothermal and Constant Heat Flux Boundary Conditions Using the Von Ka´rma´n Integral Method

Volume 1 ◽  
2004 ◽  
Author(s):  
Eric B. Ratts ◽  
J. Steven Brown
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boundary Conditions ◽  
Flat Plate ◽  
Entropy Generation ◽  
Single Phase ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Fundamental Study ◽  
Flux Boundary Conditions

This paper is a fundamental study on the irreversibility of single-phase laminar convective heat transfer over a flat plate with isothermal and constant heat flux boundary conditions. It quantifies the losses due to viscous momentum transfer losses and heat transfer losses and presents the irreversibility of the convective flow based on the entropy generation (EG) method. This paper determines the entropy generation for incompressible, single phase, laminar flow for large and small Prandtl numbers over a flat plate with isothermal and constant heat flux boundary conditions using von Ka´rma´n’s integral theory.

Second Law Analysis of Nanofluid Flow Through Circular Pipe

2010 ◽  
Author(s):  
H. Shokouhmand ◽  
M. Moghaddami ◽  
M. Siavashi
Keyword(s):  
Experimental Data ◽  
Boundary Condition ◽  
Heat Flux ◽  
Entropy Generation ◽  
Constant Heat Flux ◽  
Circular Pipe ◽  
Constant Heat ◽  
Flux Boundary Condition ◽  
Entropy Generation Number ◽  
Generation Number

This paper aims to numerically investigate the effects of adding nanoparticles on the entropy generation of water-Al2O3 nanofluid flows through a circular pipe under constant wall temperature also constant heat flux thermal boundary conditions in laminar regime. Approved formulations of mixtures are used for density and specific heat of the nanofluids. Nanofluid model proposed by Koo and Kleinstreuer [1] based on experimental data of Das et al. [2] is employed for conductivity of the nanofluids and an experimental correlation presented by Rea et al. [3] is used to model the viscosity of the nanofluid. The problem has been simulated numerically using a CFD finite-volume code and results are validated with the available experimental data. It is found that for the case of constant heat flux boundary condition, adding nanoparticles decreases the entropy generation and improves the thermal performance of water-Al2O3 flow. Moreover optimum Reynolds number to minimize the ratio of nanofluid entropy generation number to water is obtained for this case. For the case of wall constant temperature boundary condition, adding nanoparticles to water leads to heat flux increase, therefore the entropy generation number remains approximately constant.

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