scholarly journals Analytical study of parameters affecting entropy generation of nanofluid turbulent flow in channel and micro-channel

2016 ◽  
Vol 20 (6) ◽  
pp. 2037-2050 ◽  
Author(s):  
Ghanbarali Sheikhzadeh ◽  
Alireza Aghaei ◽  
Hamidreza Ehteram ◽  
Mahmoud Abbaszadeh
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Tio2 Nanoparticles ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Geometrical Parameters ◽  
Bejan Number ◽  
Micro Channel ◽  
Minimum Entropy

In this study, thermo-physical and geometrical parameters affecting entropy generation of nanofluid turbulent flow such as the volume fraction, Reynolds number and diameter of the channel and micro-channel with circular cross section under constant flux are examined analytically. Water is used as a base fluid of nanofluid with nanoparticles of Ag, Cu, CuO and TiO2. The study is conducted for Reynolds numbers of 20000, 40000 and 100000, volume fractions of 0, 0.01, 0.02, 0.03 and 0.04, channel diameters of 2, 4, 6 and 8 cm and micro-channel diameters of 20, 40, 60 and 80 micrometers. Based on the results, the most of the generated entropy in channel is due to heat transfer, and also, with increasing the diameter of the channel, Bejan number increases. The contribution of entropy generation due to heat transfer in the micro-channel is very poor and the major contribution of entropy generation is due to friction. The maximum amount of entropy generation in channel belongs to nanofluids with Ag, Cu, CuO and TiO2 nanoparticles, respectively, while in the micro-channel this behavior is reversed; and the minimum entropy generation happens in nanofluids with Ag, Cu, CuO and TiO2 nanoparticles, respectively. In channel and micro-channel, for all nanofluids except for the water-TiO2, with increasing volume fraction of nanoparticles, the entropy generation decreases. In channel and micro-channel, the total entropy generation increases as Reynolds number augments.

scholarly journals Optimal Design of Nanoparticle Enhanced Phan-Thien–Tanner Flow of a Viscoelastic Fluid in a Microchannel

Entropy ◽  
2018 ◽  
Vol 20 (12) ◽  
pp. 895
Author(s):  
Mohammad Abdollahzadeh Jamalabadi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Circular Cross Section ◽  
Major Influence ◽  
Parameter Study ◽  
Bejan Number ◽  
Total Entropy ◽  
Minimum Entropy

The excellent thermal characteristics of nanoparticles have increased their application in the field of heat transfer. In this paper, a thermophysical and geometrical parameter study is performed to minimize the total entropy generation of the viscoelastic flow of nanofluid. Entropy generation with respect to volume fraction (<0.04), the Reynolds number (20,000–100,000), and the diameter of the microchannel (20–20,000 μm) with the circular cross-section under constant flux are calculated. As is shown, most of the entropy generation owes to heat transfer and by increasing the diameter of the channel, the Bejan number increases. The contribution of heat entropy generation in the microchannel is very poor and the major influence of entropy generation is attributable to friction. The maximum quantity of in-channel entropy generation happens in nanofluids with TiO2, CuO, Cu, and Ag nanoparticles, in turn, despite the fact in the microchannel this behavior is inverted, the minimum entropy generation occurs in nanofluids with CuO, Cu, Ag, and TiO2 nanoparticles, in turn. In the channel and microchannel for all nanofluids except water-TiO2, increasing the volume fraction of nanoparticles decreases entropy generation. In the channel and microchannel the total entropy generation increases by augmentation the Reynolds number.

Thermodynamic optimization of nanofluid flow over a non-isothermal wedge with nonlinear radiation and activation energy

2021 ◽  
Author(s):  
M R Acharya ◽  
P Mishra ◽  
Satyananda Panda
Keyword(s):  
Heat Transfer ◽  
Activation Energy ◽  
Reynolds Number ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Mathematical Formulation ◽  
Bejan Number ◽  
Nanofluid Flow ◽  
Entropy Generation Number ◽  
Generation Number

Abstract This paper analyses the augmentation entropy generation number for a viscous nanofluid flow over a non-isothermal wedge including the effects of non-linear radiation and activation energy. We discuss the influence of thermodynamically important parameters during the study, namely, the Bejan number, entropy generation number, and the augmentation entropy generation number. The mathematical formulation for thermal conductivity and viscosity of nanofluid for Al2O3 − EG mixture has been considered. The results were numerically computed using implicit Keller-Box method and depicted graphically. The important result is the change in augmentation entropy generation number with Reynolds number. We observed that adding nanoparticles (volume fraction) tend to enhance augmentation entropy generation number for Al2O3 − EG nanofluid. Further, the investigation on the thermodynamic performance of non-isothermal nanofluid flow over a wedge reveals that adding nanoparticles to the base fluid is effective only when the contribution of heat transfer irreversibility is more than fluid friction irreversibility. This work also discusses the physical interpretation of heat transfer irreversibility and pressure drop irreversibility. This dependency includes Reynolds number and volume fraction parameter. Other than these, the research looked at a variety of physical characteristics associated with the flow of fluid, heat and mass transfer.

Performance evaluation and entropy generation of chevron-type plate-fin equipped with ribs and holes

2021 ◽  
pp. 095440622110127
Author(s):  
F Nejati Barzoki ◽  
M Khoshvaght-Aliabadi ◽  
GA Sheikhzadeh ◽  
AA Abbasian Arani ◽  
A Feizabadi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Entropy Generation ◽  
Geometrical Parameters ◽  
Bejan Number ◽  
Entropy Generation Number ◽  
Generation Number ◽  
Performance Indexes ◽  
The Relationship

The complexity caused by an enhanced technique may significantly enhance the heat transfer along with a penalty in the pressure drop. Thus, it is needed to assess the counteracting effects between the enhanced heat transfer and the augmented pressure drop in practical applications. In order to comprehensively evaluate the hydrothermal performance of the chevron-type plate-fin (CTPF) equipped with ribs and holes, this study focuses on the relationship between hydraulic and thermal characteristics. Firstly, the relationship between the Colburn factor and the friction factor is presented, then two performance indexes are applied using these factors to evaluate the use of ribs and holes in the CTPIt F is found that the simultaneous use of ribs and holes shows better overall performances as compared with the use of ribs or holes individually. At the same geometrical parameters, the highest values of 1.52 and 1.07 are recorded for these performance indexes. In order to further improve the overall performance of the CTPF, the effects of geometrical parameters are also investigated. With the decrease of corrugation amplitude ( a) and the increase of corrugation length ( l), rib height ( h), and rib thickness ( t), the CTPF performs better overall performances. And, for the models with different levels of hole width ( w), the better performance is seen when this parameter is at the middle level. However, in the studied models, the best overall hydrothermal performance is detected for the model with a = 2.5 mm, l = 60 mm, h = 2.5 mm, t = 10 mm, and w = 10 mm, and highest performance indexes of 2.52 and 1.15 are reported for this model. Likewise, an entropy generation analysis is carried out, and the obtained results are discussed based on the Bejan number and entropy generation number. The results show that the increase of Reynolds number can lead to decrease of Bejan number and to increase of entropy generation number. For Reynolds number ranging from 4000 to 10000, the best model, which is described above, shows 17% decrease in the entropy generation number comparing with the reference model. Finally, two correlations are developed to predict the Bejan number and entropy generation number of the current study.

Entropy generation and heat transfer analysis for ferrofluid flow between two rotating disks with variable conductivity

2021 ◽  
pp. 095440622199118
Author(s):  
Anupam Bhandari
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Differential Equations ◽  
Entropy Generation ◽  
Heat Transfer Analysis ◽  
Entropy Generation Rate ◽  
Geometrical Parameters ◽  
Rotating Disks ◽  
Coupled Differential Equations ◽  
Lower Disk

Present model analyze the flow and heat transfer of water-based carbon nanotubes (CNTs) [Formula: see text] ferrofluid flow between two radially stretchable rotating disks in the presence of a uniform magnetic field. A study for entropy generation analysis is carried out to measure the irreversibility of the system. Using similarity transformation, the governing equations in the model are transformed into a set of nonlinear coupled differential equations in non-dimensional form. The nonlinear coupled differential equations are solved numerically through the finite element method. Variable viscosity, variable thermal conductivity, thermal radiation, and volume concentration have a crucial role in heat transfer enhancement. The results for the entropy generation rate, velocity distributions, and temperature distribution are graphically presented in the presence of physical and geometrical parameters of the flow. Increasing the values of ferromagnetic interaction number, Reynolds number, and temperature-dependent viscosity enhances the skin friction coefficients on the surface and wall of the lower disk. The local heat transfer rate near the lower disk is reduced in the presence of Harman number, Reynolds number, and Prandtl number. The ferrohydrodynamic flow between two rotating disks might be useful to optimize the use of hybrid nanofluid for liquid seals in rotating machinery.

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.

Numerical Investigation of Local Entropy Generation for Laminar Flow in Rotating-Disk Systems

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Mohammad Shanbghazani ◽  
Vahid Heidarpoor ◽  
Marc A. Rosen ◽  
Iraj Mirzaee
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Laminar Flow ◽  
Entropy Generation ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Bejan Number ◽  
Local Entropy ◽  
Fluid Friction ◽  
Local Entropy Generation

The entropy generation is investigated numerically in axisymmetric, steady-state, and incompressible laminar flow in a rotating single free disk. The finite-volume method is used for solving the momentum and energy equations needed for the determination of the entropy generation due to heat transfer and fluid friction. The numerical model is validated by comparing it to previously reported analytical and experimental data for momentum and energy. Results are presented in terms of velocity distribution, temperature, local entropy generation rate, Bejan number, and irreversibility ratio distribution for various rotational Reynolds number and physical cases, using dimensionless parameters. It is demonstrated that increasing rotational Reynolds number increases the local entropy generation rate and irreversibility rate, and that the irreversibility is mainly due to heat transfer while the irreversibility associated with fluid friction is minor.

scholarly journals Entropy Generation and Bejan Number Analysis of MHD Casson Fluid Flow in a Micro-Channel with Navier Slip and Convective Boundary Conditions

2020 ◽  
Vol 7 (4) ◽  
Author(s):  
M. Venkateswarlu ◽  
P. Bhaskar
Keyword(s):  
Heat Transfer ◽  
Friction Coefficient ◽  
Entropy Generation ◽  
Mhd Flow ◽  
Casson Fluid ◽  
Skin Friction Coefficient ◽  
Bejan Number ◽  
Micro Channel ◽  
Convective Boundary Conditions ◽  
Convective Boundary

The analysis of MHD flow has been a concern of consideration for research scientists and engineers. In this treatise, the steady MHD flow of an incompressible and electrically conducting Casson fluid in a micro-channel with heat generation and viscous dissipation, in the presence of hydrodynamic slip and convective boundary conditions, is examined. Exact solutions of non-dimensional steady governing equations are obtained in closed form. Transient fluid velocity, temperature, entropy generation, and Bejan number are depicted by the line graphs whereas rate of heat transfer and skin-friction coefficient are computed in tabular form for pertinent flow parameters. It is established that the entropy generation rate and Bejan number increases for increasing values of the Casson parameter and heat generation parameter. In particular, the Casson parameter accelerates the skin-friction coefficient while it provides resistance to the rate of heat transfer near the channel walls. Casson fluid finds significant applications in biomechanics, polymer processing industries, and food processing.

Numerical Study on Mixed Convection and Entropy Generation of a Nanofluid in a Lid-Driven Square Enclosure

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
R. K. Nayak ◽  
S. Bhattacharyya ◽  
I. Pop
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Numerical Study ◽  
Control Volume ◽  
Transport Equations ◽  
Bejan Number ◽  
Square Enclosure ◽  
Wide Range

A numerical investigation of mixed convection due to a copper–water nanofluid in an enclosure is presented. The mixed convection is governed by moving the upper lid of the enclosure and imposing a vertical temperature gradient. The transport equations for fluid and heat are modeled by using the Boussinesq approximation. A modified form of the control volume based SIMPLET algorithm is used for the solution of the transport equations. The fluid flow and heat transfer characteristics are studied for a wide range of Reynolds number and Grashof number so as to have the Richardson number greater or less than 1. The nanoparticle volume fraction is considered up to 20%. Heat flow patterns are analyzed through the energy flux vector. The rate of enhancement in heat transfer due to the addition of nanoparticles is analyzed. The entropy generation and Bejan number are evaluated to demonstrate the thermodynamic optimization of the mixed convection. We have obtained the enhancement rate in heat transfer and entropy generation in nanofluid for a wide range of parameter values.

Heat transfer and entropy generation analysis of Cu-water nanofluid in a vertical channel

2018 ◽  
Vol 15 (5) ◽  
pp. 604-613
Author(s):  
Essma Belahmadi ◽  
Rachid Bessaih
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Mixed Convection ◽  
Friction Factor ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Vertical Channel ◽  
Simple Algorithm ◽  
Content Type

Purpose The purpose of this study is to analyze heat transfer and entropy generation of a Cu-water nanofluid in a vertical channel. The channel walls are maintained at a hot temperature Tw. An up flow penetrates the channel at a uniform velocity v0 and a cold temperature T0 (T0 < Tw). The effects of Reynolds number Re, Grashof number Gr and solid volume fraction ϕ on streamlines, isotherms, entropy generation, friction factor, local and mean Nusselt numbers are evaluated. Design/methodology/approach The Cu-water nanofluid is used in this study. The software Ansys-fluent 14.5, based on the finite-volume method and SIMPLE algorithm, is used to simulate the mixed convection problem with entropy generation in a vertical channel. Findings The results show that the increase of Reynolds and Grashof numbers and solid volume fraction improves heat transfer and reduces entropy generation. Correlations for the mean Nusselt number and friction factor in terms of Reynolds number and solid volume fraction are obtained. The present results are compared with those found in the literature, which reveal a very good agreement. Originality/value The originality of this work is to understand the heat transfer and entropy generation for mixed convection of a Cu-water nanofluid in a vertical channel.

scholarly journals Impact of surface texture on entropy generation in nanofluid

2019 ◽  
pp. 469-469
Author(s):  
Ahmer Mehmood ◽  
Sajid Khan ◽  
Muhammad Iqbal ◽  
Sufian Munawar
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Surface Texture ◽  
Volume Fraction ◽  
Thermal Contact ◽  
Heat Transfer Process ◽  
Bejan Number ◽  
Heat Transfer Augmentation ◽  
Keller Box Method ◽  
Layer Flow

We consider a heat transfer augmentation problem to minimize the entropy generation by assuming boundary layer flow of nanofluid over a moving wavy surface. The nanofluid demonstrates great potential in enhancing the heat transfer process due to its high thermal conductivity. The famous Tiwari and Das model has been used in the present article. Two types of water based nanofluids containing Cu and Fe3O4 nanoparticles are considered. Moreover, the surface texture is taken to be sinusoidal wavy to improve the thermal contact. The governing equations are transformed into a system of non-similar partial differential equations by using suitable dimensionless variables and solved by the Keller-Box method. The effects of involved parameters like amplitude wavelength ratio, group parameters, and volume fraction on the total entropy number and the Bejan number are analyzed graphically. It is showed Fe3O4 base nanofluid is more effective to lessen the entropy production as compared to Cu base nanofluid.

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