Viscous Dissipation Effect on Entropy Generation of Nanofluid Flow in Microchannels

2013 ◽  
Author(s):  
Tiew Wei Ting ◽  
Yew Mun Hung ◽  
Ningqun Guo
Keyword(s):  
Forced Convection ◽  
Viscous Dissipation ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Second Law Of Thermodynamics ◽  
Nanoparticle Volume Fraction ◽  
Fluid Friction ◽  
Closed Form Solutions ◽  
Dissipation Effect ◽  
Dissipation Term

An analytical study of the viscous dissipation effect on entropy generation of forced convection of water-alumina nanofluid in a circular microchannel subjected to exponential wall heat flux is reported. Closed form solutions of the temperature distributions in the streamwise direction for the models with and without viscous dissipation term in the energy equation are obtained. The two models are compared by analyzing their relative deviations in entropy generation for different Reynolds number and nanoparticle volume fraction. The incorporation of viscous dissipation prominently affects the temperature distribution and consequently the entropy generation. The increase in the entropy generation is mainly attributable to the increase in the fluid friction irreversibility. The addition of nanoparticle increases the effective thermal conductivity and viscosity of nanofluid which induces escalation in the heat transfer and fluid friction irreversibilities, respectively. By taking the viscous dissipation effect into account, the exergetic effectiveness for forced convection of nanofluid in microchannels attenuate with increasing nanoparticle volume fraction. From the aspect of the second law of thermodynamics, the widespread conjecture that nanofluids possess advantage over pure fluid associated with higher overall effectiveness is invalidated.

Viscous Dissipation Effect on Streamwise Entropy Generation of Nanofluid Flow in Microchannel Heat Sinks

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Tiew Wei Ting ◽  
Yew Mun Hung ◽  
Ningqun Guo
Keyword(s):  
Viscous Dissipation ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Second Law Of Thermodynamics ◽  
Reynolds Numbers ◽  
Heat Sinks ◽  
Fluid Friction ◽  
Closed Form Solutions ◽  
Dissipation Effect ◽  
Dissipation Term

The effects of viscous dissipation on the entropy generation of water–alumina nanofluid convection in circular microchannels subjected to exponential wall heat flux are investigated. Closed-form solutions of the temperature distributions in the streamwise direction are obtained for the models with and without viscous dissipation term in the energy equation. The two models are compared by analyzing their relative deviations in entropy generation for different Reynolds numbers and nanoparticle volume fractions. The incorporation of viscous dissipation prominently affects the temperature distribution and consequently the entropy generation. When the viscous dissipation effect is neglected, the total entropy generation and the fluid friction irreversibility are nearly twofold overrated while the heat transfer irreversibility is underestimated significantly. By considering the viscous dissipation effect, the exergetic effectiveness for forced convection of nanofluid in microchannels attenuates with the increasing nanoparticle volume fraction and nanoparticle diameter. The increase in the entropy generation of nanofluid is mainly attributed to the intensification of fluid friction irreversibility. From the aspect of the second-law of thermodynamics, the widespread conjecture that nanofluids possess advantage over pure fluid associated with higher overall effectiveness is invalidated.

scholarly journals Unsteady squeezing flow of magnetohydrodynamic carbon nanotube nanofluid in rotating channels with entropy generation and viscous dissipation

2019 ◽  
Vol 11 (1) ◽  
pp. 168781401882310 ◽  
Author(s):  
Abdullah Dawar ◽  
Zahir Shah ◽  
Waris Khan ◽  
Muhammad Idrees ◽  
Saeed Islam
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Velocity Profile ◽  
Physical Properties ◽  
Viscous Dissipation ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Rotation Parameter ◽  
Squeezing Flow ◽  
Nanoparticle Volume Fraction

The most favorable gift of modern science is nanofluid. The nanofluid can able to move freely through micro channels with the spreading of nanoparticles. Due to improved convection between the base liquid surfaces and nanoparticles, the nano suspensions express high thermal conductivity. Also, the benefits of suspending nanoparticles in base fluids are increased heat capacity, surface area, effective thermal conductivity, collision, and interaction among particles. This research aim to study squeezing flow of carbon nanotubes based on water (H2O) in rotating channels. Entropy generation is evaluated and for this purpose, second law of thermodynamics is employed. The influences of thermal radiation, viscous dissipation, and applied magnetic field on nanofluid are taken into account. The flow of the nanofluid is considered in unsteady three dimensions. The transformed ordinary differential equations (ODEs) are solved by homotopy analysis method with the help of similarity variables. Results obtained for single and multi-wall carbon nanotubes are compared. Plots have been presented in order to examine how the velocities, temperature, and entropy profiles become affected by numerous physical parameters. Generally, the velocity profiles escalate when the upper plate of the channel moves toward the lower stretching one and reduces when the upper plate is moving away from the lower one. The velocity profile in y-direction escalates with the escalation in nanoparticle volume fraction and suction parameter while the rotation parameter bids dual behavior with the escalating values. The velocity profile in x-direction bids the oscillatory behavior with the enhancement in nanoparticle volume fraction, rotation parameter, and magnetic parameter. The physical properties of carbon nanotubes, thermo physical properties of carbon nanotubes and nanofluid of some base fluids, and thermal conductivity of carbon nanotubes with different volume fractions are shown through tables.

scholarly journals Fluid Flow and Entropy Generation Analysis of Al2O3–Water Nanofluid in Microchannel Plate Fin Heat Sinks

Entropy ◽  
2019 ◽  
Vol 21 (8) ◽  
pp. 739 ◽  
Author(s):  
Hao Ma ◽  
Zhipeng Duan ◽  
Liangbin Su ◽  
Xiaoru Ning ◽  
Jiao Bai ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Microchannel Plate ◽  
Heat Sinks ◽  
Entropy Generation Rate ◽  
Nanoparticle Volume Fraction ◽  
Channel Aspect Ratio

The flow in channels of microdevices is usually in the developing regime. Three-dimensional laminar flow characteristics of a nanofluid in microchannel plate fin heat sinks are investigated numerically in this paper. Deionized water and Al2O3–water nanofluid are employed as the cooling fluid in our work. The effects of the Reynolds number (100 < Re < 1000), channel aspect ratio (0 < ε < 1), and nanoparticle volume fraction (0.5% < Φ < 5%) on pressure drop and entropy generation in microchannel plate fin heat sinks are examined in detail. Herein, the general expression of the entropy generation rate considering entrance effects is developed. The results revealed that the frictional entropy generation and pressure drop increase as nanoparticle volume fraction and Reynolds number increase, while decrease as the channel aspect ratio increases. When the nanoparticle volume fraction increases from 0 to 3% at Re = 500, the pressure drop of microchannel plate fin heat sinks with ε = 0.5 increases by 9%. It is demonstrated that the effect of the entrance region is crucial for evaluating the performance of microchannel plate fin heat sinks. The study may shed some light on the design and optimization of microchannel heat sinks.

Analysis of entropy generation and natural convection in an inclined partially porous layered cavity filled with a nanofluid

2017 ◽  
Vol 95 (3) ◽  
pp. 238-252 ◽  
Author(s):  
T. Armaghani ◽  
Muneer A. Ismael ◽  
Ali J. Chamkha
Keyword(s):  
Natural Convection ◽  
Rayleigh Number ◽  
Layer Thickness ◽  
Porous Layer ◽  
Entropy Generation ◽  
Thermal Performance ◽  
Volume Fraction ◽  
Numerical Study ◽  
Nanoparticle Volume Fraction ◽  
Thermodynamic Irreversibility

The present numerical study investigates the analysis of thermodynamic irreversibility generation and the natural convection in inclined partially porous layered cavity filled with a Cu–water nanofluid. The finite difference method with up-wind scheme is used to solve the governing equations. The study is achieved by examining the effects of nanoparticle volume fraction, inclination angle, and the porous layer thickness. Besides, the computations are achieved within the laminar range of the Rayleigh number. The results show that at Ra = 104, a reduction of total entropy generation is recorded with increasing nanoparticle volume fraction when the porous layer thickness is greater than 0.2. Moreover, when Ra is less than 105, the nanoparticle volume fraction increases the heat transfer irreversibility, and improves the overall thermal performance. It is found also that for a low Rayleigh number, the largest porous layer thickness and the highest cavity orientation improve the thermal performance. On the contrary, at high Rayleigh numbers, these parameter ranges give the worst thermal performance.

Viscous dissipation effect on entropy generation in curved square microchannels

Energy ◽  
2011 ◽  
Vol 36 (8) ◽  
pp. 5416-5423 ◽  
Author(s):  
Jiangfeng Guo ◽  
Mingtian Xu ◽  
Jun Cai ◽  
Xiulan Huai
Keyword(s):  
Viscous Dissipation ◽  
Entropy Generation ◽  
Dissipation Effect

scholarly journals Assisted convective heat transfer and entropy generation in a solar collector filled with nanofluid

2016 ◽  
Vol 13 (2) ◽  
pp. 135-150
Author(s):  
R. Nasrin ◽  
M.A. Alim ◽  
M. Hasanuzzzaman
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Entropy Generation ◽  
Solar Collector ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Bulk Temperature ◽  
Outlet Temperature ◽  
Nanoparticle Volume Fraction ◽  
Collector Efficiency

Heat transfer phenomena of flat plate solar collector filled with different nanofluids has been investigated numerically. Galerkin’s Finite Element Method is used to solve the problem. Heat transfer rate, average bulk temperature, average sub-domain velocity, outlet temperature, thermal efficiency, mean entropy generation and Bejan number has been investigated by varying the solid nanoparticle volume fraction of water/Cu, water/Ag and water/Cu/Ag nanofluids from 0% to 3%. It is found that the solid nanoparticle volume fraction has great effect on heat transfer phenomena. It is observed that the increases of the solid volume fraction (up to 2%) enhances the heat transfer rate and collector efficiency where after 2% the rate of change almost constant. Higher heat transfer rate and collector efficiency has been obtained 19% and 13% for water/Ag nanofluid respectively.

scholarly journals Transpiration and Viscous Dissipation Effects on Entropy Generation in Hybrid Nanofluid Flow over a Nonlinear Radially Stretching Disk

Entropy ◽  
2018 ◽  
Vol 20 (9) ◽  
pp. 668 ◽  
Author(s):  
Umer Farooq ◽  
Muhammad Afridi ◽  
Muhammad Qasim ◽  
D. Lu
Keyword(s):  
Boundary Layer ◽  
Viscous Dissipation ◽  
Entropy Generation ◽  
Numerical Solutions ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Research Work ◽  
Dissipation Function ◽  
Hybrid Nanofluid ◽  
Layer Flow

The present research work explores the effects of suction/injection and viscous dissipation on entropy generation in the boundary layer flow of a hybrid nanofluid (Cu–Al2O3–H2O) over a nonlinear radially stretching porous disk. The energy dissipation function is added in the energy equation in order to incorporate the effects of viscous dissipation. The Tiwari and Das model is used in this work. The flow, heat transfer, and entropy generation analysis have been performed using a modified form of the Maxwell Garnett (MG) and Brinkman nanofluid model for effective thermal conductivity and dynamic viscosity, respectively. Suitable transformations are utilized to obtain a set of self-similar ordinary differential equations. Numerical solutions are obtained using shooting and bvp4c Matlab solver. The comparison of solutions shows excellent agreement. To examine the effects of principal flow parameters like suction/injection, the Eckert number, and solid volume fraction, different graphs are plotted and discussed. It is concluded that entropy generation inside the boundary layer of a hybrid nanofluid is high compared to a convectional nanofluid.

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