A temperature-only system degradation analysis based on thermal entropy and the degradation-entropy generation methodology

Abstract Energy management and sustainability in thermal systems require maximum utilization of resources with minimal losses. However, it is rarely unattainable due to the ever-increasing need for a high-performance system combined with device size reduction. The numerical study examined convective heat transfer of an alpha-Alumina-water nanofluid in variable-width corrugated minichannel heat sinks. The objective is to study the impact of nanoparticle volume fractions and flow area variation on the entropy generation rate. The determining variables are 0.005 – 0.02 volume fractions, the fluid velocity 3 – 5.5 m/s and heat flux of 85 W/cm2. The numerical results show an acceptable correlation with the experiment results. The results indicate the thermal entropy production drop with an increase in nanoparticles volume fraction. Contrastingly, the frictional resistance entropy suggests the opposite trend due to the turbulence effect on the fluid viscosity. The induction of Alumina-Water nanofluid with enhanced thermal conductivity declined the entropy generation rate compared to water alone. The increase in width ratio by 16% between the cases translates to at least a 9% increase in thermal entropy production. The outcome of this study can provide designers and operators of thermal systems more insight into entropy management in corrugated heatsinks.

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Entropy Generation Rates in Two-Dimensional Rayleigh–Taylor Turbulence Mixing

Entropy ◽

10.3390/e20100738 ◽

2018 ◽

Vol 20 (10) ◽

pp. 738 ◽

Cited By ~ 3

Author(s):

Xinyu Yang ◽

Haijiang He ◽

Jun Xu ◽

Yikun Wei ◽

Hua Zhang

Keyword(s):

Time Evolution ◽

Entropy Generation ◽

Generation Rate ◽

Entropy Generation Rate ◽

Two Dimensional ◽

Spatial Averaging ◽

Mixing Process ◽

Thermal Entropy ◽

Large Gradient ◽

Turbulence Mixing

Entropy generation rates in two-dimensional Rayleigh–Taylor (RT) turbulence mixing are investigated by numerical calculation. We mainly focus on the behavior of thermal entropy generation and viscous entropy generation of global quantities with time evolution in Rayleigh–Taylor turbulence mixing. Our results mainly indicate that, with time evolution, the intense viscous entropy generation rate s u and the intense thermal entropy generation rate S θ occur in the large gradient of velocity and interfaces between hot and cold fluids in the RT mixing process. Furthermore, it is also noted that the mixed changing gradient of two quantities from the center of the region to both sides decrease as time evolves, and that the viscous entropy generation rate ⟨ S u ⟩ V and thermal entropy generation rate ⟨ S θ ⟩ V constantly increase with time evolution; the thermal entropy generation rate ⟨ S θ ⟩ V with time evolution always dominates in the entropy generation of the RT mixing region. It is further found that a “smooth” function ⟨ S u ⟩ V ∼ t 1 / 2 and a linear function ⟨ S θ ⟩ V ∼ t are achieved in the spatial averaging entropy generation of RT mixing process, respectively.

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Entropy Generation in Natural Convection of Water Near Its Density Maximum in a Square Cavity

Advanced Energy Systems ◽

10.1115/imece2004-61090 ◽

2004 ◽

Author(s):

You-Rong Li ◽

Nu-Bo Deng ◽

Shuang-Ying Wu ◽

Lan Peng ◽

Dan-Ling Zeng

Keyword(s):

Natural Convection ◽

Entropy Generation ◽

Initial Temperature ◽

Temperature Fields ◽

Local Entropy ◽

Balance Equations ◽

Square Cavity ◽

Density Maximum ◽

Thermal Entropy ◽

Local Entropy Generation

This paper is focused on the entropy generation due to heat transfer and viscous flow in natural convection of water near its density maximum in a square cavity. The present hydrodynamic and temperature fields are obtained by solving numerically the mass, momentum and energy balance equations, using the finite difference method. Local entropy generation distributions are obtained based on the resulting velocity and temperature fields by solving the entropy generation equation. The effect of the Grashof numbers on the total entropy generation is studied. Local entropy generation distribution was found to be dependent on the Grashof number and the dimensionless initial temperature. The results also show that thermal entropy generation is relatively dominant over viscous entropy generation.

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Entropy generation and second law analysis of pulsed impinging jet

International Journal of Numerical Methods for Heat &amp Fluid Flow ◽

10.1108/hff-05-2014-0148 ◽

2015 ◽

Vol 25 (5) ◽

pp. 1089-1106 ◽

Cited By ~ 10

Author(s):

Kazem Esmailpour ◽

Behnam Bozorgmehr ◽

Seyed Mostafa Hosseinalipour ◽

Arun S. Mujumdar

Keyword(s):

Heat Transfer ◽

Temperature Field ◽

Entropy Generation ◽

Impinging Jet ◽

Entropy Generation Rate ◽

Second Law ◽

Pulsation Frequency ◽

Content Type ◽

Thermal Entropy ◽

Plate Distance

Purpose – The purpose of this paper is to examine entropy generation rate in the flow and temperature ﬁeld due pulsed impinging jet on to a flat plate. Heat transfer of pulsed impinging jets has been investigated by many researchers. Entropy generation is one of the parameters related to the second law of thermodynamics which must be analyzed in processes with heat transfer and fluid flow in order to design efficient systems. Effect of velocity profile parameters and various nozzle to plate distances on viscous and thermal entropy generation are investigated. Design/methodology/approach – In this study, the flow and temperature field of a pulsed turbulent impinging jet are simulated numerically by the finite volume method with appropriate boundary conditions. Then, flow and temperature results are used to calculate the rate of entropy generation due to heat transfer and viscous dissipation. Findings – Results show that maximum viscous and thermal entropy generation occurs in the lowest nozzle to plate distance and entropy generation decreases as the nozzle to plate distance increases. Entropy generation in the two early phase of a period in the most frequencies is more than steady state whereas a completely opposite behavior happens in the two latter phase. Increase in the pulsation frequency and amplitude leads to enhancement in entropy generation because of larger temperature and velocity gradients. This phenomenon appears second and even third peaks in entropy generation plots in higher pulsation frequency and amplitude. Research limitations/implications – The predictions may be extended to include various pulsation signal shape, multiple jet configuration, the radiation effect and phase difference between jets. Practical implications – The results of this paper are a valuable source of information for active control of transport phenomena in impinging jet configurations which is used in different industrial applications such as cooling, heating and drying processes. Originality/value – In this paper the entropy generation of pulsed impinging jet was studied for the first time and a comprehensive discussion on numerical results is provided.

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Thermal entropy generation and exergy efficiency analyses of coiled wire inserted nanodiamond + Fe3O4/water hybrid nanofluid in a tube

Journal of Thermal Analysis and Calorimetry ◽

10.1007/s10973-021-11080-y ◽

2021 ◽

Author(s):

L. Syam Sundar ◽

Solomon Mesfin ◽

E. Venkata Raman ◽

V. Punnaiah ◽

Ali J. Chamkha ◽

...

Keyword(s):

Entropy Generation ◽

Exergy Efficiency ◽

Hybrid Nanofluid ◽

Thermal Entropy

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Free convection heat transfer and entropy generation analysis of water-Fe3O4/CNT hybrid nanofluid in a concentric annulus

International Journal of Numerical Methods for Heat &amp Fluid Flow ◽

10.1108/hff-08-2018-0424 ◽

2019 ◽

Vol 29 (3) ◽

pp. 915-934 ◽

Cited By ~ 61

Author(s):

Amin Shahsavar ◽

Pouyan Talebizadeh Sardari ◽

D. Toghraie

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Rayleigh Number ◽

Entropy Generation ◽

Average Nusselt Number ◽

Generation Rate ◽

Entropy Generation Rate ◽

Hybrid Nanofluid ◽

Content Type ◽

Thermal Entropy

Purpose This paper aims to numerically investigate the heat transfer and entropy generation characteristics of water-based hybrid nanofluid in natural convection flow inside a concentric horizontal annulus. Design/methodology/approach The hybrid nanofluid is prepared by suspending tetramethylammonium hydroxide-coated Fe3O4 (magnetite) nanoparticles and gum arabic (GA)-coated carbon nanotubes (CNTs) in water. The effects of nanoparticle volume concentration and Rayleigh number on the streamlines, isotherms, average Nusselt number and the thermal, frictional and total entropy generation rates are investigated comprehensively. Findings Results show the advantageous effect of hybrid nanofluid on the average Nusselt number. Furthermore, the study of entropy generation shows the increment of both frictional and thermal entropy generation rates by increasing Fe3O4 and CNT concentrations at various Rayleigh numbers. Increasing Rayleigh number from 103 to 105, at Fe3O4 concentration of 0.9 per cent and CNT concentration of 1.35 per cent, increases the average Nusselt number, thermal entropy generation rate and frictional entropy generation rate by 224.95, 224.65 and 155.25 per cent, respectively. Moreover, increasing the Fe3O4 concentration from 0.5 to 0.9 per cent, at Rayleigh number of 105 and CNT concentration of 1.35 per cent, intensifies the average Nusselt number, thermal entropy generation rate and frictional entropy generation rate by 18.36, 22.78 and 72.7 per cent, respectively. Originality/value To the best knowledge of the authors, there are not any archival publications considering the detailed behaviour of the natural convective heat transfer and entropy generation of hybrid nanofluid in a concentric annulus.

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Thermodynamic Analysis of Fe3O4Nanofluid Flowing Through A Circular Tube

International Journal of Engineering and Advanced Technology - Regular Issue ◽

10.35940/ijeat.e7306.088619 ◽

2019 ◽

Vol 8 (6) ◽

pp. 530-533 ◽

Cited By ~ 1

Keyword(s):

Entropy Generation ◽

Particle Concentration ◽

Circular Tube ◽

Reynolds Numbers ◽

Constant Heat Flux ◽

Entropy Generation Rate ◽

Bejan Number ◽

Total Entropy ◽

Particle Volume ◽

Thermal Entropy

Present work is an experimental study of entropy generation of Fe3O4 -water nanofluid flowing through a circular tube. Flow is maintained in the turbulent region and tube is exposed to constant heat flux along the length. Experiments are conducted to study the entropy generation rate for different conditions such as particle volume concentrations varying from 1% to 6% and also for the different Reynolds numbers varying from 6000 to 22000. Measured data from experimentation is taken as input to calculate thermal entropy and frictional entropy generation separately. Based on these thermal entropy and frictional entropy generation total entropy generation and Bejan number are calculated and results are analyzed. Experimentally, it is proved that the changes in the thermal and frictional entropy generations are converse, such a way that, as particle concentration increases entropy generation due to heat transfer decreases whereas entropy generation due to friction increases. Finally experimental results reveal that there exits an optimum particle volume concentration where the total entropy generation is minimal. The same result has also appended by calculating the Bejan number.

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Entropy generation analysis of free convection from a constant temperature vertical plate using similarity solution

Thermal Science ◽

10.2298/tsci140103092m ◽

2016 ◽

Vol 20 (6) ◽

pp. 1855-1866 ◽

Cited By ~ 2

Author(s):

Mohammad Mohaghegh ◽

Esfahani Abolfazli

Keyword(s):

Boundary Layer ◽

Exact Solution ◽

Differential Equations ◽

Free Convection ◽

Constant Temperature ◽

Entropy Generation ◽

Similarity Solution ◽

Integral Method ◽

Vertical Plate ◽

Thermal Entropy

This paper presents a similarity solution analysis of entropy generation due to heat transfer and fluid flow which has been carried out for laminar free convection from a constant temperature vertical plate in an infinite quiescent fluid. The governing partial differential equations are transformed into a set of ordinary differential equations using similarity variables. So an analytical expression, in terms of entropy generation, entropy generation number, Bejan number and irreversibility distribution ratio are derived using velocity and temperature similarity (exact) solution. The rate of entropy generation is investigated and discussed in details. The results presented by the similarity solution are compared with integral method results. The similarity solution presents more appropriate and correct distribution of entropy generation in boundary layer because more accuracy than integral method. It shows true position of maximum entropy generation and value of it. Also, the result shows that the exact solution minimizes the rate of total entropy generation in the boundary layer compared to integral solution. By introducing group parameter (GP number) which is the ratio of friction entropy to thermal entropy generation, one can recognize that one of the thermal entropy and friction entropy generation is dominated in the boundary layer.

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