Entropy Generation Rates through the Dissipation of Ordered Regions in Helium Boundary-Layer Flows

Isaacson, L. K.

doi:10.3390/e19060278

Cited by 4 publications

(10 citation statements)

References 27 publications

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“…We collected 12 papers in this special issue, covering both engineering applications [8][9][10][11][12] and fundamental studies [13][14][15][16][17][18][19] with respect to CFD of flow and heat transfer problems and interpretation of the CFD results with the SLA.…”

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confidence: 99%

“…The SLA was also intensively applied to fundamental studies, such as convective heat transfer problems [13][14][15][16][17][18]. Four papers among these studies are about forced convection: Ji et al [13] analyzed the entropy generation of fully-turbulent convective heat transfer of nano-fluids in a circular tube according to their RANS results.…”

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confidence: 99%

“…Based on the numerical results, they argued that the SLA can be helpful for the design of micro-reactors and micro-combustor systems. Isaacson [15] studied the entropy generation rates in helium boundary layer flows. The influences of temperature and pressure were considered.…”

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confidence: 99%

“…One of the barriers is due to the accuracy of the CFD results. In the papers of this special issue, the turbulent flow and temperature fields were generally calculated with RANS methods [8,12,13,15] or DDES methods [9,10,19]. However, the accuracy of the entropy generation rates are very sensitive to the turbulence model.…”

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Second-Law Analysis: A Powerful Tool for Analyzing Computational Fluid Dynamics (CFD) Results

Jin

2017

Entropy

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Second-law analysis (SLA) is an important concept in thermodynamics, which basically assesses energy by its value in terms of its convertibility from one form to another. Highly-valued forms of energy in this context are called exergy, defined as those energies from which the maximum theoretical work is obtainable when the energy is interacting with the environment to equilibrium (see Moran et al. [1], for example).The counterpart of exergy, also called available work, is anergy, so that with this concept energy can generally be regarded as the sum of exergy and anergy. As a consequence of the second law of thermodynamics, exergy can be lost but cannot be created. Therefore, in a reversible process, exergy is preserved, whereas irreversibility (like losses in a flow field) leads to a loss of exergy (in favor of the corresponding increasing anergy).Losses in flow and heat transfer fields can, thus, be determined by their impact on the exergy, i.e., by determining the exergy losses. These losses of exergy are thermodynamically linked to the generation of entropy by the so-called Gouy Stodola theorem. It states that the lost exergy corresponds to the product of entropy generation and the environmental temperature (see, again, Moran et al. [1]).From a thermodynamic point of view, the quality of a flow or heat transfer process can be assessed by the entropy generation rate in this process (see Herwig [2]). However, entropy almost never appears in the textbooks of fluid dynamics and heat transfer (see, e.g., Batchelor, et al. [3] and Incropera, et al. [4]). This concept is widely ignored perhaps because the irreversibility effect is often fundamentally important in these two disciplines.After Bejan [5,6] laid the foundation with respect to analyzing and optimizing thermal systems with the SLA approach, the SLA of flow and heat transfer problems received more and more attention. Applying the SLA in computational fluid dynamics (CFD), Kock and Herwig [7] extended this concept to an in-depth analysis of turbulent flows and identified four different mechanisms of entropy generation: dissipation in a mean and fluctuating velocity field and heat flux in a mean and fluctuating temperature field. They also suggested how to calculate the entropy generation rates with the Reynolds Averaged Navier-Stokes (RANS) results. Herwig [2] stated that, with the help of the SLA, one may answer four important questions regarding a momentum and/or heat transfer process:• Which is the ideal process (no entropy generation)? • Where does entropy generation occur in a non-ideal process? • Why does entropy generation occur at a certain location and with certain strength? • How can entropy generation be reduced overall or locally?The purpose of this special issue is to demonstrate how the CFD results can be better interpreted by the SLA. We collected 12 papers in this special issue, covering both engineering applications [8-12] and

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Second-Law Analysis: A Powerful Tool for Analyzing Computational Fluid Dynamics (CFD) Results

Jin

2017

Entropy

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“…In Section 2, the laminar boundary-layer flow configuration considered in this study is described. In Section 3, eighteen sets of initial conditions for the integra- Isaacson [3] [4] [5], and Hellberg and Orszag [7] are transformed into the spectral plane and written as modified Lorenz equations. Computational results for the time-dependent spectral velocity components are discussed.…”

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confidence: 99%

Entropy Generation through the Interaction of Laminar Boundary-Layer Flows: Sensitivity to Initial Conditions

Isaacson¹

2018

JMP

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A modified form of the Townsend equations for the fluctuating velocity wave vectors is applied to the interaction of a longitudinal vortex with a laminar boundary-layer flow. These three-dimensional equations are cast into a Lorenz-format system of equations for the spectral velocity component solutions. Tsallis-form empirical entropic indices are obtained from the solutions of the modified Lorenz equations. These solutions are sensitive to the initial conditions applied to the time-dependent coupled, non-linear differential equations for the spectral velocity components. Eighteen sets of initial conditions for these solutions are examined. The empirical entropic indices yield corresponding intermittency exponents which then yield the entropy generation rates for each set of initial conditions. The flow environment consists of the flow of hydrogen gas with impurities at a given temperature and pressure in the interaction of a longitudinal vortex with a laminar boundary layer flow. Results are presented that indicate a strong correlation of predicted entropy generation rates and the corresponding applied initial conditions. These initial conditions may be ascribed to the turbulence levels in the boundary layer, thus indicating a source for the subsequent entropy generation rates by the interactive instabilities.

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Evaluation on the flow characteristics of helium working fluid in generation Ⅳ nuclear power station

Yuan

Zheng

Yue

et al. 2022

Nuclear Engineering and Design

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Entropy Generation Rates through the Dissipation of Ordered Regions in Helium Boundary-Layer Flows

Cited by 4 publications

References 27 publications

Second-Law Analysis: A Powerful Tool for Analyzing Computational Fluid Dynamics (CFD) Results

Second-Law Analysis: A Powerful Tool for Analyzing Computational Fluid Dynamics (CFD) Results

Entropy Generation through the Interaction of Laminar Boundary-Layer Flows: Sensitivity to Initial Conditions

Evaluation on the flow characteristics of helium working fluid in generation Ⅳ nuclear power station

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