Direct and indirect methods of calculating entropy generation rates in turbulent convective heat transfer problems

Herwig, Heinz; Kock, Fabian

doi:10.1007/s00231-006-0086-x

Cited by 262 publications

(108 citation statements)

References 7 publications

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“…In our previous study [25], we showed that the entropy generation due to heat transfer and fluid friction inside the receiver's absorber tube gives nearly the same optimum flow rates as the analytical method [31]. The method used in our previous investigation [25] directly calculates the entropy generation using computational fluid dynamics according to the equations derived by Kock and Herwig [32].…”

Section: Introductionmentioning

confidence: 92%

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Minimum entropy generation due to heat transfer and fluid friction in a parabolic trough receiver with non-uniform heat flux at different rim angles and concentration ratios

Mwesigye

Bello‐Ochende

2014

Energy

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In this paper, Monte Carlo ray-tracing and computational fluid dynamics are used to numerically investigate the minimum entropy generation due to heat transfer and fluid friction in a parabolic trough receiver. The analysis was carried out for rim angles in the range 40 o -120 o , concentration ratios in the range 57-143, Reynolds numbers in the range 1.02×10 4 -1.36 ×10 6 and fluid temperatures in the range 350 -650K. Results show existence of an optimal Reynolds number at any given combination of fluid temperature, concentration ratio and rim angle for which the total entropy generation is a minimum. The total entropy generation was found to increase as the rim angle reduced, concentration ratio increased and fluid temperature reduced. The high entropy generation rates at low rim angles are mainly due to high peak temperatures in the absorber tube at these low rim angles. Keywords:

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Section: Introductionmentioning

confidence: 92%

“…The entropy generation is determined from the heat transfer irreversibility (S''' gen ) H and fluid friction irreversibility (S''' gen ) F according to the following equations [32].…”

Section: Entropy Generationmentioning

confidence: 99%

Minimum entropy generation due to heat transfer and fluid friction in a parabolic trough receiver with non-uniform heat flux at different rim angles and concentration ratios

Mwesigye

Bello‐Ochende

2014

Energy

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“…In these studies, entropy generation is often determined as an integral value within a finite solution domain, either by global balances or by the integration of the local entropy generation density. A general and systematic comparison of various approaches can be found in [21] and [22].…”

Section: Literature About Entropy and The Sla Approachmentioning

confidence: 99%

How to Determine Losses in a Flow Field: A Paradigm Shift towards the Second Law Analysis

Herwig

Schmandt

2014

Entropy

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Assuming that CFD solutions will be more and more used to characterize losses in terms of drag for external flows and head loss for internal flows, we suggest to replace single-valued data, like the drag force or a pressure drop, by field information about the losses. These information are gained when the entropy generation in the flow field is analyzed, an approach that often is called second law analysis (SLA), referring to the second law of thermodynamics. We show that this SLA approach is straight-forward, systematic and helpful when it comes to the physical interpretation of the losses in a flow field. Various examples are given, including external and internal flows, two phase flow, compressible flow and unsteady flow. Finally, we show that an energy transfer within a certain process can be put into a broader perspective by introducing the entropic potential of an energy.

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“…The alternative way is work.T h i s other kind of energy transfer is not caused by temperature gradients and is not accompanied by entropy changes. For further details see Moran & Shapiro (2003); Baehr & Kabelac (2009) ;Herwig & Kautz (2007), for example. The energy transferred in the form of heat from a thermodynamics point of view is internal energy stored in the material by various mechanisms on the molecular level (translation, vibration, rotation of molecules).…”

Section: What Is the Meaning Of "Quality"?mentioning

confidence: 99%

“…For details of the derivation see Herwig & Kock (2007); Herwig et al (2010). When the flow is non-isothermal, T in (15) is different at different locations.…”

Section: Fluid Flow Assessmentmentioning

confidence: 99%

Heat Transfer and Its Assessment

Herwig¹,

Wenterodt²

2011

Heat Transfer - Theoretical Analysis, Experimental Investigations and Industrial Systems

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Direct and indirect methods of calculating entropy generation rates in turbulent convective heat transfer problems

Cited by 262 publications

References 7 publications

Minimum entropy generation due to heat transfer and fluid friction in a parabolic trough receiver with non-uniform heat flux at different rim angles and concentration ratios

Minimum entropy generation due to heat transfer and fluid friction in a parabolic trough receiver with non-uniform heat flux at different rim angles and concentration ratios

How to Determine Losses in a Flow Field: A Paradigm Shift towards the Second Law Analysis

Heat Transfer and Its Assessment

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