Numerical Predictions of Local Entropy Generation in an Impinging Jet

Drost, M.K.; White, Mark D.

doi:10.1115/1.2911209

Cited by 68 publications

(18 citation statements)

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“…Numerical studies on the entropy generation in convective heat transfer problems were carried out by different researchers. A numerical solution procedure for predicting local entropy generation for a fluid impinging on a heated wall was developed by Drost and White [11]. Abu-Nada [12][13][14] analyzed the convection flow over backward facing step in a duct to investigate the amount of entropy generation in this type of flow.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of entropy generation in laminar forced convection flow over inclined backward and forward facing steps in a duct under bleeding condition

2014

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A numerical investigation of entropy generation in laminar forced convection of gas flow over a recess including two inclined backward and forward facing steps in a horizontal duct under bleeding condition is presented. For calculation of entropy generation from the second law of thermodynamics in a forced convection flow, the velocity and temperature distributions are primary needed. For this purpose, the 2-D Cartesian co-ordinate system is used to solve the governing equations which are conservations of mass, momentum, and energy. These equations are solved numerically using the computational fluid dynamic techniques to obtain the temperature and velocity fields, while the blocked region method is employed to simulate the inclined surface. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. The numerical results are presented graphically and the effects of bleeding coefficient and recess length as the main parameters on the distributions of entropy generation number and Bejan number are investigated. Also, the effect of Reynolds number and bleeding coefficient on total entropy generation which shows the amount of flow irreversibilities is presented for two recess length. The use of present results in the design process of such thermal system would help the system attain the high performance during exploitation. Comparison of numerical results with the available data published in open literature shows a good consistency.

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Section: Introductionmentioning

confidence: 99%

Numerical investigation of entropy generation in laminar forced convection flow over inclined backward and forward facing steps in a duct under bleeding condition

2014

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“…These results were obtained by minimizing entropy generation in realistic models built for several levels of complexity. The generation of entropy at the local level in heat exchangers was studied by several researchers [5][6][7]. The EGM method experienced tremendous growth during the 1980s and 1990s.…”

Section: Introductionmentioning

confidence: 99%

Thermal Optimization of Channel Flows with Discrete Heating Sections

Furukawa¹,

Yang²

2003

Journal of Non-Equilibrium Thermodynamics

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The conventional means of thermal optimization (TO) suffers from complications in simultaneously optimizing a number of parameters which govern the process. This is particularly severe when thermal-fluid flow phenomena are involved, for example, optimization of electronic cooling devices. In order to revolutionize the means of optimizing a system involving both thermal and fluid flow phenomena, a new entropy generation minimization (EGM) method is developed utilizing the second law of thermodynamics which implies that the minimization of entropy generation is equivalent to thermal optimization. In this study, both TO and EGM are performed on the design of packages of parallel boards with discrete block heat sources. The board spacing for minimum entropy generation agrees very well with that calculated by maximizing the thermal conductance induced by both heat transfer and viscous friction.

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“…However, particular attention needs to be paid to the nature of the flow and to the solution approach. While in laminar flows all entropy generation is directly found in the CFD solution [18,2,70,33,79,59], this is not true for turbulent flows, unless a Direct Numerical Simulation (or DNS) is used. However, with current computational resources, the use of DNS is still impractical even for moderately large Reynolds numbers.…”

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confidence: 99%

Numerical evaluation of entropy generation in isolated airfoils and Wells turbines

et al. 2018

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In recent years, a number of authors have studied entropy generation in Wells turbines. This is potentially a very interesting topic, as it can provide important insights into the irreversibilities of the system, as well as a methodology for identifying, and possibly minimizing, the main sources of loss. Unfortunately, the approach used in these studies contains some crude simplifications that lead to a severe underestimation of entropy generation and, more importantly, to misleading conclusions. This paper contains a re-examination of the mechanisms for entropy generation in fluid flow, with a particular emphasis on RANS equations. An appropriate methodology for estimating entropy generation in isolated airfoils and Wells turbines is presented. Results are verified for different flow conditions, and a comparison with theoretical values is presented. 1Wells turbines have been studied extensively, both experimentally [15,31,24,63,74,53,57,48] and numerically [40,62,17,76,30,72,32,27], but mainly from a first-law perspective. More recently, a number of authors [66,67,68,69,71] have focused on the irreversibilities in this component, trying to link the amount of available work (exergy) and the entropy produced.The application of second-law analyses is not novel, as such analyses have been done by many authors, but mainly from a system perspective: Bejan [8,9] presents an extensive review of the application to different thermodynamic systems. Similar approaches have been used in the analysis of thermal power plants [39], wind turbines [56,6,7,60,52], and vortex generators [33].Computational Fluid Dynamics (CFD), aside from making possible a more rapid and economic evaluation of many systems (compared to experimental testing), can provide a better and more detailed understanding of many phenomena, by capturing a level of detail that would be extremely difficult in an experimental study. It allows a very fine decomposition of the overall problem that can be used to locate the sources of irreversibility within the system. Entropy generation by thermal and viscous sources can be calculated directly by post-processing the fields of thermo-and fluid-dynamic variables available from the numerical solution [8]. However, particular attention needs to be paid to the nature of the flow and to the solution approach. While in laminar flows all entropy generation is directly found in the CFD solution [18,2,70,33,79,59], this is not true for turbulent flows, unless a Direct Numerical Simulation (or DNS) is used. However, with current computational resources, the use of DNS is still impractical even for moderately large Reynolds numbers. To make high-Reynolds-number flows treatable, the governing equations are either averaged (leading to the Reynolds Averaged Navier Stokes equations, or RANS) or filtered (leading to the Large Eddy Simulation approach, or LES).Moore and Moore [49, 50] present a methodology for calculating entropy production in viscous flows, using RANS equations. They divide the mean entropy production into the contr...

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Numerical Predictions of Local Entropy Generation in an Impinging Jet

Cited by 68 publications

References 0 publications

Numerical investigation of entropy generation in laminar forced convection flow over inclined backward and forward facing steps in a duct under bleeding condition

Numerical investigation of entropy generation in laminar forced convection flow over inclined backward and forward facing steps in a duct under bleeding condition

Thermal Optimization of Channel Flows with Discrete Heating Sections

Numerical evaluation of entropy generation in isolated airfoils and Wells turbines

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