Fin Geometry for Minimum Entropy Generation in Forced Convection

1982 ◽  
Vol 104 (4) ◽  
pp. 616-623 ◽  
Author(s):  
D. Poulikakos ◽  
A. Bejan
Keyword(s):  
Cross Section ◽  
Entropy Generation ◽  
General Result ◽  
Analytical Methods ◽  
Rectangular Cross Section ◽  
Entropy Generation Rate ◽  
Minimum Entropy ◽  
Pin Fins ◽  
Extended Surfaces ◽  
Minimum Entropy Generation

This paper establishes a theoretical framework for the minimization of entropy generation (the waste of exergy, or useful energy) in extended surfaces (fins). The entropy generation rate formula for a general fin is derived first. Based on this general result, analytical methods and graphic results are developed for selecting the optimum dimensions of pin fins, rectangular plate fins, plate fins with trapezoidal cross section, and triangular plate fins with rectangular cross section.

scholarly journals Effect of Using Extra Fins on the Pin Fin Classic Geometry for Enhancement Heat Sink Performance using EGM Method

2018 ◽  
Vol 24 (4) ◽  
pp. 1 ◽  
Author(s):  
Kadhum Audaa Jehhef
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Cross Section ◽  
Entropy Generation ◽  
Heat Sink ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Minimum Entropy ◽  
Pin Fin ◽  
Pin Fins

In the present study, the effect of new cross-section fin geometries on overall thermal/fluid performance had been investigated. The cross-section included the base original geometry of (triangular, square, circular, and elliptical pin fins) by adding exterior extra fins along the sides of the origin fins. The present extra fins include rectangular extra fin of 2 mm (height) and 4 mm (width) and triangular extra fin of 2 mm (base) 4 mm (height). The use of entropy generation minimization method (EGM) allows the combined effect of thermal resistance and pressure drop to be assessed through the simultaneous interaction with the heat sink. A general dimensionless expression for the entropy generation rate is obtained by considering a control volume around the pin fin including a base plate and applying the conservations equations of mass and energy with the entropy balance. The dimensionless numbers used includes the aspect ratio (ε), Reynolds number (Re), Nusselt number (Nu), and the drag coefficients (CD). Fourteen different cross-section fin geometries are examined for the heat transfer, fluid friction, and the minimum entropy generation rate. The results showed that the Nusselt number increases with increasing the Reynolds number for all employed models. The ellipse models (ET and ER-models) give the highest value in the Nusselt number as compared with the classical pin fins. The fin of the square geometry with four rectangular extra fins (SR-models) gives an agreement in Nusselt number as compared with the previous study.  

The Role of Fin Geometry in Heat Sink Performance

2003 ◽  
Author(s):  
Waqar A. Khan ◽  
J. R. Culham ◽  
M. M. Yovanovich
Keyword(s):  
Aspect Ratio ◽  
Entropy Generation ◽  
Heat Sink ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Rectangular Plates ◽  
Minimum Entropy ◽  
Axis Ratio ◽  
Pin Fins ◽  
Minimum Entropy Generation

The following study will examine the effect on overall thermal/fluid performance associated with different fin geometries, including, rectangular plates as well as square, circular and elliptical pin fins. The use of EGM allows the combined effect of thermal resistance and pressure drop to be assessed through the simultaneous interaction with the heat sink. A general expression for the entropy generation rate is obtained by using the conservations equations for mass, energy, and entropy. The formulation for the dimensionless entropy generation rate is developed in terms of dimensionless variables, including the aspect ratio, Reynolds number, Nusselt number and the drag coefficient. Selected fin geometries are examined for the minimum entropy generation rate corresponding to different parameters including axis ratio, aspect ratio, and approach velocity. The results clearly indicate that the preferred fin profile is very dependent on these parameters.

Second-Law Analysis on Wavy Plate Fin-and-Tube Heat Exchangers

1998 ◽  
Vol 120 (3) ◽  
pp. 797-800 ◽  
Author(s):  
W. W. Lin ◽  
D. J. Lee
Keyword(s):  
Entropy Generation ◽  
Operating Conditions ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Second Law ◽  
Spanwise Direction ◽  
Minimum Entropy ◽  
Tube Heat Exchanger ◽  
Second Law Analysis ◽  
Minimum Entropy Generation

Second-law analysis on the herringbone wavy plate fin-and-tube heat exchanger was conducted on the basis of correlations of Nusselt number and friction factor proposed by Kim et al. (1997), from which the entropy generation rate was evaluated. Optimum Reynolds number and minimum entropy generation rate were found over different operating conditions. At a fixed heat duty, the in-line layout with a large tube spacing along streamwise direction was recommended. Furthermore, within the valid range of Kim et al.’s correlation, effects of the fin spacing and the tube spacing along spanwise direction on the second-law performance are insignificant.

Genetic Algorithm-Based Optimal Design of Plate Fins Following Minimum Entropy Generation Considerations

2005 ◽  
Vol 219 (8) ◽  
pp. 757-765 ◽  
Author(s):  
R. K. Jha ◽  
S Chakraborty
Keyword(s):  
Heat Transfer ◽  
Genetic Algorithm ◽  
Optimal Design ◽  
Forced Convection ◽  
Entropy Generation ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Minimum Entropy ◽  
Minimum Entropy Generation ◽  
Continuous Plate

This paper deals with estimation of the optimal dimensions of arrays of plate fins cooled by forced convection. The optimization is achieved by minimizing the entropy generation rate using genetic algorithm-based evolutionary computing techniques. Results are presented for staggered plate fins configuration and continuous plate fins configuration. The effects of heat transfer and fluid friction on entropy generation rate are also reported.

The Equivalence of Maximum Power and Minimum Entropy Generation Rate in the Optimization of Power Plants

1996 ◽  
Vol 118 (2) ◽  
pp. 98-101 ◽  
Author(s):  
Adrian Bejan
Keyword(s):  
Heat Transfer ◽  
Power Plant ◽  
Entropy Generation ◽  
Heat Input ◽  
Power Plants ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Total Entropy ◽  
Minimum Entropy ◽  
Minimum Entropy Generation

It is shown that to maximize the power output of a power plant is equivalent to minimizing the total entropy generation rate associated with the power plant. This equivalence is illustrated by using two of the oldest and simplest models of power plants with heat transfer irreversibilities. To calculate the total entropy generation rate correctly, one must recognize that the optimization process (e.g., the variability of the heat input) requires “room to move,” i.e., an additional, usually overlooked, contribution to the total entropy generation rate.

Entropy Generation in Isothermal Laminar Flow Through Bifurcated Tubes With Wall Suction

2010 ◽  
Author(s):  
Enrico Sciubba
Keyword(s):  
Entropy Generation ◽  
Fluid Velocity ◽  
Entropy Generation Rate ◽  
Minimum Entropy ◽  
Wall Suction ◽  
Entropy Generation Minimization ◽  
Simplifying Assumptions ◽  
Flow Through ◽  
Wetted Area ◽  
Minimum Entropy Generation

The paper presents an analysis of the entropy generation in the bifurcation of a fluid-carrying tube in the presence of wall suction. The objective is to minimize the entropy generation rate due to the viscous flow within the tubes. Several simplifying assumptions are made to reduce the problem to a multi-objective optimization in 3 independent variables: the aspect ratio of the domain served by the flow, the diameter ratio of the primary and secondary branches, and the length of the secondary branch (the location of both the “source” of the fluid and the “sink”, i.e. the place of desired delivery of the fluid, being a datum). The wall suction is assumed to be proportional to the wetted area. For three different initial assumptions (constant Re, constant fluid velocity, constant fluid volume) it is shown that an “optimal shape” exists and is identified by the minimum entropy generation. But, this minimum is always higher than the value pertaining to the unsplit tube with no wall suction. The study demonstrates that, for a given design goal (i.e., for an assigned “function” the configuration is called to perform) Entropy Generation Minimization is a feasible “topological Lagrangian” for the bifurcation geometry.

scholarly journals Analysis of Effect of Heat Pipe Parameters in Minimising the Entropy Generation Rate

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Rakesh Hari ◽  
Chandrasekharan Muraleedharan
Keyword(s):  
Heat Pipe ◽  
Entropy Generation ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Minimum Entropy ◽  
Pipe System ◽  
Thermodynamic Irreversibility ◽  
Design Variables ◽  
Minimum Entropy Generation ◽  
Flat Heat Pipe

Heat transfer and fluid flow in the heat pipe system result in thermodynamic irreversibility generating entropy. The minimum entropy generation principle can be used for optimum design of flat heat pipe. The objective of the present work is to minimise the total entropy generation rate as the objective function with different parameters of the flat heat pipe subjected to some constraints. These constraints constitute the limitations on the heat transport capacity of the heat pipe. This physical nonlinear programming problem with nonlinear constraints is solved using LINGO 15.0 software, which enables finding optimum values for the independent design variables for which entropy generation is minimum. The effect of heat load, length, and sink temperature on design variables and corresponding entropy generation is studied. The second law analysis using minimum entropy generation principle is found to be effective in designing performance enhanced heat pipe.

scholarly journals Entropy Generation of Forced Convection during Melting of Ice Slurry

Entropy ◽  
2019 ◽  
Vol 21 (5) ◽  
pp. 514
Author(s):  
Beata Niezgoda-Żelasko
Keyword(s):  
Heat Exchange ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Minimum Entropy ◽  
Ice Slurry ◽  
Slurry Flow ◽  
Exchange Processes ◽  
Minimum Entropy Generation

This paper looks at entropy generation during ice slurry flow in straight pipes and typical heat exchanger structures used in refrigeration and air-conditioning technology. A dimensionless relationship was proposed to determine the interdependency between flow velocity and the volume fraction of ice, for which the entropy generation rates were at the minimum level in the case of non-adiabatic ice slurry flow. For pipe flow, the correlation between the minimum entropy generation rate and the overall enhancement efficiency was analyzed. As regards heat exchange processes in heat exchangers, the authors analyzed the relationship between the minimum entropy generation rate and the heat exchange surface area and exchanger efficiency.

scholarly journals Effects of gaseous slip flow and temperature jump on entropy generation rate in rectangular microducts

2020 ◽  
Vol 24 (5 Part A) ◽  
pp. 3001-3011
Author(s):  
Abuzar Ghaffari ◽  
Waqar Khan ◽  
Irfan Mustafa
Keyword(s):  
Aspect Ratio ◽  
Entropy Generation ◽  
Temperature Jump ◽  
Slip Flow ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Generation Model ◽  
Minimum Entropy ◽  
Dimensionless Numbers ◽  
Minimum Entropy Generation

In this study, the influence of slip flow and temperature jump on the entropy generation rate are investigated in rectangular microducts. The Knudsen numbers are considered in the range between 0.001 and 0.1, and the aspect ratio lies between 0 and 1. The dimensionless governing equations are solved numerically using Chebyshev spectral collocation method, and the dimensionless velocity and temperature gradients are employed in the entropy generation model. The influences of the dimensionless numbers including Bejan number and irreversibility distribution ratio on the entropy generation rates are investigated and discussed through surface plots and contour diagrams. It is demonstrated that the minimum entropy generation rate exists corresponding to an optimal aspect ratio for each dimensionless number. This minimum entropy generation rate depends upon the nature of dimensionless numbers.

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