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.

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.

The Role of Fin Geometry in Heat Sink Performance

2006 ◽  
Vol 128 (4) ◽  
pp. 324-330 ◽  
Author(s):  
W. A. Khan ◽  
J. R. Culham ◽  
M. M. Yovanovich
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Entropy Generation ◽  
Heat Sink ◽  
Control Volume ◽  
Generation Rate ◽  
Heat Transfer Fluid ◽  
Entropy Generation Rate ◽  
Minimum Entropy ◽  
Axis Ratio

The following study will examine the effect on overall thermal/fluid performance associated with different fin geometries, including, rectangular plate fins as well as square, circular, and elliptical pin fins. The use of entropy generation minimization, 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 base plate and applying the conservations equations for mass and energy with the entropy balance. 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 heat transfer, fluid friction, and the minimum entropy generation rate corresponding to different parameters including axis ratio, aspect ratio, and Reynolds number. 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.

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.

Thermal and Entropy generation analysis of magnetohydrodynamic tangent hyperbolic slip flow towards a stretching sheet

2021 ◽  
pp. 095440892110411
Author(s):  
Shafiq Ahmad ◽  
Zafar H Khan ◽  
Salman Zeb ◽  
Muhammad Hamid
Keyword(s):  
Thermal Conductivity ◽  
Entropy Generation ◽  
Slip Flow ◽  
Variable Thermal Conductivity ◽  
Weissenberg Number ◽  
Temperature Fields ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Bejan Number ◽  
Generation Model

This article examined the effects of boundary layer flow and heat transport of a two-dimensional incompressible magnetohydrodynamic tangent hyperbolic fluid under slip boundary conditions and variable thermal conductivity. The entropy generation model is also analysed for the said fluid. Non-similarity transformations transformed the governing equations of the fluid and entropy generation model into dimensionless form. Maple software is used to solve the transformed equations numerically. Effects of different dimensionless parameters on entropy generation rate, Bejan number, velocity and temperature fields are studied thoroughly through graphs. It is observed that for higher values of velocity slip parameter and power-law index, the entropy generation rate decreases while the Bejan number increases. Also, for the Hartmann number, Weissenberg number and Brinkman number, we found an increase in the entropy generation rate, and reverse behaviour is observed for the Bejan number. Nusselt number, temperature profile and Bejan’s number increase with an increase in variable thermal conductivity.

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.

Entropy Generation Minimization in a Pressure-Driven Microflow of Viscoelastic Fluid With Slippage at the Wall: Effect of Conjugate Heat Transfer

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Rajkumar Sarma ◽  
Pranab Kumar Mondal
Keyword(s):  
Heat Transfer ◽  
Viscoelastic Fluid ◽  
Entropy Generation ◽  
Conjugate Heat Transfer ◽  
Applied Pressure ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Minimum Entropy ◽  
Viscoelastic Parameter ◽  
Entropy Generation Minimization

We focus on the entropy generation minimization for the flow of a viscoelastic fluid through a parallel plate microchannel under the combined influences of applied pressure gradient, interfacial slip, and conjugate heat transfer. We use the simplified Phan–Thien–Tanner model (s-PTT) to represent the rheological behavior of the viscoelastic fluid. Using thermal boundary conditions of the third kind, we solve the transport equations analytically to obtain the velocity and temperature distributions in the flow field, which are further used to calculate the entropy generation rate in the analysis. In this study, the influential role of the following dimensionless parameters on entropy generation rate is examined: the viscoelastic parameter (εDe2), slip coefficient (k¯), channel wall thickness (δ), thermal conductivity of the wall (γ), Biot number (Bi) and Peclet number (Pe). We show that there exists a particular value of the abovementioned parameters that lead to a minimum entropy generation rate in the system. We believe the results of this analysis could be of helpful in the optimum design of microfluidic system/devices typically used in thermal management, such as micro-electronic devices, microreactors, and microheat exchangers.

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