Finite element based numerical simulation has been carried out for analysis of heat flow visualization and entropy generation during natural convection within inclined square cavities with hot wall (DA), cold wall (BC) and adiabatic walls (AB and CD). The numerical results are presented in terms of isotherms (θ), streamlines (ψ), heatlines (Π), entropy generation due to heat transfer irreversibility (Sθ) and fluid friction irreversibility (Sψ). Further, detailed discussion on variation of the total entropy generation (Stotal), average Bejan number (Beav) and average Nusselt number (Nu), with Rayleigh number (Ra) is also presented. It is found that, large heat transfer rate (NuDA) with less entropy generation (Stotal) occurs for φ = 15° cavities at convection dominant mode (Ra = 105) irrespective of Pr. Thus, inclined square cavities with φ = 15° may be used for all thermal processing operations involving various fluids (Pr = 0.025 and 998). © 2013 Published by Elsevier Ltd.

Tanmay Basak

Department Of Chemical Engineering

Satyajit Roy

Department of Mathematics

entropy

flow visualization

Heat convection

Heat transfer

Natural convection

Visualization

entropy generation

Finite element simulations

HEATLINES

Square cavity

STREAMLINES

finite element method

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

International Communications in Heat and Mass Transfer

Efficient visualization techniques are required to understand the flow physics for any numerical simulation. For convective heat transfer problems, most widely used techniques to visualize the fluid flow and heat transfer are streamlines and isotherms respectively. These methods are not sufficient to address the degrees of complexity associated with the complicated convective problems. Thus, different visualization techniques have been developed to represent the results depending on the problem. In this article, an effort has been made to collate visualization techniques in literature for convective heat transfer system like, heatlines, energy streamlines, energy flux vectors, proper orthogonal decomposition (POD), Poincare map etc. The fundamentals of different techniques are briefly discussed, applications of these techniques are shown with proper examples. The usefulness and limitations of these techniques are also discussed. Heatline is found to be the best visualization tool for two dimensional steady situations. However, in 3D and transient scenario Lagrangian approach or POD can be used. © 2017 Elsevier Ltd

International Journal of Heat and Mass Transfer

Heatlines and other visualization techniques for confined heat transfer systems

The entropy generation minimization (EGM) technique is an important tool for the optimization of the thermal systems via the analysis of the associated irreversibilities measured by the entropy generation. This article presents a detailed review of works on the entropy generation analysis during natural convection in various enclosures and processes involving different practical applications. The mathematical formulations of the fundamental governing equations for natural convection followed by the equations of the entropy generation are presented. The calculation procedure of the entropy generation for various test cases is reported briefly with the finite difference and finite volume techniques for some test cases and the detailed discussion of the evaluation of the entropy generation via the finite element method is addressed. Further, the problem formulation and results in terms of the entropy generation are discussed for natural convection in enclosures of various shapes (square/rectangular, trapezoidal, triangular, parallellogrammic/rhombic, curved/wavy). The brief discussion on the entropy generation analysis during various practical applications is also addressed. Overall, the minimum entropy generation vs enhanced heat transfer rate is the main issue in all the case studies with various enclosures involving a number of practical applications to achieve the optimal configuration with the high energy efficiency. The need of the renewable energy is increasing day by day. Thus, the conversion of the renewable energy to a useful form is one of the most challenging processes and natural convection plays an important role in the conversion. The loss of the available energy via the entropy production during natural convection is highly important for the design of suitable energy systems. This review article further provides basis for future research on the entropy generation analysis during natural convection in order to improve the energy efficiency which may be applicable for various renewable energy systems. © 2017 Elsevier Ltd

Renewable and Sustainable Energy Reviews

Entropy generation vs energy efficiency for natural convection based energy flow in enclosures and various applications: A review

Analysis of natural convection within inclined porous square cavities for various inclination angles (φ=15°, 30° and 60°) is carried out via the heatline and entropy generation approaches. The cases 1 and 2 correspond to the isothermal and non-isothermal heating of the bottom wall, respectively, involving the cold side walls and adiabatic top wall. The governing equations are solved via the Galerkin finite element method to obtain the results in terms the isotherms (θ), streamlines (ψ), heatlines (Π), entropy generation maps (Sθ and Sψ), total entropy generation (Stotal), average Bejan number (Beav) and average Nusselt number (Nu¯AB) at various Darcy numbers (10−5≤Dam≤10−2), Prandtl numbers (Prm=0.025 and 998.24) at Rayleigh number, Ram=106. The locations of Sθ,max and Sψ,max are identified and the magnitudes of Sθ,max and Sψ,max are larger for the case 1 compared to those for the case 2 involving all Dam, Prm and φ. Also, the magnitudes of Stotal, Beav and Nu¯AB are larger for the case 1 compared to the case 2. The case 2 is the efficient heating strategy with the optimal thermal management compared to the case 1 based on significantly lesser Stotal for all Dam, Prm and φ. The optimal φ involving the lesser Stotal and larger Nu¯AB is highly influenced by Dam and Prm. Various ranges of the optimal φ involving the higher thermal efficiency are identified for different Dam and Prm for each of the cases (cases 1 and 2). © 2016 Elsevier Ltd

International Journal of Mechanical Sciences

Analysis of thermal management during natural convection within porous tilted square cavities via heatline and entropy generation

This article analyzes the detailed heat transfer phenomena during natural convection within tilted square cavities with isothermally cooled walls (BC and DA) and hot wall AB is parallel to the insulated wall CD. A penalty finite element analysis with bi-quadratic elements has been used to investigate the results in terms of streamlines, isotherms and heatlines. The present numerical procedure is performed over a wide range of parameters (10 3 ≤ Ra ≤ 10 5,0.015 ≤ Pr ≤ 1000,0°≤ ≤ 90°). Secondary circulations cells are observed near corner regions of cavity for all 's at Pr = 0.015 with Ra = 10 5. Two asymmetric flow circulation cells are found to occupy the entire cavity for = 15°at Pr = 0.7 and Pr = 1000 with Ra = 10 5. Heatlines indicate that the cavity with inclination angle = 15°corresponds to large convective heat transfer from the wall AB to wall DA whereas the heat transfer to wall BC is maximum for = 75°. Heat transfer rates along the walls are obtained in terms of local and average Nusselt numbers and they are explained based on gradients of heatfunctions. Average Nusselt number distributions show that heat transfer rate along wall DA is larger for lower inclination angle ( = 15°) whereas maximum heat transfer rate along wall BC occur for higher inclination angle ( = 75°). © 2012 Elsevier Ltd. All rights reserved.

Analysis of Bejan's heatlines on visualization of heat flow and thermal mixing in tilted square cavities

Numerical predictions of natural convection with liquid fluids contained in an inclined arc-shaped enclosure

Experimental investigation of cooling of heated circular disc using inclined circular jet

Entropy

Entropy Generation at Natural Convection in an Inclined Rectangular Cavity

First and second law analysis of fully developed gaseous slip flow in trapezoidal silicon microchannels considering viscous dissipation effect

Finite element simulations on heat flow visualization and entropy generation during natural convection in inclined square cavities

Journal	Data powered by TypesetInternational Communications in Heat and Mass Transfer
Publisher	Data powered by TypesetElsevier Ltd
ISSN	07351933
Open Access	No