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1 – 10 of over 76000
Article
Publication date: 20 April 2010

S.Z. Shuja, B.S. Yilbas and M. Kassas

The purpose of this paper is to study flow over two heat generating porous blocks situated in a cavity, and examine the effects of porous blocks geometric orientations in the…

Abstract

Purpose

The purpose of this paper is to study flow over two heat generating porous blocks situated in a cavity, and examine the effects of porous blocks geometric orientations in the cavity (configurations) and the amount of heat generation in the blocks on entropy generation rate due to heat transfer and fluid flow.

Design/methodology/approach

Four configurations of blocks and three heat fluxes are accommodated in the simulations. The equilibrium flow equations are used to compute the flow field. Entropy generation in the flow system due to fluid friction and heat transfer is also computed. A control volume approach is used to discretize the governing equations of flow and heat transfer. In the simulations, flow Reynolds number is kept 100 at cavity inlet and blocks' porosity is set to 0.9726.

Findings

The volumetric entropy generation rate attains high values around the blocks and configuration 4 results in reasonably low values of entropy generation rate due to heat transfer and fluid flow.

Research limitations/implications

The simulations are limited to low Reynolds numbers due to practical applications. However, at high Reynolds numbers, flow separation in the cavity results in complex flow structure, which is difficult to simulate.

Practical implications

The thermodynamic irreversibility of the thermal system in the cavity becomes low for certain configuration of blocks in the cavity. The power loss, in this case, becomes less.

Originality/value

The work introduces original findings for cooling applications. When porous blocks are used for electronic cooling, the blocks configurations are very important. This is clearly demonstrated in this study.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 20 no. 3
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 13 February 2017

Kelly Pledger Weeks, Matthew Weeks and Nicolas Long

The purpose of this paper is to examine the relationship between stereotypes, in-group favoritism, and in-group bolstering effects across generations.

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Abstract

Purpose

The purpose of this paper is to examine the relationship between stereotypes, in-group favoritism, and in-group bolstering effects across generations.

Design/methodology/approach

Based on the trends found in a qualitative study on generational stereotypes, questions on work ethic, work-life balance, and use of technology were administered to 255 participants identified as Millennials, Generation X, and Baby Boomers. Hypotheses predicted that with a strong stereotype, traditional in-group favoritism will not be found; however, an in-group bolstering effect will emerge. In the absence of a strong stereotype, traditional in-group favoritism is expected.

Findings

Generally, there was a strong stereotype that Baby Boomers are worse at technology than Generation X and Generation X is worse than Millennials. There was also a strong stereotype that Millennials do not do what it takes to get the job done as much as other generations. In the presence of these stereotypes, traditional in-group favoritism was not found, but in-groups bolstered themselves by rating themselves more favorably than other groups rated them. Although these findings did not hold for every item studied, there was moderate support for all three hypotheses.

Practical implications

As employees become aware of their biases, they can collaborate better with employees who are different than they are. Practical recommendations are suggested.

Originality/value

The paper applies theory of in-group favoritism to the perceptions of generational cohorts.

Details

Equality, Diversity and Inclusion: An International Journal, vol. 36 no. 1
Type: Research Article
ISSN: 2040-7149

Keywords

Article
Publication date: 2 November 2010

Esmail M.A. Mokheimer

The aim of this article is to present the results of a parametric analysis of the entropy generation due to mixed convection in the entry‐developing region between two…

Abstract

Purpose

The aim of this article is to present the results of a parametric analysis of the entropy generation due to mixed convection in the entry‐developing region between two differentially heated isothermal vertical plates.

Design/methodology/approach

The entropy generation was estimated via a numerical solution of the mass, momentum and energy conservation equations governing the flow and heat transfer in the vertical channel between the two parallel plates. The resultant temperature and velocity profiles were used to estimate the entropy generation and other heat transfer parameters over a wide range of the operating parameters. The investigated parameters include the buoyancy parameter (Gr/Re), Eckert number (Ec), Reynolds number (Re), Prandtl number (Pr) and the ratio of the dimensionless temperature of the two plates (θT).

Findings

The optimum values of the buoyancy parameter (Gr/Re) optimum at which the entropy generation assumes its minimum for the problem under consideration have been obtained numerically and presented over a wide range of the other operating parameters. The effect of the other operating parameters on the entropy generation is presented and discussed as well.

Research limitations/implications

The results of this investigation are limited to the geometry of vertical channel parallel plates under isothermal boundary conditions. However, the concept of minimization of entropy generation via controlling the buoyancy parameter is applicable for any other geometry under any other thermal boundary conditions.

Practical implications

The results presented in this paper can be used for optimum designs of heat transfer equipment based on the principle of entropy generation minimization with particular focus on the optimum design of plate and frame heat exchanger and the optimization of electronic packages and stacked packaging of laminar‐convection‐cooled printed circuits.

Originality/value

This paper introduces the entropy generation minimization via controlling the operating parameters and clearly identifies the optimum buoyancy parameter (Gr/Re) at which entropy generation assumes its minimum under different operating conditions.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 20 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 18 September 2007

S.Z. Shuja, B.S. Yilbas and M.O. Budair

The purpose of this paper is to examine entropy generation rate in the flow field due jet emanating from an annular nozzle and impinging on to a flat plate. Since the flow field…

Abstract

Purpose

The purpose of this paper is to examine entropy generation rate in the flow field due jet emanating from an annular nozzle and impinging on to a flat plate. Since the flow field changes with the geometric configuration of the annular nozzle, the influence of nozzle outer cone angle on the entropy generation rate is considered.

Design/methodology/approach

The steady flow field pertinent to jet impingement on to a flat plate is modeled with appropriate boundary conditions. A control volume approach is introduced to discretize the governing equations of flow and to simulate the physical situation numerically. Entropy generation rate due to heat transfer and fluid friction is formulated. The resulting entropy equations are solved numerically.

Findings

Thermodynamic irreversibility, which is quantified through entropy generation rate, gives insight into the thermodynamics losses in the flow system. Entropy generation rate is highly affected by the nozzle outer cone angle. In this case, increasing nozzle outer cone angle enhances the entropy generation rate, particularly due to fluid friction.

Research limitations/implications

The predictions may be extended to include the nozzle area ratio and mass flow rate variation.

Practical implications

The paper is a very useful source of physical information for improving nozzle design, particularly that which is used in a laser thick material cutting operation. It disseminates information for those working on both laser machining applications and entropy generation in flow systems.

Originality/value

This paper discusses the physical issues related to the entropy generation rate and offers practical help to an individual starting out on an academic career.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 17 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 30 November 2018

Amin Shahsavar, Pouyan Talebizadeh Sardari and D. Toghraie

This paper aims to numerically investigate the heat transfer and entropy generation characteristics of water-based hybrid nanofluid in natural convection flow inside a concentric…

Abstract

Purpose

This paper aims to numerically investigate the heat transfer and entropy generation characteristics of water-based hybrid nanofluid in natural convection flow inside a concentric horizontal annulus.

Design/methodology/approach

The hybrid nanofluid is prepared by suspending tetramethylammonium hydroxide-coated Fe3O4 (magnetite) nanoparticles and gum arabic (GA)-coated carbon nanotubes (CNTs) in water. The effects of nanoparticle volume concentration and Rayleigh number on the streamlines, isotherms, average Nusselt number and the thermal, frictional and total entropy generation rates are investigated comprehensively.

Findings

Results show the advantageous effect of hybrid nanofluid on the average Nusselt number. Furthermore, the study of entropy generation shows the increment of both frictional and thermal entropy generation rates by increasing Fe3O4 and CNT concentrations at various Rayleigh numbers. Increasing Rayleigh number from 103 to 105, at Fe3O4 concentration of 0.9 per cent and CNT concentration of 1.35 per cent, increases the average Nusselt number, thermal entropy generation rate and frictional entropy generation rate by 224.95, 224.65 and 155.25 per cent, respectively. Moreover, increasing the Fe3O4 concentration from 0.5 to 0.9 per cent, at Rayleigh number of 105 and CNT concentration of 1.35 per cent, intensifies the average Nusselt number, thermal entropy generation rate and frictional entropy generation rate by 18.36, 22.78 and 72.7 per cent, respectively.

Originality/value

To the best knowledge of the authors, there are not any archival publications considering the detailed behaviour of the natural convective heat transfer and entropy generation of hybrid nanofluid in a concentric annulus.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 3
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 May 2001

S.Z. Shuja and B.S. Yilbas

A laminar swirling jet impinging on to an adiabatic solid wall is investigated. The flow field is computed and entropy analysis is carried out for different flow configurations…

Abstract

A laminar swirling jet impinging on to an adiabatic solid wall is investigated. The flow field is computed and entropy analysis is carried out for different flow configurations. The numerical scheme employing a control volume approach is introduced when solving the governing equations of flow and energy. In order to examine the effect of the nozzle exit velocity profile and the swirling velocity on the flow field and entropy generation rate, six nozzle exit velocity profiles and four swirl velocities are considered. It is found that the influence of swirl velocity on the flow field is more pronounced as the velocity profile number reduces. In this case, two circulation cells are generated in the flow field. The total entropy generation increases with increasing swirl velocity for low velocity profile numbers. The Merit number improves for low swirling velocity and high velocity profile numbers.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 11 no. 3
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 21 May 2021

S. Das, S. Chakraborty and R. N. Jana

This study aims to expose the flow phenomena and entropy generation during a; magnetohydrodynamic (MHD) Poiseuille flow of water-based nanofluids (NFs) in a porous channel subject…

Abstract

Purpose

This study aims to expose the flow phenomena and entropy generation during a; magnetohydrodynamic (MHD) Poiseuille flow of water-based nanofluids (NFs) in a porous channel subject to hydrodynamic slip and convective heating boundary conditions. The flow caused by the uniform pressure; gradient between infinite parallel plates is considered steady and fully developed. The nanoparticles; namely, copper, alumina and titanium oxide are taken with pure water as the base fluid. Viscous dissipation and Joule heating impacts are also incorporated in this investigation.

Design/methodology/approach

The reduced governing equations are solved analytically in closed form. The physical insights of noteworthy parameters on the important flow quantities are demonstrated through graphs and analyzed elaborately. The thermodynamic analysis is performed by calculating entropy generation; rate and Bejan number. A graphical comparison between solutions corresponding to NFs and regular fluid in the channel is also provided.

Findings

The analysis of the results divulges that entropy generation minimization can be achieved by an appropriate combination of the geometrical and physical parameters of thermomechanical systems. It is reported that ascent in magnetic parameter number declines the velocity profiles, while the inverse pattern is witnessed with augmentation in hydrodynamic slip parameters. The temperature dissemination declines with the growth of Biot numbers. It is perceived that the entropy generation rate lessens with an upgrade in magnetic parameter, whereas the reverse trend of Bejan number is perceived with expansion in magnetic parameter and Biot number. The important contribution of the result is that the entropy generation rate is controlled with an appropriate composition of thermo-physical parameter values. Moreover, in the presence of a magnetic field and suction/injection at the channel walls, the shear stresses at the channel walls are reduced about two times.

Practical implications

In various industrial applications, minimizing entropy generation plays a significant role. Miniaturization of entropy is the utilization of the energy of thermal devices such as micro heat exchangers, micromixers, micropumps and cooling microelectromechanical devices.

Originality/value

An attentive review of the literature discloses that quite a few studies have been conducted on entropy generation analysis of a fully developed MHD Poiseuille flow of NFs through a permeable channel subject to the velocity slip and convective heating conditions at the walls.

Details

World Journal of Engineering, vol. 18 no. 6
Type: Research Article
ISSN: 1708-5284

Keywords

Article
Publication date: 30 September 2014

Kathryn Eileen Holden and Deana M. Raffo

– The purpose of this study is to examine the potential relationship between generational membership and perspectives on female leadership.

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Abstract

Purpose

The purpose of this study is to examine the potential relationship between generational membership and perspectives on female leadership.

Design/methodology/approach

Participants from Generation X (birth years from 1961 to 1980) and Generation Y (birth years from 1981 to 2000) rated 10 descriptor words, which came from Kouzes and Posner’s ten most admired leadership characteristics. Participants were put into three gender conditions: rating a male leader, female leader or gender-neutral leader.

Findings

Differences did not emerge for the gender conditions, probably due to the methodology implemented. However, findings indicated that Generation X members admired competency and honesty more than Generation Y members, while Generation Y members admired ambitiousness and determination more than Generation X members.

Social implications

By examining the perceptions of different generations, we can begin to track potential changes in this country’s perspective on female leadership.

Originality/value

This study addresses how generation may be specifically linked to attitudes toward leadership; however, few empirical research projects have been done on the subject. Because this area of research has not been explored thoroughly, the present study has the potential to yield new and illuminating results. The present study may be one of the first steps in determining if our views on female leadership are changing.

Details

Gender in Management: An International Journal, vol. 29 no. 7
Type: Research Article
ISSN: 1754-2413

Keywords

Article
Publication date: 7 June 2021

Zhenshuang Wang, Wanchen Xie and Jingkuang Liu

The growth of the Chinese economy has resulted in a significant increase in construction and demolition waste (CDW), and regional differences in CDW generation are gradually…

Abstract

Purpose

The growth of the Chinese economy has resulted in a significant increase in construction and demolition waste (CDW), and regional differences in CDW generation are gradually increasing. The purpose of this study is to investigate the regional differences in CDW generation and the driving factors that influence CDW generation in different areas of China. To provide a systematic advisement for local governments to select the appropriate policy, reduce CDW generation.

Design/methodology/approach

The generation of CDW was calculated by region, based on the area estimation method, from 2005 to 2018. The relationship between CDW generation and economic development, and the driving factors of CDW generation in different regions of China, was investigated using the environmental Kuznets curve (EKC) model and the STIRPAT theoretical model.

Findings

CDW generation of China increased at the average annual growth rate of 10.86% from 2005 to 2018. The main areas of CDW generation were concentrated in the eastern and central regions, while the proportion of CDW generation in the northeast region decreased gradually, and the changes varied significantly across different regions. The EKC between CDW generation and economic development was established for the whole country, North China, Northeast China, East China, Central South China, Southwest China and Northwest China. Three main factors based on the STIRPAT theoretical model were identified and explained into a framework to reduce CDW generation. The results provided a useful theoretical basis and data support guide for devising effective policies and regulations for the Chinese context.

Practical implications

The findings from this study can ultimately support policymakers and waste managers in formulating effective policies for waste management strategies and CDW-specific legislation. Additionally, it can help the coordinated reduction of CDW generation across regions in China and can support construction enterprises (in their development strategies), similar developing economies and foreign firms planning to operate in China.

Originality/value

This study contributes to the field through the STIRPAT model on driving factors of CDW generation in the Chinese context, in different regions.

Details

Engineering, Construction and Architectural Management, vol. 29 no. 6
Type: Research Article
ISSN: 0969-9988

Keywords

Article
Publication date: 3 May 2016

J. Srinivas, J.V. Ramana Murthy and Ali J Chamkha

– The purpose of this paper is to examine the flow, heat transfer and entropy generation characteristics for an inclined channel of two immiscible micropolar fluids.

Abstract

Purpose

The purpose of this paper is to examine the flow, heat transfer and entropy generation characteristics for an inclined channel of two immiscible micropolar fluids.

Design/methodology/approach

The flow region consists of two zones, the flow of the heavier fluid taking place in the lower zone. The flow is assumed to be governed by Eringen’s micropolar fluid flow equation. The resulting governing equations are then solved using the homotopy analysis method.

Findings

The following findings are concluded: first, the entropy generation rate is more near the plates in both the zones as compared to that of the interface. This indicates that the friction due to surface on the fluids increases entropy generation rate. Second, the entropy generation rate is more near the plate in Zone I than that of Zone II. This may be due to the fact that the fluid in Zone I is more viscous. This indicates the more the viscosity of the fluid is, the more the entropy generation. Third, Bejan number is the maximum at the interface of the fluids. This indicates that the amount of exergy (available energy) is maximum and irreversibility is minimized at the interface between the fluids. Fourth, as micropolarity increases, entropy generation rate near the plates decreases and irreversibility decreases. This indicates an important industrial application for micropolar fluids to use them as a good lubricant.

Originality/value

The problem is original as no work has been reported on entropy generation in an inclined channel with two immiscible micropolar fluids.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 3/4
Type: Research Article
ISSN: 0961-5539

Keywords

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