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Article
Publication date: 1 October 2006

A. Mezrhab, H. Bouali, H. Amaoui and C. Abid

The purpose of this paper is to study the radiation‐natural convection interactions in a vertical divided vented channel. The effects of the surface emissivity, the vent opening…

374

Abstract

Purpose

The purpose of this paper is to study the radiation‐natural convection interactions in a vertical divided vented channel. The effects of the surface emissivity, the vent opening position and size on the heat transfer and the flow structures inside the channel were studied.

Design/methodology/approach

The governing differential equations are solved by a finite volume method, with adopting the SIMPLER algorithm for pressure‐velocity coupling. The view factors were determined by using a boundary elements approximation and a Monte Carlo method.

Findings

The effect of the radiation exchange is very important, it increases the average hot wall Nusselt number by more than 100 per cent. The contribution of the channel wall emissivity in the heat transfer is more important than that of the plate emissivity. The average hot wall Nusselt number increases with increasing the vent opening size, only in presence of the radiation exchange, and this increase is more pronounced, particularly when the vent opening is located near the channel inlet.

Research limitations/implications

The flow is assumed to be incompressible, laminar and two dimensional. The radiative surfaces are assumed diffuse‐grey. The working fluid, air, is considered as transparent with respect to the radiation.

Practical implications

The industrial applications of this study are solar collectors, thermal building, electronic cooling, aeronautics, chemical apparatus, nuclear engineering, etc.

Originality/value

In comparison to the preceding studies, the originality of this paper is the taking into account of the radiation exchange in a vented and divided channel.

Details

Engineering Computations, vol. 23 no. 7
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 January 2006

H. Bouali and A. Mezrhab

This paper presents a numerical investigation of the interaction of surfaces radiation with developing laminar free convective heat transfer in a divided vertical channel. The…

543

Abstract

Purpose

This paper presents a numerical investigation of the interaction of surfaces radiation with developing laminar free convective heat transfer in a divided vertical channel. The influence of the radiation on the heat transfer and on the air flow is studied for various sizes (width and length) of the plate.

Design/methodology/approach

The specifically developed numerical code is based on the utilization of the finite volume method. The SIMPLER algorithm for the pressure‐velocity coupling is adopted. The view factors are determined by using boundary elements to fit the surfaces, an algorithm solving the shadow effect and a Monte Carlo method for the numerical integrations.

Findings

Results obtained show that the radiation: plays a very important role on the paces of the isotherms, especially at Ra≥1,600; increases considerably the average wall Nusselt number; and increases the mass flow rate and the average channel Nusselt number at high Rayleigh numbers. The plate location has a significant effect on the heat transfer only in presence of the radiation exchange. The increase of both length and width of the plate causes a decrease of the heat transfer and the mass flow rate.

Research limitations/implications

The use of the code is limited to the flow that is assumed to be incompressible, laminar and two dimensional. The radiative surfaces are assumed diffuse‐gray.

Practical implications

Natural convection in vertical channels formed by parallel plates has received significant attention because of its interest and importance in industrial applications. Some applications are solar collectors, fire research, electronic cooling, aeronautics, chemical apparatus, building constructions, nuclear engineering, etc.

Originality/value

In comparison to the most of the previous studies on natural convection in partitioned channels, the radiation exchange was neglected. This study takes into account the radiation exchange in a divided channel.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 16 no. 1
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 20 September 2018

Mikhail A. Sheremet, Ioan Pop and Alin V. Rosca

The purpose of this study is a numerical analysis of transient natural convection in an inclined square cavity filled with an alumina-water nanofluid under the effects of…

177

Abstract

Purpose

The purpose of this study is a numerical analysis of transient natural convection in an inclined square cavity filled with an alumina-water nanofluid under the effects of sinusoidal wall temperature and thermal radiation by using a single-phase nanofluid model with empirical correlations for effective viscosity and thermal conductivity.

Design/methodology/approach

The domain of interest includes the nanofluid-filled cavity with a sinusoidal temperature distribution along the left vertical wall. Horizontal walls are supposed to be adiabatic, while right vertical wall is kept at constant low temperature. Temperature of left wall varies sinusoidally along y-coordinate. It is assumed in the analysis that the thermophysical properties of the fluid are independent of temperature and the flow is laminar. The governing equations have been discretized using the finite difference method with the uniform grid. Simulations have been carried out for different values of the Rayleigh number, cavity inclination angle, nanoparticles volume fraction and radiation parameter.

Findings

It has been found that a growth of radiation parameter leads to the heat transfer enhancement and convective flow intensification. At the same time, an inclusion of nanoparticles illustrates a reduction in the average Nusselt number and fluid flow rate.

Originality/value

The originality of this work is to analyze unsteady natural convection in a square cavity filled with a water-based nanofluid in the presence of a sinusoidal temperature distribution along one wall. The results would benefit scientists and engineers to become familiar with the analysis of convective heat and mass transfer in nanofluids and the way to predict the properties of nanofluid convective flow in advanced technical systems, in industrial sectors including transportation, power generation, chemical sectors, electronics, etc.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 8
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 22 March 2013

A.B. Ansari and S.A. Gandjalikhan Nassab

The purpose of this paper is to focus on thermal characteristics behavior of forced convection flow in a duct over forward facing step (FFS), in which all of the heat transfer…

169

Abstract

Purpose

The purpose of this paper is to focus on thermal characteristics behavior of forced convection flow in a duct over forward facing step (FFS), in which all of the heat transfer mechanisms, including convection, conduction and radiation, take place simultaneously in the fluid flow.

Design/methodology/approach

The fluid is treated as a gray, absorbing, emitting and scattering medium. The Navier‐Stokes and energy equations are solved numerically by computational fluid dynamics (CFD) techniques to obtain the velocity and temperature fields. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. Since the gas is considered as a radiating medium, all of the convection, conduction and radiation heat transfer take place simultaneously in the gas flow. For computation of the radiative term in the gas energy equation, the radiative transfer equation (RTE) is solved numerically by the discrete ordinate method (DOM) to find the radiative heat flux distribution inside the radiating medium. By this numerical approach, the velocity, pressure and temperature fields are calculated.

Findings

The effect of wall emissivity, optical thickness, albedo coefficient and the radiation‐conduction parameter on heat transfer behavior of the system are also investigated. The numerical results for two cases of convection‐conduction and conduction‐radiation problems are compared with the available data published in open literature and good agreement was obtained.

Originality/value

This is the first time in which flow over FFS in a duct, considering all heat transfer mechanisms including conduction, convection and radiation, is solved numerically.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 23 no. 2
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 20 June 2022

Ajit Kumar, Sumit Kumar Mehta, Sukumar Pati and László Baranyi

The purpose of this paper is to analyze the heat and momentum transfer for steady two-dimensional incompressible nanofluid flow through a wavy channel with linearly varying…

185

Abstract

Purpose

The purpose of this paper is to analyze the heat and momentum transfer for steady two-dimensional incompressible nanofluid flow through a wavy channel with linearly varying amplitude in the entrance region.

Design/methodology/approach

The mass, momentum and energy conservation equations for laminar flow of Cu-water nanofluids are computationally solved using the finite element method. A parametric study is carried out by varying the dimensionless length of the channel section with varying amplitude (EL), Reynolds number (Re) and nanoparticle volume fraction (Φ) in the ranges 0 ≤ EL ≤ 25.5, 105 ≤ Re ≤ 900 and 0 ≤ Φ ≤ 0.04.

Findings

A higher heat transfer rate is seen in the wavy channel compared to a plane channel beyond a critical value of Re (Recrit) whose value varies with EL; moreover, the overall heat transfer decreases with EL. The heat transfer rate increases with phi for all EL values investigated. The combined effects of the increase in the overall heat transfer and the associated pressure drop in the wavy channel compared to the parallel plate channel are presented as performance factor (PF) against EL. For the highest value of EL (= 25.5), PF monotonically decreases with Re. For smaller values of EL (= 5.5 and 11.5) and also for EL = 0, PF decreases with Re in the lower and the higher Re regimes, while it increases in the intermediate Re regime. In all cases, PF is higher for φ = 0.04 than for the base fluid. The sensitivity of the average Nusselt number to nanoparticle volume fraction follows a non-monotonic trend with the change in Re, φ and EL.

Practical implications

This study finds relevance in several applications such as solar collectors, heat exchangers and heat sinks.

Originality/value

To the best of the authors’ knowledge, the analysis of forced convection flow of nanofluid through a wavy channel with linearly varying amplitude is reported for the first time in the literature.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 33 no. 1
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 12 November 2024

Shokoofa Mostofi, Sohrab Kordrostami, Amir Hossein Refahi Sheikhani, Marzieh Faridi Masouleh and Soheil Shokri

This study aims to improve the detection and quantification of cardiac issues, which are a leading cause of mortality globally. By leveraging past data and using knowledge mining…

18

Abstract

Purpose

This study aims to improve the detection and quantification of cardiac issues, which are a leading cause of mortality globally. By leveraging past data and using knowledge mining strategies, this study seeks to develop a technique that could assess and predict the onset of cardiac sickness in real time. The use of a triple algorithm, combining particle swarm optimization (PSO), artificial bee colony (ABC) and support vector machine (SVM), is proposed to enhance the accuracy of predictions. The purpose is to contribute to the existing body of knowledge on cardiac disease prognosis and improve overall performance in health care.

Design/methodology/approach

This research uses a knowledge-mining strategy to enhance the detection and quantification of cardiac issues. Decision trees are used to form predictions of cardiovascular disorders, and these predictions are evaluated using training data and test results. The study has also introduced a novel triple algorithm that combines three different combination processes: PSO, ABC and SVM to process and merge the data. A neural network is then used to classify the data based on these three approaches. Real data on various aspects of cardiac disease are incorporated into the simulation.

Findings

The results of this study suggest that the proposed triple algorithm, using the combination of PSO, ABC and SVM, significantly improves the accuracy of predictions for cardiac disease. By processing and merging data using the triple algorithm, the neural network was able to effectively classify the data. The incorporation of real data on various aspects of cardiac disease in the simulation further enhanced the findings. This research contributes to the existing knowledge on cardiac disease prognosis and highlights the potential of leveraging past data for strategic forecasting in the health-care sector.

Originality/value

The originality of this research lies in the development of the triple algorithm, which combines multiple data mining strategies to improve prognosis accuracy for cardiac diseases. This approach differs from existing methods by using a combination of PSO, ABC, SVM, information gain, genetic algorithms and bacterial foraging optimization with the Gray Wolf Optimizer. The proposed technique offers a novel and valuable contribution to the field, enhancing the competitive position and overall performance of businesses in the health-care sector.

Details

Journal of Modelling in Management, vol. 20 no. 2
Type: Research Article
ISSN: 1746-5664

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Article
Publication date: 18 July 2008

Mohammed Jami, Ahmed Mezrhab and Hassan Naji

This paper attempts to deal with the presentation of a numerical investigation of the laminar‐free convective heat transfer in a square enclosure containing a solid cylinder…

702

Abstract

Purpose

This paper attempts to deal with the presentation of a numerical investigation of the laminar‐free convective heat transfer in a square enclosure containing a solid cylinder located at an arbitrary position. Effects of the cylinder position on the heat transfer and the flow structures inside the cavity are to be studied and highlighted.

Design/methodology/approach

The numerical code is based on the hybrid scheme with the lattice Boltzmann and the alternating‐directional implicit (ADI) splitting scheme. The energy equation is solved by ADI scheme and the flow field velocities have been computed using the lattice Boltzmann method (LBM). The bounce‐back condition combined with quadratic interpolation is used at solid boundaries.

Findings

The predicted results show that the cylinder location has a significant effect on the heat transfer. It is observed that: when the inner body does not generate heat, most of the heat transfer takes place if the body is located at the center of the enclosure. When the cylinder generates heat and is displaced from the left towards the right and from the lower part towards the upper part of the cavity, the heat transfer rate decreases on the hot wall and increases on the cold wall.

Research limitations/implications

The fluid flow (air) is assumed to be incompressible, laminar and 2D. The viscous heat dissipation is neglected in the energy equation and all physical proprieties are constant except for the density, whose variation with temperature is allowed for in the buoyancy term.

Practical implications

Natural convection in heated enclosures, housing inner bodies has received significant attention because of its interest and importance in industrial applications. Some applications are solar collectors, fire research, electronic cooling, aeronautics, chemical apparatus, building constructions, nuclear engineering, etc.

Originality/value

The paper contributes to the development of the LBM. In particular, it was found that the inherent numerical instabilities of this LBE are not modified by coupling with temperature. This is a good improvement compared to what is observed in the simulations of thermal systems using the full LBE formulation where the energy conservation is taken into account.

Details

Engineering Computations, vol. 25 no. 5
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 4 September 2018

Igor Miroshnichenko, Mikhail Sheremet and Ali J. Chamkha

The purpose of this paper is to conduct a numerical analysis of transient turbulent natural convection combined with surface thermal radiation in a square cavity with a local…

161

Abstract

Purpose

The purpose of this paper is to conduct a numerical analysis of transient turbulent natural convection combined with surface thermal radiation in a square cavity with a local heater.

Design/methodology/approach

The domain of interest includes the air-filled cavity with cold vertical walls, adiabatic horizontal walls and isothermal heater located on the bottom cavity wall. It is assumed in the analysis that the thermophysical properties of the fluid are independent of temperature and the flow is turbulent. Surface thermal radiation is considered for more accurate analysis of the complex heat transfer inside the cavity. The governing equations have been discretized using the finite difference method with the non-uniform grid on the basis of the special algebraic transformation. Turbulence was modeled using the kε model. Simulations have been carried out for different values of the Rayleigh number, surface emissivity and location of the heater.

Findings

It has been found that the presence of surface radiation leads to both an increase in the average total Nusselt number and intensive cooling of such type of system. A significant intensification of convective flow was also observed owing to an increase in the Rayleigh number. It should be noted that a displacement of the heater from central part of the bottom wall leads to significant modification of the thermal plume and flow pattern inside the cavity.

Originality/value

An efficient numerical technique has been developed to solve this problem. The originality of this work is to analyze unsteady turbulent natural convection combined with surface thermal radiation in a square air-filled cavity in the presence of a local isothermal heater. The results would benefit scientists and engineers to become familiar with the analysis of turbulent convective–radiative heat transfer in enclosures with local heaters, and the way to predict the heat transfer rate in advanced technical systems, in industrial sectors including transportation, power generation, chemical sectors and electronics.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

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Book part
Publication date: 24 October 2018

Nicole Rouvinez-Bouali

Abstract

Details

Leadership and Power in International Development
Type: Book
ISBN: 978-1-78754-116-0

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Article
Publication date: 5 June 2018

Asma Mejri, Sonia Ayachi-Ghannouchi and Ricardo Martinho

The purpose of this paper is to measure the flexibility of business process models. The authors give the notions of flexible process distance, which corresponds to the number of…

878

Abstract

Purpose

The purpose of this paper is to measure the flexibility of business process models. The authors give the notions of flexible process distance, which corresponds to the number of change operations needed for transforming one process model into another, considering the different perspectives (functional, operational, behavioral, informational, and organizational).

Design/methodology/approach

The proposed approach is a quantitative-based approach to measure the flexibility of business process models. In this context, the authors presented a method to compute the distance between two process models. The authors measured the distance between a process model and a process variant in terms of the number of high-level change operations (e.g. to insert or delete actors) needed to transform the process model into the respective variant when a change occurred, considering the different perspectives and the flexible features.

Findings

To evaluate the flexibility-measurement approach, the authors performed a comprehensive simulation using an emergency care (EC) business process model and its variants. The authors used a real-world EC process and illustrated the possible changes faced in the emergency department (possible variants). Simulation results were promising because they fit the flexibility needs of the EC process users. This was validated using the authors’ previous work which consists in a guidance approach for business process flexibility.

Research limitations/implications

The authors defined six different distances between business process models, which are summarized in the definition of total process distance. However, changes in one perspective may lead to changes in other perspectives. For instance, adding a new activity may lead to adding a new actor.

Practical implications

The results of this study would help companies to obtain important information about their processes and to compare the desired level of flexibility with their actual process flexibility.

Originality/value

This study is probably the first flexibility-measurement approach which incorporates features for capturing changes affecting the functional, operational, informational, organizational, and behavioral perspectives as well as elements related to approaches enhancing flexibility.

Details

Business Process Management Journal, vol. 24 no. 4
Type: Research Article
ISSN: 1463-7154

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