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1 – 10 of 435
Article
Publication date: 1 March 1992

P.K. GHOSH, A. SARKAR and V.M.K. SASTRI

Natural convection in a square cavity with a centrally located partition is considered. While one of the side walls is fully active, the other is partly insulated…

Abstract

Natural convection in a square cavity with a centrally located partition is considered. While one of the side walls is fully active, the other is partly insulated. Numerical simulation, based on the finite element method, has been carried out for different lengths of the active surface. The results have been compared with the cases when the cavity is without partition as well as the case of a partitioned cavity with fully active side walls.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 2 no. 3
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 16 January 2020

Mokhtar Ferhi and Ridha Djebali

This paper aims to perform the lattice Boltzmann simulation of conjugate natural convection heat transfer, heat flow visualization via heatlines approach and entropy…

Abstract

Purpose

This paper aims to perform the lattice Boltzmann simulation of conjugate natural convection heat transfer, heat flow visualization via heatlines approach and entropy generation in a partitioned medium filled with Ag-MgO (15-85%)/water.

Design/methodology/approach

The lattice Boltzmann method (LBM) is used to predict the dynamic and thermal behaviors. Experimental correlations for dynamic viscosity and thermal conductivity versus solid volume fraction are used. The study is conducted for the ranges of Rayleigh number 103 ≤ Ra ≤ 106, the partitioner thickness 0.01 ≤ δ ≤ 0.9, its position 0.15 ≤ Xs ≤ 0.85 and the hybrid nano-suspensions volume fraction 0% ≤ ϕ ≤ 2%.

Findings

The effects of varying of controlling parameters on the convective flow patterns, temperature contours, heat transfers, the heatlines and the entropy generation are presented. It has been found that the maximum rate of heat transfer enhancement occurs for low Ra numbers (103) and is close to 13.52%. The solid thickness d and its horizontal position Xs have a substantial influence on the heat transfer rate, flow structure, heatline, total entropy generation and Bejan number. Besides, the maximum heat transfer is detected for high Ra and δ ≈ 1 and the percentage of augmentation is equal to 65.55% for ϕ = 2%. According to the horizontal position, the heat transfer remains invariant for Ra = 103 and takes a maximum value near the active walls for Ra ≥ 104. The total entropy generation increases with Ra and decreases with ϕ for Ra = 106. The increase of ϕ from 0 to 2% leads to a reduction in close to 40.76%. For this value of Ra, the entropy is the maximum for δ = 0.4 and Xs = 0.35 and Xs = 0.65%. Moreover, as the Ra increases the Bejan number undergoes a decrease. The Bejan number is the maximum for Ra = 103 independently to δ and Xs. The superior thermal performance manifests at low Ra and high value of δ independently to the positions of the conducting body.

Originality/value

The originality of this paper is to analyze the hybrid nano-additive effects on the two-dimensional conjugate natural convection in a partitioned medium using the LBM. The experimental correlations used for the effective thermal conductivity and dynamic viscosity give credibility to our study. Different approaches such as heatlines and entropy generation are used.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 10
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 27 May 2014

M. Sathiyamoorthy and Ali J. Chamkha

– The purpose of this paper is to optimize the heat transfer rate in square cavity by attaching fin at the bottom wall.

Abstract

Purpose

The purpose of this paper is to optimize the heat transfer rate in square cavity by attaching fin at the bottom wall.

Design/methodology/approach

The problem is formulated and solved using finite element method. Accuracy of the method is validated by comparisons with previously published work.

Findings

It was found that attaching fin reduces heat transfer rate in the cavity.

Originality/value

Although the problem is not very original it is important in that many applications have heating on adjacent walls.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 24 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 November 1998

A. Mezrhab and L. Bchir

The heat transfer by radiation and natural convection in a two‐dimensional, air‐filled square enclosure with a vertical partition of finite thickness and varying height…

Abstract

The heat transfer by radiation and natural convection in a two‐dimensional, air‐filled square enclosure with a vertical partition of finite thickness and varying height was investigated numerically in the laminar regime. The horizontal end walls are assumed to be adiabatic, and the vertical walls are at different temperatures. Calculations are made by using a finite volume method and an efficient numerical procedure is introduced for calculating the view factors, with shadow effects included. The results indicate that the partition does not significantly modify the heat transfer rate through the cavity, especially at high Rayleigh numbers, provided that its height is less than 90 per cent of the cavity height. The effects of radiation on the velocity and the temperature fields and the overall heat transfer rates as a function of the widths of the vents, solid/fluid conductivity ratio and Rayleigh number are documented.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 8 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 19 October 2018

H. Zargartalebi, M. Ghalambaz, A. Chamkha, Ioan Pop and Amir Sanati Nezhad

A numerical model of an unsteady laminar free convection flow and heat transfer is studied in a cavity that comprises a vertical flexible thin partition.

Abstract

Purpose

A numerical model of an unsteady laminar free convection flow and heat transfer is studied in a cavity that comprises a vertical flexible thin partition.

Design/methodology/approach

The left and right vertical boundaries are isothermal, while the horizontal boundaries are insulated. Moreover, the thin partition, placed in the geometric centerline of the enclosure, is considered to be hyper elastic and diathermal. Galerkin finite-element methods, the system of partial differential equations along with the appropriate boundary conditions are transformed to a weak form through the fluid-structure interaction and solved numerically.

Findings

The heat transfer characteristics of the enclosure with rigid and flexible partitions are compared. The effect of Rayleigh number and Young’s modulus on the maximum nondimensional stress and final deformed shape of the membrane is addressed.

Originality/value

Incorporation of vertical thin flexible membrane in middle of a cavity has numerous industrial applications, and it could noticeably affect the heat and mass transfer in the enclosure.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 9
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 13 June 2019

Mohammad Ghalambaz, S.A.M. Mehryan, Muneer A. Ismael, Ali Chamkha and D. Wen

The purpose of the present paper is to model a cavity, which is equally divided vertically by a thin, flexible membrane. The membranes are inevitable components of many…

Abstract

Purpose

The purpose of the present paper is to model a cavity, which is equally divided vertically by a thin, flexible membrane. The membranes are inevitable components of many engineering devices such as distillation systems and fuel cells. In the present study, a cavity which is equally divided vertically by a thin, flexible membrane is model using the fluid–structure interaction (FSI) associated with a moving grid approach.

Design/methodology/approach

The cavity is differentially heated by a sinusoidal time-varying temperature on the left vertical wall, while the right vertical wall is cooled isothermally. There is no thermal diffusion from the upper and lower boundaries. The finite-element Galerkin technique with the aid of an arbitrary Lagrangian–Eulerian procedure is followed in the numerical procedure. The governing equations are transformed into non-dimensional forms to generalize the solution.

Findings

The effects of four pertinent parameters are investigated, i.e., Rayleigh number (104 = Ra = 107), elasticity modulus (5 × 1012 = ET = 1016), Prandtl number (0.7 = Pr = 200) and temperature oscillation frequency (2p = f = 240p). The outcomes show that the temperature frequency does not induce a notable effect on the mean values of the Nusselt number and the deformation of the flexible membrane. The convective heat transfer and the stretching of the thin, flexible membrane become higher with a fluid of a higher Prandtl number or with a partition of a lower elasticity modulus.

Originality/value

The authors believe that the modeling of natural convection and heat transfer in a cavity with the deformable membrane and oscillating wall heating is a new subject and the results have not been published elsewhere.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 5 May 2015

Da-Wei Zhang and He Yang

The purpose of this paper is to explore the basic loading state in local loading forming process of large-sized complicated rib-web component, which is important for…

Abstract

Purpose

The purpose of this paper is to explore the basic loading state in local loading forming process of large-sized complicated rib-web component, which is important for understanding process characteristic, controlling metal flow and designing preformed geometry of the local loading forming process. Moreover the analytical models for different loading states are established to quickly predict the metal flow.

Design/methodology/approach

Through analysis of geometric characteristic of large-sized complicated rib-web component and the deformation characteristic on planes of metal flow by local loading method, a representative cross-section is put forward and designed, which could reflect the local loading forming characteristics of large-sized complicated rib-web component. Finite element method (FEM) is used to analyze the stress and metal flow, and the analytical models of metal flow are established by using slab method (SM).

Findings

Three local loading states and one whole loading state are found in the local loading forming process of representative cross-section. Further, four loading states also exist in local loading forming process of large-sized complicated rib-web components. With the metal distribution in the process, some local loading states may turn into whole loading state. For the representative cross-section, the relative error of metal distribution between SM and FEM results is less than 15 per cent, and the relative error of metal in the rib cavity between SM and FEM results is less than 10 per cent.

Originality/value

Metal flow can be controlled by adjusting the loading states in the process. According to the metal flow laws in different loading states, a simple unequal-thickness billet can be designed to achieve initial metal distribution, and then, the secondary metal distribution can be achieved in the process.

Details

Aircraft Engineering and Aerospace Technology: An International Journal, vol. 87 no. 3
Type: Research Article
ISSN: 0002-2667

Keywords

Article
Publication date: 14 December 2020

Saeid Hejri, Daryoush Kamali and Emad Hasani Malekshah

The purpose of this study is analysis of the natural convection and entropy production in a two-dimensional section of the considered heat exchanger. For this purpose, the…

Abstract

Purpose

The purpose of this study is analysis of the natural convection and entropy production in a two-dimensional section of the considered heat exchanger. For this purpose, the lattice Boltzmann method which is equipped with Bhatnagar–Gross–Krook model is used. This model proposes a significant accurate prediction for thermal and hydro-dynamical behaviors over free convection phenomenon. The heat exchanger is filled with Fe2O3-water nanofluid. To improve the accuracy of prediction, it is neglected to use the theoretical models for properties of nanofluid. At this end, some experimental observations are conducted, and the required rheological and thermal properties of nanofluid are measured based on laboratory work..

Design/methodology/approach

The present work focuses on the influence of different factors on the thermal behaviors and entropy production of a heat exchanger. The heat exchanger is consisted by an inner tube, an outer tube and some fins which are implanted at the surface of inner tube.

Findings

The effects of various factors like structure of inner fins, nanoparticle concentration and Rayleigh number over the heat transfer rate, local and volumetric entropy production, Bejan number, flow configuration and temperature distributions are provided.

Originality/value

The originality of this work is using a new-developed numerical method for treating natural convection and experimental measurements for thermal and rheological properties of nanofluid.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 9 November 2015

Francesco Pomponi and Poorang A. E. Piroozfar

– The purpose of this paper is to establish how UK offices and double skin façade (DSF) technologies can be best matched for refurbishment purposes.

Abstract

Purpose

The purpose of this paper is to establish how UK offices and double skin façade (DSF) technologies can be best matched for refurbishment purposes.

Design/methodology/approach

This research uses a mixed methodology including primary and secondary data collection, analysis and interpolation through document analysis, comprehensive critical literature review, and case study approach.

Findings

In total, 22 benchmarks have been developed to represent 75 per cent of the existing office stock in the UK. Through a comparison with 36 case studies of European buildings refurbished with DSFs, two benchmarks showed to be most suitable for a DSF refurbishment and most appropriate configurations for a successful DSF refurbishment have been identified. Findings have been also checked against a large sample of DSF buildings in the UK.

Research limitations/implications

The benchmarks delivered in this study can be developed further into parametric models, where variations can be obtained by changing the parameters provided. A follow-up study can be designed to help define the exact share of existing stock represented by each benchmark and to foster research where a more typological or statistical approach might be intended.

Practical implications

Findings from this research can be of practical use to academics and practitioners alike involved in research related to office refurbishments, DSFs, and the UK existing office stock. The design for this research can also be adapted to similar studies on its own or further developed to suit different contexts.

Social implications

Improvements to existing buildings can preserve established communities, with a clear social advantage.

Originality/value

This paper represents the first attempt to systemically shed light on how existing UK offices and DSF technologies can be best matched in refurbishments. The benchmarks developed, the DSF case studies, and guidelines for suitable DSF technologies in UK office refurbishments represent the original contribution of this research.

Article
Publication date: 14 June 2021

Pascalin Tiam Kapen, Cédric Gervais Njingang Ketchate, DIdier Fokwa and Ghislain Tchuen

This paper aims to investigate a linear and temporal stability analysis of hybrid nanofluid flow between two parallel plates filled with a porous medium and whose lower…

Abstract

Purpose

This paper aims to investigate a linear and temporal stability analysis of hybrid nanofluid flow between two parallel plates filled with a porous medium and whose lower plate is fixed and the upper plate animated by a uniform rectilinear motion.

Design/methodology/approach

The nanofluid is composed of water as a regular fluid, silver (Ag) and alumina (Al2O3) as nanoparticles. The mathematical model takes into account other effects such as the magnetic field and the aspiration (injection/suction). Under the assumption of a low magnetic Reynolds number, a modified Orr–Sommerfeld-type eigenvalue differential equation governing flow stability was derived and solved numerically by Chebyshev’s spectral collocation method. The effects of parameters such as volume fraction, Darcy number, injection/suction Reynolds number, Hartmann number were analyzed.

Findings

It was found the following: the Darcy number affects the stability of the flow, the injection/suction Reynolds number has a negligible effect, the volume fraction damped disturbances and the magnetic field plays a very important role in enlarging the area of flow stability.

Originality/value

The originality of this work resides in the linear and temporal stability analysis of hydromagnetic Couette flow for hybrid nanofluid through porous media with small suction and injection effects.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 32 no. 2
Type: Research Article
ISSN: 0961-5539

Keywords

1 – 10 of 435