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Article

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

The gas assisted Iaser heating of engineering surfaces finds wide application in industry. Numerical simulation of the heating process may considerably reduce the cost…

Abstract

The gas assisted Iaser heating of engineering surfaces finds wide application in industry. Numerical simulation of the heating process may considerably reduce the cost spent on experimentation. In the present study, 2‐dimensional axisymmetric flow and energy equations are solved numerically using a control volume approach for the case of a gas assisted laser heating of steel surfaces. Various turbulence models including standard kε, kε YAP, low Reynolds number kε and RSTM models are tested. The low Reynolds number kε model is selected to account for the turbulence. Variable properties of both solid and gas are taken into account during the simulation. Air is considered as an assisting gas impinging the workpiece surface coaxially with the laser beam. In order to validate the presently considered methodology, the study is extended to include comparison of present predictions with analytical solution for the case available in the literature. It is found that the assisting gas jet has some influence on the temperature profiles. This effect is minimum at the irradiated spot center and it amplifies considerably in the gas side. In addition, account for the variable properties results in lower surface temperatures as compared to the constant properties case.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 12 no. 2
Type: Research Article
ISSN: 0961-5539

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Article

Nirmal Kumar Manna, Nirmalendu Biswas and Pallab Sinha Mahapatra

This study aims to enhance natural convection heat transfer for a porous thermal cavity. Multi-frequency sinusoidal heating is applied at the bottom of a porous square…

Abstract

Purpose

This study aims to enhance natural convection heat transfer for a porous thermal cavity. Multi-frequency sinusoidal heating is applied at the bottom of a porous square cavity, considering top wall adiabatic and cooling through the sidewalls. The different frequencies, amplitudes and phase angles of sinusoidal heating are investigated to understand their major impacts on the heat transfer characteristics.

Design/methodology/approach

The finite volume method is used to solve the governing equations in a two-dimensional cavity, considering incompressible laminar flow, Boussinesq approximation and Brinkman–Forchheimer–Darcy model. The mean-temperature constraint is applied for enhancement analysis.

Findings

The multi-frequency heating can markedly enhance natural convection heat transfer even in the presence of porous medium (enhancement up to ∼74 per cent). Only the positive phase angle offers heat transfer enhancement consistently in all frequencies (studied).

Research limitations/implications

The present research idea can usefully be extended to other multi-physical areas (nanofluids, magneto-hydrodynamics, etc.).

Practical implications

The findings are useful for devices working on natural convection.

Originality/value

The enhancement using multi-frequency heating is estimated under different parametric conditions. The effect of different frequencies of sinusoidal heating, along with the uniform heating, is collectively discussed from the fundamental point of view using the average and local Nusselt number, thermal and hydrodynamic boundary layers and heatlines.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 10
Type: Research Article
ISSN: 0961-5539

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Article

Noureddine Abouricha, Mustapha El Alami and Khalid Souhar

The purpose of this paper is to model the convective flows in a room equipped by a glass door and a heated floor of length l = 0.8 × H and submitted to a sinusoidal…

Abstract

Purpose

The purpose of this paper is to model the convective flows in a room equipped by a glass door and a heated floor of length l = 0.8 × H and submitted to a sinusoidal temperature profile and mono alternative temperature profile.

Design/methodology/approach

The paper opts for a numerical study of convective flows in a large scale cavity using the Lattice Boltzmann Method (LBM) by considering a two dimensions (2D) square cavity of side H and filled by air (Pr = 0.71). All the vertical walls, the ceiling and the rest of the floor are thermally insulated, the hot portion of length l = 0.8×H is heated with two imposed temperature profiles of amplitude values 0.2 ≤  a  ≤ 0.6 and for two different periods ζ = ζ0 and ζ = 0.4×ζ0. One of the vertical walls has a cold portion θc = 0 that represents the glass door.

Findings

A systematic study of the flow structure and heat transfer is carried out considering principal control parameters: amplitude “a” and period ζ for Rayleigh number Ra = 108. Effects of these parameters on results are presented in terms of isotherms, streamlines, profiles of velocities, temperature in the cavity, global and local Nusselt number. It has been found that an increase in amplitude or period increases the amplitude of the temperature in the core of cavity. The Nusselt number increases when the amplitude “a” of the imposed temperature increases, but this later is not affected by variation of the period.

Originality/value

The authors used LBM to simulate the convective flows in a cavity at high Ra, heated from below by tow imposed temperature profiles. Indeed, they simulate a local equipped by a solar water heater (SWH). The floor is subjected to a periodic heating: Sinusoidal heating (Case 1) for which the temperature varies sinusoidally (SWH without a supplement), and mono alternation heating (Case 2), the temperature evolves like a redressed signal (SWH with a supplement). The considered method has been successfully validated and compared with the previous work. The study has been conducted using several control parameters such as the signal amplitude and period in the case of turbulent convection. This allowed us to obtain a considerable set of results that can be used for engineering.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 5
Type: Research Article
ISSN: 0961-5539

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Article

Himanshu Upreti and Manoj Kumar

The purpose of this paper is to examine the effect of non-linear thermal radiation, Joule heating and viscous dissipation on the mixed convection boundary layer flow of…

Abstract

Purpose

The purpose of this paper is to examine the effect of non-linear thermal radiation, Joule heating and viscous dissipation on the mixed convection boundary layer flow of MHD nanofluid flow over a thin moving needle.

Design/methodology/approach

The equations directing the flow are reduced into ODEs by implementing similarity transformation. The Runge–Kutta–Fehlberg method with a shooting technique was implemented.

Findings

Numerical outcomes for the coefficient of skin friction and the rate of heat transfer are tabulated and discussed. Also, the boundary layer thicknesses for flow and temperature fields are addressed with the aid of graphs.

Originality/value

Till now, no numerical study investigated the combined influence of Joule heating, non-linear thermal radiation and viscous dissipation on the mixed convective MHD flow of silver-water nanofluid flow past a thin moving needle. The numerical results for existing work are new and their novelty verified by comparing them with the work published earlier.

Details

Multidiscipline Modeling in Materials and Structures, vol. 16 no. 1
Type: Research Article
ISSN: 1573-6105

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Article

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

The purpose of this study is to present the significance of Joule heating, viscous dissipation, magnetic field and slip condition on the boundary layer flow of an…

Abstract

Purpose

The purpose of this study is to present the significance of Joule heating, viscous dissipation, magnetic field and slip condition on the boundary layer flow of an electrically conducting Boussinesq couple-stress fluid induced by an exponentially stretching sheet embedded in a porous medium under the effect of the magnetic field of the variable kind. The heat transfer phenomenon is accounted for under thermal radiation, Joule and viscous dissipation effects.

Design/methodology/approach

The governing nonlinear partial differential equations are transformed to the nonlinear ordinary differential equations (ODEs) by using some appropriate dimensionless variables and then the consequential nonlinear ODEs are solved numerically by making the use of the well-known shooting iteration technique along with the standard fourth-order Runge–Kutta integration scheme. The impact of emerging flow parameters on velocity and temperature profiles, streamlines, local skin friction coefficient and Nusselt number are described comprehensively through graphs and tables.

Findings

Results reveal that the velocity profile is observed to diminish considerably within the boundary layer in the presence of a magnetic field and slip condition. The enhanced radiation parameter is to decline the temperature field. The slip effect is favorable for fluid flow.

Originality/value

Till now, slip effect on Boussinesq couple-stress fluid over an exponentially stretching sheet embedded in a porous medium has not been explored. The present results are validated with the previously published study and found to be highly satisfactory.

Details

Multidiscipline Modeling in Materials and Structures, vol. 16 no. 5
Type: Research Article
ISSN: 1573-6105

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Article

D.K. Flattery

Infra‐red ovens and furnaces have been in use in the microelectronics industry for a long time, but recent design advancements and process developments have provided the…

Abstract

Infra‐red ovens and furnaces have been in use in the microelectronics industry for a long time, but recent design advancements and process developments have provided the precise furnace control dictated by surface mount technology. This paper addresses the process implemented by state‐of‐the‐art infra‐red equipment and the impact which that technology has on the surface mount industry. The temperature cycles that current infra‐red equipment utilises to reflow surface mount devices differ from the competing technologies in several distinct areas. Infra‐red equipment provides controlled preheat rates in the critical initial heating stages, followed by temperature equilibration and final reflow. The radiative and other processes involved in the preheat of product are discussed, with particular attention paid to the removal of volatile organics from the solder paste and the stress induced on all elements of the assembly. The control of temperature uniformity is discussed, and the effects of geometry, thermal complexity, and absorptivity are examined with reference to heat transfer theory. The ability of infra‐red equipment to provide close control of the ambient atmosphere during reflow cycles is outlined. Control of the atmosphere can benefit process control, reliability, and cosmetics. Inert atmospheres, such as pure nitrogen, can provide faster processing, more rapid and easier cleaning of fluxes, better solderability of secondary joints, and better cosmetics for the assembly. The inclusion of small amounts of hydrogen in the ambient can induce changes in the contact angle of the flux to polymers and ceramics, providing benefits for other process considerations, such as component shifting, solder balling and flux removal.

Details

Microelectronics International, vol. 3 no. 1
Type: Research Article
ISSN: 1356-5362

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Article

Don Liu, Hui-Li Han and Yong-Lai Zheng

This paper aims to present a high-order algorithm implemented with the modal spectral element method and simulations of three-dimensional thermal convective flows by using…

Abstract

Purpose

This paper aims to present a high-order algorithm implemented with the modal spectral element method and simulations of three-dimensional thermal convective flows by using the full viscous dissipation function in the energy equation. Three benchmark problems were solved to validate the algorithm with exact or theoretical solutions. The heated rotating sphere at different temperatures inside a cold planar Poiseuille flow was simulated parametrically at varied angular velocities with positive and negative rotations.

Design/methodology/approach

The fourth-order stiffly stable schemes were implemented and tested for time integration. To provide the hp-refinement and spatial resolution enhancement, a modal spectral element method using hierarchical basis functions was used to solve governing equations in a three-dimensional space.

Findings

It was found that the direction of rotation of the heated sphere has totally different effects on drag, lateral force and torque evaluated on surfaces of the sphere and walls. It was further concluded that the angular velocity of the heated sphere has more influence on the wall normal velocity gradient than on the wall normal temperature gradients and therefore, more influence on the viscous dissipation than on the thermal dissipation.

Research limitations/implications

This paper concerns incompressible fluid flow at constant properties with up to medium temperature variations in the absence of thermal radiation and ignoring the pressure work.

Practical implications

This paper contributes a viable high-order algorithm in time and space for modeling convective heat transfer involving an internal heated rotating sphere with the effect of viscous heating.

Social implications

Results of this paper could provide reference for related topics such as enhanced heat transfer forced convection involving rotating spheres and viscous thermal effect.

Originality/value

The merits include resolving viscous dissipation and thermal diffusion in stationary and rotating boundary layers with both h- and p-type refinements, visualizing the viscous heating effect with the full viscous dissipation function in the energy equation and modeling the forced advection around a rotating sphere with varied positive and negative angular velocities subject to a shear flow.

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

Muhammad Sohail and Sana Tariq

Thermal and species transport of magneto hydrodynamic Casson liquid over a stretched surface is investigated theoretically in this examination for the three-dimensional…

Abstract

Purpose

Thermal and species transport of magneto hydrodynamic Casson liquid over a stretched surface is investigated theoretically in this examination for the three-dimensional boundary layer flow of a yield exhibiting material. The phenomenon of heat and species relocation is based upon modified Fourier and Fick’s laws that involves the relaxation times for the transportation of heat and mass. Conservation laws are modeled under boundary layer analysis in the Cartesian coordinates system. The purpose of this paper is to find the influence of different emerging parameters on fluid velocity, temperature and transport of species.

Design/methodology/approach

Reconstructed nonlinear boundary layer ordinary differential equations are analyzed through eigenvalues and eigenvectors. Due to the complexity and non-existence of the exact solution of the transformed equations, a convergent series solution by the homotopy algorithm is also derived. The reliability of the applied scheme is presented by comparing the obtained results with the previous findings.

Findings

Physical quantities of interest are displayed through graphs and tables and discussed for sundry variables. It is discerned that higher magnetic influence slows down fluid motion, whereas concentration and temperature profiles upsurge. Reliability of the recommended scheme is monitored by comparing the obtained results for the dimensionless stress as a limiting case of previous findings and an excellent agreement is observed. Higher values of Schmidt number reduce the concentration profile, whereas mounting the values of Prandtl number reduces the dimensionless temperature field. Moreover, heat and species transfer rates increase by mounting the values of thermal and concentration relaxation times.

Originality/value

The phenomenon of heat and species relocation is based upon modified Fourier and Fick’s laws which involves the relaxation times for the transportation of heat and mass. Conservation laws are modeled under boundary layer analysis in the Cartesian coordinates system.

Details

Multidiscipline Modeling in Materials and Structures, vol. 16 no. 3
Type: Research Article
ISSN: 1573-6105

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Article

Li Zhou and Calum G. Turvey

– The purpose of this paper is to investigate the linkages between climate change, income dynamics and nutrition intake in rural China.

Abstract

Purpose

The purpose of this paper is to investigate the linkages between climate change, income dynamics and nutrition intake in rural China.

Design/methodology/approach

Using a system of simultaneous equations in a three-stage least squares model instrumented with carbohydrates, fats, proteins and farm income the authors found generally that the greatest impact on nutrition would be from changes in temperature.

Findings

The authors do not find that modest changes in precipitation affect nutrient intake, but extreme events such as drought do. Furthermore, the authors found a strong income effect and this income effect is opposite the heating effect. This may suggest that large swings in nutrient intake brought about by climate change may be countermanded by equivalent increases in income. The authors also found that in terms of general measures of elasticity that market effects, especially in the price of meats, can impact carbohydrate, fat and protein intake as much as global warming.

Originality/value

The authors believe that three aspects of this manuscript will make it interesting. First, in the short term, poorer households would be the most vulnerable and sensitive to climate change. However, in the long term, all households in rural China appear able to deal with changing climatic conditions through adaptation. Second, the authors do not find evidences to prove the existence of a poverty nutrition trap in rural China. Third, the results also indicate that, the nutrition intake of households in rural China is more prone to gradual changes, rather than extreme events.

Details

China Agricultural Economic Review, vol. 7 no. 2
Type: Research Article
ISSN: 1756-137X

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Article

Ammar Mushtaq, M. Mustafa, T. Hayat and A. Alsaedi

– The purpose of this paper is to consider a laminar two-dimensional incompressible flow of an electrically conducting fluid over a moving flat plate with a parallel free stream.

Abstract

Purpose

The purpose of this paper is to consider a laminar two-dimensional incompressible flow of an electrically conducting fluid over a moving flat plate with a parallel free stream.

Design/methodology/approach

The governing equations are first reduced into self-similar forms and then solved for the numerical solutions by shooting method.

Findings

The results are compared with the available studies is some special cases and found in excellent agreement. It is noticed that an increase in the magnetic field strength leads to a decrease in the momentum boundary layer thickness and enhancement in the rate of heat transfer from the plate. It is also observed that temperature and heat transfer from the plate increase when radiation effect is strengthened.

Originality/value

A recently proposed idea of nonlinear radiative heat transfer with Joule heating and viscous dissipation effects is analyzed.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

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