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Article
Publication date: 2 February 2015

M.S. Abdul Aziz, M.Z. Abdullah and C.Y. Khor

This paper aims to investigate the thermal fluid–structure interactions (FSIs) of printed circuit boards (PCBs) at different component configurations during the wave…

Abstract

Purpose

This paper aims to investigate the thermal fluid–structure interactions (FSIs) of printed circuit boards (PCBs) at different component configurations during the wave soldering process and experimental validation.

Design/methodology/approach

The thermally induced displacement and stress on the PCB and its components are the foci of this study. Finite volume solver FLUENT and finite element solver ABAQUS, coupled with a mesh-based parallel code coupling interface, were utilized to perform the analysis. A sound card PCB (138 × 85 × 1.5 mm3), consisting of a transistor, diode, capacitor, connector and integrated circuit package, was built and meshed by using computational fluid dynamics pre-processing software. The volume of fluid technique with the second-order upwind scheme was applied to track the molten solder. C language was utilized to write the user-defined functions of the thermal profile. The structural solver analyzed the temperature distribution, displacement and stress of the PCB and its components. The predicted temperature was validated by the experimental results.

Findings

Different PCB component configurations resulted in different temperature distributions, thermally induced stresses and displacements to the PCB and its components. Results show that PCB component configurations significantly influence the PCB and yield unfavorable deformation and stress.

Practical implications

This study provides PCB designers with a profound understanding of the thermal FSI phenomenon of the process control during wave soldering in the microelectronics industry.

Originality/value

This study provides useful guidelines and references by extending the understanding on the thermal FSI behavior of molten solder for PCBs. This study also explores the behaviors and influences of PCB components at different configurations during the wave soldering process.

Details

Soldering & Surface Mount Technology, vol. 27 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 15 May 2009

Mohamed A. Antar and Maged A.I. El‐Shaarawi

The purpose of this paper is to investigate the problem of entropy generation around a spinning/non‐spinning solid sphere subjected to uniform heat flux boundary condition…

Abstract

Purpose

The purpose of this paper is to investigate the problem of entropy generation around a spinning/non‐spinning solid sphere subjected to uniform heat flux boundary condition in the forced‐convection regime.

Design/methodology/approach

The governing continuity, momentum, energy and entropy generation equations are numerically solved for a wide range of the controlling parameters; Reynolds number and the dimensionless spin number.

Findings

The dimensionless overall total entropy generation increases with the dimensionless spin number. The effect of increasing the spin number on the fluid‐friction component of entropy generation is more significant compared to its effect on heat transfer entropy generation.

Research limitations/implications

Since the boundary‐layer analysis is used, the flow is presented up to only the point of external flow separation.

Practical implications

Entropy generation analysis can be used to evaluate the design of many heat transfer systems and suggest design improvements.

Originality/value

A review in the open literature indicated that no study is available for the entropy generation in the unconfined flow case about a spinning sphere.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 19 no. 3/4
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 27 September 2011

Reimund Neugebauer, Bernhard Müller, Mathias Gebauer and Thomas Töppel

The purpose of this paper is to show the innovative approach of manufacturing filigree and highly complex components by means of laser beam melting.

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Abstract

Purpose

The purpose of this paper is to show the innovative approach of manufacturing filigree and highly complex components by means of laser beam melting.

Design/methodology/approach

The paper describes the unique geometric freedom of the laser beam melting technology and its possibility of quick, tool‐less production of complex components allow the manufacturing of functionally superior components in a short time.

Findings

Principally concludes the following: additive manufacturing proved to give superior properties to the component compared to conventional manufacturing methods.

Originality/value

This study provides context for the development and manufacturing of an individual heattransfer component for an electric‐driven formula race car.

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Article
Publication date: 6 January 2012

Rafid Al‐Khoury

The purpose of this paper is to introduce a spectral model capable of simulating fully transient conductive‐convective heat transfer processes in an axially‐symmetric…

Abstract

Purpose

The purpose of this paper is to introduce a spectral model capable of simulating fully transient conductive‐convective heat transfer processes in an axially‐symmetric shallow geothermal system consisting of a borehole heat exchanger embedded in a soil mass.

Design/methodology/approach

The proposed model combines the exactness of the analytical methods with important extent of generality in describing the geometry and boundary conditions of the numerical methods. It calculates the temperature distribution in all involved borehole heat exchanger components and the surrounding soil mass using the discrete Fourier transform, for the time domain, and the Fourier‐Bessel series, for the spatial domain.

Findings

The paper calculates the temperature distribution in all involved borehole heat exchanger components and the surrounding soil mass in a robust and computationally very efficient procedures. Analysis which might take long time in a work station, if use is made of standard numerical procedures, takes only 1 second in an Intel PC with the proposed model.

Practical implications

The model is capable of simulating fully transient heat transfer in a shallow geothermal system subjected to short and long‐term time varying boundary conditions. The CPU time for calculating temperature distributions in all involved components; pipe‐in, pipe‐out, grout, and soil, using 2048 FFT samples, for the time domain, and 100 Fourier‐Bessel series samples, for the spatial domain, was in the order of 1 second in an Intel PC. The accuracy and computational efficiency of the model makes it, if elaborated, vital for engineering practice.

Originality/value

The proposed model is original and generic. The idea behind it is new and has not been utilized in this field of application. The model can be extended easily to include other types of borehole heat exchangers embedded in multi‐layer systems.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 22 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 1 August 1995

Himadri Chattopadhyay and Sukanta K. Dash

The conception of a heat function, just like the stream function used ina laminar two dimensional incompressible flow field visualization, has beenintroduced to visualize…

Abstract

The conception of a heat function, just like the stream function used in a laminar two dimensional incompressible flow field visualization, has been introduced to visualize the convective heat transfer or the flow of energy around a sphere when the sphere is either being cooled or heated by a stream of fluid flowing around it. The heat function is developed in a spherical polar coordinate and is used to generate the heat lines around the sphere. The heat lines essentially show the magnitude and direction of energy transfer around the sphere with and without the existence of a finite radial velocity at the surface. The steady state hydrodynamic field around the sphere is numerically obtained up to a maximum Reynolds number of 100 and the corresponding thermal field has been obtained by solving the steady state energy equation. The field properties thus obtained are utilized to form the heat function, which becomes an effective tool for visualization of convective heat transfer.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 5 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 10 December 2018

A.A. Avramenko, N.P. Dmitrenko, I.V. Shevchuk, A.I. Tyrinov and V.I. Shevchuk

The paper aims to consider heat transfer in incompressible flow in a rotating flat microchannel with allowance for boundary slip conditions of the first and second order…

Abstract

Purpose

The paper aims to consider heat transfer in incompressible flow in a rotating flat microchannel with allowance for boundary slip conditions of the first and second order. The novelty of the paper encompasses analytical and numerical solutions of the problem, with the latter based on the lattice Boltzmann method (LBM). The analytical solution of the problem includes relations for the velocity and temperature profiles and for the Nusselt number depending on the rotation rate of the microchannel and slip velocity. It was demonstrated that the velocity profiles at high rotation rates transform from parabolic to M-shaped with a minimum at the channel axis. The temperature profiles tend to become uniform (i.e. almost constant). An increase in the channel rotation rate contributes to the increase in the Nusselt number. An increase in the Prandtl number causes a similar effect. The trend caused by the effect of the second-order slip boundary conditions depends on the closure hypothesis. It is shown that heat transfer in a flat microchannel can be successfully modeled using the LBM methodology, which takes into account the second-order boundary conditions.

Design/methodology/approach

The paper is based on the comparisons of an analytical solution and a numerical solution, which employs the lattice Boltzmann method. Both mathematical approaches used the first-order and second-order slip boundary conditions. The results obtained using both methods agree well with each other.

Findings

The analytical solution of the problem includes relations for the velocity and temperature profiles and for the Nusselt number depending on the rotation rate of the microchannel and slip velocity. It was demonstrated that the velocity profiles at high rotation rates transform from parabolic to M-shaped with a minimum at the channel axis. The temperature profiles tend to become uniform (i.e. almost constant). The increase in the channel rotation rate contributes to the increase in the Nusselt number. An increase in the Prandtl number causes the similar effect. The trend caused by the effect of the second-order slip boundary conditions depends on the closure hypothesis. It is shown that heat transfer in a flat microchannel can be successfully modeled using the LBM methodology, which considers the second-order boundary conditions.

Originality/value

The novelty of the paper encompasses analytical and numerical solutions of the problem, whereas the latter are based on the LBM.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 5
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 21 September 2010

Rafid Al‐Khoury

This paper aims to present a framework for deriving analytical and semi‐numerical models for coupled conductive‐convective heat transfer processes in a borehole heat

Abstract

Purpose

This paper aims to present a framework for deriving analytical and semi‐numerical models for coupled conductive‐convective heat transfer processes in a borehole heat exchanger subjected to general initial and boundary conditions.

Design/methodology/approach

The discrete Fourier transform and the spectral element method have been utilized for deriving two spectral models for a single U‐tube borehole heat exchanger in contact with a soil mass.

Findings

Verification and numerical examples have shown that the developed models are accurate and computationally very efficient. It is illustrated that one spectral element is capable of producing results which are more accurate than those produced by 200 finite elements.

Practical implications

The gained computational efficiency and accuracy will boost considerably the possibilities for more insight into geothermal analysis, which will improve the procedure for designing competitive energy extraction systems.

Originality/value

The models are capable of calculating exactly the temperature distribution in all involved borehole heat exchanger components and their thermal interactions.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 20 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 3 January 2017

Nhat Minh Nguyen, Eric Monier-Vinard, Najib Laraqi, Valentin Bissuel and Olivier Daniel

The purpose of this paper is to supply an analytical steady-state solution to the heat transfer equation permitting to fast design investigation. The capability to…

Abstract

Purpose

The purpose of this paper is to supply an analytical steady-state solution to the heat transfer equation permitting to fast design investigation. The capability to efficiently transfer the heat away from high-powered electronic devices is a ceaseless challenge. More than ever, the aluminium or copper heat spreaders seem less suitable for maintaining the component sensitive temperature below manufacturer operating limits. Emerging materials, such as annealed pyrolytic graphite (APG), have proposed a new alternative to conventional solid conduction without the gravity dependence of a heat-pipe solution.

Design/methodology/approach

An APG material is typically sandwiched between a pair of aluminium sheets to compose a robust graphite-based structure. The thermal behaviour of that stacked structure and the effect of the sensitivity of the design parameters on the effective thermal performances is not well known. The ultrahigh thermal conductivity of the APG core is restricted to in-plane conduction and can be 200 times higher than its through-the-thickness conductivity. So, a lower-than-anticipated cross-plane thermal conductivity or a higher-than-anticipated interlayer thermal resistance will compromise the component heat transfer to a cold structure. To analyse the sensitivity of these parameters, an analytical model for a multi-layered structure based on the Fourier series and the superposition principle was developed, which allows predicting the temperature distribution over an APG flat-plate depending on two interlayer thermal resistances.

Findings

The current work confirms that the in-plane thermal conductivity of APG is among the highest of any conduction material commonly used in electronic cooling. The analysed case reveals that an effective thermal conductivity twice as higher than copper can be expected for a thick APG sheet. The relevance of the developed analytical approach was compared to numerical simulations and experiments for a set of boundary conditions. The comparison shows a high agreement between both calculations to predict the centroid and average temperatures of the heating sources. Further, a method dedicated to the practical characterization of the effective thermal conductivity of an APG heat-spreader is promoted.

Research limitations/implications

The interlayer thermal resistances act as dissipation bottlenecks which magnify the performance discrepancy. The quantification of a realistic value is more than ever mandatory to assess the APG heat-spreader technology.

Practical implications

Conventional heat spreaders seem less suitable for maintaining the component-sensitive temperature below the manufacturer operating limits. Having an in-plane thermal conductivity of 1,600 W.m−1.K−1, the APG material seems to be the next paradigm for solving endless needs of a thermal designer.

Originality/value

This approach is a practical tool to tailor sensitive parameters early to select the right design concept by taking into account potential thermal issues, such as the critical interlayer thermal resistance.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 1
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 4 December 2017

Mahmoud Salari, Mohammad Mehdi Rashidi, Emad Hasani Malekshah and Masoud Hasani Malekshah

Because the local Re numbers, ratio of inertia to viscous forces, are not same at different regions of the enclosures, the present study aims to deal with the influences…

Abstract

Purpose

Because the local Re numbers, ratio of inertia to viscous forces, are not same at different regions of the enclosures, the present study aims to deal with the influences of using the turbulent/transition models on numerical results of the natural convection and flow field within a trapezoidal enclosure.

Design/methodology/approach

The three-dimensional (3D) trapezoidal enclosure with different inclined side walls of 75, 90 and 105 degrees are considered, where the side walls are heated and cooled at Ra = 1.5 × 109 for all cases. The turbulent models of the k-ε-RNG, k- ω-shear-stress transport (SST) and the newly developed transition/turbulent model of Reθ-γ-transition SST are utilized to analyze the fluid flow and heat transfer characteristics within the enclosure and compared their results with validated results.

Findings

Comprehensive comparisons have been carried out for all cases in terms of flow and temperature fields, as well as turbulent quantities, such as turbulent kinetic energy and turbulent viscosity ratio. Furthermore, the velocity and thermal boundary layers have been investigated, and the approximate transition regions for laminar, transitional and turbulent regimes have been determined. Finally, the heat transfer coefficient and skin friction coefficient values have been presented and compared in terms of different turbulent models and configurations. The results show that the transition/turbulence model has better prediction for the flow and heat fields than fully turbulent models, especially for local parameters for all abovementioned governing parameters.

Originality value

The originality of this work is to analyze the 3D turbulent/transitional natural convection with different turbulence/transition models in a trapezoidal enclosure.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 12
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 21 September 2012

Sheri Kurgin, Jean M. Dasch, Daniel L. Simon, Gary C. Barber and Qian Zou

The purpose of this paper is to evaluate the cooling ability of minimum quantity lubrication (MQL) cutting fluid.

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1085

Abstract

Purpose

The purpose of this paper is to evaluate the cooling ability of minimum quantity lubrication (MQL) cutting fluid.

Design/methodology/approach

An experimental system is devised to find the heat transfer coefficient of MQL under simulated reaming conditions. Cooling rate of the specimen is measured with an infrared camera. The effect of air pressure and oil volume on cooling rate is tested. Metal cutting tests are performed to evaluate the effect of heat transfer coefficient on workpiece temperature.

Findings

Convective heat transfer coefficient for MQL increases with increasing air pressure. Oil volume has an indeterminate effect on the heat transfer coefficient; however, it is a dominant factor for controlling temperature during reaming.

Practical implications

The results of the study can provide guidance to optimize the temperature controlling ability of MQL for production.

Originality/value

There is limited information available in literature regarding the heat transfer coefficient of metal working fluids, particularly for MQL. In particular, experiments designed to investigate the effect of air pressure and oil volume on the heat transfer coefficient of the mist have not been previously documented. This information may be used to improve the overall cooling ability of MQL mist, thus increasing its effectiveness at controlling tool wear and maintaining part quality. The other major contribution of this work is to separate the role of the cooling and lubrication for controlling temperature while reaming aluminum. Prior to this study, there has been relatively little research performed for the reaming metal cutting operation, and still less for reaming with MQL. The nature of how metal working fluids control temperature is not fully understood, and this work provides insight as to whether cooling or lubrication plays the dominant role for reaming.

Details

Industrial Lubrication and Tribology, vol. 64 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

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