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Article
Publication date: 22 March 2021

Z.B. Xing, Xingchao Han, Hanbing Ke, Q.G. Zhang, Zhiping Zhang, Huijin Xu and Fuqiang Wang

A combination of highly conductive porous media and nanofluids is an efficient way for improving thermal performance of relevant applications. For precisely predicting the…

Abstract

Purpose

A combination of highly conductive porous media and nanofluids is an efficient way for improving thermal performance of relevant applications. For precisely predicting the flow and thermal transport of nanofluids in porous media, the purpose of this paper is to explore the inter-phase coupling numerical methods.

Design/methodology/approach

Based on the lattice Boltzmann (LB) method, this study combines the convective flow, non-equilibrium thermal transport and phase interactions of nanofluids in porous matrix and proposes a new multi-phase LB model. The micro-scale momentum and heat interactions are especially analyzed for nanoparticles, base fluid and solid matrix. A set of three-phase LB equations for the flow/thermal coupling of base fluid, nanoparticles and solid matrix is established.

Findings

Distributions of nanoparticles, velocities for nanoparticles and the base fluid, temperatures for three phases and interaction forces are analyzed in detail. Influences of parameters on the nanofluid convection in the porous matrix are examined. Thermal resistance of nanofluid convective transport in porous structures are comprehensively discussed with the models of multi-phases. Results show that the Rayleigh number and the Darcy number have significant influences on the convective characteristics. The result with the three-phase model is mildly larger than that with the local thermal non-equilibrium model.

Originality/value

This paper first creates the multi-phase theoretical model for the complex coupling process of nanofluids in porous structures, which is useful for researchers and technicians in fields of thermal science and computational fluid dynamics.

Details

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

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Article
Publication date: 18 September 2007

Wenjun Liu and Bozhi Yang

The goal of this review paper is to provide information on several commonly used thermography techniques in semiconductor and micro‐device industry and research today.

Abstract

Purpose

The goal of this review paper is to provide information on several commonly used thermography techniques in semiconductor and micro‐device industry and research today.

Design/methodology/approach

The temperature imaging or mapping techniques include thin coating methods such as liquid crystal thermography and fluorescence microthermography, contact mechanical methods such as scanning thermal microscopy, and optical techniques such as infrared microscopy and thermoreflectance. Their principles, characteristics and applications are discussed.

Findings

Thermal issues play an important part in optimizing the performance and reliability of high‐frequency and high‐packing density electronic circuits. To improve the performance and reliability of microelectronic devices and also to validate thermal models, accurate knowledge of local temperatures and thermal properties is required.

Originality/value

The paper provides readers, especially technical engineers in industry, a general knowledge of several commonly used thermography techniques in the semiconductor and micro‐device industries.

Details

Sensor Review, vol. 27 no. 4
Type: Research Article
ISSN: 0260-2288

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Article
Publication date: 2 January 2018

Wei Qiang Lim, Mutharasu Devarajan and Shanmugan Subramani

This paper aims to study the influence of the Cu-Al2O3 film-coated Cu substrate as a thermal interface material (TIM) on the thermal and optical behaviour of the…

Abstract

Purpose

This paper aims to study the influence of the Cu-Al2O3 film-coated Cu substrate as a thermal interface material (TIM) on the thermal and optical behaviour of the light-emitting diode (LED) package and the annealing effect on the thermal and optical properties of the films.

Design/methodology/approach

A layer-stacking technique has been used to deposit the Cu-Al2O3 films by means of magnetron sputtering, and the annealing process was conducted on the synthesized films.

Findings

In this paper, it was found that the un-annealed Cu-Al2O3–coated Cu substrate exhibited low value of thermal resistance compared to the bare Cu substrate and to the results of previous works. Also the annealing effect does not have a significant impact on the changes of properties of the films.

Research limitations/implications

It is deduced that the increase of the Cu layer thickness can further improve the thermal properties of the deposited film, which can reduce the thermal resistance of the package in system-level analysis.

Practical implications

The paper suggested that the Cu-Al2O3–coated Cu substrate can be used as alternative TIM for the thermal management of the application of LEDs.

Originality value

In this paper, the Cu substrate has been used as the substrate for the Cu-Al2O3 films, as the Cu substrate has higher thermal conductivity compared to the Al substrate as shown in previous work.

Details

Microelectronics International, vol. 35 no. 1
Type: Research Article
ISSN: 1356-5362

Keywords

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Article
Publication date: 29 April 2014

Yogesh Jaluria

Multiple length and time scales arise in a wide variety of practical and fundamental problems. It is important to obtain accurate and validated numerical simulation…

Abstract

Purpose

Multiple length and time scales arise in a wide variety of practical and fundamental problems. It is important to obtain accurate and validated numerical simulation results, considering the different scales that exist, in order to predict, design and optimize the behavior of practical thermal processes and systems. The purpose of this paper is to present modeling at the different length scales and then addresses the question of coupling the different models to obtain the overall model for the system or process.

Design/methodology/approach

Both numerical and experimental methods to obtain results at the different length scales, particularly at micro and nanoscales, are considered. Even though the paper focusses on length scales, multiple time scales lead to similar concerns and are also considered. The two circumstances considered in detail are multiple length scales in different domains and those in the same domain. These two cases have to be modeled quite differently in order to obtain a model for the overall process or system. The basic considerations involved in such a modeling are discussed. A wide range of thermal processes are considered and the methods that may be used are presented. The models employed must be validated and the accuracy of the simulation results established if the simulation results are to be used for prediction, control and design.

Findings

Of particular interest are concerns like verification and validation, imposition of appropriate boundary conditions, and modeling of complex, multimode transport phenomena in multiple scales. Additional effects such as viscous dissipation, surface tension, buoyancy and rarefaction that could arise and complicate the modeling are discussed. Uncertainties that arise in material properties and in boundary conditions are also important in design and optimization. Large variations in the geometry and coupled multiple regions are also discussed.

Research limitations/implications

The paper is largely focussed on multiple-scale considerations in thermal processes. Both numerical modeling/simulation and experimentation are considered, with the latter being used for validation and physical insight.

Practical implications

Several examples from materials processing, environmental flows and electronic systems, including data centers, are given to present the different techniques that may be used to achieve the desired level of accuracy and predictability.

Originality/value

Present state of the art and future needs in this interesting and challenging area are discussed, providing the impetus for further work. Different methods for treating multiscale problems are presented.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 24 no. 4
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 2 January 2018

Van Huyen Vu, Benoît Trouette, Quy Dong TO and Eric Chénier

This paper aims to extend the hybrid atomistic-continuum multiscale method developed by Vu et al. (2016) to study the gas flow problems in long microchannels involving…

Abstract

Purpose

This paper aims to extend the hybrid atomistic-continuum multiscale method developed by Vu et al. (2016) to study the gas flow problems in long microchannels involving density variations.

Design/methodology/approach

The simulation domain is decomposed into three regions: the bulk where the continuous Navier–Stokes and energy equations are solved, the neighbourhood of the wall simulated by molecular dynamics and the overlap region which connects the macroscopic variables (density, velocity and temperature) between the two former regions. For the simulation of long micro/nanochannels, a strategy with multiple molecular blocks all along the fluid/solid interface is adopted to capture accurately the macroscopic velocity and temperature variations.

Findings

The validity of the hybrid method is shown by comparisons with a simplified analytical model in the molecular region. Applications to compressible and condensation problems are also presented, and the results are discussed.

Originality/value

The hybrid method proposed in this paper allows cost-effective computer simulations of large-scale problems with an accurate modelling of the transfers at small scales (velocity slip, temperature jump, thin condensation films, etc.).

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 1
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 March 2019

Samir Mekid and Salem Bashmal

Novel nanomaterials and nano-devices require further functional aspects that can be designed and supported using new nanomanipulation techniques allowing specific…

Abstract

Purpose

Novel nanomaterials and nano-devices require further functional aspects that can be designed and supported using new nanomanipulation techniques allowing specific functions at the design phase. The nano-manipulator becomes a key instrument for technology bridging sub-nano to mesoscale. The integration of various operations in nano-devices requires sub-nanometer precision and highly stable manipulator. This paper aims to review various design concepts of recent nanomanipulators, their motion characteristics, basic functions, imagine and automation with control techniques for the sake of establishing new design features based on recent requirements.

Design/methodology/approach

The paper reviews various existing nanomanipulators, their motion characteristics, basic functions, imagine and automation with control techniques. This will support precision machine design methodology and robotics principles.

Findings

The availability of a nano-precision instrument with integrated functions has proved to be extremely helpful in addressing various fundamental problems in science and engineering such as exploring, understanding, modeling and testing nano-machining process; exact construction of nano-structure arrays; and inspection of devices with complex features.

Originality/value

New functional specifications have emerged from this review to support the design and make of new advanced nanomanipulators with more features availability to support manipulation within the same reference datum needed for research and education.

Details

Journal of Engineering, Design and Technology, vol. 17 no. 3
Type: Research Article
ISSN: 1726-0531

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Article
Publication date: 7 August 2020

Sumit Kumar Mehta and Sukumar Pati

The purpose of this paper is to analyze the thermal, hydraulic and entropy generation characteristics for the magneto-hydrodynamic (MHD) pressure-driven flow of Al2O3

Abstract

Purpose

The purpose of this paper is to analyze the thermal, hydraulic and entropy generation characteristics for the magneto-hydrodynamic (MHD) pressure-driven flow of Al2O3-water nanofluid through an asymmetric wavy channel.

Design/methodology/approach

Galerkin finite element method is used to solve the governing transport equations numerically within the computational domain using the appropriate boundary conditions. The temperature and flow fields are computed by varying Reynolds number (Re), Hartmann number (Ha) and nano-particle volume fraction (ϕ) in the following range: 10 ≤ Re ≤ 500, 0 ≤ Ha ≤ 75 and 0 ≤ ϕ ≤ 5%.

Findings

The formation of the recirculation zones in the wavy passages, the size of it and the strength of the vortices formed can be modulated by the application of the magnetic field. The overall heat transfer rate increases with Ha for all ϕ both for a lower and higher regime of Re although the enhancement is more for lower values of Re and nanofluids as compared to base fluid and for intermediate values of Re, the effect of a magnetic field is almost insignificant. The magnetic performance factor (PFmagnetic) decreases with Ha although the rate of decrement varies with Re. The increase ϕ also enhances PFmagnetic especially at lower and higher values of Re. The addition of nano-particle enhances the entropy generation at lower values of the Re, while the opposite effect is seen for higher values of Re.

Practical implications

The present study has enormous practical relevance for the design of heat exchanger applied for solar collectors, process plants, textile and aerospace applications.

Originality/value

The combined effects on the heat transfer rate and the associated pressure drop penalty due to the applied magnetic field for the flow of nanofluid through an asymmetric wavy channel have not been reported to date. The effect of the magnetic field on the formation of recirculation zones and hot spot intensity in the asymmetric wavy channel has been examined in detail. The PFmagnetic is investigated first time for the MHD nanofluid flow through a wavy channel.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 3 May 2016

Z.A. Raza, F. Anwar, N. Ahmad, A. Rehman and N. Nasir

The paper aims to improve the protective and comfort properties of both woven and knitted acrylic fabrics by applying a hybrid waterborne polyurethane/fluorocarbon…

Abstract

Purpose

The paper aims to improve the protective and comfort properties of both woven and knitted acrylic fabrics by applying a hybrid waterborne polyurethane/fluorocarbon hydrophobic finish.

Design/methodology/approach

In this study, it was found that the transportation of water from fabrics is one of the important textile parameters. To improve this property, a polyurethane-based finish (Dicrylan BSRN®) and an oil- and water-repellent finish (Oleophobol ZSR®) were applied by using the pad-dry-cure method. After applying the finishes, the resultant fabric samples were investigated for various textile properties.

Findings

The application of Oleophobol ZSR® increased the absorbency time, indicating that the fabric became hydrophobic, whereas the application of Dicrylan BSRN® finish improved the moisture management properties of the woven acrylic. The tensile strength of the woven acrylic fabric was not significantly affected by the application of these finishes. The contact angle of treated knitted fabrics increased and air permeability decreased with an increase in the concentration of Oleophobol ZSR®.

Practical implications

Moisture management is one of the crucial performance criteria in today’s apparel industry. Therefore, fluorochemicals are one of the major precursors used in water-repellent finishes and waterproof membranes in outdoor garments. Based on this fact, this research work focused on the textile sector, where moisture management is required.

Originality/value

This is the first report about the combined application of waterborne polyurethane and fluorochemical-based finishes on acrylic fabrics to tune their comfort and hydrophobic properties.

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Article
Publication date: 4 July 2016

Jyoti Prakash and Vishnu P. Agrawal

Multiple attribute decision making (MADM) is a conceptual agenda used for evaluation and selection of optimal nanofluid to assure best performance of heat exchanger. Most…

Abstract

Purpose

Multiple attribute decision making (MADM) is a conceptual agenda used for evaluation and selection of optimal nanofluid to assure best performance of heat exchanger. Most of the studies focus on nanofluids focus on individual ability at one time. Relatively, not even a single study is available for selection of nanofluid for heat exchanger using concurrent design and MADM approach. The purpose of this paper is to propose a concurrent design methodology using MADM approach to assist improved design of heat exchanger concurrently for all the x-abilities in an integrated manner.

Design/methodology/approach

A combined methodology of applying MADM approach using concurrent design for x-abilities is called CE-MADM approach. Implementation of nanofluid to improve thermal performance of heat exchanger entails thorough evaluation of nanofluids in various x-abilities (performance, maintenance, thermophysical properties and modelisation) to make exhaustive management decision. Sensitivity analysis is also proposed to study the behaviour of height of variation of density, heat capacity, thermal expansion and thermal conductivity with varying particle volume fraction and variation of relative closeness of available alternates from ideally best possible solution.

Findings

MADM approach considering various x-abilities concurrently provide an approach for relative ranking of available nanofluids for optimum performance. Fishbone diagrams of all x-abilities are constructed to identify all the attributes and converge large number of attributes into single numerical index that are concurrently responsible for the cause thus saving time for easy evaluation, comparison and ranking by decision makers. Sensitivity analysis to demonstration height of variation of pertinent attributes with varying particle volume fraction. A MATLAB programming is established to execute calculations involved in the procedure.

Originality/value

This paper comprises a predictable and effective mathematical approach to improve design of heat exchanger with nanofluid bearing in mind all the required x-abilities concurrently. This combined approach of CE-MADM is never applied before in the field of nanofluid to predict best possible results in feasible conditions considering all the x-abilities. Sensitivity analysis is also presented from the assumed mathematical equations of thermophysical properties.

Details

Benchmarking: An International Journal, vol. 23 no. 5
Type: Research Article
ISSN: 1463-5771

Keywords

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Article
Publication date: 16 October 2009

Bingshan Hu, Liwen Wang, Yanzheng Zhao and Z. Fu

Wall climbing robots' volume is needed to be very small in fields that workspace is limited, such as anti‐terror scouting, industry pipe network inspecting and so on. The…

Abstract

Purpose

Wall climbing robots' volume is needed to be very small in fields that workspace is limited, such as anti‐terror scouting, industry pipe network inspecting and so on. The purpose of this paper is to design a miniature wall climbing robot with biomechanical suction cups actuated by shape memory alloy (SMA) actuators.

Design/methodology/approach

Based on characteristics of biologic suction apparatuses, the biomechanical suction cup is designed first. Theory analysis of the suction cup is made considering elastic plate's deflection and SMAs constitutive model. A triangular close linkage locomotion mechanism is chosen for the miniature robot because of its simple structure and control. The robot's gait, kinematics, and control system are all illustrated in this paper.

Findings

Experiments indicate that the suction cup can be used as an adhesion mechanism for miniature wall climbing robots, and the miniature robot prototype with biomechanical suction cups can move in straight line and turn with a fixed angle on an inclined glass wall.

Originality/value

This paper describes how a miniature wall climbing robot with biomechanical suction cups actuated by SMA without any air pump is designed.

Details

Industrial Robot: An International Journal, vol. 36 no. 6
Type: Research Article
ISSN: 0143-991X

Keywords

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