N. Guerroudj and H. Kahalerras
The purpose of this paper is to study numerically the fluid flow and heat transfer in an inclined channel provided with heated porous blocks on its lower plate.
Abstract
Purpose
The purpose of this paper is to study numerically the fluid flow and heat transfer in an inclined channel provided with heated porous blocks on its lower plate.
Design/methodology/approach
The Brinkman‐Forchheimer extended Darcy model with the Boussinesq approximation is adopted for the flow in the porous regions. The governing equations with the appropriate boundary conditions are solved by the control volume method. The effect of some pertinent parameters such as the buoyancy force intensity, the porous blocks shape and height, the porous medium permeability and the Reynolds number are analyzed for various inclination angles ranging from −90° to +90°.
Findings
The results reveal, essentially, that the inclination angle of the channel can alter substantially the fluid flow and heat transfer mechanisms, especially at high Richardson and Darcy numbers. In this case, the maximum and minimum global Nusselt numbers are reached for α=+90° and α=−90°, respectively.
Research limitations/implications
The results obtained in this work are valid for an inclined channel with porous blocks attached on the heated parts of the lower plate, whereas the upper wall is thermally insulated.
Practical implications
The results obtained in this worky can be used in the thermal control of electronic components. The use of porous blocks mounted on the heat sources will increase the rate of heat removal in order to maintain the electronic components at an acceptable operating temperature.
Originality/value
The paper provides an interesting method to improve the cooling of electronic devices by use of a porous medium.
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Ali Mohammad Rashidi, Mehrad Paknezhad and Tooraj Yousefi
This study aims to clarify the relationship between inclination angle of hot surface of CPU and its temperature in absence and presence of aluminum foam as a cooling system. It…
Abstract
Purpose
This study aims to clarify the relationship between inclination angle of hot surface of CPU and its temperature in absence and presence of aluminum foam as a cooling system. It proposes application of the artificial neural [multi-layer perceptron (MLP) and radial basis function] networks and adaptive neuron-fuzzy inference system (ANFIS) to predict interface temperature of central processing unit (CPU)/metal foam heat sink.
Design/methodology/approach
To provide a consistent set of data, the surface of an aluminum cone with and without installing Duocel aluminum foam was heated in a natural convection using an electrical resistor. The hot surface temperature was measured using five K-type thermocouples (±0.1°C). To develop the predictive models, ambient temperature, input power and inclination angle are taken as input which varied from 23°C to 32°C, 4 to 20 W and 0° to 90°, respectively. The hot surface temperature is taken as the output.
Findings
The results show that in the presence of foam, the hot surface temperature was less sensitive to the variations of angle, and the maximum enhancement of the heat transfer coefficient was 23 per cent at the vertical position. Both MLP network and ANFIS are comparable, but the values predicted by MLP network are in more conformity with the measured values.
Originality/value
The effect of metal foam on the inclination angle/hot surface temperature dependence is identified. The optimum angle is clarified. The applicability of the MLP networks to predict interface temperature of CPU/heat sink is approved.
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Mikhail A. Sheremet, Hakan F. Öztop and Nidal Abu-Hamdeh
The purpose of this study is to work on heat transfer enhancement within different engineering cavities is the major aim of most technical solutions. Such intensification can be…
Abstract
Purpose
The purpose of this study is to work on heat transfer enhancement within different engineering cavities is the major aim of most technical solutions. Such intensification can be obtained by using “smart” liquids known as nanoliquids and solid fins. Therefore, free convective thermal transmission within square nanoliquid chamber under the influence of complex fins is studied. The considered fins are the combination of wall-mounted adiabatic fin and an adiabatic block over this fin.
Design/methodology/approach
Influences of the Rayleigh number, location of the local adiabatic block and nanoparticles concentration on liquid motion and energy transport are studied. Finite difference technique was used to solve the governing equations.
Findings
It has been ascertained that the energy transport intensification can be reached for the middle position of this local block within the cavity.
Originality/value
The main originality of this work is to use intermittent block in a nanofluid filled cavity under differentially heated conditions. One constant and location of one of the passive element is constant and other one is fixed, which is the intermittent block, is used to control heat and fluid flow. Thus, distance between blocks is allowed to control of the velocity and kinetic energy. In this way, temperature distribution also can be controlled inside the square cross-sectional closed space. Another originality of the work is to use nanoparticle added main flow for this geometry. Thus, energy efficiency can be controlled via adiabatic intermittent blocks without spending any extra energy.
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D. Srinivasacharya and P. Vijay Kumar
– The purpose of this paper is to study the mixed convection in a nanofluid along an inclined wavy surface embedded in a porous medium.
Abstract
Purpose
The purpose of this paper is to study the mixed convection in a nanofluid along an inclined wavy surface embedded in a porous medium.
Design/methodology/approach
The complex wavy surface is transformed to a smooth surface by employing a coordinate transformation. Using the similarity transformation, the governing equations are transformed into a set of ordinary differential equations and then lineralized using the successive linearization method. The Chebyshev pseudo spectral method is then used to solve linearized differential equations.
Findings
The effects of Brownian motion parameter, thermophoresis parameter, amplitude of the wavy surface, angle of inclination of the wavy surface for aiding and opposing flows on the non-dimensional velocity, temperature, nanoparticle volume fraction, heat and nanoparticle mass transfer rates are studied and presented graphically.
Originality/value
This is the first instance in which mixed convection, inclined wavy surface and nanofluid is employed to model fluid flow.
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Banjara Kotresha and N. Gnanasekaran
This paper aims to discuss about the two-dimensional numerical simulations of fluid flow and heat transfer through high thermal conductivity metal foams filled in a vertical…
Abstract
Purpose
This paper aims to discuss about the two-dimensional numerical simulations of fluid flow and heat transfer through high thermal conductivity metal foams filled in a vertical channel using the commercial software ANSYS FLUENT.
Design/methodology/approach
The Darcy Extended Forchheirmer model is considered for the metal foam region to evaluate the flow characteristics and the local thermal non-equilibrium heat transfer model is considered for the heat transfer analysis; thus the resulting problem becomes conjugate heat transfer.
Findings
Results obtained based on the present simulations are validated with the experimental results available in literature and the agreement was found to be good. Parametric studies reveal that the Nusselt number increases in the presence of porous medium with increasing thickness but the effect because of the change in thermal conductivity was found to be insignificant. The results of heat transfer for the metal foams filled in the vertical channel are compared with the clear channel in terms of Colburn j factor and performance factor.
Practical implications
This paper serves as the current relevance in electronic cooling so as to open up more parametric and optimization studies to develop new class of materials for the enhancement of heat transfer.
Originality/value
The novelty of the present study is to quantify the effect of metal foam thermal conductivity and thickness on the performance of heat transfer and hydrodynamics of the vertical channel for an inlet velocity range of 0.03-3 m/s.
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Younes Menni, Ahmed Azzi, Ali J. Chamkha and Souad Harmand
The purpose of this paper is to carry out a numerical study on the dynamic and thermal behavior of a fluid with a constant property and flowing turbulently through a…
Abstract
Purpose
The purpose of this paper is to carry out a numerical study on the dynamic and thermal behavior of a fluid with a constant property and flowing turbulently through a two-dimensional horizontal rectangular channel. The upper surface was put in a constant temperature condition, while the lower one was thermally insulated. Two transverse, solid-type obstacles, having different shapes, i.e. flat rectangular and V-shaped, were inserted into the channel and fixed to the top and bottom walls of the channel, in a periodically staggered manner to force vortices to improve the mixing, and consequently the heat transfer. The flat rectangular obstacle was put in the first position and was placed on the hot top wall of the channel. However, the second V-shaped obstacle was placed on the insulated bottom wall, at an attack angle of 45°; its position was varied to find the optimum configuration for optimal heat transfer.
Design/methodology/approach
The fluid is considered Newtonian, incompressible with constant properties. The Reynolds averaged Navier–Stokes equations, along with the standard k-epsilon turbulence model and the energy equation, are used to control the channel flow model. The finite volume method is used to integrate all the equations in two-dimensions; the commercial CFD software FLUENT along with the SIMPLE-algorithm is used for pressure-velocity coupling. Various values of the Reynolds number and obstacle spacing were selected to perform the numerical runs, using air as the working medium.
Findings
The channel containing the flat fin and the 45° V-shaped baffle with a large Reynolds number gave higher heat transfer and friction loss than the one with a smaller Reynolds number. Also, short separation distances between obstacles provided higher values of the ratios Nu/Nu0 and f/f0 and a larger thermal enhancement factor (TEF) than do larger distances.
Originality/value
This is an original work, as it uses a novel method for the improvement of heat transfer in completely new flow geometry.
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Xue Xinhua, Zhang Wohua and Xingguo Yang
The paper aims to clarify the relationship between the micro-structures of porous media and the coefficient of permeability. Most materials involve different types of defects like…
Abstract
Purpose
The paper aims to clarify the relationship between the micro-structures of porous media and the coefficient of permeability. Most materials involve different types of defects like caves, pores and cracks, which are important characters of porous media and have a great influence on the physical properties of materials. To study the seepage mechanical characteristics of damaged porous media, the constitutive model of porous media dealing with coupled modeling of pores damage and its impact on permeability property of a deforming media was studied in this paper.
Design/methodology/approach
The paper opted for an exploratory study using the approach of continuum damage mechanics (CDM).
Findings
The paper provides some new insights on the fluid dynamics of porous media. The dynamic evolution model of permeability coefficient established in this paper can be used to model the fluid flow problems in damaged porous media. Moreover, the modified Darcy's law developed in this paper is considered to be an extension of the Darcy's law for fluid flow and seepage in a porous medium.
Research limitations/implications
Owing to the limitations of time, conditions, funds, etc., the research results should be subject to multifaceted experiments before their innovative significance can be fully verified.
Practical implications
The paper includes implications for the development of fluid dynamics of porous media.
Originality/value
This paper fulfils an identified need to study the relationship between the micro-structures of porous media and the coefficient of permeability.
Details
Keywords
The purpose of this paper is to perform the stimulation in order to examine the effects on the heat transfer coefficient and the flowfield properties at the vicinity of the gap…
Abstract
Purpose
The purpose of this paper is to perform the stimulation in order to examine the effects on the heat transfer coefficient and the flowfield properties at the vicinity of the gap due to variations in the width-to-depth ratio.
Design/methodology/approach
The governing equations were discreted by using the finite volume method, and based on pressure-velocity coupled algorithm, the heat transfer coefficients outside and inside the gaps, defined by the width-to-depth ratio of 1, 2/3, 1/2, 1/3 and 1/4, were obtained by the Fluent software.
Findings
The number of vortex inside the gap depends on the width-to-depth ratio, and the maximum value of the heat transfer coefficient emerges on the downstream surface.
Originality/value
The study gives a feasible method to simulate the flowfield and the heat transfer inside the gap, which will help the design of the thermal protection system for reentry vehicles.