Convective–radiative heat transfer in a cavity filled with a nanofluid under the effect of a nonuniformly heated plate

2018 ◽  
Vol 28 (6) ◽  
pp. 1392-1409 ◽  
Author(s):  
Mikhail Sheremet ◽  
Sivaraj Chinnasamy
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Convective Heat ◽  
Transfer Rate ◽  
Staggered Grid ◽  
Heated Plate ◽  
Radiation Parameter ◽  
Square Cavity ◽  
Content Type ◽  
Industrial Sectors

PurposeThe purpose of this study is to examine the radiation effect on the natural convective heat transfer of an alumina–water nanofluid in a square cavity in the presence of centered nonuniformly heated plate.Design/methodology/approachThe square cavity filled with alumina–water nanofluid has a nonuniformly heated plate placed horizontally or vertically at its center. The plate is heated isothermally with linearly varying temperature. The vertical walls are cooled isothermally with a constant temperature, while the horizontal walls are insulated. The governing equations have been discretized using finite volume method on a uniformly staggered grid system. Simulations were carried out for different values of the heated plate nonuniformity parameter (λ= –1, 0 and 1), the nanoparticles solid volume fraction (Φ= 0.01 − 0.04) and the radiation parameter (Rd= 0 – 2) at the Rayleigh number ofRa= 1e+07.FindingsIt is found that the total heat transfer rate is enhanced with an increase in the radiation parameter for both the horizontal and vertical plates. The role of nanoparticles addition to the base fluid can have dual effects on the heat transfer rate by augmenting and dampening for the absence of radiation while it dampens the heat transfer rate for the presence of radiation.Originality/valueThe originality of this work is to analyze steady natural convection in a square cavity filled with a water-based nanofluid in the presence of centered nonuniformly heated plate. The results would benefit scientists and engineers to become familiar with the analysis of convective heat and mass transfer in nanofluids, and the way to predict the properties of nanofluid convective flow in advanced technical systems, in industrial sectors including transportation, power generation, chemical sectors, electronics, etc.

3D natural convection on a horizontal and vertical thermally active plate in a closed cubical cavity

2016 ◽  
Vol 26 (8) ◽  
pp. 2528-2542 ◽  
Author(s):  
Abimanyu Purusothaman ◽  
Abderrahmane Baïri ◽  
Nagarajan Nithyadevi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Convection Heat Transfer ◽  
Numerical Code ◽  
Heated Plate ◽  
Algebraic Equations ◽  
Content Type ◽  
Cubical Cavity

Purpose The purpose of this paper is to examine numerically the natural convection heat transfer in a cubical cavity induced by a thermally active plate. Effects of the plate size and its orientation with respect to the gravity vector on the convective heat transfer and the flow structures inside the cavity are studied and highlighted. Design/methodology/approach The numerical code is based on the finite volume method with semi-implicit method for pressure-linked equation algorithm. The convective and diffusive terms in momentum equations are handled by adopting the power law scheme. Finally, the discretized sets of algebraic equations are solved by the line-by-line tri-diagonal matrix algorithm. Findings The results show that plate orientation and size plays a significant role on heat transfer. Also, the heat transfer rate is an increasing function of Rayleigh number for both orientations of the heated plate. Depending on the thermal management of the plate and its application (as in electronics), the heat transfer rate is maximized or minimized by selecting appropriate parameters. Research limitations/implications The flow is assumed to be 3D, time-dependent, laminar and incompressible with negligible viscous dissipation and radiation. The fluid properties are assumed to be constant, except for the density in the buoyancy term that follows the Boussinesq approximation. Originality/value The present work will give some additional knowledge in designing sealed cavities encountered in some engineering applications as in aeronautics, automobile, metallurgy or electronics.

The Effect of Inclined Vertical Slats on the Free Convective Heat Transfer Rate From an Isothermal Heated Vertical Surface

2004 ◽  
Author(s):  
Patrick H. Oosthuizen ◽  
Lan Sun ◽  
David Naylor
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Heat Transfer Rate ◽  
Convective Heat ◽  
Heat Generation ◽  
Transfer Rate ◽  
Heated Surface ◽  
Heated Plate ◽  
Study Results ◽  
Free Convective Heat Transfer

Free convective heat transfer from a wide heated vertical isothermal plate with adiabatic surfaces above and below the heated surface has been considered. There are a series of equally spaced vertical thin, flat surfaces (termed “slats”) near the heated surface, these surfaces being, in general, inclined to the heated surface. The slats are pivoted about their center-point and thus as their angle is changed, the distance of the tip of the slat from the plate changes. The temperature of the vertical isothermal surfaces has been assumed to be greater than the ambient temperature. Various cases have been considered to examine the effect of the geometry of the adiabatic surfaces above and below the heated plate, the effect of heat conduction in the slats and the effect of heat generation in the slats. The situation considered is an approximate model of a window with a vertical blind, the particular case where the window is hotter than the room air being considered. The heat generation that can occur in the slats is then the result of solar energy passing through the window and being absorbed by the slats. The flow has been assumed to be laminar and steady. Fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces. The governing equations have been written in dimensionless form and the resulting dimensionless equations have been solved using a commercial finite-element package. Because of the application that motivated the study, results have only been obtained for a Prandtl number of 0.7. The effect of the other dimensionless variables on the mean dimensionless heat transfer rate from the heated surface has been examined.

Analysis of natural convection in a square cavity with a thin partition for linearly heated side walls

2014 ◽  
Vol 24 (5) ◽  
pp. 1057-1072 ◽  
Author(s):  
M. Sathiyamoorthy ◽  
Ali J. Chamkha
Keyword(s):  
Heat Transfer ◽  
Finite Element Method ◽  
Finite Element ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Design Methodology ◽  
Square Cavity ◽  
Content Type ◽  
Side Walls ◽  
Method Accuracy

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.

Effect of magnetic field-dependent thermal conductivity on natural convection of magnetic nanofluid inside a square enclosure

2019 ◽  
Vol 29 (4) ◽  
pp. 1466-1489 ◽  
Author(s):  
Mohammadhossein Hajiyan ◽  
Shohel Mahmud ◽  
Mohammad Biglarbegian ◽  
Hussein A. Abdullah ◽  
A. Chamkha
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Hartmann Number ◽  
Magnetic Nanofluid ◽  
Content Type ◽  
Square Enclosure ◽  
Field Dependent

Purpose The purpose of this paper is to investigate the convective heat transfer of magnetic nanofluid (MNF) inside a square enclosure under uniform magnetic fields considering nonlinearity of magnetic field-dependent thermal conductivity. Design/methodology/approach The properties of the MNF (Fe3O4+kerosene) were described by polynomial functions of magnetic field-dependent thermal conductivity. The effect of the transverse magnetic field (0 < H < 105), Hartmann Number (0 < Ha < 60), Rayleigh number (10 <Ra <105) and the solid volume fraction (0 < φ < 4.7%) on the heat transfer performance inside the enclosed space was examined. Continuity, momentum and energy equations were solved using the finite element method. Findings The results show that the Nusselt number increases when the Rayleigh number increases. In contrast, the convective heat transfer rate decreases when the Hartmann number increases due to the strong magnetic field which suppresses the buoyancy force. Also, a significant improvement in the heat transfer rate is observed when the magnetic field is applied and φ = 4.7% (I = 11.90%, I = 16.73%, I = 10.07% and I = 12.70%). Research limitations/implications The present numerical study was carried out for a steady, laminar and two-dimensional flow inside the square enclosure. Also, properties of the MNF are assumed to be constant (except thermal conductivity) under magnetic field. Practical implications The results can be used in thermal storage and cooling of electronic devices such as lithium-ion batteries during charging and discharging processes. Originality/value The accuracy of results and heat transfer enhancement having magnetic field-field-dependent thermal conductivity are noticeable. The results can be used for different applications to improve the heat transfer rate and enhance the efficiency of a system.

A Numerical Study of the Effect of an Irradiated Slatted Top Down – Bottom Up Blind on the Convective Heat Transfer Rate From a Recessed Window to an Adjacent Room

2012 ◽  
Author(s):  
Patrick H. Oosthuizen ◽  
J. T. Paul
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Heat Transfer Rate ◽  
Convective Heat ◽  
Transfer Rate ◽  
Numerical Study ◽  
Solar Irradiation ◽  
Radiant Heat Transfer ◽  
Top Down ◽  
Bottom Up

Top Down – Bottom Up blinds have become quite popular in recent times. However the effects of such blind systems on the convective heat transfer from the window to the surrounding room have not been extensively studied and the effect of solar irradiation of the blind on the window heat transfer has not received significant attention. The purpose of the present work was therefore to numerically investigate the effect of solar irradiation of Top Down – Bottom Up slatted blinds on this convective heat transfer. An approximate model of the window-blind system has been adopted. The solar radiation falling on the blinds is assumed to produce a uniform rate of heat generation in the blind. The Boussinesq approximation has been used. Radiant heat transfer effects have been neglected. Conditions under which laminar, transitional and turbulent flows occur have been considered. The main emphasis is on the effect of the magnitude of the irradiation and of the size of the blind openings at the top and bottom of the window on the convective heat transfer rate from the window to the room.

scholarly journals A numerical study of free convective heat transfer in a double-glazed window with a between-pane Venetian blind

2021 ◽  
Author(s):  
Tony Avedissian
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Heat Transfer Rate ◽  
Convective Heat ◽  
Transfer Rate ◽  
Numerical Study ◽  
Thermal Conductivity Ratio ◽  
Number Range ◽  
Free Convective Heat Transfer ◽  
Venetian Blind

The free convective heat transfer in a double-glazed window with a between-pane Venetian blind has been studied numerically. The model geometry consists of a two-dimensional vertical cavity with a set of internal slats, centred between the glazings. Approximately 700 computational fluid dynamic solutions were conducted, including a grid sensitivity study. A wide set of geometrical and thermo-physical conditions was considered. Blind width to cavity width ratios of 0.5, 0.65, 0.8, and 0.9 were studied, along with three slat angles, 0º (fully open, +/- 45º (partially open), and 75º (closed). The blind to fluid thermal conductivity ratio was set to 15 and 4600. Cavity aspects of 20, 40, and 60, were examined over a Rayleigh number range of 10 to 10⁵, with the Prandtl number equal to 0.71. The resulting convective heat transfer data are presented in terms of average Nusselt numbers. Depending on the specific window/blind geometry, the solutions indicate that the blind can either reduce or enhance the convective heat transfer rate across the glazings. The present study does not consider radiation effects in the numerical solution. Therefore, a post-processing algorithm is presented that incorporates the convective and radiative influences, in order to determine the overall heat transfer rate across the window/blind system.

Electric Field Effects on Natural Convection in Enclosures

1986 ◽  
Vol 108 (4) ◽  
pp. 749-754 ◽  
Author(s):  
D. A. Nelson ◽  
E. J. Shaughnessy
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Convective Heat Transfer ◽  
Heat Transfer Rate ◽  
Convective Heat ◽  
Transfer Rate ◽  
Stokes Equations ◽  
Experimental Studies ◽  
Navier Stokes ◽  
First Order Theory

The enhancement of convective heat transfer by an electric field is but one aspect of the complex thermoelectric phenomena which arise from the interaction of fluid dynamic and electric fields. Our current knowledge of this area is limited to a very few experimental studies. There has been no formal analysis of the basic coupling modes of the Navier–Stokes and Maxwell equations which are developed in the absence of any appreciable magnetic fields. Convective flows in enclosures are particularly sensitive because the limited fluid volumes, recirculation, and generally low velocities allow the relatively weak electric body force to exert a significant influence. In this work, the modes by which the Navier–Stokes equations are coupled to Maxwell’s equations of electrodynamics are reviewed. The conditions governing the most significant coupling modes (Coulombic forces, Joule heating, permittivity gradients) are then derived within the context of a first-order theory of electrohydrodynamics. Situations in which these couplings may have a profound effect on the convective heat transfer rate are postulated. The result is an organized framework for controlling the heat transfer rate in enclosures.

Heat transfer enhancement in microchannels using ribs and secondary flows

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Karthikeyan Paramanandam ◽  
Venkatachalapathy S. ◽  
Balamurugan Srinivasan
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Heat Transfer Enhancement ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Secondary Flows ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Content Type ◽  
Flow And Heat Transfer

Purpose The purpose of this paper is to study the flow and heat transfer characteristics of microchannel heatsinks with ribs, cavities and secondary channels. The influence of length and width of the ribs on heat transfer enhancement, secondary flows, flow distribution and temperature distribution are examined at different Reynolds numbers. The effectiveness of each heatsink is evaluated using the performance factor. Design/methodology/approach A three-dimensional solid-fluid conjugate heat transfer numerical model is used to study the flow and heat transfer characteristics in microchannels. One symmetrical channel is adopted for the simulation to reduce the computational cost and time. Flow inside the channels is assumed to be single-phase and laminar. The governing equations are solved using finite volume method. Findings The numerical results are analyzed in terms of average Nusselt number ratio, average base temperature, friction factor ratio, pressure variation inside the channel, temperature distribution, velocity distribution inside the channel, mass flow rate distribution inside the secondary channels and performance factor of each microchannels. Results indicate that impact of rib width is higher in enhancing the heat transfer when compared with its length but with a penalty on the pressure drop. The combined effects of secondary channels, ribs and cavities helps to lower the temperature of the microchannel heat sink and enhances the heat transfer rate. Practical implications The fabrication of microchannels are complex, but recent advancements in the additive manufacturing techniques makes the fabrication of the design considered in this numerical study feasible. Originality/value The proposed microchannel heatsink can be used in practical applications to reduce the thermal resistance, and it augments the heat transfer rate when compared with the baseline design.

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