Effect of Variable Sidewall Temperatures on the Combined Surface Radiation—Convection in a Discretely Heated Enclosure

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
S. Saravanan ◽  
N. Raja
Keyword(s):  
Heat Transfer ◽  
Transfer Rate ◽  
Surface Radiation ◽  
Computational Results ◽  
Heat Transfer Characteristics ◽  
Total Heat Transfer ◽  
Flow And Heat Transfer ◽  
Volume Method ◽  
Made In

This paper reports the changes made in the flow and heat transfer characteristics of a closed enclosure in the presence of sidewalls with symmetrical linear heating. The flow inside the enclosure is primarily driven by a centrally placed discrete heater with thermal radiation included at all surfaces involved. Finite volume method-based computational results corresponding to the resulting steady-state were obtained. The factors causing augmentation and suppression of heat transfer are discussed for two types of sidewall heating. Moreover, it is found that the role of radiation is well stronger than convection in determining the total heat transfer rate when the sidewall heating is decreasing with height.

The Effect of Asymmetrically Confined Circular Cylinder and Opposing Buoyancy on Fluid Flow and Heat Transfer

2017 ◽  
Vol 374 ◽  
pp. 18-28 ◽  
Author(s):  
Houssem Laidoudi ◽  
Mohamed Bouzit
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Transfer Rate ◽  
Richardson Number ◽  
Convection Heat Transfer ◽  
Heat Transfer Characteristics ◽  
Thermal Buoyancy ◽  
Flow And Heat Transfer ◽  
Mixed Convection Heat Transfer

In this paper, a two-dimensional numerical investigation is carried out to understand the effects of opposing thermal buoyancy and Prandtl number on fluid flow and mixed convection heat transfer characteristics of symmetrically and asymmetrically confined cylinder submerged in Newtonian fluid. The detailed flow and temperature field are illustrated in term of streamlines and isotherm contours to interpret the flow and thermal transport visualization. The numerical results are presented and discussed for the range of conditions as: Ri = 0 to -4, Pr = 0.7 to 50, eccentricity factor ε = 0 to 0.7 at Re = 40 and for a fixed blockage parameter B = 0.2. The effect of opposing buoyancy is brought about by varying Richardson numbers. The overall drag coefficient and average Nusselt number are computed to elucidate the role of Prandt number, eccentricity factor and Richardson number on the flow and heat transfer. At ε = 0, it is found that, when the buoyancy is opposed the flow becomes asymmetrically and some rotating zones appear under and above the cylinder. Moreover, the eccentricity factor has a tendency to decrease the rotating regions and to increase the heat transfer rate. For example an increase in eccentricity factor from 0 to 0.6 increases Nu by 77% at Ri = 4.

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.

Magnetohydrodynamics Flow and Heat Transfer Around a Solid Cylinder Wrapped With a Porous Ring

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Mohammad Sadegh Valipour ◽  
Saman Rashidi ◽  
Reza Masoodi
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Nusselt Number ◽  
Critical Radius ◽  
Governing Equations ◽  
Heat Transfer Characteristics ◽  
Electrically Conductive ◽  
Flow And Heat Transfer ◽  
Volume Method ◽  
Physical Phenomena

The problem of the effect of an external magnetic field on fluid flow and heat transfer characteristics is relevant to several physical phenomena. In this paper, flow and heat transfer of an electrically-conductive fluid around a cylinder, wrapped with a porous ring and under the influence of a magnetic field, is studied numerically. The ranges of the Stuart (N), Reynolds (Re), and Darcy (Da) numbers are 0–7, 1–40, and 10−8–10−1, respectively. The Darcy–Brinkman–Forchheimer model was used for simulating flow in the porous layer. The governing equations provide a coupling between flow and magnetic fields. The governing equations, together with the relevant boundary conditions, are solved numerically using the finite-volume method (FVM). The effect of the Stuart, Reynolds, and Darcy numbers on the flow patterns and heat transfer rate are explored. Finally, two empirical equations for the average Nusselt number were suggested, in which the effect of a magnetic field and the Darcy numbers are taken into account. It was found that in the presence of a magnetic field, the drag coefficient and the critical radius of the insulation increases, while the wake length and Nusselt number decrease.

scholarly journals CFD simulation of natural convection and heat transfer in a flat solar thermal collector with fins on the glazing - horizontal case

2019 ◽  
Vol 3 (2) ◽  
pp. 1
Author(s):  
Adel Laaraba
Keyword(s):  
Heat Transfer ◽  
Solar Collector ◽  
Transfer Rate ◽  
Cfd Simulation ◽  
Solar Thermal ◽  
Heat Transfer Characteristics ◽  
Convection And Heat Transfer ◽  
Flow And Heat Transfer ◽  
Solar Thermal Collector ◽  
Different Temperatures

This study is based on a CFD simulation of a flat horizontal solar thermal collector containing fins on its inner face of the glazing. The walls of the solar collector with insulation are considered adiabatic and the rest of the walls are at constant different temperatures. The principal objective of this work is to study the effects of the number of fins that changed from 0 to 30, as well as their length varied from 0 to 0.8 on the air flow and heat transfer characteristics. It has been observed that the heat transfer rate is strongly affected by the number of fins and the length of the fins. The obtained result showed that the increase of the fins reduces the heat loss by convection by 54 %.

Forced Convection Enhancement Over Heated Blocks by Using Slot-Jet

2019 ◽  
Vol 36 (1) ◽  
pp. 119-131 ◽  
Author(s):  
H. Amirat ◽  
A. Korichi
Keyword(s):  
Heat Transfer ◽  
Transfer Rate ◽  
Simple Algorithm ◽  
Ansys Fluent ◽  
Flow And Heat Transfer ◽  
Commercial Code ◽  
Field Temperature ◽  
Jet Velocity ◽  
Convective Fluid ◽  
Volume Method

ABSTRACTNumerical simulations of convective fluid flow and heat transfer in a channel containing heated blocks with slot-jet behind the blocks are performed. The finite volume method with the simple algorithm is adopted and Ansys Fluent © CFD commercial code is used. The effect of slot-jet on flow structure and heat transfer modification is examined. The incidence of influent parameters such as slot-jet position, relative inlet slot-jet velocity and Reynolds number value has been explored. The results show that both the main inlet velocity as well as the relative slot-jet velocity in addition to the slot position modifies the flow field, temperature contours and heat transfer rate.

Effects of Inlet and Outlet Ports of Ventilated Square Cavity on Flow and Heat Transfer

2020 ◽  
Vol 26 ◽  
pp. 78-85
Author(s):  
Houssem Laidoudi ◽  
Mustapha Helmaoui ◽  
Belbachir Azeddine ◽  
Adel Ayad ◽  
Abedallah Ghenaim
Keyword(s):  
Heat Transfer ◽  
Transfer Rate ◽  
Average Nusselt Number ◽  
Governing Equations ◽  
Square Cavity ◽  
Outlet Port ◽  
Flow And Heat Transfer ◽  
The Mean ◽  
Drag And Lift ◽  
Volume Method

This paper deals with numerical simulations of forced convection from a pair of identical cylinders arranged in tandem manner inside a square cavity of single inlet and outlet ports. The gap distance between the cylinders is fixed with half of square length. The main purpose of this study is to see the effect of inlet and outlet port positions on fluid flow and heat transfer rate. The governing equations of continuity, momentum and energy have been solved using finite-volume method in laminar, steady and two dimensional directions. The work has been done in the range of these conditions: Re = 1 to 40, at fixed Pr = 7.01. Three positions of inlet and outlet port have been selected. The mean results of flow patterns and distribution temperature are illustrated under the contours of streamline and isotherm respectively. The drag and lift coefficients of each cylinder is computed and discussed. The average Nusselt number of both cylinders is also presented and discussed. It was found that the inlet and outlet ports have significant effects on heat transfer from the confined cylinders.

scholarly journals Rarefied flow and heat transfer characteristics of rectangular cavities with heated concave surface

2019 ◽  
Vol 11 (7) ◽  
pp. 168781401986098 ◽  
Author(s):  
Ammar Alkhalidi ◽  
Suhil Kiwan ◽  
Wael Al-Kouz ◽  
Wahib Owhaib ◽  
Aiman Alshare
Keyword(s):  
Heat Transfer ◽  
Critical Angle ◽  
Heat Transfer Characteristics ◽  
Rarefied Flow ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Building Insulation ◽  
New Correlation ◽  
Reduce Heat Loss ◽  
Volume Method

This article utilizes the finite volume method to solve the problem incorporating rarefied flow and heat transfer characteristics inside concaved cavities. Cavities are used in many applications, one of which is building insulation to reduce heat loss from walls. In this article, the influence of the aspect ratio ( B/ H), the tilt angle ( θ), Knudsen number ( Kn), and Rayleigh number ( Ra) on these characteristics were studied. Parameters ranges were [Formula: see text]. This study shows that the average Nusselt number ( Nu) decreases as the B/H and Kn increase. Whereas, Nu increases with increasing Ra. In addition, the Nu increases as θ increases to a given critical angle (60°), and beyond this angle, Nu decreases with increasing Ra. A new correlation of Nu including all parameters investigated in this work is introduced. This study reveals that concaved cavities could be used as thermal insulation bodies.

scholarly journals Flow and Heat Transfer Investigation of Forced Convection of Nanofluid in a Wavy Channel at Different Wavelengths and Phase Difference

2018 ◽  
Vol 36 (2) ◽  
pp. 137
Author(s):  
Mazaher Rahimi Esboee ◽  
Esmaeil Abokazempour ◽  
Abbas Ramiar ◽  
Amir Arya ◽  
Ali Akbar Ranjbar ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Phase Lag ◽  
Wavy Channel ◽  
Flow And Heat Transfer ◽  
Flow Geometry ◽  
Fluid Properties ◽  
Volume Method

Changing the fluid properties and flow geometry are two common ways of making an improvement in heat transfer rate. Recent investigations on nanofluid, as such suspensions are often called, indicate that the suspended nanoparticles remarkably change the transport properties and heat transfer characteristics of the suspension. Bending walls can also improve heat transfer by increasing the total heat transfer surface and changing the behavior of the flow. In this work a two dimensional incompressible laminar nanofluid flow in a wavy channel with sinusoidal curved walls is numerically investigated. The finite volume method, and Rhie and Chow interpolation with a collocated mesh are used for solving the governing equations. The effects of the volume fraction of nanoparticles, Reynolds number, the wavelength, Phase lag and amplitude on the heat transfer rate are studied. The present work showed good agreement with existing experimental and Numerical results. Increasing the amplitude of the wave and nanoparticles volume fraction, and decreasing wavelength of the wave, has great effects on enhancement of heat transfer rate.

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