Natural Convection Research Papers - Academia.edu (original) (raw)

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- Air flow, Natural Convection, Passive Cooling, Radioactivity

Experimental investigation was conducted to measure the convective heat transfer coefficient and thermal performance of plate fins and plate cubic pin-fins heat sinks, under natural convection regime. The investigation was conducted for Rayleigh number from 8×10 6 to 9.5×10 6 and input heat of 10 W to 120 W. The fin spacing and fin numbers are varied between 5-12 mm and 5-9, respectively. The results demonstrated that plate cubic pin-fins heat sinks have lower thermal resistance and higher heat transfer, compared to plate fins heat sinks. Heat transfer enhancement of new-designed heat sinks is about 10% to 41.6% higher, compared to normal pin-fins. Increasing fin spaces in all types of studied heat sinks cause lower thermal resistance. But, increasing fin numbers does not cause better heat transfer. The best heat sink design was a plate cubic pin-fin heat sink with 7 fins and 8.5 mm fin spacing. Finally, empirical equations have been developed to correlate the average Nusselt number as

- by Mohammad Reza Safaei
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- Convection, Heat Transfer, Heat Exchanger, Natural Convection
- by Matti Sillanpää
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- Mechanical Engineering, Chemical Engineering, Chemistry, Biomass
- by Bruno de Campos Salles Anselmo and +1
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- Materials Science, Mechanics, Natural Convection
- by Haim Bau
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- Materials Science, Heat Transfer, Power Plant, Natural Convection
- by Marc Medrano
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- Mechanical Engineering, Heat Transfer, Natural Convection, Heat transfer coefficient
- by G. Barozzi
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- Heat Transfer, Heat and Mass Transfer, Natural Convection, Laminar Flow

Natural convection effects of the numerical solution for unsteady, laminar, free convection flow over an incompressible viscous fluid past a no n-isothermal vertical cone with surface temperature T ' w(x) = T ' ∞ + ax n varying as power function of distance from the apex (x = 0) is presented here. The dimensionless governing equations of the flow that

- by Ali Chamkha
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- Heat Transfer, Pure Mathematics, Natural Convection, Free Convection

Analytical investigation was conducted on the transient natural convection flow past an oscillating infinite vertical plate in present of magnetic field and radiative heat transfer. The classical solution of this problem for impulsively moving plate is given by Seth in [2] and is found to be a special case of the solution to be presented. The governing model equations are solved analytically with the help of Laplace transform technique. The results are expressed in terms of the velocity and temperature profiles as well as the skin-friction and Nusselt number.

- by Sharidan Shafie
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- Natural Convection, Laplace Transform, Porous Medium
- by Adrian Bejan
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- Engineering, Heat Transfer, Heat and Mass Transfer, Numerical Simulation
- by Dhifaoui Belgacem
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- Dynamics, Solar Energy, Natural Convection, Energy Storage

Laminar steady state natural convection in a two-dimensional symmetrical trapezoidal enclosure has been studied using a finite element method. In this investigation, the top wall is considered adiabatic, both inclined sidewalls are maintained at a constant cold temperature and an isoflux heat source is provided at the bottom surface. The pressure-velocity form of the Navier-Stokes equations and energy equation are used to represent the mass, momentum and energy conservations of the fluid medium in the enclosure. Galerkin weighted residual method of finite element formulation with triangular mesh elements is employed. The fluid investigated here is air of Prandtl number fixed at 0.7. The Rayleigh number is varied from 10^3 to 10^6 while the sidewall inclination angle is varied from -15° to 45°. The results are presented in terms of streamline and isotherm plots as well as the variation of average Nusselt number with Rayleigh number for different base wall tilt angles of 0°, 15°, and 30°. The results show that the average Nusselt number increases with the increase of Rayleigh number and the effect of the sidewall inclination angle on heat transfer is significantly reduced at higher Rayleigh number. Effects of sidewall inclination angle on convection heat transfer characteristics decrease with the increase of base wall tilt angle at higher Rayleigh number and Rayleigh number equal to 10^5 can be considered as a critical limit for the present.

- by Dr. Sumon Saha
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- Computational Fluid Dynamics, Heat Transfer, Fluid Dynamics, Natural Convection
- by Sarder Firoz Ahmmed
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- Scientific, Natural Convection, Viscosity, Prandtl Number
- by Majid Ghassemi
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- Engineering, Magnetohydrodynamics, Finite Volume Methods, Energy
- by Abdul Aziz
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- Engineering, Mechanical Engineering, Applied Mathematics, Modeling
- by Oronzio Manca
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- Engineering, Convection, Heat Transfer, System Design
- by Kübra Özdemir
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- Pepper, Food Chemistry, Multidisciplinary, Natural Convection
- by Jean-Claude Roy and +1
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- Engineering, Chemical Engineering, Food Science, Heat and Mass Transfer

Natural convective heat transfer and fluid flow in an open porous cavity filled with a nanofluid is studied numerically using the Tiwari and Das nanofluid model. The transport equations for mass, momentum and energy formulated in dimensionless stream function and temperature are solved numerically using a second-order accurate finite difference method. Particular efforts are focused on the effects of the governing parameters on the heat and fluid flow. It is found that an increase in undulation number of the wavy vertical wall leads to an attenuation of convective flow and a decrease in the heat transfer rate.

- by Dr Aroon Shenoy
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- Nanofluids, Natural Convection, Nanofluid, Nanofluid (Heat Transfer)
- by Oronzio Manca
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- Engineering, Visualization, Heat Transfer, Instrumentation
- by Sylvie Lorente
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- Engineering, Heat and Mass Transfer, Mathematical Sciences, Natural Convection
- by Jean Koster
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- Natural Convection
- by Ridha Djebali
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- Applied Mathematics, Heat Transfer, Numerical Simulation, Natural Convection
- by Sai Fok
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- Materials Science, Computational Fluid Dynamics, Numerical Analysis, Numerical Simulation

The analytical solution for a vertical heated plate subjected to conjugate heat transfer due to natural convection at the surface and conduction below is presented. The heated surface is split into two regions; the uniform heat flux region toward upstream and remaining fraction as the uniform wall temperature region. The fractional areas under the two regions are considered variable. Adopting thermally thin wall regime approximation, the possible solutions were investigated and found to satisfactorily deal with longitudinal conduction and temperature variation in the transverse direction. A test setup was developed and the experiments were conducted to obtain relevant data for comparison with the analytical solutions. The ranges for Rayleigh number and heat conduction parameter (α) during various test conditions were 2×108–6×108, and 0.001–1, respectively. The limiting solutions for stipulated conditions are analyzed and compared with experimental data. Reasonable agreement is obser...

- by Vipin Yadav
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- Mechanical Engineering, Chemical Engineering, Heat Transfer, Natural Convection

A numerical simulation has been carried out to investigate the buoyancy induced flow and heat transfer characteristics inside a wavy walled enclosure. The enclosure consists of two parallel wavy and two straight walls. The top and the bottom walls are wavy and kept isothermal. Two straight-vertical sidewalls are considered adiabatic. Governing equations are discretized using the control volume based Finite-Volume method with collocated variable arrangement. Simulation was carried out for a range of surface waviness ratios, =0.00-0.25; aspect ratios, A=0.25-0.5; and Rayleigh numbers Ra=100-107 for a fluid having Prandtl number equal to 1.0. Results are presented in the form of local and global Nusselt number distributions, streamlines, and isothermal lines for different values of surface waviness and aspect ratios. For a special case of =0 and A=1.0, the average Nusselt number distribution is compared with available reference. The results suggest that natural convection heat transfer is changed considerably when surface waviness changes and also depends on the aspect ratio of the domain. In addition to the heat transfer results, the heat transfer irreversibility (HTI) in terms of Bejan number (Be) was measured. For a set of selected values of the parameters (, A, and Ra), a contour of the Bejan number is presented at the end of this paper.

- by Prodip Das
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- Engineering, Heat Transfer, Numerical Simulation, Mathematical Sciences

The temperature field in an air layer enclosed between two isothermal vertical plates with different temperatures has been investigated with the help of a Zehnder-Mach interferometer. Local heat transfer coefficients were derived from the temperature gradients in the air normal to the plate surfaces. Below a certain Grashof number and above a certain value of the height to thickness ratio. heat is transferred from the hot to the cold boundary by conduction in the central part of the layer. Convection contributes only in the corner regions. For large Grashof numbers and below a certain limit of the height to thickness ratio, boundary layers exist along the surfaces of the enclosure, whereas in the central core the temperature is uniform in horizontal planes. The temperature increases, however, in vertical direction. Fluctuations in the flow and wave motions were observed in some of the experiments. Relations for local and average heat transfer are presented.Le champ termique d'une couche d'air comprise entre deux plaques verticales isothermes ayant des températures différentes a été étudié au moyen d'un interféromètre de Mach-Zehnder. Les coefficients locaux de transmission de chaleur ont été déterminés à partir des gradients de température de l'air, perpendiculaires aux plaques. Au-dessous d'un certain nombre de Grashof et au-dessus d'une certaine valeur du rapport hauteur/épaisseur, la chaleur se transmet par conduction dans la partie centrale de la couche, de la frontière chaude à la frontiére froide. La convection n'intervient que prés des angles. Pour de grands nombres de Grashof et au-dessous d'une certaine limite du rapport hauteur/ épaisseur, des couches limites existent le long des surfaces de l'enceinte, alors que dans la partie centrale la température est uniforme dans des plans horizontaux. Cependant, la température croit suivant la verticale. Des fluctuations dans l'écoulement et des mouvements d'ondes ont été observés dans quelques unes des expériences. Des relations pour la transmission de chaleur moyenne et locale sont présentées.Das Temperaturfeld einer Luftschicht zwischen zwei senkrechten, verschieden temperierten Platten wurde mit Hilfe des Zehnder-Mach-Interferometers untersucht. Aus den Temperaturgradienten der Luft normal zur Plattenoberfläche wurden örtliche Wärmeübergangskoeffizienten abgeleitet. Unterhalb einer gewissen Grashofzahl und oberhalb eines gewissen Verhältnisses Höhe zu Breite wird Wärme im Mittelteil nur durch Leitung übertragen und nur in den Ecken auch durch Konvektion. Für grosse Grashofzahlen und oberhalb einer gewissen Grenze des Höhe-Breite-Verhältnisses existiert eine Grenzschicht längs der Schichtoberflächen, während im Mittelteil die Temperatur in horizontalen Ebenen gleichförmig ist, in senkrechter Richtung aber ansteigt. Bei einigen Versuchen wurden fluktuierende Strömung und Wellenbewegungen beobachtet. Beziehungen für den örtlichen und mittleren Wärmeübergang werden angegeben.

- by walid hassen
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- Engineering, Heat and Mass Transfer, Mathematical Sciences, Natural Convection
- by Oronzio Manca
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- Mechanical Engineering, Applied Mathematics, Heat Transfer, Numerical Analysis
- by Majid Molki
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- Engineering, Heat Transfer, Electrostatics, Electrohydrodynamics

Steady state natural convection from heat sink with narrow plate-fins having parallel arrangement mounted on inclined base was experimentally investigated. Aluminum heat sink with two different lengths viz. 100mm and 200mm were modeled. Fin thickness was kept constant at 5mm. Fin height was selected 10mm, 20mm and 30mm for 100mm length of fin while it was 20mm, 40mm and 60mm for 200mm length of fin. Heat sink was kept at aspect ratio of 0.1, 0.2 and 0.3. Rectangular base was made incline for 0°, 10°, 20°, 45°, 70°, 80° and 90° keeping upward facing fins. Heat input was varied from 60 W to 100 W. Effect of fin height, fin length, inclination of base was determined. Range of angle of inclination was suggested showing equivalent heat transfer rate. Also, effect of aspect ratio over natural convection was examined.

- by Avdhoot Walunj
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- Heat Transfer, Natural Convection
- by Clement Sankat and +1
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- Natural Convection, Osmotic Dehydration, Ambient Temperature, Moisture Content
- by Allan Hayhurst and +1
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- Numerical Simulation, Natural Convection, Thermal Conductivity, Heat Conduction
- by Hervé Combeau
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- Mechanical Engineering, Applied Mathematics, Natural Convection, Phase Change
- by Zhaoli Guo
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- Engineering, Mathematical Sciences, Natural Convection, Physical sciences
- by Guy Lauriat and +1
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- Mechanical Engineering, Natural Convection, Heat Flux, Room Temperature
- by mohamed ali
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- Heat Transfer, Heat and Mass Transfer, Natural Convection, Laminar Flow
- by Perapong Tekasakul
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- Mechanical Engineering, Computational Fluid Dynamics, Modeling, Natural rubber

Experiments were carried out on natural convection heat transfer from square pin fin heat sinks subject to the influence of its geometry and heat flux. A total of 50 fins were bolted into the upper surface of the base plate. The area of the base plate is 250mm by 250mm. The base plate and the fins were made of aluminum .Over the tested range of Rayleigh number, 12.45

- by Cesar Trevino
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- Engineering, Materials Science, Heat and Mass Transfer, Mathematical Sciences
- by Abiodun AJIBADE
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- Mechanical Engineering, Heat Transfer, Natural Convection, Boundary Conditions
- by Ahmet Koca
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- Mechanical Engineering, Heat Transfer, Numerical Analysis, Entropy
- by Chaedong Kang
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- Engineering, History, Materials Science, Refrigeration
- by Lyes Khezzar and +1
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- Mechanical Engineering, Applied Mathematics, Heat Transfer, Natural Convection
- by J. Banaszek
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- Materials Engineering, Mechanical Engineering, Kinetics, Model validation

This work reports the laboratory test results of a Li-ion battery designed for electric scooter applications. Four different modes of heat dissipation were investigated in this experimental study: (1) natural convection cooling; (2)... more

- by Mohammed Farid
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- Engineering, Heat Transfer, Power, Natural Convection
- by Marcelo J. Lemos
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- Engineering, Heat Transfer, Heat and Mass Transfer, Turbulence modeling