Effects of Oscillation on Free Convection From a Vertical Finite Plate

1964 ◽  
Vol 86 (2) ◽  
pp. 149-158 ◽  
Author(s):  
V. D. Blankenship ◽  
J. A. Clark
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Vibrational Amplitude ◽  
Finite Plate ◽  
Potential Flows ◽  
Steady Heat ◽  
Inertia Forces ◽  
Theoretical Results

The effect of transverse oscillation on free convection from a vertical, finite plate is studied analytically. A second paper will consider the experimental results. Consideration is given to perturbations up to second order for potential flows with small vibrational amplitude and high frequency. Theoretical results are given for velocity, temperature, heat-transfer rate, and shear stress. It is shown that oscillations slightly decrease the steady heat-transfer rate for laminar flow. This reduction is thought to be a result of an interaction between the viscous and inertia forces in the laminar boundary layer which causes a net decrease in the connective flow near the plate.

Experimental Effects of Transverse Oscillations on Free Convection of a Vertical, Finite Plate

1964 ◽  
Vol 86 (2) ◽  
pp. 159-165 ◽  
Author(s):  
V. D. Blankenship ◽  
J. A. Clark
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Free Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Experimental Results ◽  
Transverse Oscillation ◽  
Finite Plate ◽  
Analytical Results ◽  
Transverse Oscillations

The effects of transverse oscillation on free convection from a vertical, finite plate is investigated experimentally. This paper supplements an earlier paper wherein analytical results were reported. In that paper it was reported that oscillation slightly decreases the heat-transfer rate for laminar flow. The experimental results are in accord. However, more important is the fact that the oscillation forces the flow to become turbulent whereby large increases in heat-transfer rate are obtained. Experimental results are given for heat-transfer rate, both laminar and turbulent, and transition.

The impacts of non-uniform magnetic field on free convection heat transfer of a magnetizable micropolar nanofluid

2019 ◽  
Vol 29 (10) ◽  
pp. 3685-3706
Author(s):  
Zafar Namazian ◽  
S.A.M. Mehryan
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Content Type ◽  
Viscosity Parameter ◽  
Micropolar Nanofluid ◽  
Free Convection Heat

Purpose The purpose of this study is to numerically study the heat transfer of free convection of a magnetizable micropolar nanofluid inside a semicircular enclosure. Design/methodology/approach The flow domain is under simultaneous influences of two non-uniform magnetic fields generated by current carrying wires. The directions of the currents are the same. Although the geometry is symmetric, it is physically asymmetric. The impacts of key parameters, including Rayleigh number Ra = 103-106, Hartman number Ha = 0-50, vortex viscosity parameter Δ = 0-4, nanoparticles volume fraction φ = 0-0.04 and magnetic number Mnf = 0-1000, on the macro- and micro-scales flows, temperature and heat transfer rate are studied. Finding The outcomes show that dispersing of the nanoparticles in the host fluid increases the strength of macro- and micro-scale flows. When Mnf = 0, the increment of the vortex viscosity parameter increases the strength of the particles micro-rotations, while this characteristic is decreased by growing Δ for Mnf ≠ 0. The increment of Δ and Ha decreases the rate of heat transfer. The increment of Ha decreases the enhancement percentage of heat transfer rate because of dispersing nanoparticles, known as En parameter. In addition, the value of Δ has no effect on En. Moreover, the average Nusselt number Nuavg and En remain constant by increasing the magnetic number Mnf for different volume fraction values. Originality/value The authors believe that all of the results, both numerical and asymptotic, are original and have not been published elsewhere yet.

Effects of Corona Discharge on Free-Convection Heat Transfer Inside a Vertical Hollow Cylinder

1984 ◽  
Vol 106 (2) ◽  
pp. 346-351 ◽  
Author(s):  
M. E. Franke ◽  
K. E. Hutson
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Corona Discharge ◽  
Heat Transfer Rate ◽  
Hollow Cylinder ◽  
Transfer Rate ◽  
Convection Heat Transfer ◽  
Inside Surface ◽  
Convection Heat ◽  
Free Convection Heat

Vortex rolls induced inside a vertical hollow cylinder are found to increase the free-convection heat transfer rate from the inside surface. The vortex rolls are induced by the corona wind generated between 0.05-mm-dia wire electrodes placed vertically on the inside surface of the vertical hollow cylinder. The increase in heat transfer rate is determined experimentally and is based on the heat input required to maintain the inside surface of the cylinder at constant temperature. The experimental results without corona discharge are compared with an analytical heat balance. A Mach-Zehnder interferometer is used for boundary layer visualization.

Application of a Three-Dimensional Immersed Boundary Method for Free Convection From Single Spheres and Aggregates

2015 ◽  
Vol 138 (4) ◽  
Author(s):  
Samuel G. Musong ◽  
Zhi-Gang Feng ◽  
Efstathios E. Michaelides ◽  
Shaolin Mao
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Heat Transfer Rate ◽  
Immersed Boundary Method ◽  
Transfer Rate ◽  
Three Dimensional ◽  
Spherical Particles ◽  
Immersed Boundary ◽  
Thermal Plume ◽  
Boundary Method

Abstract A three-dimensional immersed boundary method (IBM) is applied for the solution of the thermal interactions between spherical particles in a viscous Newtonian fluid. At first, the free convection of an isolated isothermal sphere immersed in a viscous fluid is analyzed as a function of the Grashof number. A new correlation for the heat transfer rate from a single sphere is obtained, which is valid in the ranges 0.5 ≤ Pr ≤ 200 and 0 ≤ Gr ≤ 500. Second, the free convection heat transfer rate from pairs of spheres (bispheres) and from small spherical clusters immersed in air (Pr = 0.72) is investigated using this numerical technique. For bispheres, their orientation and the thermal plume interactions within a range of interparticle distances may cause the enhancement of the heat transfer rate above the values observed for two isolated spheres. For the simple triangular particle clusters, where the particles are in contact, it was observed that the average heat transfer rate per sphere decreases with the increased number of spheres in the cluster.

scholarly journals Free Convection of Ag/H2O Nanofluid in Square Cavity with Different Position and Orientation of Egg Shaped Cylinder

2021 ◽  
Vol 53 (4) ◽  
pp. 210409
Author(s):  
Atheer Saad Hashim
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Free Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Orientation Angle ◽  
Numerical Results ◽  
Vertical Position ◽  
Square Cavity

A numerical simulation was conducted to study the free convection of Ag/H2O nanofluid between a square cavity with cold walls and an egg shaped cylinder with a hot wall. Utilizing the egg equation, dimensionless governing equations were solved using the Galerkin Finite Element Method (GFEM). In this work, several parameters were studied, i.e. Rayleigh number (103 ≤ Ra ≤ 106), volume fraction (0 ≤ φ ≤ 0.05), position (-0.2 ≤ Y ≤ 0.2), and orientation angle (-90° ≤ γ ≤ 90°). The numerical results are presented as streamline contours, isotherm contours, and local and average Nusselt numbers. Moreover, the results were used to analyze the fluids’ structure, temperature distribution, and heat transfer rate. The numerical results confirmed that the stream intensity value increased with an increase of the Rayleigh number as well as the movement of the cylinder towards the bottom wall for all values of the orientation angle. Variation of the vertical position of the cylinder inside the cavity had a noticeable effect on , which increased by 50% at γ = -90°, and by 58% at γ = -45°. However, at Y = -0.2,  increased by 58% at γ = -45° and decreased by 7% at γ = -90°. The highest heat transfer rate was obtained at high Rayleigh number (Ra = 106), volume fraction (φ = 0.05), negative position (Y = -0.2), and the highest positive orientation angle (γ = 90°).

FREE CONVECTION FROM A HORIZONTAL HEATED CYLINDER LOCATED BELOW A CEILING

1999 ◽  
Vol 23 (1A) ◽  
pp. 19-35 ◽  
Author(s):  
G.B. Lawrence ◽  
G.E. Jardin ◽  
D. Naylor ◽  
A.D. Machin
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Free Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Average Nusselt Number ◽  
Two Dimensional ◽  
Number Range ◽  
Heated Cylinder ◽  
Made In

Steady two-dimensional laminar free convection from a horizontal heated cylinder located beneath a wide ceiling at ambient temperature has been studied. A finite element numerical solution has been obtained for a Prandtl number of Pr = 0.7 and a Rayleigh number range (based on the cylinder diameter) of 102 ≤ Ra ≤ 105. Numerically predicted temperature field and local Nusselt number distributions were compared to experimental measurements made in air using a Mach-Zehnder interferometer. For cylinder- to-ceiling spacings greater than about one diameter, the ceiling was found to have almost no influence on the heat transfer rate from the cylinder. At very close cylinder-to-ceiling spacings, the average Nusselt number increased substantially because of conduction effects. However, for 103 ≤ Ra ≤ 105, the effect of the ceiling on the numerically predicted overall heat transfer rate was less than ±10%, provided the cylinder was more than about one quarter of a diameter away form the ceiling.

Combined Convective Heat Transfer from Vertical Cylinders in a Horizontal Air-Stream

1978 ◽  
Vol 5 (2) ◽  
pp. 115-117
Author(s):  
P. H. Oosthuizen ◽  
R. Leung
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Convective Heat Transfer ◽  
Heat Transfer Rate ◽  
Convective Heat ◽  
Transfer Rate ◽  
Circular Cylinders ◽  
Transfer Rates ◽  
Air Stream ◽  
Vertical Cylinders

Mean heat transfer rates from a series of circular cylinders mounted vertically in a horizontal air-stream have been measured. Five cylinders were used, having diameters of approximately 19 to 25 mm and heights of approximately 150 to 300 mm. Heat transfer rates from these cylinders were measured at a number of different air velocities ranging from zero to about 1.6 m/s. The results indicate that the heat transfer rate in the combined convection range is higher than it would be under the same conditions with purely free convection or purely forced convection. An attempt has been made to correlate the combined convective heat transfer rates in terms of the heat transfer rates that would exist under the same conditions in these two limiting cases of purely forced and purely free convection.

Effect of Vortices Induced by Corona Discharge on Free-Convection Heat Transfer From a Vertical Plate

1969 ◽  
Vol 91 (3) ◽  
pp. 427-432 ◽  
Author(s):  
M. E. Franke
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Free Convection ◽  
Electric Field ◽  
Corona Discharge ◽  
Heat Transfer Rate ◽  
High Voltage ◽  
Transfer Rate ◽  
Thermal Boundary Layer ◽  
Transfer Rates

Experimental results are presented to show that columnar, counterrotating, vertical vortices can be produced on a heated, vertical, flat plate under free-convection conditions in air using a high-voltage d-c electric field. The vortices result from the corona discharge on 0.002-in.-dia parallel wires of alternate high voltage and ground potential placed vertically on the surface of a phenolic laminate plate. Heat-transfer rates are measured using an energy-balance method, and the thermal boundary layer is made visible using a Mach-Zehnder interferometer. Experimental curves are presented to illustrate the increase in the heat-transfer rate with increase in the electric-field power. Interference photographs and frames from a motion picture show the effects of the vortices on the thermal boundary layer. The convective part of the heat transfer from the 10 × 10 in. plate is more than doubled before the electric-field power becomes as large as 5 percent of the increase in the heat-transfer rate. Local heat-transfer rates are highest at the high-voltage wires and lowest at the grounded wires.

A Three Dimensional Immersed Boundary Method for Free Convection From Single Spheres and Aggregates

2014 ◽  
Author(s):  
Zhi-Gang Feng ◽  
Samuel G. Musong ◽  
Efstathios E. Michaelides
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Heat Transfer Rate ◽  
Immersed Boundary Method ◽  
Transfer Rate ◽  
Numerical Technique ◽  
Three Dimensional ◽  
Immersed Boundary ◽  
Average Heat ◽  
Boundary Method

A novel numerical technique that utilizes a three-dimensional Immersed Boundary Method (IBM) to solve the thermal interactions between spherical particles in a fluid is developed. At first, the natural convection of an isolated isothermal sphere immersed in a viscous fluid is analyzed and a new correlation for the heat transfer rate from a single sphere is obtained for 0.5≤Pr≤200 and 0 ≤ Gr ≤500. Secondly, the free convection heat transfer rate of a pair of spheres (bi-sphere) and spherical clusters immersed in air (Pr=0.72) were investigated using this numerical technique. The interactions depend on the separation distance between the spheres. It was observed that an increase in the separation of two spheres in tandem or side-by-side within a certain range may enhance the average heat transfer rate, when the interparticle distance is more than five radii. The average heat transfer rate of a cluster of touching, identical spheres with the same Grashof number was found to decrease as the number of spheres increased in the cluster.

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