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.

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.

The Effect of Conductive and Non-Conductive Flow Diverters on Free Convection Heat Transfer From a Vertical Array of Horizontal Isothermal Cylinders

2009 ◽  
Author(s):  
Pooyan Razi ◽  
Behnam Moghadassian ◽  
Hossein Shokouhmand
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Vertical Array ◽  
Free Convection Heat ◽  
Isothermal Cylinders ◽  
Rayleigh Numbers ◽  
Flow Diverters

In this paper, a numerical solution method (finite volume) has been applied to investigate the effect of conductive and non-conductive flow diverters on free convection heat transfer from a vertical array of horizontal isothermal cylinders. Cylinder vertical spacings (center to center distance = S) of 2D, 3D and 4D has been investigated, which D is the cylinder diameter. Rectangular plate diverters have been placed between cylinders. Diverters are tilted at different angels with respect to horizon. The calculation has been done for various Rayleigh numbers based on the cylinder-diameter in the range between 103 and 104. The results show that in the case of 2D cylinder spacing, both conductive and non-conductive flow diverters decrease the heat transfer rate of cylinders at low Rayleigh numbers. However, as the distance between the cylinders increases to 3D and 4D, adding flow diverters leads to an increase in the heat transfer rate of the array. Also, in the cases of 3D and 4D spacing, the use of non-conductive flow diverters results in more increase in heat transfer rate in comparison with the rate of heat transfer resulted by applying conductive diverters.

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