Effect of Vibration on Heat Transfer for Flow Normal to a Cylinder

1969 ◽  
Vol 91 (1) ◽  
pp. 140-144 ◽  
Author(s):  
J. M. Faircloth ◽  
W. J. Schaetzle
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Horizontal Plane ◽  
Critical Reynolds Number ◽  
Wire Vibration ◽  
Surface Vibrations ◽  
Sinusoidal Current ◽  
The Wire ◽  
Forced Air

An experimental investigation of the effect that surface vibrations have on the heat transfer by forced convection was studied. A no. 40 gauge wire was vibrated in the horizontal plane by a sinusoidal current and simultaneously exposed to a forced air current in the same plane. The frequency and amplitude of the wire vibration were varied within the ranges of 20 to 40 Hz and 0.3 to 0.5 in., respectively. The Reynolds number experienced by the wire varied between 0 and 15. The results of the investigation revealed that above a critical Reynolds number the instantaneous convective coefficient was increased from 20 to 30 percent.

scholarly journals Convective cooling of tandem heated triangular cylinders placed in a channel

2010 ◽  
Vol 14 (1) ◽  
pp. 183-197 ◽  
Author(s):  
Afshin Mohsenzadeh ◽  
Mousa Farhadi ◽  
Kurosh Sedighi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Numerical Simulations ◽  
Incompressible Flow ◽  
Horizontal Plane ◽  
Plane Channel ◽  
Reynolds Numbers ◽  
Convective Cooling ◽  
Wall Proximity ◽  
Fluid Characteristics

Numerical simulations of forced convective incompressible flow in a horizontal plane channel with adiabatic walls over two isothermal tandem triangular cylinders of equal size are presented to investigate the effect of wall proximity of obstacles, gap space (i.e. gap between two squares), and Reynolds number. Computations have been carried out for Reynolds numbers of (based on triangle width) 100, 250, and 350. Results show that, wall proximity has different effect on first and second triangle in fluid characteristics especially in lower gap spaced, while for heat transfer a fairly same behavior was seen.

Experimental Investigation of the Air Flow Behavior and Heat Transfer Characteristics in Microchannels With Different Channel Lengths

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Zhi Tao ◽  
Zhibing Zhu ◽  
Haiwang Li
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Critical Reynolds Number ◽  
Flow Behavior ◽  
Channel Length ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Poiseuille Number ◽  
Channel Lengths

This paper attempts to experimentally investigate the influence of channel length on the flow behavior and heat transfer characteristics in circular microchannels. The diameters of the channels were 0.4 mm and the length of them were 5 mm, 10 mm, 15 mm, and 20 mm, respectively. All experiments were performed with air and completed with Reynolds number in the range of 300–2700. Results of the experiments show that the length of microchannels has remarkable effects on the performance of flow behavior and heat transfer characteristics. Both the friction factor and Poiseuille number drop with the increase of channel length, and the experimental values are higher than the theoretical ones. Moreover, the channel length does not influence the value of critical Reynolds number. Nusselt number decrease as the increase of channel length. Larger Nusselt numbers are obtained in shorter channels. The results also indicate that in all cases, the friction factor decreases and the Poiseuille number increases with the increase of the Reynolds number. It is also observed that the value of critical Reynolds number is between 1500 and 1700 in this paper, which is lower than the value of theoretical critical Reynolds number of 2300.

Heat Transfer Performance of Titanium Oxide in Ethylene Glycol Based Nanofluids under Transition Flow

2014 ◽  
Vol 660 ◽  
pp. 684-688 ◽  
Author(s):  
Khamisah Abdul Hamid ◽  
Wan Hamzah Azmi ◽  
Rizalman Mamat ◽  
Nur Ashikin Usri
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Ethylene Glycol ◽  
Titanium Oxide ◽  
Transition Region ◽  
Constant Heat Flux ◽  
Transition Flow ◽  
Enhancement Of Heat Transfer ◽  
Number Range

The needs to improve the efficiency of coolants undeniably become one of the concerns in cooling systems technologies nowadays. Nanofluid as coolant is invented and studied where it can provide better option for users due to augmentation in properties. This study provides experimental investigation on Titanium Oxide dispersed in water and ethylene glycol mixture under transition region with Reynolds number range of 2000 < Re <10000. Three volume concentrations are used which are 0.5 %, 1.0 % and 1.5 % for heat transfer experimental investigation under working temperature of 30 °C at constant heat flux of 600 W. The Nusselt number of the nanofluid increase with the increasing of Reynolds number at 1.5 % concentration, slightly higher than based fluid. The finding on the heat transfer coefficient shows enhancement of 2.1 % achieved by Titanium Oxide nanofluid at 1.5 % volume concentration. For 0.5 % and 1.0 % concentration, no enhancement of heat transfer achieved for the fluid flow under transition region at temperature of 30 °C.

Experimental Investigation of Heat Transfer in Microchannels

2003 ◽  
Author(s):  
Poh-Seng Lee ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Copper Substrate ◽  
Deionized Water ◽  
Entrance Length ◽  
Continuum Approach ◽  
Channel Depth ◽  
Rectangular Channels ◽  
Classical Correlations

Heat transport in microchannels is experimentally investigated to explore the validity of classical correlations for conventional-sized rectangular channels in predicting the thermal behavior and the onset of transition in microchannels. The microchannels considered range in width from 194 μm to 534 μm, with the channel depth being nominally five times the width in each case. Ten microchannels were machined into a 2.54 cm by 2.54 cm copper substrate for each test piece. The experiments were conducted with deionized water, with the Reynolds number ranging from approximately 300 to 3500. The results show that the heat transfer in microchannels is satisfactorily predicted with a classical, continuum approach. However, the applicable classical correlations need to be chosen carefully to match the boundary and entrance length conditions imposed in the experiment.

Viscous Dissipation and Variable Properties Effect on Two Dimensional Conjugate Heat Transfer of Nanofluids in Microchannels

2011 ◽  
Author(s):  
A. Ramiar ◽  
A. A. Ranjbar
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Viscous Dissipation ◽  
Conjugate Heat Transfer ◽  
Energy Equation ◽  
Critical Reynolds Number ◽  
Two Dimensional ◽  
Variable Properties ◽  
Enhance Heat Transfer

Laminar two dimensional forced convective heat transfer of Al2O3–water nanofluid in a horizontal microchannel has been studied numerically, considering axial conduction, viscous dissipation and variable properties effects. The existing criteria in the literature for considering viscous dissipation in energy equation are compared for different cases and the most proper one is applied for the rest of the paper. The results showed that nanoparticles enhance heat transfer characteristics of the channel and inversely, viscous dissipation causes the Nusselt number and friction factor to decrease. The viscous dissipation effect may be emphasized by increasing Reynolds number and decreased by raising the exerted heat flux. Also, it was found that there is a critical Reynolds number below which the average Nusselt number of the nanofluid changes abnormally with Reynolds number as a result of variable properties effect.

A Correlation of Leading Edge Transition and Heat Transfer on Swept Cylinders in Supersonic Flow

1965 ◽  
Vol 69 (649) ◽  
pp. 49-52 ◽  
Author(s):  
D. R. Topham
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Supersonic Flow ◽  
Critical Reynolds Number ◽  
Leading Edge ◽  
Turbulent Boundary Layers ◽  
Momentum Thickness ◽  
Heating Rates ◽  
Stagnation Line ◽  
Show Evidence

Summary:—It is shown that stagnation line heating rates for laminar, transitional and turbulent boundary layers measured on swept cylinders at supersonic speeds, can be correlated in terms of a Reynolds number based on the spanwise momentum thickness at the stagnation line.A critical Reynolds number for transition along the stagnation line is determined and experimental results show evidence of transition up to M= 10.

A note on fluctuating heat transfer at small Péclet numbers

1960 ◽  
Vol 7 (3) ◽  
pp. 442-448 ◽  
Author(s):  
C. R. Illingworth
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Energy Equation ◽  
Large Temperature ◽  
Hot Wire ◽  
Unsteady Heat Transfer ◽  
Air Stream ◽  
Working Principle ◽  
The Wire ◽  
Approximate Equations

The hot-wire anemometer, used for recording speed variations in turbulent flow, involves in its working principle the unsteady heat transfer from a hot fixed surface to a fluctuating air stream moving past the surface. If the wire is maintained at a constant (high) temperature, the rate of loss of heat from the wire changes with the velocity of the incident stream, and the compensating rate of gain of heat, produced by the Joule heating effect of the electric current, changes, correspondingly. The accompanying change of current can be measured, and used to calculate the varying velocity of the air stream. The hot wire may have a diameter as low as 10−4 in. and the Reynolds number of the flow is then of the order of 0.05 for each ft. per sec of velocity. With low velocities, of the order of 10 or 20 ft./sec, the flow past the wire is in the range of small Reynolds number, and the exact equations of flow may be approximated by simpler equations in the manner of Oseen's theory (Lamb 1932). The approximate equations are not easy to solve when the flow is compressible, as it will be in the presence of the large temperature differences imposed by the heat of the wire. If, however, the temperature differences are assumed to be small, the approximate energy equation is no longer linked with the equations of continuity and momentum, and it may be solved without knowledge of the velocity field. The purpose of this note is to give the solution for the temperature field when a warm circular cylinder or a warm sphere is held at rest in a fluctuating stream.

scholarly journals Numerical investigation of fluid flow and heat transfer characteristics in sine, triangular, and arc-shaped channels

2007 ◽  
Vol 11 (1) ◽  
pp. 17-26 ◽  
Author(s):  
Zakir Hossain ◽  
Sadrul Islam
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Critical Reynolds Number ◽  
Navier Stokes ◽  
Heat Transfer Characteristics ◽  
Single Wave ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Wavy Channels

Time dependent Navier-Stokes and energy equations have been solved to investigate the fluid flow and heat transfer characteristics in wavy channels. Three different types of two dimensional wavy geometries (e.g. sine-shaped, triangular, and arc-shaped) are considered. All of them are of single wave and have same geometric dimensions. Periodic boundary conditions are used to attain fully developed flow. The flow in the channels has been observed to be steady up to a critical Reynolds number, which depends on the geometric configuration. Beyond the critical Reynolds number a self-sustained oscillatory flow has been observed. As a result of this oscillation, there is increased mixing between core and the near-wall fluids, thereby increasing the heat transfer rate. For the same geometric dimensions, flow becomes unsteady at relatively lower Reynolds number in the arc-shaped channel. .

Heat Transfer From Two Elliptic Cylinders in Tandem Arrangement

1986 ◽  
Vol 108 (3) ◽  
pp. 525-531 ◽  
Author(s):  
T. Ota ◽  
H. Nishiyama ◽  
J. Kominami ◽  
K. Sato
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Angle Of Attack ◽  
Major Axis ◽  
Heat Transfer Characteristics ◽  
Axis Ratio ◽  
Tandem Arrangement ◽  
Axis Length ◽  
Streamwise Distance

An experimental investigation has been conducted to clarify heat transfer characteristics of two elliptic cylinders having an axis ratio 1:2. They were placed in tandem arrangements and their angles of attack to the upstream uniform flow were identical. The testing fluid was air and the Reynolds number based on the major axis length c ranged from about 15,000 to 80,000. The angle of attack was varied from 0 to 90 deg at 30 deg intervals and the nondimensional cylinder spacing l/c from 1.25 to 4.0, where l denotes the streamwise distance between the cylinder centers. It has been found that the heat transfer features vary drastically with the angle of attack and also with the cylinder spacing.

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