Heat Transfer to Pneumatically Conveyed Glass Particles of Fixed Size

1963 ◽  
Vol 85 (2) ◽  
pp. 164-171 ◽  
Author(s):  
C. A. Depew ◽  
L. Farbar
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Constant Heat Flux ◽  
Vertical Tube ◽  
Spherical Particles ◽  
Analytical Treatment ◽  
Radial Temperature ◽  
Air Stream ◽  
The Difference ◽  
Two Phases

The phenomenon of heat transfer to an air stream laden with solid spherical particles flowing up a vertical tube with constant heat flux was investigated experimentally and analytically. Two particle sizes, 30 and 200 microns in diameter, were employed. The air flow conditions were held constant at Reynolds numbers of 13,500 and 27,400 while solids were added up to gravimetric ratios of seven. The analytical treatment parallels available solutions for single-phase flow. An approximate solution was obtained under the assumption that the difference in the temperature of the two phases is small, and that the radial temperature profiles of the two phases in the fully developed region are similar. Qualitative agreement with the experimental results is obtained. Large changes in the local Nusselt number were obtained in the experiments using 30-micron particles, in contrast to small effects due to 200-micron particles.

An Experimental and Theoretical Study of Heat Transfer in Vertical Tube Flows

1978 ◽  
Vol 100 (1) ◽  
pp. 86-91 ◽  
Author(s):  
R. Greif
Keyword(s):  
Heat Transfer ◽  
Turbulent Flows ◽  
Theoretical Study ◽  
Numerical Solutions ◽  
Reynolds Numbers ◽  
Vertical Tube ◽  
Laminar Flows ◽  
Radial Temperature ◽  
Rayleigh Numbers ◽  
Good Agreement

An experimental and theoretical study was carried out for the heat transfer in laminar and turbulent tube flows with air and argon. Radial temperature profiles were measured at a location 108 tube diameters from the inlet of the vertical, electrically heated test section. The temperature of the tube wall was also measured. The experimental data were in good agreement with the results obtained from numerical solutions of the conservation equations and from simplified, fully developed solutions. For turbulent flows the Reynolds numbers varied from 10,000 to 19,500; for laminar flows the Reynolds numbers varied from 1850 to 2100 while the Rayleigh numbers varied from 70 to 80.

Heat Transfer From Rectangular Plates Inclined at Different Angles of Attack and Yaw to an Air Stream

1985 ◽  
Vol 107 (2) ◽  
pp. 307-312 ◽  
Author(s):  
D. G. Motwani ◽  
U. N. Gaitonde ◽  
S. P. Sukhatme
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Rectangular Plates ◽  
Average Heat Transfer Coefficient ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
Aspect Ratios ◽  
Air Stream ◽  
Angle Of Yaw

Average heat transfer coefficients during forced convection air flow over inclined and yawed rectangular plates have been experimentally determined. Tripping wires at the edges ensured that a turbulent boundary layer prevailed over the plates. The experiments were carried out for a constant surface temperature and covered two plates of different aspect ratios, angles of attack from 0 to 45 deg, angles of yaw from 0 to 30 deg, and Reynolds numbers from 2 times; 104 to 3.5 times; 105. The results show that the average heat transfer coefficient is essentially insensitive to the aspect ratio and angle of yaw. However, it is a function of Reynolds number and the angle of attack. Correlation equations for various angles of attack are suggested.

Heat Transfer in the Flow of Gases Around Oil Sand Spheres

1988 ◽  
Vol 110 (4) ◽  
pp. 276-278
Author(s):  
M. A. Abdrabboh ◽  
G. A. Karim
Keyword(s):  
Heat Transfer ◽  
Oil Sands ◽  
Reynolds Numbers ◽  
Spherical Particles ◽  
Dimensionless Temperature ◽  
Convective System ◽  
Oil Sand ◽  
Low Reynolds Numbers ◽  
Convection Heating ◽  
Free And Forced Convection

An experimental study was conducted for the combined free and forced convection heating of preshaped molded spherical particles of Athabasca oil sands in hot gaseous streams of air at low Reynolds numbers. Based on a quasi-steady system, the lumped-heat-capacity approximation was employed to estimate the heat transfer coefficient of the transient convective system for each prescribed set of experimental stream conditions. Correlation of the results was made in terms of the dimensionless Nusselt number as a function of the particle Reynolds number and a dimensionless temperature difference. The simple closed-form analytical expression of the correlation was shown to fit the experimental data well.

scholarly journals Experimental Investigation of The Influence of Mechanical Forced Vibrations and Heat Flux on Coefficient of Heat Transfer

2018 ◽  
Vol 6 (3) ◽  
pp. 124-129
Author(s):  
Adil Bash ◽  
Aadel Alkumait ◽  
Hamza Yaseen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Forced Vibration ◽  
Vibration Amplitude ◽  
Internal Flow ◽  
Reynolds Numbers ◽  
Constant Heat Flux ◽  
Working Fluid ◽  
New Correlation

The aim of this paper to verify the influence of vertical forced vibration on the coefficient of heat transfer of the laminar internal flow in a spiral fluted tube. With adopted the water as a working fluid, and flowing Reynolds numbers at the entrance between 228 and 1923, the tube heated under constant heat flux levels ranging from 618-3775 W/m2. The frequencies of vibration ranging from 13 to 30 Hz, and the amplitudes of vibration from 0.001 to 0.002 mm. The results appeared that the coefficient of heat transfer significantly affected by mechanical forced vibration in a flowing of the heated tube. When the vibration amplitude increases, the Nusselt number Significantly increases, with the maximum increases of 8.4% at the amplitude of vibration 0.0022 mm and the frequency 13 Hz. Generally, the coefficient of heat transfer increases with increasing Reynolds number and heat flux. At last, by using the parameters of vibration amplitude, frequency, heat flux and Reynolds number, a new correlation has been derived depends on experimental data.

scholarly journals EFFECT OF CAVITY RATIO ON HEAT TRANSFER BY FREE LOAD FROM HEATED PLATES UPWARD WITH CONSTANT HEAT FLUX

2021 ◽  
Vol 9 (12) ◽  
pp. 686-695
Author(s):  
Waleed Abdulhadiethbayah ◽  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Free Convection ◽  
Electronic Devices ◽  
Experimental Studies ◽  
Constant Heat Flux ◽  
Rate Of Change ◽  
Constant Heat ◽  
The Difference

Many engineering and industrial applications always seek to find ways to dissipate heat from heated surfaces used in these industries. As it is involved in the cooling of electronic parts and electrical transformers, as well as the design of solar collectors, in addition to being a process of heat exchange between hot surfaces and the fluids in contact with them. Since most electronic devices or their parts are cooled by removing the heat generated inside them by using air as a heat transfer medium and in a free convection way, and the fact that heat transfer by free convection occurs in many fields, so there were many studies that dealt with this topic. The free load is generated by the buoyant force (Bouncy force) As a result of the difference in the density of the fluid adjacent to the heated surface due to the difference in temperatures between the fluid and the surface. The laminar flow along surfaces has been extensively studied analytically [1,2,3,4] In the horizontal, inclined and vertical case, whether by constant heat flux or constant surface temperature, there are also many experimental studies of heat transfer by free convection from horizontal, inclined and vertical surfaces with constant heat flux or constant surface temperature [5,6,7,8]. Some experimental studies have also been conducted on heat transfer by convection from heated surfaces in the form of a disk (ring)The outcome of these studies was to extract an exponential mathematical relationship between the average of Nusselt number and the Kirchhoff number or Rayleigh number and the following formula: (Nu=C(Ra) n It is one of the most suitable formulas for heat transfer by free convection from heated surfaces in all its forms and over a wide range of Rayleigh number . It is noted that not all of these studies dealt with the study of the effect of the cavity ratio on heat transfer by free convection from square-shaped surfaces, which is the form that is more applied in electronic devices. Therefore, the current research means studying the rate of change in the average of Nusselt number, which represents a function of the rate of change in the rate of heat transfer by convection, as well as studying the thermal gradient above the surface, and this was done through using three hollow surfaces in proportions (0.25,0.5,0.75) of the total area.

Heat Transfer in Rotating Narrow Rectangular Ducts With Heated Sides Oriented at 60° to the r-z Plane

2000 ◽  
Vol 123 (2) ◽  
pp. 288-295 ◽  
Author(s):  
Fred T. Willett ◽  
Arthur E. Bergles
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Ambient Pressure ◽  
Thin Foil ◽  
Reynolds Numbers ◽  
Constant Heat Flux ◽  
Width Ratio ◽  
Test Results ◽  
Trailing Edge ◽  
Rotation Numbers

Gas turbine blade life is often limited by the effectiveness of the cooling in the trailing edge convective cavity, which generally has a narrow cross-section. Previous research on rotational effects considered cavity shapes quite different from those of typical trailing edge cavities. In this research, experiments were conducted to determine the effect of rotation on heat transfer in ducts of narrow cross-section (height-to-width ratio of 1:10), oriented with the heated sides at 60° to the r-z plane. In the experiment, a high-molecular-weight gas (Refrigerant-134A) at ambient pressure and temperature conditions was used to match the dimensionless parameters at engine conditions. Thin foil heaters were used to produce a constant heat flux at the long sides of the duct; the narrow sides were unheated. Duct Reynolds numbers were varied up to 20,000; rotation numbers were varied up to 0.25. The test results show the effect of rotation and aspect ratio on duct leading and trailing side heat transfer. In addition, the results show the variation in heat transfer coefficient with transverse location in the duct, demonstrating the effect of rotation not only on lead and trail side heat transfer, but also on forward and aft end heat transfer.

Heat Transfer to a Pvd Rotor Blade at High Subsonic Passage Throat Mach Numbers

1978 ◽  
Vol 192 (1) ◽  
pp. 225-235 ◽  
Author(s):  
B. W. Martin ◽  
A. Brown ◽  
S. E. Garrett
Keyword(s):  
Heat Transfer ◽  
Rotor Blade ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Suction Surface ◽  
Pressure Surface ◽  
Air Stream ◽  
Mach Numbers

This paper reports heat-transfer measurements round a PVD rotor blade using a transient method. Instrumented syndanio-asbestos blades forming part of a cascade are suddenly introduced into a heated air stream, the temperature-time response of surface thermocouples attached to copper inserts in the blades then being used to determine local heat-transfer coefficients for (a) passage throat Mach numbers between 0.79 and 0.94 (b) turbulence intensities from 4.15 to 9.05 per cent (c) blade chord Reynolds numbers from 7.8 times 105 to 8.9 times 105. Measured transition lengths on the suction surface, over which the heat transfer nearly trebles, are somewhat short in relation to other measurements. The onset of transition, which is downstream of predictions for the higher Reynolds numbers but accords with the trends of existing correlations, is little influenced by turbulence intensity variations in the above range. Over the pressure surface the heat transfer is less than for a fully-turbulent boundary layer. Comparisons with other high Mach-number measurements suggest that much further work is needed before the effects of scale of turbulence are fully understood.

scholarly journals Numerical Investigation of Heat Transfer Enhancement in a Rectangular Heated Pipe for Turbulent Nanofluid

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Hooman Yarmand ◽  
Samira Gharehkhani ◽  
Salim Newaz Kazi ◽  
Emad Sadeghinezhad ◽  
Mohammad Reza Safaei
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Volume Fraction ◽  
Rectangular Channel ◽  
Thermal Characteristics ◽  
Reynolds Numbers ◽  
Constant Heat Flux ◽  
Energy Equations ◽  
Volume Method ◽  
Good Agreement

Thermal characteristics of turbulent nanofluid flow in a rectangular pipe have been investigated numerically. The continuity, momentum, and energy equations were solved by means of a finite volume method (FVM). The symmetrical rectangular channel is heated at the top and bottom at a constant heat flux while the sides walls are insulated. Four different types of nanoparticles Al2O3, ZnO, CuO, and SiO2at different volume fractions of nanofluids in the range of 1% to 5% are considered in the present investigation. In this paper, effect of different Reynolds numbers in the range of 5000 < Re < 25000 on heat transfer characteristics of nanofluids flowing through the channel is investigated. The numerical results indicate that SiO2-water has the highest Nusselt number compared to other nanofluids while it has the lowest heat transfer coefficient due to low thermal conductivity. The Nusselt number increases with the increase of the Reynolds number and the volume fraction of nanoparticles. The results of simulation show a good agreement with the existing experimental correlations.

Drag coefficient of a sphere in a non-stationary flow: new results

2007 ◽  
Vol 463 (2088) ◽  
pp. 3323-3345 ◽  
Author(s):  
G Jourdan ◽  
L Houas ◽  
O Igra ◽  
J.-L Estivalezes ◽  
C Devals ◽  
...  
Keyword(s):  
Drag Coefficient ◽  
Stationary Flow ◽  
Reynolds Numbers ◽  
Spherical Particles ◽  
Steady Flows ◽  
Two Phase ◽  
Spider Web ◽  
Wide Range ◽  
The Difference ◽  
Sphere Drag

The drag coefficient of a sphere placed in a non-stationary flow is studied experimentally over a wide range of Reynolds numbers in subsonic and supersonic flows. Experiments were conducted in a shock tube where the investigated balls were suspended, far from all the tube walls, on a very thin wire taken from a spider web. During each experiment, many shadowgraph photos were taken to enable an accurate construction of the sphere's trajectory. Based on the sphere's trajectory, its drag coefficient was evaluated. It was shown that a large difference exists between the sphere drag coefficient in steady and non-steady flows. In the investigated range of Reynolds numbers, the difference exceeds 50%. Based on the obtained results, a correlation for the non-stationary drag coefficient of a sphere is given. This correlation can be used safely in simulating two-phase flows composed of small spherical particles immersed in a gaseous medium.

scholarly journals Ekman Layer Scrubbing and Shroud Heat Transfer in Centrifugal Buoyancy-Driven Convection

2021 ◽  
Vol 143 (7) ◽  
Author(s):  
Feng Gao ◽  
John W. Chew
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Boussinesq Approximation ◽  
Ekman Layer ◽  
Open Cavity ◽  
Mean Flow ◽  
Large Eddy ◽  
The Mean ◽  
The Difference ◽  
Buoyancy Driven Convection

Abstract This paper presents large-eddy and direct numerical simulations of buoyancy-driven convection in sealed and open rapidly rotating cavities for Rayleigh numbers in the range 107–109, and axial throughflow Reynolds numbers 2000 and 5600. Viscous heating due to the Ekman layer scrubbing effect, which has previously been found responsible for the difference in sealed cavity shroud Nusselt number predictions between a compressible N–S solver and an incompressible counterpart using the Boussinesq approximation, is discussed and scaled up to engine conditions. For the open cavity with an axial throughflow, laminar Ekman layer behavior of the mean flow statistics is confirmed up to the highest condition in this paper. The Buoyancy number Bo is found useful to indicate the influence of an axial throughflow. For the conditions studied the mean velocities are subject to Ra, while the velocity fluctuations are affected by Bo. A correlation, Nu′=0.169(Ra′)0.318, obtained with both the sealed and open cavity shroud heat transfer solutions, agrees with that for free gravitational convection between horizontal plates within 16% for the range of Ra′ considered.

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