Experimental Study of Fully Developed Convection in a Copper Horizontal Tube With Uniform Heat Flux Using Nanofluids

2009 ◽  
Author(s):  
Naser Zarezadeh ◽  
Majid Saffar-Avval
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Turbulent Flow ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Horizontal Tube ◽  
Continuous Phase ◽  
Constant Heat Flux ◽  
Uniform Heat Flux

The term of nanofluid refers to a solid-liquid mixture with a continuous phase which is a nanometer sized nanoparticle dispersed in conventional base fluids. Recent investigations on nanofluids indicate that the suspended nanoparticles markedly change the transport properties and heat transfer characteristics of the suspension. There are less published articles on deriving the forced convective heat transfer of nanofluids than articles on the effective thermal conductivity of nanofluids. Fully developed turbulent flow and heat transfer of two different nanofluids (Al2O3 and TiO2) in water flowing through a circular tube under constant heat flux condition have been experimentally studied. The results showed enhancement of convective heat transfer using the nanofluids. The Nusselt numbers of nanofluids were obtained for different nanoparticle concentrations as well as various Reynolds numbers. Experimental results emphasize the enhancement of heat transfer due to the nanoparticles presence in the fluid. Nusselt number increases by increasing the concentration of nanoparticles in nanofluid. And values of Nusselt number were calculated and these results have been introduced by experimental correlations for turbulent flow.

Experimental Investigation of Natural Convective Heat Transfer From Horizontal, Inclined and Vertical Cylinder With Constant Heat Flux

2010 ◽  
Author(s):  
A. Gharehghani ◽  
R. Hoseini ◽  
M. M. Salahi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Constant Heat Flux ◽  
Experimental Results ◽  
Constant Heat ◽  
Constant Length

In this study, natural convective heat transfer from cylindrical slender rods with different length and diameters and different angles of inclination (from horizontal to vertical) at constant heat flux condition was measured. For each inclination angle, average natural heat transfer coefficient was obtained. The effects of the angle of inclination and that of the diameter and length of cylinders on heat transfer rates were examined. The angles of 0°, 15°, 30°, 45°, 60°, 75° and 90° were studied. Experimental results show that increasing the diameter of the cylinder, with constant length and the Rayleigh number based on length causes the decrease of the Nusselt number. Increasing the length of the cylinders, with constant diameter and Rayleigh number based on diameter causes the decrease of the Nusselt number. Increasing either the angle of inclination or length decreases the effect of diameter on the heat transfer rate. Experimental results in terms of Nusselt number were correlated as a function of modified Rayleigh number and dimensionless parameters containing diameter, length and orientation angle.

Analysis of flow and heat transfer over stretching/shrinking and porous surfaces

2021 ◽  
pp. 875608792110258
Author(s):  
Azhar Ali ◽  
Dil Nawaz Khan Marwat ◽  
Aamir Ali
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Current Model ◽  
Uniform Heat Flux ◽  
Similarity Transformations ◽  
Flow And Heat Transfer ◽  
Special Cases ◽  
Porous Surfaces

Flows and heat transfer over stretching/shrinking and porous surfaces are studied in this paper. Unusual and generalized similarity transformations are used for simplifying governing equations. Current model includes all previous cases of stretched/shrunk flows with thermal effects discussed so far. Moreover, we present three different cases of thermal behavior (i) prescribed surface temperature (ii) Variable/uniform convective heat transfer at plat surface and (iii) prescribed variable/uniform heat flux. Stretching/shrinking velocity Uw(x), porosity [Formula: see text], heat transfer [Formula: see text], heat flux [Formula: see text] and convective heat transfer at surface are axial coordinate dependent. Boundary layer equations and boundary conditions are transformed into nonlinear ODEs by introducing unusual and generalized similarity transformations for the variables. These simplified equations are solved numerically. Final ODEs represent suction/injection, stretching/shrinking, temperature, heat flux, convection effects and specific heat. This current problem encompasses all previous models as special cases which come under the scope of above statement (title). The results of classical models are scoped out as a special case by assigning proper values to the parameters. Numerical result shows that the dual solutions can be found for different possible values of the shrinking parameter. A stability analysis is accomplished and apprehended in order to establish a criterion for determining linearly stable and physically compatible solutions. The significant features and diversity of the modeled equations are scrutinized by recovering the previous problems of fluid flow and heat transfer from a uniformly heated sheet of variable (uniform) thickness with variable (uniform) stretching/shrinking and injection/suction velocities.

Investigation on Convective Heat Transfer over a Rotating Disk with Bottom Wall Subjected to Uniform Heat Flux

2012 ◽  
Vol 249-250 ◽  
pp. 443-451
Author(s):  
Jing Zhou Zhang ◽  
Xiao Ming Tan ◽  
Xing Dan Zhu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Numerical Study ◽  
Rotating Disk ◽  
Outer Radius ◽  
Bottom Wall ◽  
Uniform Heat Flux ◽  
Uniform Heat

A three-dimensional numerical study on the flow and heat transfer characteristics over a rotating disk with bottom wall subjected to uniform heat flux was conducted with the use of RNG k- turbulent model. And some experiments were also made for validation. The effects of rotating angular speed and pin configuration on the temperature maps and convective heat transfer characte-ristics on rotating surface are analyzed. As the increase of rotating velocity, the impingement of pumping jet on the centre of rotating disk became stronger and the transition from laminar to turbu-lent occurred at the outer radius of rotating disk, which resulted in heat transfer enhancement. The pins on the disk made the pumping action of a rotating disk weaker. Simultaneously, they also acted as disturbing elements to the cyclone flow near the rotating disk surface, which made the overall heat transfer to be enhanced. Under the same extend areas of different pins, needle pin has higher convective heat transfer capacity than the discrete ring pin.

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