An Investigation Into the Heat Transfer and Fluid Flow Around a Circular Cylinder in Buoyancy Assisting Cross Flow

2002 ◽  
Author(s):  
Tara Dalton ◽  
Vanessa Egan ◽  
David Newport ◽  
Mark Davies ◽  
Maurice Whelan
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Circular Cylinder ◽  
Speckle Pattern ◽  
Convection Heat Transfer ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Temperature Fields ◽  
Axial Fan ◽  
Heated Cylinder

There is considerable interest in mixed convection heat transfer in relation to electronic cooling applications but the physics of this flow in certain situations has yet to be understood. In this paper, an investigation of the heat transfer and fluid flow around a two dimensional circular cylinder is made. The experimental configuration comprised a long heated cylinder suspended in a glass walled enclosure. The airflow within the enclosure was controlled using a baffled axial fan to give a range of low Reynolds numbers from 30 to 83. For three Grashof numbers of 2.40E+04, 3.77E+04 and 5.99E+04, the mean Nusselt number around the cylinder was measured for buoyancy assisting cross flow. Optical techniques were employed to extract the full flow and temperature fields about the cylinder. Digital Speckle Pattern Interferometry (DSPI) was employed to measure the temperature field, and Particle Image Velocimetry (PIV) for the velocity field. The presence of the assisting flow was found to stabilise a naturally oscillatory buoyant flow and led to an increase in the heat transfer coefficient over that found in natural flow.

Numerical Study of Mixed Convection around a Heated Circular Cylinder

2016 ◽  
Vol 836 ◽  
pp. 85-89
Author(s):  
Vivien S. Djanali ◽  
Ahmad Nurdian Syah ◽  
Syaiful Rizal
Keyword(s):  
Heat Transfer ◽  
Circular Cylinder ◽  
Mixed Convection ◽  
Buoyancy Force ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Main Flow ◽  
Heat Transfer Characteristics ◽  
Convection Regime ◽  
Heated Cylinder

Wake and heat transfer characteristics around a heated circular cylinder were studied numerically in this paper. Heat transfer from a heated cylinder to the freestream flow was in mixed convection regime, with the free convection-bouyancy driven flow in opposite direction to the forced convection-main flow. Numerical simulations were performed for three Reynolds numbers of 100, 135 and 200, with the Richardson (Ri = Gr/Re2) numbers varied from 0 to 1. Results showed that buoyancy force significantly altered wake formation behind the heated cylinder, further resulted in increasing drag and decreasing Nusselt number.

Direct Numerical Simulation of Flow and Heat Transfer From a Sphere in a Uniform Cross-Flow

2000 ◽  
Vol 123 (2) ◽  
pp. 347-358 ◽  
Author(s):  
P. Bagchi ◽  
M. Y. Ha ◽  
S. Balachandar
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Vortex Shedding ◽  
Axisymmetric Flow ◽  
Three Dimensional ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Temperature Fields ◽  
Flow And Heat Transfer

Direct numerical solution for flow and heat transfer past a sphere in a uniform flow is obtained using an accurate and efficient Fourier-Chebyshev spectral collocation method for Reynolds numbers up to 500. We investigate the flow and temperature fields over a range of Reynolds numbers, showing steady and axisymmetric flow when the Reynolds number is less than 210, steady and nonaxisymmetric flow without vortex shedding when the Reynolds number is between 210 and 270, and unsteady three-dimensional flow with vortex shedding when the Reynolds number is above 270. Results from three-dimensional simulation are compared with the corresponding axisymmetric simulations for Re>210 in order to see the effect of unsteadiness and three-dimensionality on heat transfer past a sphere. The local Nusselt number distribution obtained from the 3D simulation shows big differences in the wake region compared with axisymmetric one, when there exists strong vortex shedding in the wake. But the differences in surface-average Nusselt number between axisymmetric and three-dimensional simulations are small owing to the smaller surface area associated with the base region. The shedding process is observed to be dominantly one-sided and as a result axisymmetry of the surface heat transfer is broken even after a time-average. The one-sided shedding also results in a time-averaged mean lift force on the sphere.

Experimental Investigations Into Mixed Convection About a Horizontal Cylinder: Part A — Heat Transfer Using Digital Speckle Pattern Interferometry

2005 ◽  
Author(s):  
Vanessa Egan ◽  
Tara Dalton ◽  
Mark R. D. Davies ◽  
Maurice Whelan
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Speckle Pattern ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Inertia Force ◽  
Convection Flow ◽  
Digital Speckle Pattern Interferometry ◽  
Unsteady Mixed Convection ◽  
Digital Speckle

Mixed convection heat transfer is commonly found in many engineering applications and is particularly relevant to the cooling of electronic components but despite this, the physics of this heat transfer regime is not fully understood. This paper presents an experimental study into buoyancy opposing cross flow, a commonly found mixed convection regime. The experimental configuration comprised a long heated cylinder suspended in a glass walled enclosure. The airflow within the enclosure was controlled using a baffled axial fan to give Reynolds numbers in the range of 32–89. The mean Nusselt numbers were measured about the cylinder for Rayleigh numbers between 1.7E+04–4.0E+04. For the acquisition of full field data the optical techniques, digital speckle pattern interferometry (DSPI) and phase measurement interferometry (PMI), were employed. Buoyancy opposing cross flow created an unsteady flow field about the cylinder at low Reynolds numbers and steady state temperatures. DSPI enabled real-time interferograms to be recorded and results are presented in the form of instantaneous interferograms showing the high frequency fluctuations of the temperature field about the cylinder. Attention is focused on understanding the trend in mean heat transfer values resulting from an increased inertia force and thus providing a significant insight into unsteady mixed convection flow.

Experimental Investigation of Fluid Flow and Internal Convection Heat Transfer in Mini/Micro Porous Media

2009 ◽  
Author(s):  
Yu-Li Huang ◽  
Pei-Xue Jiang ◽  
Rui-Na Xu
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Porous Media ◽  
Fluid Flow ◽  
Convection Heat Transfer ◽  
Reynolds Numbers ◽  
Solid Particles ◽  
Convection Heat ◽  
Friction Factors ◽  
Internal Convection

The flow characteristics of different gases such as air, helium and carbon dioxide and internal convection heat transfer between the solid particles and the fluid in mini/micro porous media were studied experimentally. The test sections for fluid flow and heat transfer were made of sintered bronze particles with average diameters of 225 μm, 125 μm, 90 μm and 40 μm. The experimentally measured friction factors with consideration of compressibility for air, helium and carbon dioxide in the porous media with average diameters of 225 μm and 125 μm agree well with the known correlation for normal size porous media (the correlation of Aerov and Tojec), especially at the relatively high Reynolds numbers. The experimentally measured friction factors for air, helium and carbon dioxide in the porous media with average diameters of 90 μm are slightly less than the correlation of Aerov and Tojec at the relatively low Reynolds numbers. The experimental values for the friction factors for air, helium and carbon dioxide in the microporousmedia with 40 μm average diameters are much less than the correlation of Aerov and Tojec. The results show that rarefaction effects occur in air, helium and hydrogen flows in the microporous media with particle diameters less than 90 μm. The internal convection heat transfer coefficients between particles and fluid for air, helium and carbon dioxide in the micro porous media were determined experimentally.

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