Free Convection in Antisymmetrically Heated Vertical Channels

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
D. Roeleveld ◽  
D. Naylor ◽  
W. H. Leong
Keyword(s):  
Temperature Field ◽  
Free Convection ◽  
Vertical Channel ◽  
Laser Interferometry ◽  
Measured Temperature ◽  
Ansys Fluent ◽  
Nusselt Numbers ◽  
Numerical Predictions ◽  
Rayleigh Numbers ◽  
Special Case

Free convection in a vertical channel with antisymmetrical heating is a special case that has not received a great deal of attention in the literature. Antisymmetrical heating is where the hot wall is heated above the ambient temperature by the same amount that the cold wall is cooled below the ambient, giving equal but opposing buoyancy forces inside the channel. An experimental model was constructed to study antisymmetrical heating inside an isothermally heated vertical channel. Flow visualization was used to obtain the flow field and laser interferometry was used to obtain the temperature field. Based on the measured temperature field, the local and average Nusselt numbers were determined, which were compared with numerical predictions obtained using ansys fluent. A range of Rayleigh numbers were studied for air with a Prandtl number of 0.71. The results show that an open-ended channel with antisymmetrical heating has some similarities to a tall enclosure. The average convective heat transfer can be approximated using an existing correlation for a tall enclosure from the literature.

scholarly journals Experimental and Numerical Study of Free Convection in a Vertical Channel with Opposing Buoyancy Forces

2021 ◽  
Author(s):  
Derek Roeleveld
Keyword(s):  
Heat Transfer ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Vertical Channel ◽  
Ansys Fluent ◽  
Fully Developed Flow ◽  
Wall Functions ◽  
Buoyancy Forces ◽  
Rayleigh Numbers ◽  
Steady Laminar

Free convective heat transfer inside a vertical channel was studied both experimentally and numerically. An experimental model of an isothermally, asymmetrically heated vertical channel was constructed to study various cases of opposing buoyancy forces. Many studies in the literature have investigated buoyancy forces in a single direction. The study presented here investigated opposing buoyancy forces, where one wall is warmer than the ambient and the other wall is cooler than the ambient. Five different temperature ratios were studied using four different channel spacings between the two channel walls. A Mach-Zehnder interferometer provided temperature field visualization. In addition, local and average heat transfer measurements were made with the interferometer. Flow visualization was conducted to determine the flow pattern inside the channel. The measured local and average Nusselt number data were compared to numerical solutions obtained using ANSYS FLUENT. A steady laminar model and a steady k-ε turbulence model with two different wall functions were used. Numerical solutions were obtained for a Prandtl number of 0.71 and Rayleigh numbers ranging from the laminar fully developed flow regime to the turbulent isolated boundary layer regime.

Investigation of Nusselt numbers in the convection of thermally viscous liquids

2008 ◽  
Vol 6 ◽  
pp. 127-131
Author(s):  
K.V. Moiseyev ◽  
A.M. Ilyasov
Keyword(s):  
Nusselt Number ◽  
Free Convection ◽  
Viscous Liquids ◽  
Nusselt Numbers ◽  
Viscosity Function ◽  
Rayleigh Numbers ◽  
Square Cell

In the paper, free convection of thermally viscous liquids in a square cell is numerically investigated. Quadratic and exponential viscosity versus temperature is considered. The influence of these dependences on the Nusselt number is studied. It is established that the dependence of the Nusselt number on the Rayleigh numbers is characterized by the average viscosity, monotonicity, and convexity of the viscosity function of temperature.

Numerical Study of the Free Convection Heat Transfer From an I-Beam Support Structure

2014 ◽  
Author(s):  
Ayoola T. Brimmo ◽  
Youssef Shatilla ◽  
Mohamed I. Hassan
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Convection Flow ◽  
Support Structure ◽  
Ansys Fluent ◽  
Aluminum Reduction ◽  
Nusselt Numbers ◽  
Convection Cooling

In this study, a computational fluid dynamics (CFD) model is used to numerically characterize the heat transfer from an I-beam support structure of an aluminum reduction pot, during the free convection cooling process. A slice of the I-beam structure is modeled on two different finite element commercial platforms, ANSYS (FLUENT) and StarCCM+, in a suitable domain of air. The K-epsilon Reynolds averaging technique is used to model the turbulence in both platforms. Validation of the modeling technique and parameters adapted is appropriately performed. The structure is segmented and space mean Nusselt numbers (Nu) characterizing the flow are calculated for each section, for Rayleigh number (Ra) ranges typically experienced by the respective section. Expressions correlating the free convection flow over this structure are deduced based on a regression analysis. To conclude, an application of the deduced correlation in modeling the free convection cooling of an aluminum reduction pot is presented.

Free Convection in Asymmetrically Heated Vertical Channels With Opposing Buoyancy Forces

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
D. Roeleveld ◽  
D. Naylor ◽  
W. H. Leong
Keyword(s):  
Nusselt Number ◽  
Flow Visualization ◽  
Average Nusselt Number ◽  
Numerical Solutions ◽  
Vertical Channel ◽  
Laser Interferometry ◽  
Ansys Fluent ◽  
Number Range ◽  
Aspect Ratios ◽  
Buoyancy Forces

Laser interferometry and flow visualization were used to study free convective heat transfer inside a vertical channel. Most studies in the literature have investigated buoyancy forces in a single direction. The study presented here investigated opposing buoyancy forces, where one wall is warmer than the ambient and the other wall is cooler than the ambient. An experimental model of an isothermally, asymmetrically heated vertical channel was constructed. Interferometry provided temperature field visualization and flow visualization was used to obtain the streamlines. Experiments were carried out over a range of aspect ratios between 8.8 and 26.4, using temperature ratios of 0, −0.5, and −0.75. These conditions provide a modified Rayleigh number range of approximately 5 to 1100. In addition, the measured local and average Nusselt number data were compared to numerical solutions obtained using ANSYS FLUENT. Air was the fluid of interest. So the Prandtl number was fixed at 0.71. Numerical solutions were obtained for modified Rayleigh numbers ranging from the laminar fully developed flow regime to the turbulent isolated boundary layer regime. A semi-empirical correlation of the average Nusselt number was developed based on the experimental data.

Developing Flow with Combined Forced–Free Convection in an Isothermal Vertical Tube

1972 ◽  
Vol 94 (2) ◽  
pp. 211-221 ◽  
Author(s):  
B. Zeldin ◽  
F. W. Schmidt
Keyword(s):  
Numerical Analysis ◽  
Free Convection ◽  
Velocity Profiles ◽  
Vertical Tube ◽  
Test Fluid ◽  
Nusselt Numbers ◽  
Numerical Predictions ◽  
Test Conditions ◽  
Developing Flow ◽  
Entrance Velocity

The influence of gravity on developing forced, laminar flow in a vertical isothermal tube was investigated by means of a numerical analysis and an associated experiment. Numerically predicted velocity profiles and Nusselt numbers for combined forced–free convection with Gr/Re = −30 are compared with their counterparts for pure forced convection, Gr/Re = 0, for air with Re = 500. The analysis was performed for both the uniform irrotational and the fully developed velocity entrance models. Velocity profiles were measured in a vertical-tube apparatus designed to provide an approximately uniform entrance velocity using air as the test fluid. These are compared with numerical predictions based on test conditions.

scholarly journals Experimental and Numerical Study of Free Convection in a Vertical Channel with Opposing Buoyancy Forces

2021 ◽  
Author(s):  
Derek Roeleveld
Keyword(s):  
Heat Transfer ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Vertical Channel ◽  
Ansys Fluent ◽  
Fully Developed Flow ◽  
Wall Functions ◽  
Buoyancy Forces ◽  
Rayleigh Numbers ◽  
Steady Laminar

Free convective heat transfer inside a vertical channel was studied both experimentally and numerically. An experimental model of an isothermally, asymmetrically heated vertical channel was constructed to study various cases of opposing buoyancy forces. Many studies in the literature have investigated buoyancy forces in a single direction. The study presented here investigated opposing buoyancy forces, where one wall is warmer than the ambient and the other wall is cooler than the ambient. Five different temperature ratios were studied using four different channel spacings between the two channel walls. A Mach-Zehnder interferometer provided temperature field visualization. In addition, local and average heat transfer measurements were made with the interferometer. Flow visualization was conducted to determine the flow pattern inside the channel. The measured local and average Nusselt number data were compared to numerical solutions obtained using ANSYS FLUENT. A steady laminar model and a steady k-ε turbulence model with two different wall functions were used. Numerical solutions were obtained for a Prandtl number of 0.71 and Rayleigh numbers ranging from the laminar fully developed flow regime to the turbulent isolated boundary layer regime.

Natural Convective Heat Transfer in a Divided Vertical Channel: Part II—Experimental Study

1993 ◽  
Vol 115 (2) ◽  
pp. 388-394 ◽  
Author(s):  
D. Naylor ◽  
J. D. Tarasuk
Keyword(s):  
Heat Transfer ◽  
Convection Heat Transfer ◽  
Vertical Channel ◽  
Channel Length ◽  
Nusselt Numbers ◽  
Numerical Predictions ◽  
Interferometric Study ◽  
Laminar Natural Convection ◽  
Nusselt Number Correlation ◽  
Good Agreement

An interferometric study has been conducted on two-dimensional laminar natural convection heat transfer in an isothermal vertical divided channel. Interferograms were obtained for air and a plate-to-channel length ratio of Lp/Lc= 1/3. Data are presented for the dividing plate located at the bottom (Li/Lc = 0) and top of the channel (Li/Lc=2/3). Comparisons of local and average Nusselt numbers are made with the numerical predictions from Part I. Although the experimental average Nusselt numbers are typically about 10 percent lower than the numerical results, the general trends of the data are in good agreement. Average Nusselt number correlation equations are presented.

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