Natural Convection from a Horizontal Cylinder—Laminar Regime

1981 ◽  
Vol 103 (3) ◽  
pp. 522-527 ◽  
Author(s):  
B. Farouk ◽  
S. I˙. Gu¨c¸eri
Keyword(s):  
Natural Convection ◽  
Horizontal Cylinder ◽  
Heat Transfer Characteristics ◽  
Convective Flows ◽  
Finite Difference Numerical Method ◽  
Temperature Boundary ◽  
Recirculation Zones ◽  
Boussinesq Fluid ◽  
Temperature Boundary Condition ◽  
Good Agreement

A finite-difference numerical method has been adopted to generate flow patterns and heat transfer characteristics for laminar, steady-state, two-dimensional natural convection around a circular cylinder submerged in an unbounded Boussinesq fluid. The approach allows the use of nonuniform as well as uniform specified temperature and heat flux distributions over the cylindrical surface. Part of the results are generated for reverse convective flows with recirculation zones which occur when part of the cylinder is below the ambient temperature while the remaining part is above. The results for uniform temperature boundary condition are in good agreement with the experimental data and other solutions available in literature.

Bouyancy-Induced Convective Heat Transfer in Cylindrical Transformers Filled With Mineral Oil With Nano-Suspensions

2005 ◽  
Author(s):  
D. G. Walker ◽  
J. L. Davidson ◽  
P. G. Taylor ◽  
K. L. Soh ◽  
Bruce Rogers
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Mineral Oil ◽  
Transformer Oil ◽  
Experimental Measurements ◽  
Transfer Performance ◽  
Heat Transfer Characteristics ◽  
Enhanced Heat Transfer ◽  
Convective Flows ◽  
Good Agreement

The heat transfer characteristics of a transformer using both standard mineral oil and nanodiamond oil was investigated numerically and compared to experimental measurements. The results of the model agree well with the standard oil measurements and with theoretical convective flows from the literature. However, the simulations could not predict the magnitude of the temperature variation in the nanodiamond oil, although the appropriate trend was observed. Because properties of the nanodiamond transformer oil are not well known, good agreement is not expected. Nevertheless, nanodiamond in transformer oil shows enhanced heat transfer performance over standard transformer oil.

Final Design Parameter Settings for a Physically-Realizable Uniform Temperature Boundary Condition Specification on a Wall of an Enclosure

2013 ◽  
Author(s):  
P. Y. C. Lee ◽  
W. H. Leong
Keyword(s):  
Boundary Condition ◽  
Natural Convection ◽  
Three Dimensional ◽  
Convection Heat Transfer ◽  
Design Parameters ◽  
Uniform Temperature ◽  
Original Design ◽  
Temperature Boundary ◽  
Contact Width ◽  
Temperature Boundary Condition

Design parameters based on a three-dimensional internal natural convection heat transfer in a cubical apparatus are presented so that a uniform temperature boundary condition specification on a wall of the apparatus can be physically achieved. Preliminary temperature measurements based on the initial design of the apparatus where the uniform boundary condition was prescribed revealed that a temperature non-uniformity existed in the excess of 4% error. In order to complete the objective of the benchmark internal natural convection study, the apparatus had to be modified so that the temperature non-uniformity can be reduced to less than 1% error. It was decided that the original design be modified by simply adding two auxiliary heaters in the vicinity of the wall where the uniform temperature profile was desired. Before the implementation of the auxiliary heaters onto the apparatus, a detailed mathematical analysis was conducted to determine the position and the contact width of the heaters, and to establish an appropriate heat flux required to reduce the temperature non-uniformity to less than 1% along the wall of the apparatus. This analysis was achieved by using the approximate analytical temperature solution obtained from the boundary value problem of a plate (which is one part of the apparatus) with boundary conditions prescribed to model the auxiliary heaters. Previously, a specific set of design parameters were used that reduced the temperature non-uniformity to less than 1% along a wall of the modified cubical apparatus. As an extension to the previous work, this paper presents a generalized set of design parameters that can equally prescribe a physically-realizable uniform temperature setting along a wall of an enclosure to within 1% error. With the range of design parameters, this would enable any designer with the flexibility in choosing what parameters can be allocated based on their need.

scholarly journals The Mass and Heat Transfer Characteristics Study of the Natural Convection Evaporation of an LNG Droplet in BOG

2021 ◽  
Vol 2076 (1) ◽  
pp. 012042
Author(s):  
Zhengyang Fei ◽  
Jiajia Deng ◽  
Jinshu Lu ◽  
Bin Wang ◽  
Dawen Xue
Keyword(s):  
Boundary Layer ◽  
Natural Convection ◽  
Droplet Size ◽  
Droplet Surface ◽  
Cfd Model ◽  
Heat Transfer Characteristics ◽  
Temperature Boundary Layer ◽  
Temperature Boundary ◽  
Mass And Heat Transfer ◽  
Lng Tank

Abstract The evaporation process of LNG droplets in BOG is closely related to the cooling down process of the LNG tank, but there isn’t an available droplet evaporation model at present. Been prepared based on the conservation of mass, momentum, and energy, a CFD model of natural convection evaporation of a single LNG saturated droplet in the BOG was developed and applied. The results show that:①There are two distinguished zones around the droplet surface, where the local temperature boundary layer of the droplet gradually thickens and rapidly thickens with the increase of the angle of inflow from 0 ° to 90 ° and from 90 ° to 180 °, respectively; ② With the increase of droplet size, the average thickness of temperature boundary layer increases gradually, which leads to the decrease of relative evaporation rate;③“blowing effect” remains almost unchanged with the increase of droplet size.

Experimental Investigation of Natural Convection Losses From Open Cavities

1984 ◽  
Vol 106 (2) ◽  
pp. 333-338 ◽  
Author(s):  
C. F. Hess ◽  
R. H. Henze
Keyword(s):  
Natural Convection ◽  
Three Dimensional ◽  
Boundary Layer Transition ◽  
Transition To Turbulence ◽  
Layer Transition ◽  
Turbulence Flow ◽  
Temperature Boundary ◽  
Open Cavities ◽  
Rayleigh Numbers ◽  
Temperature Boundary Condition

Experimental results for natural convection in a cavity are reported. Both constrained and unconstrained cavity geometries were studied. Detailed velocity profiles were obtained using Laser doppler velocimetry for Rayleigh numbers between 3 × 1010 and 2 × 1011, corresponding to a constant elevated wall temperature boundary condition. Characteristics of two-dimensional and three-dimensional flows obtained with dye flow visualization are discussed, including boundary layer transition to turbulence, flow patterns in the cavity, and flow outside of the cavity. Local Nusselt number is correlated with local Rayleigh number for constrained and unconstrained cavities.

Onset of Natural Convection from a Suddenly Heated Horizontal Cylinder

1980 ◽  
Vol 102 (4) ◽  
pp. 636-639 ◽  
Author(s):  
J. R. Parsons ◽  
J. C. Mulligan
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Stability ◽  
Heat Capacity ◽  
Natural Convection ◽  
Stability Analysis ◽  
Horizontal Cylinder ◽  
Finite Cylinder ◽  
Global Motion ◽  
Experimental Apparatus

A study of the onset of transient natural convection from a suddenly heated, horizontal cylinder of finite diameter is presented. The termination of the initial conductive and “locally” conuectiue heat transfer regime which precedes the onset of global natural convection is treated as a thermal stability phenomenon. An analysis is presented wherein the effects of finite cylinder diameter, cylinder heat capacity, and cylinder thermal conductivity are included in calculations of the convective delay time. A simple experimental apparatus is described and data presented. The thermal stability analysis is confirmed experimentally and data is presented which indicates localized natural convection prior to global motion.

scholarly journals CuO–Water Nanofluid Magnetohydrodynamic Natural Convection inside a Sinusoidal Annulus in Presence of Melting Heat Transfer

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
M. Sheikholeslami ◽  
R. Ellahi ◽  
C. Fetecau
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Natural Convection ◽  
Hartmann Number ◽  
Volume Fraction ◽  
Melting Heat ◽  
Melting Heat Transfer ◽  
Limiting Case ◽  
Good Agreement ◽  
Melting Parameter

Impact of nanofluid natural convection due to magnetic field in existence of melting heat transfer is simulated using CVFEM in this research. KKL model is taken into account to obtain properties of CuO–H2O nanofluid. Roles of melting parameter (δ), CuO–H2O volume fraction (ϕ), Hartmann number (Ha), and Rayleigh (Ra) number are depicted in outputs. Results depict that temperature gradient improves with rise of Rayleigh number and melting parameter. Nusselt number detracts with rise of Ha. At the end, a comparison as a limiting case of the considered problem with the existing studies is made and found in good agreement.

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