Effect of the thermal boundary conditions and physical properties variation on transient natural convection of high Prandtl number fluids

2009 ◽  
pp. 813-818
Author(s):  
O. Younis ◽  
J. Pallares ◽  
F. X. Grau
Keyword(s):  
Natural Convection ◽  
Prandtl Number ◽  
Boundary Conditions ◽  
Physical Properties ◽  
Transient Natural Convection ◽  
Thermal Boundary Conditions ◽  
High Prandtl Number

Natural Convection in a Non-Uniformly Heated Vertical Annular Cavity

2017 ◽  
Vol 377 ◽  
pp. 189-199 ◽  
Author(s):  
M. Sankar ◽  
S. Kiran ◽  
G.K. Ramesh ◽  
Oluwole Daniel Makinde
Keyword(s):  
Natural Convection ◽  
Boundary Conditions ◽  
Outer Wall ◽  
Uniform Heating ◽  
Cylindrical Wall ◽  
Thermal Boundary Conditions ◽  
Nusselt Numbers ◽  
Implicit Finite Difference Scheme ◽  
Implicit Finite Difference ◽  
Model Equations

Natural convection from the linearly heated inner and/or outer walls of a vertical annular cavity has been numerically investigated. The bottom wall is uniformly heated and top cylindrical wall is thermally insulated. In this analysis, we considered two different thermal boundary conditions, namely case (I) and case (II) to understand the effect of non-uniform heating of inner and/or outer walls on the convective flow and subsequently the local and global heat transfer rate. For case (I), the inner and outer walls are heated linearly, while the linearly heated inner wall and cooled outer wall is considered in case (II). An implicit finite difference scheme is applied to solve the model equations of the problem. The numerical simulations in terms of streamlines and isotherms, local and global Nusselt numbers are presented to illustrate the effects of Rayleigh number and non-uniform thermal boundary conditions for a fixed Prandtl number of Pr = 0.7.

Natural convection flow in a vertical micro-annulus with time-periodic thermal boundary conditions

2018 ◽  
Vol 14 (5) ◽  
pp. 1064-1081
Author(s):  
Basant Kumar Jha ◽  
Michael O. Oni
Keyword(s):  
Nusselt Number ◽  
Natural Convection ◽  
Boundary Conditions ◽  
Skin Friction ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Content Type ◽  
Thermal Boundary Conditions ◽  
The Impact ◽  
Time Periodic

PurposeThe purpose of this paper is to investigate the impact of time-periodic thermal boundary conditions on natural convection flow in a vertical micro-annulus.Design/methodology/approachAnalytical solution in terms of Bessel’s function and modified Bessel’s function of order 0 and 1 is obtained for velocity, temperature, Nusselt number, skin friction and mass flow rate.FindingsIt is established that the role of Knudsen number and fluid–wall interaction parameter is to decrease fluid temperature, velocity, Nusselt number and skin friction.Research limitations/implicationsNo laboratory practical or experiment was conducted.Practical implicationsCooling device in electronic panels, card and micro-chips is frequently cooled by natural convection.Originality/valueIn view of the amount of works done on natural convection in microchannel, it becomes interesting to investigate the effect that time-periodic heating has on natural convection flow in a vertical micro-annulus. The purpose of this paper is to examine the impact of time-periodic thermal boundary conditions on natural convection flow in a vertical micro-annulus.

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