Natural convection of a viscoplastic fluid in an enclosure filled with solid obstacles

In this study a computational investigation of two-dimensional, steady-state, natural convection of viscoplastic fluid in a square enclosure has been presented. The enclosure has been locally heated from the bottom wall using a constant heat flux source and symmetrically cooled from both the side walls. The other walls are maintained as insulated surfaces. Finite volume based code has been used in the simulation and Bingham model has been used to model the rheology of the enclosed viscoplastic fluids. Simulations have been made for three different heating lengths of the bottom wall. The flow phenomenon and heat transfer inside the enclosure have been investigated for different properties of viscoplastic fluid, heating conditions and heated length. It has been observed that for a particular thermal condition the heat transfer coefficient or the Nusselt number decrease with the increase in yield stress value of the fluid due to weakening of convective circulation.

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Periodic Natural Convection Inside a Fluid Saturated Porous Medium Made of Disconnected Solid Obstacles: A Continuum Approach

Volume 1: Heat Transfer in Energy Systems; Thermophysical Properties; Theory and Fundamentals in Heat Transfer; Nanoscale Thermal Transport; Heat Transfer in Equipment; Heat Transfer in Fire and Combustion; Transport Processes in Fuel Cells and Heat Pipes; Boiling and Condensation in Macro, Micro and Nanosystems ◽

10.1115/ht2016-7294 ◽

2016 ◽

Cited By ~ 1

Author(s):

S. M. Mirehei ◽

J. L. Lage

Keyword(s):

Porous Medium ◽

Natural Convection ◽

Numerical Study ◽

Saturated Porous Medium ◽

Continuum Modeling ◽

Periodic Heating ◽

Interference Phenomenon ◽

Modeling Approach ◽

Fluid Saturated Porous Medium ◽

Solid Obstacles

Results of a numerical study considering the periodic natural convection inside a fluid saturated porous medium are presented. The porous medium is obtained by placing four, large and uniformly distributed solid obstacles of regular (square) shape inside the enclosure, a structure that hinders the option of seeking a porous-continuum modeling approach. The periodic heating is achieved by imposing a time-periodic and spatially uniform high temperature condition at one of the walls of the enclosure, while the other wall is maintained at a constant, uniform and low temperature; the horizontal surfaces are set as adiabatic. Heat transfer results are obtained then by following a continuum modeling approach, and reported on a parametric form with the Prandtl number fixed equal to 7, and the Rayleigh number inside the enclosure varying from 103 to 107. The boundary layer interference phenomenon, observed for the case of constant horizontal heating, is also observed in the case of periodic heating. The visualization of the natural convection process via isotherms and streamlines, together with the periodic (time-varying) Nusselt number, allows the identification of a singular dynamic behavior, including the storage of thermal energy inside the enclosure.

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