Abstract:
A numerical study of natural convective heat transfer from a
horizontal upward facing circular isothermal heated element
that is imbedded in a large flat adiabatic surrounding surface
has been undertaken. The heated element is either recessed by a
small amount into the surrounding flat horizontal adiabatic
surface or it protrudes by a small amount out of the surrounding
flat horizontal adiabatic surface. The element is at a higher
temperature than the surrounding fluid and attention has been
restricted to the case where the element is facing upward. The
range of conditions considered is such that laminar, transitional,
and turbulent flows can occur. The flow has been assumed to
be two-dimensional and steady and in dealing with the
buoyancy forces the Boussinesq approach has been adopted.
The numerical solution has been obtained using the commercial
CFD solver ANSYS FLUENT©. The k-epsilon turbulence
model with account being taken of buoyancy force effects has
been used. The heat transfer rate from the heated element
expressed in terms of the Nusselt number is dependent on the
Rayleigh number, on whether the heated element is recessed
into or protrudes from the surrounding adiabatic surface, on the
dimensionless height the element is recessed into or protrudes
from the surrounding adiabatic surface, and on the Prandtl
number. Results have been obtained for a Prandtl number of
0.74, i.e., effectively the value for air. The effect of the
dimensionless height that the element is recessed or protrudes
from the surrounding adiabatic surface on the variation of the
Nusselt number with Rayleigh number has been studied. The
diameter of the circular heated element has been used as the
reference length scale and recess and protrusion height-todiameter
ratios of between 0 and 0.25 have been considered.
Description:
Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016.
