Abstract:
Natural convective heat transfer from a horizontal, upward
facing circular isothermal heated surface imbedded in a large
flat adiabatic surface has been numerically studied. The heated
circular surface is covered with a series of waves which are
arranged in an axially-symmetric (concentric) manner around
the vertical axis of the horizontal circular surface. Surface
waves with a triangular cross-sectional shape and with a
rectangular cross-sectional shape have been considered.
Conditions under which the flow is laminar, transitional, and
turbulent have been considered. The flow has been assumed to
be axially-symmetric and steady. Fluid properties have been
assumed constant except for the density change with
temperature that gives rise to the buoyancy forces which has
been treated using the Boussinesq approach. The commercial
CFD solver ANSYS FLUENT© was used to obtain the
numerical solutions. The standard k-epsilon turbulence model
was employed with full account being taken of buoyancy force
effects. The heat transfer rate from the heated surface expressed
in terms of the Nusselt number is dependent on the Rayleigh
number, the number of surface waves, the shape of the surface
waves, the dimensionless height of the surface waves, and the
Prandtl number. Results have only been obtained for the case
where there are five surface waves and for a Prandtl number of
0.74. A detailed study of the variation of the Nusselt number
with Rayleigh number for various dimensionless surface wave
heights has been undertaken. The heat transfer rates for the
wavy surface have been compared with those which would
exist in the case of a non-wavy (wave height of zero) surface.
Description:
Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .
