Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.
Natural convective flow through a vertical plane channel
has been considered. Both of the heated walls are kept at the
same temperature. These heated walls have sharp-edged wavy
surfaces. Conditions under which both laminar and turbulent
flow exists in the channel have been considered. Now using a
wavy heated wall can increase the heat transfer rate in external
natural convective flows. Using wavy heated walls in vertical
channel flows could therefore potentially also increase the heat
transfer rate. However the added flow resistance resulting from
the wall waviness will normally decrease the flow through the
channel which would tend to decrease the heat transfer rate
from the heated walls. Therefore a need existed to examine
what effect the wall waviness does have on the heat transfer
rate in natural convective flow through a vertical channel and it
was for this reason that the present study was undertaken. The
flow has been assumed to be steady and the Boussinesq
approximation has been adopted. The basic k-epsilon
turbulence model with the effects of the buoyancy forces fully
accounted for has been used. The solution has the Rayleigh
number, the Prandtl number, the ratio of channel width to the
heated channel height, the ratio of the amplitude of the wall
waviness to the heated channel height, and the ratio of the pitch
of the wall waviness to the heated channel height as parameters.
Results have only been obtained for a Prandtl number of 0.74
(the value for air at temperatures near ambient) and for a single
value of the dimensionless pitch of the wall waviness. This
leaves the Rayleigh number, the width to heated height ratio of
the channel, and the amplitude of the wall waviness to the
heated channel height ratio as parameters. Results have been
obtained for a range of values of these parameters and the effect
of these parameters on the mean Nusselt number has been
studied.
