Optimization and Computational Fluid Dynamics - Department of ...

8 Multi-objective Optimization in Convective Heat Transfer 263
though easier to optimize, cannot provide the same performances obtained by
NURBS channels. It has been shown that, as in similar studies, very different
channel shapes offer almost the same flow and heat transfer performance,
i.e., non-uniqueness of the shape optimization problem. The 3D channels have
been obtained by extrusion at variable angles of linear piecewise and NURBS
channels. The former has been optimized while for the latter, a parametric
analysis has been done. In both cases, the presence of secondary motions,
and in particular steady longitudinal vortices, leads to a significant increase
of the heat transfer rate in comparison with the 2D channels.
The optimization of the CC periodic module has been carried out considering
both hot and cold fluid streams, without the necessity of imposing
artificial constant-temperature or constant-flux boundary conditions. In this
case, a major effort was the proper linking of the different software packages
and additional utilities. The first results are very encouraging since one of
the optimized geometries leads to almost the same heat transfer performance
of the original design, but with a significant pressure drop reduction of about
20% and without increase of the heat transfer surface.
The procedure described has been proven robust and efficient, and in principle,
could be applied to even more complex problems.
Acknowledgements Financial support for this research is provided by MIUR, PRIN
2004, Surface Optimization for Heat Transfer Problems, and PRIN 2005, Study and Optimization
of Buoyancy-controlled Thermal Systems, and is gratefully acknowledged.
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