Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.
Randomly packed beds are widely used in a variety of
industries, because of their low cost and ease of use compared
with other packing methods. However, the pressure drops in
such packed beds are usually much higher than those in other
packings, and the overall heat transfer performances may be
greatly lowered. In order to reduce the pressure drops and
improve the overall heat transfer performances of packed beds,
structured packings are considered to be promising choices. In
this paper, some of our recent contributions on the
hydrodynamic and heat transfer characteristics in some novel
structured packed beds are introduced, where the effects of
packing form and particle shape are carefully investigated, and
the numerical and experimental results are also compared in
detail. Firstly, it is found that, with proper selection of packing
form and particle shape, the pressure drops in the structured
packed beds can be greatly reduced and the overall heat transfer
performances will be improved. The traditional correlations of
flow and heat transfer extracted from random packings are
found to overpredict the pressure drops and Nusselt numbers
for all the structured packings, and some modified correlations
are obtained. Secondly, it is revealed that, both the effects of
packing form and particle shape are significant on the flow and
heat transfer in structured packed beds. With the same particle
shape (sphere), the overall heat transfer efficiency of SC
packing is the highest. With the same packing form, such as
FCC or SC packings, the overall heat transfer performance of
ellipsoidal particle model is better. Furthermore, with the same
particle shape and packing form, such as BCC packing with
spheres, the overall heat transfer efficiency of uniform packing
is higher than that of non-uniform packing.
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