C. Chagny et al., Chaotic heat transfer for heat exchanger design and comparison with a regular regime for a large range of Reynolds numbers, APPL TH ENG, 20(17), 2000, pp. 1615-1648
An experimental comparison is made over a large range of Reynolds numbers (
from 30 to 30,000) between two shell-and-tube heat exchangers having the sa
me heat-transfer area and same number of bends, but different configuration
s: one has a helical configuration (regular flow), the other has a chaotic
one (chaotic advection flow). Both are composed of 33 bends with circular t
ube cross section (inside diameter 23 mm) and are immersed in a closed shel
l. The working fluids are Newtonian with different Prandtl numbers (820, 23
0, 75 and 6.5) in order to cover the large-Reynolds-number range. The compa
rison is made by using a criterion L that takes into account thermal perfor
mance and energy expenditure. The results show that at low Reynolds numbers
, heat transfer is higher and heating more homogeneous for chaotic advectio
n flow, with no increase in energy expenditure. At high Reynolds numbers, t
he configuration has no influence on heat transfer. When the Prandtl number
increases, the heat transfer increases. The flows have also been visualize
d by laser-induced fluorescence to assess the improvement of mixing in the
chaotic configuration. (C) 2000 Elsevier Science Ltd. All rights reserved.