Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.
This study investigates experimentally the convective
boiling heat transfer and the critical heat flux (CHF) of
ethanol–water mixtures in a diverging microchannel with
artificial cavities. Experimental results show that the boiling
heat transfer and the CHF are significantly influenced by the
molar fraction (xm) as well as the mass flux. The CHF increases
from xm=0 to 0.1, and then decreases rapidly from xm=0.1 to 1
at a given mass flux of 175 kg/m2s. The maximum CHF is
reached at xm=0.1 due to the Marangoni effect, indicating that
small additions of ethanol into water could significantly
increase the CHF. On the other hand, the CHF increases with
increasing the mass flux at a given molar fraction of 0.1. None
of existing correlations for the CHF on flow boiling of pure
component in a microchannel could present the correct trend as
the CHF data on flow boiling of ethanol–water mixtures, and
none of those correlations could predict the CHF precisely.
However, the experimental results of the CHF show an
excellent agreement with an empirical correlation for the CHF
prediction of flow boiling of the mixtures, proposed by Lin et al.
[1]. That, the overall mean absolute error of this correlation is
8.49% and more than 80% of the experimental data are
predicted within a ±15% error band, confirms the correlation
may accurately catch the Marangoni effect on the CHF of
ethanol–water mixtures (present study) as well as methanol–
water mixtures (our previous study [1]), and it is expected that
this correlation may be applied for other convective boiling of
binary mixtures.
