In this study, the flow and heat transfer characteristics of the forced
pulsating Al2O3/water nanofluid were numerically studied. The pulsating
excitation of the nanofluid is provided by the Helmhertz self-excited
oscillating cavity. The large eddy simulation method is used to solve the
equation, and the local Nusselt number and heat transfer performance index
are used to analyze the heat transfer characteristics of the nanofluid in
the self-excited oscillation heat exchange tube. In addition, the effect of
different downstream tube diameters on heat transfer enhancement is
discussed. The research results show that the existence of the
countercurrent vortex can increase the disturbance of the near-wall fluid,
thereby improving the mixing degree of the near-wall fluid and the central
mainstream. As the countercurrent vortex migrates downstream, pulse enhanced
heat transfer is realized. Furthermore, it was also found that when the
downstream tube diameter d2=1.8d1, the periodic effect of the local Nusselt
number of the wall is the best and the heat transfer performance index has
the most stable pulsation effect within a pulsation cycle. But when
d2=2.0d1, the change curve of heat transfer performance index in a pulsating
period is the highest, the maximum value is 3.95.
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