  In this paper, by using a phase-change lattice Boltzmann (LB) model coupled
with an electric field model, we numerically investigate the performance and
enhancement mechanism of pool boiling of dielectric fluids on pillar-structured
surfaces under an electric field. The numerical investigation reveals that
applying an electric field causes both positive and negative influences on the
pool boiling of dielectric fluids on pillar-structured surfaces. It is found
that, under the action of an electric field, the electric force prevents the
bubbles nucleated in the channels from crossing the edges of the pillar tops.
On the one hand, such an effect results in the bubble coalescence in the
channels and blocks the paths of liquid supply for the channels, which leads to
the deterioration of pool boiling in the medium-superheat regime. On the other
hand, it prevents the coalescence between the bubbles in the channels and those
on the pillar tops, which suppresses the formation of a continuous vapor film
and therefore delays the occurrence of boiling crisis. Meanwhile, the electric
force can promote the departure of the bubbles on the pillar tops. Accordingly,
the critical heat flux (CHF) can be improved. Based on the revealed mechanism,
wettability-modified regions are applied to the pillar tops for further
enhancing the boiling heat transfer. It is shown that the boiling performance
on pillar-structured surfaces can be enhanced synergistically with the CHF
being increased by imposing an electric field and the maximum heat transfer
coefficient being improved by applying mixed wettability to the
pillar-structured surfaces.
