Thermal fluid characteristics of the lattice cooling channel have
been investigated by measuring distributions of heat transfer coefficient.
The heat transfer coefficient distributions have been obtained
by visualizing steady-state local temperatures using temperature
sensitive liquid crystal and foil heater. The measurement
has been performed for all surfaces consisting of a single passage,
while past studies focused only on the bottom (primary) surface. By
comparing heat transfer coefficient distributions on the primary
surface, sidewalls and turning regions with velocity field which
was measured in the previous study, the heat transfer mechanism of
the lattice cooling channel is discussed.
The lattice cooling channel consists of two sets of inclined parallel
ribs, which cross each other at right angles. Reynolds number
is varied from 2,000 to 9,000, which is based on hydraulic diameter
and bulk velocity in a sub-channel. Heat transfer patterns on the
sub-channel before and after turning are compared.
Overall, the heat transfer distribution was well-correlated with
the velocity field. In the sub-channel before turning, heat transfer is
enhanced at the entrance of the primary surface due to flow acceleration.
Heat transfer is also enhanced on the sidewalls. Whether
the coolant turns or not, shear force exerted by the crossing flow at
the diamond-shaped openings generates swirl flow motion, leading
to enhanced heat transfer. In the sub-channel after turning, this
trend is further increased due to longitudinal vortex formed by the
turning. Moreover, comparison of heat transfer patterns on the
sidewalls with that on the primary surface suggested that they are
comparable due to the flow interaction. It suggests that contribution
of the rib surface on total heat release should be taken into account
for reasonable cooling design.