Based on the test results shown in Figs. 4–6, it can be
concluded that when flow distribution to each channel is
relatively uniform, which corresponds to the flow condition
before the dryout vapor quality, the effects of heat flux, mass
flux and saturation pressure on the heat transfer coefficients
are very small. However, when flow conditions are unstable
after the dryout vapor quality, the heat transfer coefficients
increase with a rise of saturation pressure, mass flux, and
heat flux under the present test conditions. Considering the
effects of hydraulic diameter on the heat transfer coefficients, the heat transfer coefficients of the 8-hole
microchannel were on the average 25% higher than those of
the 7-hole microchannel under the same mass flux, heat flux,
and saturation pressure. This may be due to the increase of
the perimeter, which contributed to the effective distribution
of the heat load to each channel. In addition, the dryout
vapor qualities of the 8-hole microchannel were smaller
than those of the 7-hole microchannel at the same test
conditions.