Similar void fraction data can be obtained in micro-channels
and conventional size channels, but the micro-channel void fraction
can be sensitive to the inlet geometry and deviate significantly
from the homogeneous flow model. The Lockhart–Martinelli model
can correlate the data obtained from pressure drop measurements
in gas–liquid flow in parallel micro-channels with hydraulic diameter
of 130 lm, the data could be fit by a single value of C = 0.24.
Only a few experimental investigations deal with heat transfer
of gas–liquid flow in conventional size channels. There is a significant
discrepancy between experimental results on heat transfer
presented for channels of dh = 1–100 mm. No data is available in
the literature on gas–liquid heat transfer in micro-channels. Heat
transfer in the test section that contains 21 parallel triangular micro-
channel of dh = 130 lm was studied experimentally in the
range of superficial velocities ULS = 0.015–0.244 m/s, UGS = 0.50–
28.6 m/s. It was shown that the heat transfer coefficient increases
with increasing liquid velocity and decreases with increasing air
velocity.