a b s t r a c t
An experimental study of heat transfer characteristics of air–water flow in horizontal micro-channels was
carried out in this work. The gas–liquid mixture from a y-shaped mixing chamber was forced to pass
through a plenum inlet and entered 21 parallel rectangular micro-channels 40 mm long in the direction
of flow. Each channel had a width and a depth of 0.45 and 0.41 mm, respectively. The test runs were done
at a heat load of 80 W, with superficial Reynolds numbers of gas and liquid ranging between 54–142 and
131–373, respectively. A Stereozoom microscope and camera system were employed to conduct flow
visualization. To explore the dependence of a Nusselt number on the flow characteristics, two inlet sections
with different designs were used in this work. The experiments revealed that the formation of small
gas slugs instead of gas core flow involves an increase in Nusselt numbers. In this work, the gas–liquid
flow gave heat transfer enhancement up to 80% over the liquid flow.