Heat transfer characteristics of gas-liquid flow in horizontal rectangular micro-channels

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.