Comparative study of flow boiling heat transfer and pressure drop of HFE-7000 in continuous and segmented microchannels

Abstract

The flow boiling heat transfer and pressure drop characteristics of HFE-7000 were experimentally investigated in two test sections with continuous and segmented structures. Each microchannel had seven parallel microchannels with the total length of each channel being 110 mm. The cross sectional area of each channel was 2 mm × 1 mm (width × height) with a rib width of 0.5 mm. The 10 mm long transversely connected zones were set every 30 mm along the flow direction in the segmented one. The experiments all used the same saturated inlet temperature of 50 ± 1 °C with mass fluxes from 300 to 500 kg/m2 s and heat fluxes from 30 to 300 kW/m2. The results showed that the interconnected areas in the segmented microchannels improved the heat transfer rates that were related to the flow patterns and fluid-structure effects. For high vapor qualities, the segmented microchannels delayed the heat transfer deterioration seen in the continuous microchannels and the critical heat flux was significantly increased. The frictional pressure drop in the segmented microchannels was less for these experimental conditions before dry out occurred. The interconnected areas in the segmented microchannels also reduced the frictional pressure drop fluctuations, especially the instabilities during the bubbly and slug flow regimes.