Two-Phase Flow Pressure Drop of R-134A in a Vertical Circular Mini/Micro Channel

This paper presents new experimental results on saturated flow boiling pressure drop in microchannels. The two-phase pressure drops were measured for vertical saturated boiling of R-134a in circular tubes with internal diameters of 1.700, 1.224, and 0.826 mm, and a uniformly heated length of 220 mm, the total flow length is 580 mm. The total pressure drops were obtained for a heat flux range of 10–30 kW/m², a mass flux range of 100–400 kg/(m²s), and outlet vapor qualities up to 0.6. Experiments were conducted at the average saturation pressure of 8.62 bar. The experimental data was compared to predictions by correlations available in the literature both for microchannels and larger diameter tubes.