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The Journal of the Royal Institute of Thailand Volume II - 2010 Sira Saisorna, Somchai Wongwises 73 measured by four sets of rotameters within the range of 5-50 sccm, 0.05-0.5, 0.2-2.0, 1-10 SCFH, respectively. For liquid flow rate measurements, an electronic balance (320 ± 0.001 g) was used to measure the weight of the liquid flowing freely from the outlet over a period of time. The test section used in this work is a fused silica channel with a diameter of 0.22 mm and a length of 120 mm. The single-phase and two-phase pressure drops across the test section were determined by two pressure transducers installed at the channel inlet. The low range pressure transducer was calibrated from 0 to 250 kPa with a ± 0.5 kPa accuracy and the high range one was calibrated from 0 to 1000 kPa with a ± 2 kPa accuracy. Type T thermocouples were used to measure fluid temperatures. The degree of uncertainty of the temperature measurements was ± 0.1 o C. The single-phase flow experiments with different fluids were the first to be performed. Following this, the two-phase flow experiments were conducted at various gas and liquid flow rates. In this work, the gas flow rate was increased by small increments, while the liquid flow rate was kept constant at a pre-selected value. The system was allowed to approach steady conditions before the fluid flow rates, flow patterns and pressure drops were recorded. Figure 1 Schematic diagram of test facility.