The test tube has been heated with a fixed

The schematic diagram of experimental water loop is shown in Fig. 1. The loop is made of SUS304 stainless steel and is capable of working up to 2 MPa. The loop has five test sections whose inner diameters are 2, 3, 6, 9 and 12 mm. Test sections were vertically oriented with water flowing upward. The test section of the inner diameter of 6 mm was used in this AP1903 work. The circulating water was distilled and deionized with about 0.2-μS/cm specific resistivity. The circulating water through the loop was heated or cooled to keep a desired inlet temperature by pre-heater or cooler. The mass velocity was measured by a mass flow meter using a vibration tube (Nitto Seiko, CLEANFLOW 63FS25, Flow range = 100 and 750 kg/min). The mass velocity was controlled by regulating the frequency of the three-phase alternating power source to the multistage canned-type circulation pump with high pump head (Nikkiso Co., Ltd., Non-Seal Pump Multi-stage Type VNH12-C4 C-3S7SP, pump flow rate = 12 m3/h, pump head = 250 m) with an inverter installed a 4-digit LED monitor (Mitsubishi Electric Corp., Inverter, Model-F720–30 K). The pump input frequency shows the net pump input power and pump discharge pressure free of slip loss. The circulating water was pressurized by saturated vapor in the pressurizer in protostomes work. The pressure at the outlet of the test tube was controlled within ±1 kPa of a desired value by using a heater controller of the pressurizer.