Bubble injection length mean

In order to compare the experimental results for dual nozzle gas injection system, the two nozzles are removed, and subsequently gas is injected through a single-hole nozzle of inner diameter of 2.0 x 10 m. The center of the nozzle exit is placed at the origin of the coordinate system. The air flow rate is set to 80 x 10 m /s, being equal to the sum of ggi and 0g2. The center of the nozzle is placed at the vertical axis of the vessel. Bubble characteristics represented by gas holdup a, bubble frequency /b, mean bubble rising velocity b, and mean bubble chord length Lb are measured by making use of a two-needle electroresistivity probe [23,37]. 

Figure 1 is a schematic diagram of the experimental setup. The test section is a horizontal rectangular channel 40 mm in height (H), 160 mm in width (W), and 6,000 mm in length (L). The rectangular channel is completely constructed of transparent acrylic resin, as shown in Figure 2. Tap water and air are used as the gas and liquid phases, respectively. Water is circulated by a 2.2 kW pump fed by a water reservoir 4.2 m away. Air bubbles are injected into the horizontal channel from the upper inner surface of the channel. An array of capillary needles produces bubbles 10-100 mm in length. Before the air and water are mixed, their volumetric flow rates are measured. After leaving the horizontal channel, the gas-liquid mixture is dumped into a tank that acts as a bubble remover when the liquid phase is recirculated it is free of bubbles. At the end of the horizontal channel tracer particles are added to the water to act as ultrasound reflectors. The mean particle diameter is 200 pm and the particle density is 1020 kg/m3. These tracer particles are assumed to...

---