Bubble removal

None of the set-ups discussed so far provides stirring of the electrolyte for bubble removal or for enhancement of the reaction rates. A standard set-up developed to study kinetic electrode processes is the rotating disc electrode [11]. The electrode is a small flat disc set in a vertical axle. The hydrodynamic flow pattern at the disc depends on rotation speed and can be calculated. An additional ring electrode set at a different potential provides information about reaction products such as, for example, hydrogen. However, because this set-up is designed to study kinetic processes and is usually equipped with a platinum disc, it becomes inconvenient if silicon samples of different geometries have to be mounted. 

Rinse a clean burette with about 10 mL of NaOH solution. Discard the rinse with plenty of water. Then set up a retort stand, burette clamp, meniscus reader, and funnel. Fill the burette with NaOH solution. Make sure that the solution fills the tube below the tap with no air bubbles. Remove the funnel. 

Samples are usually placed in 1mm thick quartz spectrophotometer cells sealed with Parafilm or similar. Samples in which the aqueous phase has a very high D to H ratio are sometimes thicker, as the level of incoherent scatter due to H will be low. Samples may be in the scattering apparatus for several hours, and so H20/D20 exchange due to faulty sealing can cause errors. For gel-like samples, it is very important that there are no air bubbles trapped in the sample. Gel or viscous samples can be centrifuged to the bottom of cells, and air bubbles removed, using a Helma Roto-Vette or similar. 

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...

An alternate method of tip bubble removal was reported by Austin.8 First, pour about 1 mL of fluid into the burette, open the stopcock to let the fluid into the tip region and close the stopcock. Now observe the tip and see if a bubble is trapped within the liquid of the tip. If there is no bubble, fill the burette to the top and proceed with your work. If there is a bubble, turn the burette so the stopcock is on top and quickly rotate the stopcock plug 180°. This procedure will lower the liquid in the tip of the burette, but if done quickly enough, it should not empty the tip. It should, however, remove the bubble from the tip region. The advantage of this approach is that it uses less solution. 

It is furthermore noteworthy that a passing air bubble removes the bacteria and the yeasts much more easily from the brush than from the bare glass, indicating weak interaction between the cells and the brush. 

Air coming in the bottom provides mixing for most small chemostats, referred to as air-lift fermenters. Spargers should never be used since the small bubbles remove too much C02 and the pores tend to become clogged. Otherwise, the chemostat is stirred with a magnetic stir bar or paddles. The stir bar requires that the chemostat have a flat bottom and be set on a magnetic stirrer, whereas the paddles are driven from the top. Anaerobic chemostats are mixed mechanically with either stir bars or paddles. 

Energy Conversion, Fnvirnnmftntal. Sftnsnr Environmental Cleaning by Micro- bubble and Nano- bubble Removal of Nano- particle from Wall Surface bv Ultrasound... 

The level of coalescence between particles, the size of the particles, and the packing arrangement dictate the size of air cavities and, thus, the size of the bubble initially formed in the melt. Once formed, the bubbles remain stationary in the melt. A relatively small bubble diameter, combined with the high viscosity of the melt, prevents the movement of the bubbles into the melt. The bubble removal is known to be a diffusion-controlled process. The identification of key parameters in the dissolution of bubbles formed in the melt has been done using a theoretical model that describes this process. The disappearance of the air bubble formed into the melt was modeled based on... 

Air Bubbles Removed Before Colored Solution Enters Flowcell, Where Color Intensity is Monitored. 

The fabric initially developed in situ has already been altered to some unknown degree, due to the presence of gas bubbles. Removal of the sediment to the surface will cause a pressure decrease resulting in an increase in bubble size. This increase in bubble size will... 

Centrifugal field Pulse-free pumping No pressure-tight interfaces needed Low-pressure load on lids Standard operation in sample prep Robust liquid handling widely decoupled fi om viscosity and surface tension Intrinsic, buoyancy-based bubble removal Coriolis force manipulates flows Rotational symmetry... 

Immerse the slide by holding it with long forceps (it is also best to wear protective gloves and eye protection) and lowering it into a container with liquid nitrogen. Make sure the slide is immersed slowly, or it may crack. Keep the slide immersed until well after the liquid nitrogen has ceased to bubble. Remove the cover slip quickly before the slide warms up. 

Using fine forceps, gently place a siliconized cover slip onto the section to spread the probe solution. If there are any air bubbles, remove them by pressing gently on the cover slip with the forceps. 

Litterst, C., Eccarius, S., Hebling, C., Zengerle, R., and Koltay, P. (2006) Increasing mu DMFC efficiency by passive CO2 bubble removal and discontinuous operation. J. Micromech. Microeng., 16 (9), S248-S253. 

As described in Chapter 10, ultrasound can be used to improve the quality of cast aluminium. The effect of ultrasound seen in Figure 3.11, in this case for glass refining, is to enhance bubble removal from glass melts, allowing it to take place in minutes rather than hours - see also Chapter 10 for further data and a fuller explanation. In Figure 3.11 the ultrasound probe is visible top centre, penetrating into... 

Figure 3.1 I Enhanced bubble removal from molten glass using ultrasound.

C. Litterst, S. Eccarius, C. Hebhng, R. Zengerle, P. Koltay, Increasing /[Pg.131]

Two liquids Tendency of surfactant molecules to accumulate at gas-liquid interface and rise with air bubbles Removal of detergents from laundry wastes ore flotation 18, 20, 49-51... 

Air bubbles removed before colored solution enters flowcell, where color intensity is monitored Colorimeter... 

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