Water speed

The function of aeration in a wastewater treatment system is to maintain an aerobic condition. Water, upon exposure to air, tends to estabUsh an equihbrium concentration of dissolved oxygen (DO). Oxygen absorption is controlled by gas solubiUty and diffusion at the gas—hquid interface. Mechanical or artificial aeration may be utilised to speed up this process. Agitating the water, creating drops or a thin layer, or bubbling air through water speeds up absorption because each increases the surface area at the interface. 

This is presumably an estimated average curve, as no numerical data are quoted, and it may be assumed to refer to bare steel. This conclusion is not supported by the results of Volkening, whose main interest was in the effect of chlorination and who shows that although corrosion increased with velocity of chlorinated sea water, when plain sea water was used velocity had little effect. There can be no doubt that painting will very much reduce the effect of water speed, as also will marine fouling or slime. 

At very high water speeds cavitation-damage (Section 8.8) is sustained by any meti high-speed bronze propellers, for instance, may suffer seriously. This form of attack is mainly mechanical, although an element of true corrosion may be present, and is not specifically associated with sea water. 

Factors that tend to increase the severity of impingement attack are increase of water speed and particularly of local turbulence, pollution of the water, and, within certain limits, increase in the size and the amount of entangled air bubbles (see also Section 1.6). 

Factors that cause increased rates of dezincification are high temperature, high chloride content of water and low water speed. Dezincification is also likely to occur preferentially beneath deposits of, for instance, sand or silt on the metal surface, or in crevices where there is a low degree of aeration. 

Deposit attack and pitting When water speeds are low and deposits settle on the surface (particularly at water speeds below about 1 m/s), pitting of copper and copper alloys is liable to occur by differential aeration effects. 

In early times 70/30 brass condenser tubes failed by dezincification and Admiralty brass (70Cu-29Zn-lSn) was brought into use. This proved little better, but some time later the addition of arsenic was found to inhibit dezincification. Failures of Admiralty brass by impingement attack became a serious problem, particularly as cooling water speeds increased with the development of the steam turbine. The introduction of alloys resistant to this type of attack was a great step forward and immediately reduced the incidences of failure. 

Colas stimulate digestive juices, and carbonated water speeds the digestion, and this combination of effects, along with the stimulant action of the two alkaloids, can make a big difference to someone who is not feeling well. 

Pennies that are the same age are not always the same color. Pennies that have been touched more often will turn darker more quickly. The moisture on your hands gets on pennies and the water speeds up the combination of oxygen molecules and copper atoms. Coin collectors sometimes cover shiny new coins with plastic to keep air and water from touching the coins. 

The aspirator s pumping mechanism is quite sophisticated, and it all begins by water streaming past the water jet nozzle. By decreasing the internal diameter at the point where the water leaves the nozzle, there is an increase in water speed passing this point. Because the MFP of the gas and vapor molecules within the aspirator is much less than the pump dimensions, aerodynamic shear causes air movement in the desired direction. This air movement will occur regardless of whether there is direct contact of the air with the water or not. Additionally, because the boundary between the rushing water is quite turbulent, air is physi-... 

In this work, a coking wastewater was treated in a continuous reactor using Ru/TiOjiS. The results of one month running are shown in Figure 5. The reactions proceed at 250°C, 7.0MPa, Oj content 20%, water speed 4L/h, 30min. The COD removal rate remained greater than 99% and the NHj-N removal rate was nearly 100%. 

We say water is hard if it contains calcium ions, magnesium ions, and in many cases, iron ions. These ions come from rocks in the ground and dissolve into the water that passes through them. For example, limestone rock is calcium carbonate, CaC03(r), and dolomite rock is a combination of calcium carbonate and magnesium carbonate, written as CaC03 MgC03(r). Water alone will dissolve very small amounts of these minerals, but carbon dioxide dissolved in water speeds the process. 

We have previously reported that, although most storms do not alter the bottom-water resultant flow vectors, the probability of large water speeds over the bottom is increased (Bokuniewicz et ai, 1975b) when the wind stress is high. We now present further evidence on this effect. A periodogram calculated for a current meter record obtained in the western end of Long Island Sound is presented in Fig. 6. Three tidal peaks are... 

Fig 7. Fluctuating components of the water speed measured at a height of 2 m above the bottom over a period of 30 days. (Same data as used in Fig. 6.)... 

From the results of this example you can see that when you reduce the pipe diameter by a fee-tor of 2, the water speed in the reduced section of the pipe increases by a fector of 4. 

The vessel and pipe was pressurized with air up to 6 bar relative pressure. Thereafter the control valve was opened and as soon as the flow was fully developed the control valve was closed very rapidly. The water speed in the pipe before closing the valve was 6.51 m/s. With a variable area flow meter the gas injection flow rate was measmed. Based on the gas and liquid flow rates the gas fraction can be determined. The calculated volume gas fraction at normal... 

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