Hydraulic flow

Depth tends to be determined from the retention time and the surface overflow rate. As surface overflow rates were reduced, the depth of sedimentation tanks was reduced to keep retention time from being excessive. It was recognized that depth was a valid design parameter and was more critical in some systems than retention time. As mixed-liquor suspended-solids (MESS) concentrations increase, the depth should also be increased. Minimum sedimentation-tank depths for variable operations should be 3.0 m (10 ft) with depths to 4.5 m (15 ft) if 3000 mg/L MESS concentrations are to be maintained under variable hydraulic conditions. With MESS concentrations above 4000 mg/L, the depth of the sedimentation tank should be increased to 6.0 m (20 ft). The key is to keep a definite freeboard over the settled-sludge blanket so that variable hydraulic flows do not lift the solids over the effluent weir. 

In any mass transfer operation, the compositions of the liquid and vapor phases are assumed to follow the relationship illustrated by the column operating line. This line represents the overall calculated profile down the column however, the composition on each individual square foot of a particular column cross-section may vary from that represented by the operating line. These variations are the result of deviations in the hydraulic flow rates of the vapor and liquid phases, as well as incomplete mixing of the phases across the entire column. 

During backwash the larger, denser panicles will accumulate at the base and the particle size will decrease moving up the column. This distribution yields a good hydraulic flow pattern and resistance to fouling by suspended solids. 

The EineLINE series of columns was designed to meet the stringent demands of hygiene required in the production of biopharmaceuticals. These stainless-steel-based columns employ a hydraulic flow adaptor and may be operated at... 

The stability of shales is governed by a complicated relationship between transport processes in shales (e.g., hydraulic flow, osmosis, diffusion of ions, pressure) and chemical changes (e.g., ion exchange, alteration of water content, swelling pressure). 

DAF is controlled under laminar hydraulic flow conditions using a very small volume of air flow amounting to about 1 to 3% of the influent groundwater flow. DAF only requires 3 to 5 min of detention time therefore it is a low-cost process for the decontamination of groundwater. 

Leakage through a synthetic liner is controlled by Fick s first law, which applies to the process of liquid diffusion through the liner membrane. The diffusion process is similar to flow governed by Darcy s law except that it is driven by concentration gradients and not by hydraulic head. Diffusion rates in membranes are very low in comparison with hydraulic flow rates even in clays. In synthetic liners, therefore, the factor that most influences liner performance is penetrations. Synthetic liners may have imperfect seams or pinholes, which can greatly increase the amount of leachate that leaks out of the landfill. 

In the recycle flow pressurization system (Figure 27.10), a portion (15-50%) of the clarified effluent from the flotation chamber is recycled, pressurized, and semisaturated with air in the air dissolving tube. The recycled flow is mixed with the unpressurized main influent stream just before admission to the flotation chamber, with the result that the air bubbles come out of aqueous phase in contact with suspended particulate matter at the inlet compartment of the flotation chamber. The system is usually employed in applications where preliminary chemical addition and flocculation are necessary and ahead of flotation. It eliminates the problems with shearing the flocculated particles since only the clarified effluent passes through the pressurizing pump and the friction valve. It should be noted, however, that the increased hydraulic flow on the flotation chamber due to the flow recirculation must be taken into account in the flotation chamber design. 

In a typical fixed-bed carbon column, the column is similar to a pressure filter and has an inlet distributor, an underdrain system, and a surface wash. During the adsorption cycle, the influent flow enters through the inlet distributor at the top of the column, and the groundwater flows downward through the bed and exits through the underdrain system. The unit hydraulic flow rate is usually 2 to 5 gpm/ft2. When the head loss becomes excessive due to the accumulated suspended solids, the column is taken off-line and backwashed. 

In a typical countercurrent moving-bed carbon column employing upflow of the water, two or more columns are usually provided and are operated in series. The influent contaminated groundwater enters the bottom of the first column by means of a manifold system that uniformly distributes the flow across the bottom. The groundwater flows upward through the column. The unit hydraulic flow rate is usually 2 to 10 gpm/ft2. The effluent is collected by a screen and manifold system at the top of the column and flows to the bottom manifold of the second column. The carbon flow is not continuous, but instead is pulsed. 

Figure 9.2 Formation of an electrical double layer responsible for electroendosmotic flow in an uncoated fused-silica capillary. The negative charges on the surface of the capillary are neutralized by positive charges of cations present in the buffer, which form an electrical layer near the surface of the capillary. When the electric held is apphed, the positive charges migrate toward the negative electrode, generating a bulk flow of the solution contained within the column. Electroosmosis exhibits a flat prohle, in contrast to hydraulic flow, which is parabolic.

The second parameter influencing the movement of all solutes in free-zone electrophoresis is the electroosmotic flow. It can be described as a bulk hydraulic flow of liquid in the capillary driven by the applied electric field. It is a consequence of the surface charge of the inner capillary wall. In buffer-filled capillaries, an electrical double layer is established on the inner wall due to electrostatic forces. The double layer can be quantitatively described by the zeta-potential f, and it consists of a rigid Stern layer and a movable diffuse layer. The EOF results from the movement of the diffuse layer of electrolyte ions in the vicinity of the capillary wall under the force of the electric field applied. Because of the solvated state of the layer forming ions, their movement drags the whole bulk of solution. 

WUC claims that the SS/SH barrier is designed to be used as either a liner or cover for waste landfills, contaminated sites, secondary containment areas, etc. in the industrial, chemical, mining, and municipal sectors. WUC claims that the SS/SH technology is also designed to be used as a barrier to hydraulic flow in the transportation and construction industries. 

The interstitial fluid content of the skin is higher than in the subcutaneous fat layer and normal fluid movement is intrinsically finked to lymphatic drainage as governed by mechanical stresses of the tissue. A model of temporal profiles of pressure, stress, and convective ISF velocity has been developed based on hydraulic conductivity, overall fluid drainage (lymphatic function and capillary absorption), and elasticity of the tissue.34 Measurements on excised tissue and in vivo measurement on the one-dimensional rat tail have defined bulk average values for key parameters of the model and the hydration dependence of the hydraulic flow conductivity. Numerous in vivo characterization studies with nanoparticles and vaccines are currently underway, so a more detailed understanding of the interstitial/lymphatic system will likely be forthcoming. 

Abstract A permeameter was developed for measurement of coupled flow phenomena in clayey materials. Results are presented on streaming potentials in a Na-bentonite induced by hydraulic flow of electrolyte solutions. Transport coefficients are derived from the experiments, assuming the theory of irreversible thermodynamics to be applicable. Hydraulic and electro-osmotic conductivities are consistent with data reported elsewhere. However the electrical conductivity of the clay is substantially lower. This is ascribed to the high compaction of the clay resulting in overlap of double layers... 

The modified correlation of Fig. 7.11 is based on data from the Crawford-Wilke work from six different tower packings having efficiency values up to 94%. All of these flooding data were based on hydraulic flow data with no mass transfer of solute. The extrapolation of Fig. 7.11 or its use outside the preceding physical property data ranges is not advised. Laboratory and/or pilot plant work is in order if data outside these values are needed. 

However, reversing the polarity of a stack has to be accompanied with a reversal of the flow streams. This always leads to some loss of product and requires a more sophisticated flow control. The flow scheme of an electrodialysis plant operated with reversed polarity is shown in Figure 5.7. In the reverse-polarity operating mode, the hydraulic flow streams are reversed simultaneously, that is, the diluate cell will become the brine cell and vice versa. In this operating mode, the polarity of the current is changed at specific time intervals ranging from a few minutes to several hours. 

The method just outlined and illustrated is route specific. It is very flexible and simple to use. It can also be easily computerized if the GP data can be fed in as numerical values. Here we have illustrated its use in the context of a cross-country pipeline, such as a crude oil, products, or perhaps slurry pipeline, which might be commonly encountered by chemical engineers. The method is completely adaptable to any hydraulic flow problem and could be used equally well for a short in-plant pumping system analysis. It can help the designer of flow systems to avoid sometimes subtle traps for slack flow and siphons that might not be immediately obvious if the mechanical energy equation is applied only once between the initial and final points of the flow system. 

Biodegradable aqueous waste Incentive based on hydraulic flow... 

This vial could be placed in two positions by the inlet lift. In the lower position of the lift, EOF driven isocratic and gradient CEC was possible. The solvent was delivered by the pump to the vial through the inner channel and removed via the outer channel using a pressure of nitrogen (right panel of Fig. 2.11). The resistance of the outlet restrictor was low. The pressure in the vial equaled the external gas pressure and was the same in the outlet vial. In this way, no hydraulic flow was generated and bubble formation was suppressed. The column continuously accepted the delivered solvent from the vial by electroosmotic flow. In this position, the flow delivered by the external pump must be low to avoid solvent overflow in the vial. 

This versatile system can be used in different modes. For example, a high speed separations are possible upon unidirectional application of both electroosmotic and hydraulic flow (Fig. 2.12). However, the primary use of this device is gradient elution CEC illustrated on the examples in Fig. 2.13. 

---