Hydraulic factoring

It should be noted that in all cases the size (and hence cost) of end-of-pipe treatment has a direct relationship to both the volume of effluent to be treated and the concentration of pollutants contained in the discharge. For example, the size of most physicochemical reactors (balancing, neutralizing, flocculation, sedimentation, flotation, oxidation, reduction, etc.) is determined by hydraulic factors such as surface loading rate and retention time. 

Pressure Drop. Since efficiency depends on hydraulic factors, a method will first be given for estimating pressure drop across a sieve tray. The total drop across the tray is taken as the sum of the drop through the holes plus the drop through the aerated mixture ... 

The following weather and hydraulic factors are needed for input to the navigation project design analysis. 

The two steps in the removal of a particle from the Hquid phase by the filter medium are the transport of the suspended particle to the surface of the medium and interaction with the surface to form a bond strong enough to withstand the hydraulic stresses imposed on it by the passage of water over the surface. The transport step is influenced by such physical factors as concentration of the suspension, medium particle size, medium particle-size distribution, temperature, flow rate, and flow time. These parameters have been considered in various empirical relationships that help predict filter performance based on physical factors only (8,9). Attention has also been placed on the interaction between the particles and the filter surface. The mechanisms postulated are based on adsorption (qv) or specific chemical interactions (10). 

Noncircular Channels Calciilation of fric tional pressure drop in noncircular channels depends on whether the flow is laminar or tumu-lent, and on whether the channel is full or open. For turbulent flow in ducts running full, the hydraulic diameter shoiild be substituted for D in the friction factor and Reynolds number definitions, Eqs. (6-32) and (6-33). The hydraiilic diameter is defined as four times the channel cross-sectional area divided by the wetted perimeter. For example, the hydraiilic diameter for a circiilar pipe is = D, for an annulus of inner diameter d and outer diameter D, = D — d, for a rectangiilar duct of sides 7, h, Dij = ah/[2(a + h)].T ie hydraulic radius Rii is defined as one-fourth of the hydraiilic diameter. 

With the hydraulic diameter subsititued for D in/and Re, Eqs. (6-37) through (6-40) are good approximations. Note that V appearing in/and Re is the actual average velocity V = Q/A for noncircular pipes it is not ( /(7CD /4). The pressure drop should be calculated from the friction factor for uoucirciilar pipes. Eqiiations relating Q to AP and D for circular pipes may not he used for noncircular pipes with D replaced by because V Q/( KDh/4). 

Isothermal Gas Flow in Pipes and Channels Isothermal compressible flow is often encountered in long transport lines, where there is sufficient heat transfer to maintain constant temperature. Velocities and Mach numbers are usually small, yet compressibihty effects are important when the total pressure drop is a large fraction of the absolute pressure. For an ideal gas with p = pM. JKT, integration of the differential form of the momentum or mechanical energy balance equations, assuming a constant fric tion factor/over a length L of a channel of constant cross section and hydraulic diameter D, yields,... 

External seals (Fig. 10-115) are installed with all seal components protected from the process fluid. The advantages of this arrangement are that (1) fewer critical materials of construction are required, (2) installation and setting are somewhat simpler because of the exposed position of the parts, and (3) stuffing-box size is not a hmiting factor. Hydraulic balancing is accomphshed by proper proportioning of the seal face and secondary seal diameters. 

Hydraulic-drive samplers are also available, but cost factors tend to be substantially greater than electromechanical units. Recent use of hydraiilic-drive systems has diminished with the availability of increased strength and durabihty electric-motor linear-drive units capable of reliable operation in high-capacity applications. 

Modules Eveiy module design used in other membrane operations has been tried in peivaporation. One unique requirement is for low hydraulic resistance on the permeate side, since permeate pressure is veiy low (O.I-I Pa). The rule for near-vacuum operation is the bigger the channel, the better the transport. Another unique need is for neat input. The heat of evaporation comes from the liquid, and intermediate heating is usually necessary. Of course economy is always a factor. Plate-and-frame construc tion was the first to be used in large installations, and it continues to be quite important. Some smaller plants use spiral-wound modules, and some membranes can be made as capiUaiy bundles. The capillaiy device with the feed on... 

An anaerobic digester is a no-recycle complete mix reactor. Thus, its performance is independent of organic loading but is controlled by hydraulic retention time (HRT). Based on kinetic theoiy and values of the pseudo constants for methane bac teria, a minimum HRT of 3 to 4 days is required. To provide a safety factor and compensate for load variation as indicated earlier, HRT is kept in the range 10 to 30 days. Thickening of feed sludge is used to reduce the tank volume required... 

The Souders-Brown correlation considers entrainment as the controlling factor. For high liquid loading situations and final design, complete tray hydraulic calculations are required. 

This case serves to point out the importance of maintaining a constant hydraulic gradient on the inside and outside of a slurry wall. This can also become a factor if slurry walls are used with groundwater pumping systems (extraction wells). Then water must be reinjected to maintain a... 

Lyachshenko number, dimensionless left hand side, dimensionless particle mass, kg pressure, N/m or force, N mass feed rate, kg/s or volumetric flowrate in mVhr drag or resistance force, N physical properties correction factor for slurries Reynolds number, dimensionless right hand side hydraulic radius, m... 

Figure 2-3. Moody or regular Fanning friction factors for any kind and size of pipe. Note the friction factor read from this chart is four times the value of the f factor read from Perry s Handbook, 6th Ed. [5]. Reprinted by permission, Pipe Friction Manual, 1954 by The Hydraulic Institute. Also see Engineering DataBook, 1st Ed., The Hydraulic Institute, 1979 [2]. Data from L. F, Moody, Friction Factors for Pipe Flow by ASME [1].

When hydraulic gradient is a factor in the tray design, the dynamic liquid seal should be used in place of hsi for the determination of effective head. 

More pumps fail as a direct result of improper installation than any other single factor. The predominant reasons for these failures include starvation, caused by inadequate or inconsistent suction conditions distortion, caused by pipe strain or improper foundation and turbulent that results from piping or entrained gas problems. Centrifugal pump installation must follow Hydraulic Institute Standards, which provide specific guidelines to prevent these installation and performance problems. This chapter will address the fundamental requirements for proper installation. 

Fluid power includes hydraulic, hydro-pneumatic and pneumatic systems. Why are hydraulics used in some applications, pneumatics in others or combination systems, in still others Both the user and the manufacturer must consider many factors when determining which type of system should be used in a specific application. 

The study of liquids is divided into two main parts liquids at rest, hydrostatics and liquids in motion, hydraulics. The effect of liquids at rest can often be expressed by simple formulas. The effects of liquids in motion are more difficult to express due to frictional and other factors whose actions cannot be expressed by simple mathematics. 

At all points in a system, the static pressure is always equal to the original static pressure less any velocity head at a specific point in the system and less the friction head required to reach that point. Since both the velocity head and friction head represent energy and energy cannot be destroyed, the sum of the static head, the velocity head, and the friction head at any point in the system must add up to the original static head. This is known as Bernoulli s principal, which states For the horizontal flow of fluids through a tube, the sum of the pressure and the kinetic energy per unit volume of the fluid is constant. This principle governs the relationship of the static and dynamic factors in hydraulic systems. 

To minimize the loss of useable energy lost to its conversion to heat energy, care must be taken in the design, installation and operation of hydraulic system. As a minimum the following factors must be considered ... 

While pumps do not directly create pressure, the system pressure created by the restrictions or work performed by the system has a direct affect on the volumetric output of the pump. As the system pressure increases, the volumetric output of the pump decreases. This drop in volumetric output is the result of an increase in the amount of leakage within the pump. This leakage is referred to as pump slippage or slip. A factor must be considered in all hydraulic pumps. 

Selection and care of the hydraulic fluid for a machine will have an important effect on how it performs and on the life of the hydraulic components. During the design of equipment that requires fluid power, many factors are considered in selecting the type of system to be used-hydraulic, pneumatic, or a combination of the two. Some of the factors required are speed and accuracy of operation, surrounding atmospheric conditions, economic conditions, availability of replacement fluid, required pressure level, operating temperature range, contamination possibilities, cost of transmission lines, limitations of the equipment, lubricity, safety to the operators, and expected service life of the equipment. 

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