Pressure, velocity

Fan Rating. Axial fans have the capabiUty to do work, ie, static pressure capabiUty, based on their diameter, tip speed, number of blades, and width of blades. A typical fan used in the petrochemical industry has four blades, operates neat 61 m/s tip speed, and can operate against 248.8 Pa (1 in. H2O). A typical performance curve is shown in Figure 11 where both total pressure and velocity pressure are shown, but not static pressure. However, total pressure minus velocity pressure equals static pressure. Velocity pressure is the work done just to collect the air in front of the fan inlet and propel it into the fan throat. No useflil work is done but work is expended. This is called a parasitic loss and must be accounted for when determining power requirements. Some manufacturers fan curves only show pressure capabiUty in terms of static pressure vs flow rate, ignoring the velocity pressure requirement. This can lead to grossly underestimating power requirements. 

In contrast, various sensors are expected to respond in a predictable and controlled manner to such diverse parameters as temperature, pressure, velocity or acceleration of an object, intensity or wavelength of light or sound, rate of flow, density, viscosity, elasticity, and, perhaps most problematic, the concentration of any of millions of different chemical species. Furthermore, a sensor that responds selectively to only a single one of these parameters is often the goal, but the first attempt typically produces a device that responds to several of the other parameters as well. Interferences are the bane of sensors, which are often expected to function under, and be immune to, extremely difficult environmental conditions. 

Chemical processes may involve a complex variety of both inorganic and organic chemicals. Hard and fast rules for selecting the appropriate materials of construction can be given when the composition is known, constant, and free of unsuspec ted contaminates when the relevant parameters of temperature, pressure, velocity, and concentra-... 

The reason that we use the term dynamic is because when the system and the pump is running, the elevations, pressures, velocities, and friction losses begin to change. In other words, they re dynamic. 

With the pump running at its Best Bffieicncy Point, and all valves in the system open, the factors of pressure, velocity, and area are in harmony at all points around the volute. All radial loads are in equilibrium (Figure 9-3)... 

Figure 7-3 shows the pressure, velocity, and total enthalpy variation for flow through several stages of an axial compressor. As indicated in Figure 7-3,... 

Because of these solutions, important technical data can be transferred from local instrumentation (control system) through data-based controllers to a control station with computers. The operator may use the many variations that the software data system provides. Technical data operation may be digital off/on messages such as the status of operation and the performance of alarms or analog measurements such as temperature, humidity, pressure, velocity, energy usage, etc. 

Plenum box A component forming an interface between ductwork and one or more air terminal devices. By virtue of its design or by the inclusion of accessories, it can also be used to equalize the pressure/velocity across air terminal devices. 

Pressure, velocity The kinetic pressure exerted in the direction of flow that is necessary to cause a fluid at rest to flow at a given velocity. 

For lower scaled pressures, velocity can be calculated with the equation proposed by Baum (1987) which produces disintegration of both cylindrical and spherical vessels into multiple fragments (Vj = O.SSoo ). Such a result can also be obtained by use of Figure 6.33. However, actual experience is that ruptures rarely... 

Bead diameter (jum) Size exclusion pore dimension" (nm) Fractionation range Maximum operating pressure/velocity (kPa)/(cm/hr) Recommended operating linear velocity (cm/hr) pH stability (short term)... 

Thus in all corrosion reactions one (or more) of the reaction products will be an oxidised form of the metal, aquo cations (e.g. Fe (aq.), Fe (aq.)), aquo anions (e.g. HFeO aq.), Fe04"(aq.)), or solid compounds (e.g. Fe(OH)2, Fej04, Fe3 04-H2 0, Fe203-H20), while the other reaction product (or products) will be the reduced form of the non-metal. Corrosion may be regarded, therefore, as a heterogeneous redox reaction at a metal/non-metal interface in which the metal is oxidised and the non-metal is reduced. In the interaction of a metal with a specific non-metal (or non-metals) under specific environmental conditions, the chemical nature of the non-metal, the chemical and physical properties of the reaction products, and the environmental conditions (temperature, pressure, velocity, viscosity, etc.) will clearly be important in determining the form, extent and rate of the reaction. 

The ideal source book for designers, which is the one in which the individual chemicals are listed together with the corrosion rates for a variety of materials under different conditions of temperature, pressure, velocity, etc. 

The nature of the environment, i.e. composition, temperature, pressure, velocity, etc. 

Different test results are available to the designer wanting friction and wear data as well as the usual mechanical short and long term data, corrosion resistance, readings, and so on. The data presented include the load and velocity capabilities of a bearing material as expressed by the product of the unit load P based on the projected bearing area and linear shaft velocity V. The symbol PV denotes the important property of the pressure-velocity relationship. 

The failure of the fluid film at nano-scale and the relation between the failure point and pressure, velocity, and viscosity have been investigated [19]. The lubricants used in the experiments are given in Table 1. 

For the computation of compressible flow, the pressure-velocity coupling schemes previously described can be extended to pressure-velocity-density coupling schemes. Again, a solution of the linearized, compressible momentum equation obtained with the pressure and density values taken from a previous solver iteration in general does not satisfy the mass balance equation. In order to balance the mass fluxes into each volume element, a pressure, density and velocity correction on top of the old values is computed. Typically, the detailed algorithms for performing this task rely on the same approximations such as the SIMPLE or SIMPLEC schemes outlined in the previous paragraph. 

Many of those working on optical sensors have been overoptimistic. While many chemical sensors and biosensor have found applications in the laboratory and in research, they are much less often applied than physical sensors, e.g. those for temperature, pressure, velocity, or strain. This may be due to several factors, of which the following are considered to be most significant ... 

HDPE same properties as LDPE but more rigid better thermal and creep behaviour lower coefficient of friction and higher pressure strength, allowing antifriction applications with higher PV (pressure velocity) factor more transparent. 

The combined pitot-static tube shown in Fig. 10-12 consists of a jacketed impact tube with one or more rows of holes, 0.51 to 1.02 mm (0.02 to 0.04 in) in diameter, in the jacket to measure the static pressure. Velocity Vq m/s (fl/s) at the point where the tip is located is given by... 

Shock Relationships and Formulas, which include Changes During Steady Reversible Compressible Flow (61-4) Pressure-Velocity Relationship (65-6) Irreversibility and Degradation (66-8) Derivation of Formulas (68-70) Pressure Efficiency Factor and Recovery Factor (70-2) and Oblique Shocks in Air (72). Shock Wave Interaction, which includes Strong Shock Waves (81) Superposition of Plane Shock Waves (81-2) ... 

Taylor (Ref 23) stated that ignition of TNT chge at some point inside the expl, results in a very rapid drop in pressure velocity behind the deton front. A fixed proportion of the whole vol of burnt gas is at rest and the radial rat e of change of the variables velocity, pressure density become finite at the deton front. The fact that the velocity drops to ze ro at some point between the deton surface the center shows that a spherical deton wave can maintain itself in the case of TNT. It is not known whether this is true in all cases Lutzky (Ref 86) determined the "Flow ... 

In an effort to understand the formidable-appearing output of many computations for a wide variety of C-H-N-O explosives at various initial loading densities, we have investigated interrelationships between such properties as pressure, velocity, density, heat of reaction, etc. These studies have led to a number of interesting observations, important among which were the facts that much simpler semiempirical formulas could be written for desk calculation of detonation velocities and detonation pressures, with about the same reliance on their answers as one could attach to the more complex computer output. These equations require as input information only the explosive s composition and loading density and an estimate of its heat of formation, and, in their comparative simplicity,... 

Further the pressure and temperature dependences of all the transport coefficients involved have to be specified. The solution of the equations of change consistent with this additional information then gives the pressure, velocity, and temperature distributions in the system. A number of solutions of idealized problems of interest to chemical engineers may be found in the work of Schlichting (SI) there viscous-flow problems, nonisothermal-flow problems, and boundary-layer problems are discussed. 

Figure 7.32. Progress of pressures, velocities, enthalpies and entropies in an ejector (Coulson and Richardson, Chemical Engineering, Pergamon, 1977, New York, Vol. 1).

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