Types of flow


Desulfurize the fuel. Most types of fuel can be desulfurized. However, as we go from gaseous to liquid to solid fuels, the desulfurization process becomes increasingly difficult.  [c.306]

As mentioned in Chapter 1, in general, the solution of the integral viscoelastic models should be based on Lagrangian frameworks. In certain types of flow  [c.86]

Types of Fuel Cells  [c.577]

The experience and capabiHty of the Westinghouse Bettis Laboratory were then appHed to designing and constmcting the first fliU-scale commercial power reactor, the 60-MWe Shippingport, Pennsylvania reactor of Duquesne Light Company. The core of the Shippingport reactor (18,34) was composed of two types of fuel. There were 32 "seed" assembHes of highly enriched (90%) uranium alloyed with zirconium and clad with Zircaloy 2 (a 98.3% Zr alloy having 1.45% Sn and 0.05% Ni), in the form of plates 3.175 mm (1/8 in.) thick. There were 113 blanket assembHes, each of 120 fuel rods composed of natural uranium as UO2 peUets in Zircaloy 2 tubes. The seed region was in the shape of a square ring, with blanket fuel both inside and outside the ring. Neither type of fuel could sustain a chain reaction by itself, the seed because of excessive neutron leakage, the blanket because of the low uranium-235 content. Together these formed a critical system, and about the same amount of power was produced by each type of fuel. The use of Zircaloy tubes fiUed with uranium dioxide peUets has become standard for the industry.  [c.214]

Flow. The principal types of flow rate sensors are differential pressure, electromagnetic, vortex, and turbine. Of these, the first is the most popular. Orifice plates and Venturi-type flow tubes are the most popular differential pressure flow rate sensors. In these, the pressure differential measured across the sensor is proportional to the square of the volumetric flow rate.  [c.65]

Fig. 2. Flow curves (shear stress vs shear rate) for different types of flow behavior. Fig. 2. Flow curves (shear stress vs shear rate) for different types of flow behavior.
Some commonly observed types of flow behavior are shown in Figure 2, in which the shear stress is plotted against shear rate. These plots are called flow curves and are frequently used to express the rheological behavior of Hquids. Newtonian flow is shown by a straight line, and shear thinning and thickening by curves. Yield stresses, Tq, are shown by intercepts on the stress (y) axis. It should be pointed out that the existence of yield stresses is controversial they may be artifacts resulting from high Newtonian viscosity at low shear rates (6). However, in many dispersed systems, particularly where severe flocculation occurs, this viscosity is so high that the material would take years to flow. Therefore, in practice, there are tme yield stresses. This parameter can be quite useful in characterizing materials. Additional information on yield is available (7—10).  [c.167]

Calculation of the pressure drop in pneumatic conveyors is dependent on the use of experimentally derived correlations. Some success has been achieved in modeling the flow of well-dispersed, gas—soflds mixtures, but these types of flow streams are not representative of most industrial pneumatic conveying situations. In an industrial plant, the most cost-effective design is one in which the soflds ate conveyed at the lowest velocity and highest soflds loading consistent with maintaining a continuous, nonplugging stream. Under these conditions, the soflds stream concentration is highest along the lower part of the horizontal pipes. This concentration changes throughout the length of the pipe, as soflds ate accelerated after the soflds inlet, retarded then re-accelerated at bends in the pipe, and accelerated as the gas expands towards the terminal end of the conveying line. The gas/particle interactions in these nonhomogeneous flows have proven to be too complex to yield a rehable general correlation for calculating pressures, based on theory alone. Information on the apphcation of two phase flow theory to pneumatic conveying design can be found in Reference 41.  [c.162]

Closed loop control has been designed for both carburetors and fuel injection metering systems. The latter are used in almost all 1990 models. Two types of fuel metering exist a single fuel injector to serve all cylinders, called single-point fuel injection and fuel injectors for each cylinder, called multipoint fuel injection. The multipoint fuel injection systems may be continuous or individual electrically activated. An electronic fuel injection valve is located in the inlet manifold just ahead of each inlet valve. All valves are connected in parallel and open for a caUbrated time as called for by the computer controller. The injected fuel is swept into the cylinder along with the air. The latest development is sequential fuel injection that meters fuel to each cylinder according to the firing order.  [c.491]

Types of Fuel Cells. 27-57  [c.2356]

Graphs of operating potential versus current density are called polarization curves, which reflect the degree of perfection that any particular fuel cell technology has attained. High cell operating potentials are the result of many years of materials optimization. Actual polarization curves will be shown below for several types of fuel cell.  [c.2410]

Resiilts of simulation studies of different types of flow sheets and measurement-error levels show that the performance of these schemes depends on the magnitude of the gross error relative to the measure of the random error. The larger the gross error, the greater the power and lower the probabihty of committing a type-II error. The complexity of the flow sheet contributes in the form of the constraint equations. Flowsheets with paraUel streams have identical constraint equations, giving equal statistical performance. For the cases studied, the power ranges from 0.1 to 0.8 (desired value 1.0), the probability of makiug type-II errors ranges from 0.2 to 0.7 (desired  [c.2572]

Gas turbines may be designed to burn either gaseous or liquid fuels, or both with or without changeover while under load. This standard covers both types of fuel.  [c.151]

Liquid fuels require atomization and treatment to inhibit sodium and vanadium content. Liquid fuels can drastically reduce the life of a unit if not properly treated. A typical fuel system is shown in Figure 4-7. The effect of fuels on gas turbines and the details of types of fuel handling systems is given in Chapter 12.  [c.161]

Types of fuel nozzles  [c.172]

To remove insoluble contaminants, various types of full-flow filters can be used. Two general types are usually selected surface filters and depth filters. Both types of filters are effective for the removal of particulate matter.  [c.550]

To meet these requirements, radically new types of fuel containers are needed to exploit fully the unique features of ANG storage, and maximize the on-board storage capability. Thus the use of immobilized carbons, in the form of briquettes which are shaped to match the geometry of the tank, is an important element, since this minimizes void volume within the container. In addition, this can help to reduce thermal gradients throughout the tank, since the thermal conductivity of immobilized carbons has been measured to be around 65% greater than that of corresponding loose particles, thus increasing the heat transfer. The much lower operating pressure of ANG compared to CNG permits non-cylindrical tank designs that can meet the above requirements and are able to be better integrated within vehicle structures, minimizing the impact on the vehicle and improving weight distribution. With CNG storage, cylindrical or spherical geometry vessels are almost mandatory, due to the very high pressures and the resulting hoop stresses generated within the vessel. However, spheres and cylinders are not amenable to efficient packaging within a modem vehicle and there is wasted space around the spherical or cylindrical vessel, (the parasitic volume), when it is fitted to a vehicle. Thus a nearly thirty percent increase in storage volume could be realized by having a rectangular rather than a circular cross section.  [c.278]

The flow patterns typically encountered in vertical pipe flow are illustrated in Figure 23. The types of flow patterns encountered are as follows  [c.119]

The forces applied by an impeller to the material contained in a vessel produce characteristic flow patterns that depend on the Impeller geometry, properties of the fluid, and the relative sizes and proportions of the tank, baffles and impeller. There are three principal types of flow patterns tangential, radial and axial. Tangential flow is observed when the liquid flows parallel to the path described by the mixer as illustrated in Figure 7.  [c.446]

Based on the pitch of the impeller with regard to the direction of rotation, there are two possible axial flow patterns that in which the impeller pumps the liquid from the bottom to the surface and that in which the impeller pumps liquid from the surface to the bottom. A combination of the three principal types of flow normally is encountered in mixing tanks. The tangential flow following a circular path around the shaft forms a vortex at the surface of the liquid. The vortex formation results from the influence of gravity forces, quantitatively determined by means of the Froude number, which increases at higher speeds, promoting vortex formation. Figure 10 presents a three-dimensional flow pattern, affording a clear image of the liquid flow in the tank obtained by projecting the path of a liquid particle in two planes. Part (A) shows the path that the particle takes at a given impeller speed.  [c.447]

Classification of Different Types of Flow 1322  [c.1317]

Classification of Different Types of Flow  [c.1322]

One widely-used picture for illustrating the different types of flow in pneumatic conveying is the so-called state diagram, - in which the pressure drop is related to the air velocity.  [c.1323]

The way in which the force /j j is modeled clearly determines the type of the pneumatic flow this has been discussed earlier in Section 14.2.2, where we considered the classification of different types of flow. In the following we will give a detailed description for the force in a way that suits a particular type of flow. This approach will be adequate for so-called dilute-phase flow or, more generally speaking, for homogeneous flow where the particles move separately.  [c.1344]

As usual, two types of flow ean oeeur, laminar and turbulent respeetively, and the analyses differ for eaeh ease.  [c.38]

This is another method of supplying an engine with the correct quantity of fuel. Three types of fuel injection are used  [c.476]

TYPES OF FUEL CELLS  [c.527]

As with batteries, differences in electrolytes create several types of fuel cells. The automobile s demanding requirements for compactness and fast start-up have led to the Proton Exchange Membrane (PEM) fuel cell being the preferred type. This fuel cell has an electrolyte made of a solid polymer.  [c.531]

Calculate 0 for types of flow selected from Figure 2-40 [33].  [c.126]

Calculate two-phase pressure drop, horizontal portions of lines. For all types of flow, except wave and fog or spray  [c.126]

Apart from the prediction of a variable viscosity, generalized Newtonian constitutive models cannot explain other phenomena such as recoil, stress relaxation, stress overshoot and extrudate swell which are commonly observed in polymer processing flows. These effects have a significant impact on the product quality in polymer processing and they should not be ignored. Theoretically, all of these phenomena can be considered as the result of the material having a combination of the properties of elastic solids and viscous fluids. Therefore mathematical modelling of polymer processing flows should, ideally, be based on the use of viscoelastic constitutive equations. Formulation of the constitutive equations for viscoelastic fluids has been the subject of a considerable amount of research over many decades. Details of the derivation of the viscoelastic constitutive equations and their classification are covered in many textbooks and review papers (see Tanner, 1985 Bird et al, 1977 Mitsoulis, 1990). Despite these efforts and the proliferation of proposed viscoelastic constitutive equations in recent years, the problem of selecting one which can yield verifiable results for a fluid under all types of flow condition.s is still unresolved (Pearson, 1994). In practice, therefore, the remaining option is to choose a constitutive viscoela.stic model that can predict the most dominant features of the fluid behaviour for a given flow situation. It should also be mentioned here that the use of a computationally costly and complex viscoelastic model in situations that are different from those assumed in the formulation of that model will in general yield unreliable predictions and should be avoided.  [c.9]

The fuel cell is a device that converts chemical energy directly into electrical energy. The fuel eell was discovered in 1839 by William Grove, who found that the eleetrolysis of water in dilute sulfuric acid using platinum electrodes can be reversed. When water is electrolyzed, hydrogen and oxygen are formed. What Grove found was that if hydrogen and oxygen are combined in a eell over platinum electrodes in dilute sulfuric acid, water is formed and, simultaneously, electricity is produced. On the anode the fuel is oxidized on the eathode oxygen is reduced. Grove s discovery, however, remained a curiosity. Only a century later was work on the hydrogen-oxygen fuel cell taken up again. Attempts were made unsuccessfully to use cheaper metal eatalysts. After WW II alkalies, and later phosphoric acid, were used instead of sulfuric acid to ensure good contact between the gas, the electrolyte, and the solid electrode. These types of fuel cells slowly started to receive limited application in static installations. With the advent of the space age, the need for improved fuel cells arose. For the Gemini and Apollo space programs, and later for the space shuttle, JPL developed and built oxygen-hydrogen fuel cells using pressurized liquefied gases. These cells worked well, but the handling of liquefied hydrogen and oxygen is not only cumbersome but also highly dangerous and can result in explosions. The need for a versatile, relatively light-weight and simple fuel cell for transportation and other uses, replacing inefficient heavy batteries, resulted in our cooperation in the 1990s with colleagues from JPL and Caltech in developing a new generation of fuel cell. The cell we developed is no longer based on hydrogen [which also can be produced from various liquid fuels by a catalytic converter device (called reformer), i.e., a small syn-gas-producing unit, with CO  [c.213]

Internal and External Flow Two main types of flow are considered in this subsection internal or condmt now, in which the fluid completely fills a closed stationary duct, and external or immersed flow, in which the fluid flows past a stationary immersed solid. With internal flow, the heat-transfer coefficient is theoretically infinite at the location where heat transfer begins. The local heat-transfer coefficient rapidly decreases and becomes constant, so that after a certain length the average coefficient in the conduit is independent of the length. The local coefficient may follow an irregffiar pattern, however, if obstructions or turbulence promoters are present in the duct. For immersed flow, the local coefficient is again infinite at the point where heating begins, after which it decreases and may show various irregularities depending upon the configuration of the body. Usually in this instance the local coefficient never becomes constant as flow proceeds downstream over the body.  [c.560]

Laminar and Turbulent Flow, Reynolds Number These terms refer to two distinct types of flow. In laminar flow, there are smooth streamlines and the fuiid velocity components vary smoothly with position, and with time if the flow is unsteady. The flow described in reference to Fig. 6-1 is laminar. In turbulent flow, there are no smooth streamlines, and the velocity shows chaotic fluctuations in time and space. Velocities in turbulent flow may be reported as the sum of a time-averaged velocity and a velocity fluctuation from the average. For any given flow geometry, a dimensionless Reynolds number may be defined for a Newtonian fluid as Re = LU p/ I where L is a characteristic length. Below a critical value of Re the flow is laminar, while above the critical value a transition to turbulent flow occurs. The geometry-dependent critical Reynolds number is determined experimentally.  [c.632]

Gases and Solids The flow of gases and sohds in horizontal pipe is usually classified as either dilute phase or dense phase flow. Unfortunately, there is no clear dihneation between the two types of flow, and the dense phase description may take on more than one meaning, creating some confusion (Knowlton, et al., Chem. Eng. Progr, 90(4), 44-54 [April 1994]). For dilute phase flow, achieved at low solids-to-gas weight ratios (loadings), and high gas velocities, the solids may be fully suspended and fairly uniformly dispersed over the pipe cross section (homogeneous flow), particularly for low-density or small particle size sohds. At lower gas velocities, the solids may bounce along the bottom of the pipe. With higher loadings and lower gas velocities, the particles may settle to the bottom of the pipe, form-  [c.655]

A useful classification of lands of reaclors is in terms of their concentration distributions. The concentration profiles of certain limiting cases are illustrated in Fig. 7-3 namely, of batch reactors, continuously stirred tanks, and tubular flow reactors. Basic types of flow reactors are illustrated in Fig. 7-4. Many others, employing granular catalysts and for multiphase reactions, are illustratea throughout Sec. 23. The present material deals with the sizes, performances and heat effects of these ideal types. They afford standards of comparison.  [c.695]

Flows can be classified into two major categories (a) incompressible and (b) compressible flow. Most liquids fall into the incompressible-flow category, while most gases are compressible in nature. A perfect fluid can be defined as a fluid that is nonviscous and noncon-ducting. Fluid flow, compressible or incompressible, can be classified by the ratio of the inertial forces to the viscous forces. This ratio is represented by the Reynolds number (NRe). At a low Reynolds number, the flow is considered to be laminar, and at high Reynolds numbers, the flow is considered to be turbulent. The hmiting types of flow are the inertialess flow, sometimes called Stokes flow, and the inviscid flow that occurs at an infinitely large Reynolds number. Reynolds numbers (dimensionless) for flow in a pipe is given as  [c.883]

Kerr (Louisiana Agr. Exp. Sta. Bull. 149) obtained plant data shown in Fig. 11-27 on various types of full-sized evaporators for cane sugar. These are invariably forward-feed evaporators concentrating to about 50° Brix, corresponding to a viscosity on the order of 0.005 Pa-s (5 cP) in the last effec-t. In Fig. 11-27 curve A is for short-tube verticals with central downtake, B is for standard horizontal tube evaporators, C is for Lillie evaporators (which were horizontal-tube machines with no liquor level but having recirculating liquor showered over the tubes), and D is for long-tube vertical evaporators. These cui ves show apparent coefficients, hut sugar solutions have boiling-point rises low enough not to affec4 the results noticeably. Kerr also obtained the data shown in Fig.  [c.1047]

This slow realization of the concept is due to the very demanding materials requirements for fuel cells. The anodes and cathodes have to be good electronic conductors and must have electrocatalytic properties to facilitate the anodic and cathodic reactions. In addition, the anodes and cathodes must be porous to allow the fuel and oxidant gases to diffuse to the reaction sites, yet they must be mechanically strong enough to support the weight of the fuel cell stacks. The electrolyte must be chemically stable in hydrogen and oxygen, and must have an ionic conductivity of at least 0.1 S/cm. Five classes of electrodes have been found to meet these requirements potassium hyciroxide, phosphoric acid, perfluorinated sulfonic acid resins, molten carbonates, and oxide-ion-conducting ceramics. Consequently, five types of fuel cell based on these electrolytes have been developed.  [c.2409]

Six or seven types of flow patterns (Figure 2-40) are usually considered in evaluating too-phase flow. Only one tsqte can exist in a line at a time, but as conditions change (velocity, roughness, elevation, etc.) the type may also change. The unit pressure drop varies significantly between the types. Figure 2-40 illustrates the typical flow regimes recognized in ttvo-phase flow.  [c.124]


See pages that mention the term Types of flow : [c.162]    [c.103]    [c.85]    [c.170]    [c.2411]    [c.2411]    [c.2480]    [c.2517]    [c.500]   
Applied Process Design for Chemical and Petrochemical Plants, Volume 1 (1999) -- [ c.124 , c.125 ]