Cavitation illustration

The actual shape of the curve illustrated in Fig. 12.4 can vary according to factors such as metal properties and cavitation intensity. (Cavitation intensity relates to the number of bubbles created in a unit volume of fluid and the amount of energy transferred during the col-... 

The cavitation damage in this spacer was due to vibrations from operation of the engine. The localized nature of the damage in this case is an illustration of a common feature of cavitation. Pits formed by initial cavitation damage become preferred sites for the development of subsequent cavitation bubble formation due to the jagged, irregular contours of the pit. This tends to localize and intensify the cavitation process, especially in later stages of pit development. 

Figure 12.13 illustrates severe damage suffered by a component of a cooling tower water pump. The jagged, undercut, spongelike metal loss characteristic of cavitation damage is apparent in Fig. 12.14. All damage occurred along the inner curvature of the specimen.

This case vividly illustrates the potential effect of surface roughness on the propagation of cavitation bubbles. Figure 12.18 represents a surface... 

Note that localized corrosion having the appearance illustrated in Figs. 12.18 through 12.20 could be associated with brief exposure to a strong acid. In this case, however, all available information indicated that the tubes had never been exposed to an acid of any type. Cavitation was caused by high-frequency vibration of the tubes. The vibration apparently induced a threshold cavitation intensity such that rough or irregular surfaces produced cavitation bubbles, and smooth internal surfaces did not. 

The pump has experienced graphitic corrosion. Figures 17.10, 17.12, and 17.14 illustrate typical appearances of graphitically corroded cast iron. In addition, cavitation damage (see Chap. 12) has produced severe metal loss in specific areas (see Fig. 17.13). The soft, friable corrosion products produced by graphitic corrosion are susceptible to cavitation damage at relatively low levels of cavitation intensity. 

The work by group of Kozyuk [84—87] has illustrated the use of hydrodynamic cavitation for obtaining free disperse system in liquids, particularly in liquid hydrocarbons. It has been found that, there is substantial improvement in the quality of the obtained free dispersion, even in the absence of any catalyst. Also the geometry of a flow-constricting baffle body [84] effectively increases the degree of cavitation to substantially improve the quality of obtained free disperse system. 

Figures 6 and 7 are derived from laboratory experiments and illustrate that flow can become turbulent close to particle walls even when the bulk flow remains laminar. The turbulent vortices bore into the particle surface, magnifying cavitations and abrading protrusions, and hence accelerating the dissolution process [(10), Chapter 4.3.5]. However, irregulari-...

The erosion effects of cavitation on solid surfaces have been extensively investigated both in terms of surface erosion [68] and corrosion [69]. The consequences of these effects on metal reactivity are important since passivating coatings are frequently present on a metal surface (e. g. oxides, carbonates and hydroxides) and can be removed by the impacts caused by collapsing cavitation bubbles. An illustration can be found with the activation of nickel powder and the determination of the change in its surface composition under the influence of cavitation by Auger spectroscopy (Fig. 3.6) [70]. 

COMMENTS The Carnot vapor cycle as illustrated by Example 2.1 is not practical. Difficulties arise in the isentropic processes of the cycle. One difficulty is that the isentropic turbine will have to handle steam of low quality. The impingement of liquid droplets on the turbine blade causes erosion and wear. Another difficulty is the isentropic compression of a liquid-vapor mixture. The two-phase mixture of the steam causes serious cavitation problems during the compression process. Also, since the specific volume of the saturated mixture is high, the pump power required is also very high. Thus, the Carnot vapor cycle is not a realistic model for vapor power cycles. 

We have studied the effect of cavitating ultrasound on the heterogeneous aqueous phase hydrogenation of a 5-2-buten-l-ol (C4 olefin) and a5-2-penten-l-ol (C5 olefin) on Pd-black (1.5+0.1 mg catalyst) to form the lra/ 5-olefins trans-2-buten-l-ol and fra/3s-2-penten-l-ol) and saturated alcohols (1-butanol and 1-pentanol, respectively). These chemistries are illustrated in Scheme 2. A full analysis of this study has been recently presented [10]. 

Part of the motivation behind so straightforward an approach derives from its ready application to certain simple systems, such as the solvation of alkanes in water. Figure 11.8 illustrates the remarkably good linear relationship between alkane solvation free energies and their exposed surface area. Insofar as the alkane data reflect cavitation, dispersion, and the hydrophobic effect, this seems to provide some support for the notion that these various terms, or at least their sum, can indeed be assumed to contribute in a manner proportional to solvent-accessible surface area (SASA). 

It is positively my experience that the most common reason for pumps cavitation is partial plugging of draw nozzles. This problem is illustrated in Fig. 25.5. This is the side draw-off from a fractionator. Slowly opening the pump s discharge control valve increases flow up to a point. Beyond this point, the pump s discharge pressure and discharge flow become erratically low. It is obvious, then, that the pump is cavitating. 

Well, dear reader, it no longer exists. Figure 25.6 illustrates the true situation. Let s say we are pumping 110 GPM from the pump discharge. But only 109 GPM can drain through the draw-off nozzle. We would then slowly lower the water level in the suction line. The water level would creep down, as would the pump s suction pressure. When the water level in the suction line dropped to 14 ft, the pump would cavitate or slip. The flow rate from the pump would drop, and the water level in the suction line to the pump would partially refill. The pump s... 

In order to illustrate the method, we can take the example of a pump as a component. It may fail to start or to stop when requested, provide too low a flow rate or too low a pressure, or present an external leak. The internal causes for pump failure may be mechanical blockage, mechanical damage, or vibrations. The external causes may be power failure, human error, cavitation, or too high a head loss. Then the effect on the operation of the system and external systems must be identified. It is also useful to describe the ways for detecting the failure. This allows establishing the corrective actions and the desired frequency of checks and maintenance operations. 

Figure 1.2 Schematic illustrating the difference between a cavitate and a clathrate (a) synthesis and conversion of a cavitand into a cavitate by inclusion of a guest into the cavity of the host molecule (b) inclusion of guest molecules in cavities formed between the host molecules in the lattice resulting in conversion of a clathrand into a clathrate (c) synthesis and self-assembly of a supramolecular aggregate that does not correspond to the classical host-guest description.

The first and second derivatives of R with respect to time are represented by R and R, respectively. Solving this equation for different values of R0 can be quite illustrative on the complex nonlinear dynamics of cavitation bubbles. Fig. 2 shows two different cases when a frequency of 20 kHz and an intensity equivalent to Py — 2.7 bar are used. In the first case (Fig. 2a), a relatively large (R0 = 2 mm) bubble couples with the sonic field through small-amplitude growth and compression cycles (stable cavitation). In contrast, a smaller bubble (P0 = 20 pm) experiences resonant coupling, which results... 

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