Functional Performance Characteristics

There are many more static mixing devices used in the polymer processing industry in fact, the number is so large that it is not possible to list them all. Two characteristics are of critical importance in application of any static mixing device in actual extrusion operations. The first one, obviously, is the mixing capacity. The second one is the resistance that the static mixer offers to flow, i. e., the pressure drop along the static mixer. 

The mixing capacity is clearly related to the number of striations and the striation thickness. Several expressions have been proposed for various static mixers that relate the number of striations to the number of mixing elements, e.g., see [260, 263]. The mixing in static mixers can generally be described as ordered plug convective mixing. The striation thickness decreases from one mixing element to the next. The reduction in striation thickness can be expressed by  

In experimental studies, however, the striation concept is not often used. This has to do with the difficulty in accurately determining the number of striations beyond the level of coarse mixing. Another measure of mixing is the coefficient of variation (COV), discussed earlier. The COV has been used in several experimental studies to compare the goodness of mixing in various static mixers. 

The other important performance characteristic is the pressure drop. A comparison of various static mixers was reported by Allocca [218] this is shown in Table 7.3. The experimental set-up that was used to quantify the mixing capability of the various static mixers is shown in Fig. 7.146. 

The comparison is based on the length required to obtain a COV of 0.05 or less. From this table it becomes clear that good mixing performance is not directly linked to pressure drop. Some relatively inefficient static mixers have low pressure drop, while others have a high pressure drop. 

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CH2—CI2—) —(—CF2— CFH—) (39). Ceramic crystals have a higher piezoelectric efficiency. Their high acoustic impedance compared to body tissues necessitates impedance matching layers between the piezoelectric and the tissue. These layers are similar in function to the antireflective coatings on a lens. Polymer piezoelectric materials possess a more favorable impedance relative to body tissues but have poorer performance characteristics. Newer transducer materials are piezoelectric composites containing ceramic crystals embedded in a polymer matrix (see Composite materials, polymer-MATRIX Piezoelectrics). 

Recreational surfaces must provide certain performance characteristics with acceptable costs, lifetimes, and appearance. Arbitrary but useful distinctions may be made for classification purposes, depending on the principal function a covering intended primarily to provide an attractive surface for private leisure activities, eg, patio surfaces a surface designed for service in a specific sport, eg, track surfaces or a grass-like surface designed for a broad range of heavy-duty recreational activities, including professional athletics, eg, artificial turf for outdoor sports. 

Stress—Strain Curve. Other than the necessity for adequate tensile strength to allow processibiUty and adequate finished fabric strength, the performance characteristics of many textile items are governed by properties of fibers measured at relatively low strains (up to 5% extension) and by the change ia these properties as a function of varyiag environmental conditions (48). Thus, the whole stress—strain behavior of fibers from 2ero to ultimate extension should be studied, and various parameters should be selected to identify characteristics that can be related to performance. 

The most effective and widely used dispersants are low molecular weight anionic polymers. Dispersion technology has advanced to the point at which polymers are designed for specific classes of foulants or for a broad spectmm of materials. Acrylate-based polymers are widely used as dispersants. They have advanced from simple homopolymers of acryflc acid to more advanced copolymers and terpolymers. The performance characteristics of the acrylate polymers are a function of their molecular weight and stmcture, along with the types of monomeric units incorporated into the polymer backbone. 

Quality systems need to possess certain characteristics for them to be fit for their purpose. ISQ/TS 16949 specifies functional requirements for quality systems rather than performance requirements. It specifies what a quality system must do but not how well it must do it. The performance required will however depend on the environment in which the system will be used. Some of these performance characteristics will be as follows ... 

A method for the estimation of composite material performance from the characteristics of fillers and the matrices and from the configuration of filler is generally called the law of mixture. In the most basic form of the law of mixture, the characteristics of a composite material are represented as a function of characteristics of constituent components and their volume fractions, as shown in Fig. 3. For a composite material (characteris-ticsiA f) that consists of component A (characteristics Xa, volume fraction ) and component B (characteristics Xf, volume fraction b), the basic formulae of the law of mixture are as follows ... 

Range 1 of the mud pump performance characteristic is defined by the performance of the smallest liner, and range 2 is defined by the remaining liners. The pressure loss in a circulating system, except for bit (p ), can be estimated from numerous theoretical formulas or from a flowrate test. Data obtained from a flowrate test can be approximated using a curve-fitting technique by the following function ... 

In the design of commercial units, nomographs 18,19 are available which give a performance characteristic (KaV/L ), where AT is a mass transfer coefficient (kg water/m2s) and V is the active cooling volume (m3/m2 plan area), as a function of 9, 9W and (V G ). For a given duty (KaV/L ) is calculated from ... 

In eveiyday life we make extensive use of macroscopic devices. A macroscopic device is an assembly of components designed to achieve a specific function. Each component of the device performs a simple act, while the entire device performs a more complex function, characteristic of the assembly. For example, the function performed by a hairdryer (production of hot wind) is the result of acts performed by a switch, a heater, and a fan, suitably connected by electric wires and assembled in an appropriate framework... 

Table 1.1 compares key aspects and performance characteristics of selected passive samplers, including the triolein-containing SPMD. Of the eight devices examined, only a few appear to have overlapping functions. Clearly, no one device can provide the desired data for all exposure scenarios. 

The performance of SOFCs with Cu—ceria—YSZ anodes has been tested with a wide variety of hydrocarbon fuels, and this has been documented elsewhere.With the exception of methane, which is known to be relatively unreactive in normal heterogeneous reactions as well, all of the hydrocarbons we examined appear to give similar performance characteristics. The fuels that were tested include /2-butane, /2-decane, toluene, and a synthetic diesel. The main difference observed between the various fuels is that some fuels tend to form tars more readily via gas-phase free-radical chemistry. Otherwise, with the exception of CH4, all hydrocarbons that were investigated showed similar power densities. This is shown in Figure 20, which displays the voltage and current densities for /2-decane, toluene, and synthetic diesel as a function of time. In this case, the hydrocarbon fuels were diluted in dry N2 to a concentration of 40 wt % hydrocarbon to prevent condensation of unreacted fuels that leave the cell. (In our studies, the active area for the fuel cell is typically 0.5 cm, and a current density of 1 A/cm would require a flow... 

ISO 8466-1 1990 - Calibration and evaluation of analytical methods and estimation of performance characteristics - Part 1 Statistical evaluation of the linear calibration function... 

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