Efficiency, factor

The efficiency factor, N (Fig. 4.4), measures peak sharpness. The sharper the peak, the better the separation, and the higher the efficiency of the column and the system. 

It is important, first, to realize that efficiency is not a function solely of the column. Bad extracolumn parameters, such as detector cell volume or tubing diameters, can make the best column in the world look terrible. Second, efficiency measurements are very poor ways of comparing or purchasing columns unless all other parameters are constant. Many columns are bought and sold because they have a higher plate count than someone else s column. The efficiency calculations could have been made with different equations, on different compounds, on different machines, at different flow rates, all of which will have a profound effect on efficiency. The only valid use of plate counts that I have found is in column comparisons where all other variables are equal, or in following column aging over a period of days or months. 

Let us look at an efficiency measurement. Efficiency, N, is usually reported in plates, a dimensionless term that is a throwback to the days of open column, flooded plate distillations. The more plates in the distillation column, the more equilibrations have occurred, and the better the separation that was produced. In an HPLC column, the larger the plate count, the sharper the peaks are, and the smaller the amount of overlap that occurs between them. 

For accurate measurement, it is important to spread the peak without changing variables affecting N. Increasing the chart speed to 2-5 times normal run speed will usually do this, but remember to correct VB for the increase. Early eluting peaks with a of 1-3 should show a plate count between 6,000 and 10,000 for a lO-jUm packing in a typical 25cm x 4mm column. 

Column length is usually optimized around a tradeoff between efficiency and run time. Doubling the column length increases back-pressure and run 

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TR measurements for correspondingly increased rejection of Rayleigh scattering. The addition of each grating typically introduces a throughput efficiency factor of roughly 30%, however, so that the overall efficiency of a... 

Three separate factors affect resolution (1) a column selectivity factor that varies with a, (2) a capacity factor that varies with k (taken usually as fej). and (3) an efficiency factor that depends on the theoretical plate number. 

Like e, t is the product of two contributions the concentration N/V of the centers responsible for the effect and the contribution per particle to the attenuation. It may help us to become oriented with the latter to think of the scattering centers as opaque spheres of radius R. These project opaque cross sections of area ttR in the light path. The actual cross section is then multiplied by the scattering efficiency factor optical cross... 

There are three generally recognized classifications for sulfur vulcanization conventional, efficient (EV) cures, and semiefficient (semi-EV) cures. These differ primarily ki the type of sulfur cross-links that form, which ki turn significantly influences the vulcanizate properties (Eig. 8) (21). The term efficient refers to the number of sulfur atoms per cross-link an efficiency factor (E) has been proposed (20). 

A Back-Pressure Efficiency Factor. Because a gaseous diffusion stage operates with a low-side pressure p which is not negligible with respect to there is also some tendency for the lighter component to effuse preferentiahy back through the barrier. To a first approximation the back-pressure efficiency factor is equal to (1 — r), where ris the pressure ratiopjpj. 

These efficiency factors are discussed in more detail in References 26—28. Actually, the barrier and back-pressure efficiencies are interrelated and caimot be formulated independently, except only as an approximation. A better formation that has been found to fit the experimental results is ... 

The efficiency factor of 0.8 is already included in the equation. Substitution of the remaining values gives... 

Data for determining the size of natural-draft towers have been presented by Chilton [Proc. Inst. Elec. Eng., 99,440 (1952)] and Rish and Steel (ASCE Swuposium on Thermal Power Plants, October 19.58). Chilton showed that the duty coefficient Df of a tower is approximately constant over its normal range of operation and is related to tower size by an efficiency factor or performance coefficient as follows ... 

Apphcation of a constant efficiency to each stage as in Fig. 13-40 will not give, in general, the same answer as obtained when the number of equilibrium stages (obtained by using the true-equilibrium cui ve) is divided by the same efficiency factor. 

When chemical equilibrium is achieved qiiickly throughout the liquid phase (or can be assumed to exist), the problem becomes one of properly defining the physical and chemical equilibria for the system. It sometimes is possible to design a plate-type absorber by assuming chemical-equilibrium relationships in conjunction with a stage efficiency factor as is done in distillation calculations. Rivas and Prausnitz [Am. Tn.st. Chem. Eng. J., 25, 975 (1979)] have presented an excellent discussion and example of the correct procedures to be followed for systems involving chemical equihbria. 

Detention efficiency. Conversion from the ideal basin sized by detention-time procedures to an actual clarifier requires the inclusion of an efficiency factor to account for the effects of turbulence and nonuniform flow. Efficiencies vaiy greatly, being dependent not only on the relative dimensions of the clarifier and the means of feeding but also on the characteristics of the particles. The cui ve shown in Fig. 18-83 can be used to scale up laboratoiy data in sizing circular clarifiers. The static detention time determined from a test to produce a specific effluent sohds concentration is divided by the efficiency (expressed as a fraction) to determine the nominal detention time, which represents the volume of the clarifier above the settled pulp interface divided by the overflow rate. Different diameter-depth combinations are considered by using the corresponding efficiency factor. In most cases, area may be determined by factors other than the bulksettling rate, such as practical tank-depth limitations. 

Experience in using the Z concept has demonstrated that the calculated Z factor should be modified by an efficiency factor to account for some of the aforementioned effects which are absent in the theoiy and, as such, this factor depends on the type of centrifuge. It is nearly 100 percent for simple spin-tube bottle centrifuge, 80 percent for tubular centrifuge, and less than 55 percent for di centrifuges. The... 

L = line length, miles Z = average gas compressibility D = pipe inside diameter, in. h2 = elevation at terminus of line, ft h = elevation at origin of line, ft Pa, = average line pressure, psia E = efficiency factor... 

E = efficiency factor. (See Panhandle nomenclature for suggested efficiency factors)... 

The literature is inconsistent on definitions. TNT equivalency is also called equivalency factor, yield factor, efficiency, or efficiency factor. 

Estimating the total release of flammable material within a reasonable amount of time (generally 2 to 5 minutes) and multiplying this by the heat of combustion of the material times an efficiency factor (generally in the range of 1% to 5% for ordinary hydrocarbons). 

Conventional TNT-equivalency methods state a proportional relationship between the total quantity of flammable material released or present in the cloud (whether or not mixed within flammability limits) and an equivalent weight of TNT expressing the cloud s explosive power. The value of the proportionality factor—called TNT equivalency, yield factor, or efficiency factor—is directly deduced from damage patterns observed in a large number of major vapor cloud explosion incidents. Over the years, many authorities and companies have developed their own practices for estimating the quantity of flammable material in a cloud, as well as for prescribing values for equivalency, or yield factor. Hence, a survey of the literature reveals a variety of methods. 

E = efficiency factor for flow, use 1.00 for new pipe without bends, elbows, valves and change of pipe diameter or elevation 0.95 for very good operating conditions 0.92 for average operating conditions 0.85 for poor operating conditions... 

E = efficiency factor, which is really an adjustment to fit the data f = fanning friction factor qns = flow rate, SCF/day... 

Gas transmission efficiency factor, vaiies with line size and surface internal condition of pipe... 

Gas transmission factor, or sometimes termed efficiency factor, see Table 2-15, f = Fanning friction factor... 

This tube has a ratio of outside to inside surface of about 3.5 and is useful in exchangers when the outside coefficient is poorer than the inside tube coefficient. The fm efficiency factor, which is determined by fm shape and size, is important to final exchanger sizing. Likewise, the effect of the inside tube fouling factor is important to evaluate carefully. Economically, the outside coefficient should be about V5 or less than the inside coefficient to make the finned unit look attractive however, this break-even point varies with the market and designed-in features of the exchanger. 

Fl = frame loss for motor-driven compressors only, values range 1.0-1.05 (note, this is not a driver efficiency factor). 

Standard Derricks 501. Load Capacities 506. Design Loadings 508. Design Specifications 511. Maintenance and Use of Drilling and Well Servicing Structures 515. Derrick Efficiency Factor 521. 

Derrick efficiency factor (DEF) is often used to rate or classify derrick or mast structural capacity [1,7,8]. The derrick efficiency factor is defined as a ratio of actual load to an equivalent load that is four times the force in the derrick leg carrying the greatest load. Thus the ratio is... 

The derrick efficiency factor can be found for static (dead load) conditions and dynamic conditions. In this section, only the static conditions will be considered. 

When the hook load is lifted, friction losses in crown block and traveling block sheaves occur. It is normally assumed that these losses are approximately 2% deduction per working line. Under dynamic conditions, there will be an efficiency factor for the block and tackle system to reflect these losses. The efficiency will be denoted as the hook-to-drawwork efficiency (e, ). The force in the fast line under dynamic conditions (i.e., hook is moving) will be... 

The volumetric efficiency factor is about 0.95 for precharged pumps. 

Pump Limitations. Table 4-116 shows there are six possible liner sizes that can be used on the Model E-700 mud pump. Each liner size must be considered to obtain the optimum circulation flowrate and appropriate liner size. The maximum pressure available for each liner size will be reduced by a safety factor of 0.90. The maximum volumetric flowrate available for each liner size will also be reduced by a volumetric efficiency factor of 0.80 and an additional safety factor of 0.90. Thus, from Table 4-116, the allowable maximum pressures and allowable maximum volumetric flowrates will be those shown in Figures 4-207 through 4-212, which are the liner sizes 5j-, 6, 6-[, 6- and 7 in., respectively. Plotted on each of these figures are the total pressure losses for the various circulation flowrates considered. The horizontal straight line on each figure is... 

As with the Langmuir adsorption isotherm, which in shape closely resembles Michaelis-Menten type biochemical kinetics, the two notable features of such reactions are the location parameter of the curve along the concentration axis (the value of Km or the magnitude of the coupling efficiency factor) and the maximal rate of the reaction (Vmax). In generic terms, Michaelis-Menten reactions can be written in the form... 

In several cases, a steady rate of filtration in never achieved. In such cases it is possible to describe the time dependence of filtration by introducing an efficiency factor fi representing the fraction of filtered particles remaining in the filter cake rather than being swept along by the bulk flow. Equation 16.7.4 then becomes... 

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