Efficiency measurement

To estimate the number of transfer units for design, the following empirical correlations which were derived from efficiency measurements employing a variety of trays and operating conditions under the aforementioned assumptions are recommended (111) ... 

Direct Scale-Up of Laboratory Distillation Ljficiency Measurements It has been found by Fair, Null, and Bolles [Ind. Eng. Chem. Process Des. Dev., 22, 53 (1983)] that efficiency measurements in 25- and 50-mm (1- and 2-in-) diameter laboratory Oldersbaw columns closely approach tbe point efficiencies [Eq. (14-129)] measured in large sieve-plate columns. A representative comparison of scales of operation is shown in Fig. 14-37. Note that in order to achieve agreement between efficiencies it is necessaiy to ensure that (1) tbe systems being distilled are tbe same, (2) comparison is made at tbe same relative approach to tbe flood point, (3) operation is at total reflux, and (4) a standard Oldersbaw device (a small perforated-plate column with downcomers) is used in tbe laboratoiy experimentation. Fair et al. made careful comparisons for several systems, utibzing as large-scale information tbe published efficiency studies of Fractionation Research, Inc. 

Criteria for Selection of Pressure and Temperature Sensors for Compressor Efficiency Measurements... 

However, any given column operated at a specific flow rate will exhibit a range of efficiencies depending on the nature and capacity ratio of the solute that is chosen for efficiency measurement. Consequently, under exceptional circumstances, the predicted conditions for the separation of the critical pair may not be suitable for another pair, and the complete resolution of all solutes may still not be obtained. 

Use energy-efficient measures such as waste heat recovery from process gases to reduce fuel usage and associated emissions. 

Example A ventilation system (Fig. 9.64) handling 20 mVs of air needs to heat the supply air from 10 °C to 20 C. Doubling the number of heat exchangers from one to two increases the heat-recovery efficiency from 50% to 75% and introduces an extra pressure drop of 300 Pa. As we can see from Table 9.19, this is probably a cost-efficient measure. 

Many different measures of local ventilation performance exist. These measures can be divided into three main categories capture velocities, capture efficiencies, and containment efficiencies. Table 10.1 shows the connections between hood types and different efficiency measurements. Section 10.5 describes procedures for measuring each of these performance measures. 

Capture efficiency measurements may be used to evaluate the function of a canopy hood (see Section 10.5). Capture velocity is not a feasible evaluation tool, since a canopy hood does not generate an air velocity close to the source. It is also possible to use exposure measurements for workers outside the plume area. Since most hot processes generate visible contaminants, visual inspection of the flow, especially around hood edges, might provide a qualitative evaluation. Many contaminants could however be invisible when diluted and smoke generators (Section 10.5) may be necessary to find leakages (temporary or permanent) around the hood edges. 

For exterior hoods, the measurement of capture velocity provides a quick check of the ideal design conditions. However, it must be remembered that capture velocity is not a direct measure of the ability of an exterior hood to provide personnel protection. Other efficiency measures are required in order to evaluate its performance in practice. The following two efficiency measurements could be useful capture efficiency and occupational hygiene efficiency. These measures complement each other. 

Measurement must address end-of-pipe performance (through measures such as injury rates and gallons spilled), process efficiency and indicators of performance (through measures such as in service failure of equipment). Using indicators should make it possible to identify problems before they result in poor performance. Process efficiency measurement helps track implementation of the project and continuous improvement in the use of resources. 

As mentioned earlier some measures will be chosen because improvements in these areas were part of the project justification. It is most likely that these will be efficiency measures. Calculation of these measures generally requires analysis of data or specific data collection exercises. There is a relatively high cost associated with preparing these measures so they should be used prudently. In choosing efficiency measures, you should use only those where you have comparative data about the current management systems. For example, if there is no information on the number of hours dedicated to PSM and ESH, don t use this to try to demonstrate the improvement in efficiency. 

For many of the efficiency measures, the relevant data is collected during audits or by analysis of records. It is likely that your company has an internal reporting cycle with which you should coordinate your meas-... 

The U.S. Department ofEnergy develops test procedures for efficiency measurements and sets minimum efficiency standards for furnaces, boilers, and water heaters. Information on energy efficiency of buildings and equipment is available from the DOE. 

Energy Efficiency Measure Typical Energy Savings (%) Payback Estimate (years)... 

Energy Efficiency Measures and Estimated Improvement Potentials for Steam Boilers. 

Much of the potential for improvement in technical energy efficiencies in industrial processes depends on how closely such processes have approached their thermodynamic limit. There are two types of energy efficiency measures (1) more efficient use in existing equipment through improved operation, maintenance or retrofit of equipment and (2) use of more efficient new equipment by introducing more efficient processes and systems at the point of capital turnover or expansion of production. More efficient practices and new technologies exist for all industrial sectors. Table 2 outlines some examples of energy efficiency improvement techniques and practices. 

Figure 9-63A. Flooding data for structured packings obtained by pressure drop measurements as well as by efficiency measurements (see Ref. 108 for sources). Reproduced by permission of the American Institute of Chemical Engineers, Fair, J. R. and Bravo, J. L., Chemical Engineering Progress, V. 66, No. 1 (1990) p. 19 all rights reserved.

By number count the great majority of particles in the outside air are likely to be less than 1 pm. By weight, these small particles will account for a very small proportion of the sample. A filter with a high efficiency measured by weight of particles trapped may be almost transparent to the small ones. Very high counts can be found in rural areas from pollen or agricultural activities. 

The information on inhibitor adsorption, derived from direct measurements and from inhibitive efficiency measurements, considered in conjunction with general knowledge of adsorption from solution indicates that inhibitor adsorption on metals is influenced by the following main factors. 

Absolute photoluminesccnce efficiency measurements in thin solid films are quite difficult, since light-trapping, waveguiding effects and, possibly, distributions in the emission dipole moments of individual chromophorcs modify the angular distribution of the emission. Dc Mello el al. ]126] have described an improved mclh-... 

Figure 13-10. Diagram illustrating the three configurations of the sphere required for the efficiency measurement, (a) The sphere is empty (b) the sample is in place and ihc laser beam is directed at the wall (c) the laser beam is directed on the sample. Reproduced with permission front [I26. ...

Furthermore, it was found that, although the catalytic efficiency measured in initial current was lower for 13, the latter was more stable. When carbon felt electrodes were coated with this polymer (approx. 1 x 10 mol on a 20x20x4 mm piece) the reduction of dibromostilbene was obtained on a mmol scale with only moderate da rease of mediator electroactivity The production of about 0.15 mmol of stilbene... 

Fig. 1 Scheme illustrating the influence of water discharge (y axis) and solute concentration (metals and nutrients on the x axis) on in-stream retention efficiency measured on the basis of the nutrient spiraling concept. The most remarkable Metal (M) effects on biofihns are indicated in the... 

Table 2 Fate and effects of metals in a stream receiving a point-source of metals (upper part of the table) or diffuse input via urban runoff (lower part of the table). Summary of the expected influence of four different hydrological situations base-flow in a rainy period a flood after a rainy period low-flow after a long period of low rainfall (water scarcity) and a flood produced after this drought. Metal concentration (M) metal retention efficiency (measured on the basis of the nutrient spiraling concept) exposure (dose and duration) bioaccumulation (in fluvial biofilms) and metal sensitivity (of biofihns)...

The use of plastics as an energy source was demonstrated on a commercial scale at ICl Materials plastics manufacturing site in Dumfries, UK. This paper covers the preparation and use of pre- and post-consumer plastics as supplementary fuels in a circulating fluidised bed boiler specially designed for co-combustion with coal. Full emissions data on the 15% mixtures of individual plastics with coal are given, together with calculations of thermal efficiencies. Measurements by an independent body (British Coal Research Establishment) confirmed that the co-combustion of coal and plastic reduces some emissions compared with coal alone. Thermal efficiencies of around 80% were achieved and this heat was used effectively during the production of plastics. 7 refs. 

Figure 1. Principle of 3-way exhaust emission control. Catalyst efficiencies measured in the laboratory with a steady feed stream composition at various simulated air/fuel ratios. Catalyst 0.042 wt % Pt/0.018 wt % Kh/alumina.

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