Efficiency calculations

In this paragraph, the efficiency calculations to evaluate both the fuel cell system alone and the overall propulsion system are reported starting from the parameters 

Finally, the total efficiency of the power train (t/py) on the driving cycle is defined by the following equation  

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C. Niedermeier and P. Tavan. Fast version of the structure adapted multipole method — efficient calculation of electrostatic forces in protein dynamics. Mol. Sim., 17 57-66, 1996. 

C. G. Lambert and T. A. Darden, and J. A. Board, Jr., A Multipole-Based Algorithm for Efficient Calculation of Forces and Potentials in Macroscopic Periodic Assemblies of Particles, J. Comp. Phys. 126 (1996), pp. 274-285. 

There are several variations of this method. The PRDDO/M method is parameterized to reproduce electrostatic potentials. The PRDDO/M/FCP method uses frozen core potentials. PRDDO/M/NQ uses an approximation called not quite orthogonal orbitals in order to give efficient calculations on very large molecules. The results of these methods are fairly good overall, although bond lengths involving alkali metals tend to be somewhat in error. 

The size of the move in step 3 of the above procedure will affect the elhciency of the simulation. In this case, an inefficient calculation is one that requires more iterations to obtain a given accuracy result. If the size is too small, it will take many iterations for the atom locations to change. If the move size is too large, few moves will be accepted. The efficiency is related to the acceptance ratio. This is the number of times the move was accepted (step 5 above) divided by the total number of iterations. The most efficient calculation is generally obtained with an acceptance ratio between 0.5 and 0.7. 

Q-Chem (we tested Version 1.2) is an ah intio program designed for efficient calculations on large molecules. Q-Chem uses ASCII input and output files. 

Overall Column Efficiency Calculated values of E, , must be corrected for entrainment, if any, by the Colburn equation [Eq. (14-101)]. The resiJting corrected efficiency is then converted to column efficiency by the relationship of Lewis [Ind. Eng. Chem., 28, 399 (1936)] ... 

Cyclone Efficiency The methods described below for pressure drop and efficiency calculations were given by Zenz in Manual on Dis-po.sal of Refinery Wa.ste.s—Atmo.spheric Emls.sion.s, chap. 11 (1975), American Petrofeum Institute Publ. 931 and improved by the Particulate Sohd Research Inc. (PSRl), Chicago. 

Expander performance will shift as plant conditions—such as gas flowrate, gas inlet, and discharge pressure—gas composition, and inlet temperature change. Calculation of expander diermal efficiency from field data is not accurate because expander discharge flow normally consists of two phases, gas and liquid. Efficiency calculations should always be cross-checked with the shaft power produced before any decision on expander performance is made. 

Fig. 28-4. Typical pollution control device as shown for efficiency calculations.

K,i = coefficient of heat removal efficiency, calculated from the air... 

Productivity is a measure of productive efficiency calculated as the ratio of what is produced to what is required to produce it. Productivity can therefore be considered as a characteristic of a process, and therefore a measure of the quality of a process. Consider two process each producing the same product but one delivers the result using less resources and hence as a consequence has a higher productivity. The process with the higher productivity could thus be regarded as being of better quality. However, measuring resource consumption alone would not be a valid means of comparison as inputs could be vastly different. Hence productivity is a quality characteristic. 

Efficient calculations with a method ought to be practical with existing computer technology. 

Example 8-42 Mass Transfer Efficiency Calculation for Baffle Tray Column (used by permission [211])... 

Bit efficiency calculated in real time gives an indication that the drill bit is damaged and that cones may be lost. Downhole vibration and shock measurements are also valuable indicators used to avoid damaging the drillstring. 

Initiator efficiencies calculated for [f-BuX] = 2.4 x 10-4 M at -60 °C (Table 8) decreased as f-BuCl/Etj AlBr/MeCl > f-BuBr/Et2 AlBr/MeCl >... 

On the basis of initiator efficiencies calculated from yields obtained at —60 °C, an overall initiator efficiency order has been developed for f-BuX/Et2 AlX/MeX systems. 

Table 1 shows energy efficiency calculations based on lower heating value (LHV). Energy efficiency ( ) based on LHV is d ned as Eqn. 1. 

Maas, U., Efficient calculation of intrinsic low-dimensional manifolds for the simplification of chemical kinetics, Comput. Visualization Sci. 1 (1998) 69-82. 

Equation 11.66 is not of much practical use in distillation, as the slopes of the operating and equilibrium lines will vary throughout the column. It can be used by dividing the column into sections and calculating the slopes over each section. For most practical purposes, providing the plate efficiency does not vary too much, a simple average of the plate efficiency calculated at the column top, bottom and feed points will be sufficiently accurate. 

Halmann reported in 1978 the first example of the reduction of carbon dioxide at a p-GaP electrode in an aqueous solution (0.05 M phosphate buffer, pH 6.8).95 At -1.0 V versus SCE, the initial photocurrent under C02 was 6 mA/ cm2, decreasing to 1 mA/cm2 after 24 h, while the dark current was 0.1 mA/cm2. In contrast to the electrochemical reduction of C02 on metal electrodes, formic acid, which is a main product at metal electrodes, was further reduced to formaldehyde and methanol at an illuminated p-GaP. Analysis of the solution after photoassisted electrolysis for 18 and 90 h showed that the products were 1.2 x 10-2 and 5 x 10 2 M formic acid, 3.2 x 10 4 and 2.8 x 10-4 M formaldehyde, and 1.1 x 10-4 and 8.1xlO 4M methanol, respectively. The maximum optical conversion efficiency calculated from Eq. (23) for production of formaldehyde and methanol (assuming 100% current efficiency) was 5.6 and 3.6%, respectively, where the bias voltage against a carbon anode was -0.8 to -0.9 V and 365-nm monochromatic light was used. In a later publication,4 these values were given as ca. 1% or less, where actual current efficiencies were taken into account [Eq. (24)]. 

An advantage of this technique is that it allows for getting as many sample points as needed at each location along the interval of interest. In particular, it is possible to obtain very good statistics even in transition regions which are rarely visited otherwise. This leads in general to an efficient calculation and small statistical errors. Nevertheless, despite its many successes, this method has some difficulties. First, the system needs to be prepared such that has the desired value (at which dA/d needs to be computed) and an equilibration run needs to be performed at this value of . Second, it is not always obvious to determine how many quadrature points are needed to calculate the integral (deff j<9 ) d . 

The objective of the method presented here is to develop a momentum distribution that will bias path dynamics along the slow manifold, permitting the efficient calculation of kinetic properties of infrequent reactions. 

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