Energy expended

Location of the system boundaries also is important in the net energy analysis of integrated biomass energy systems. Thus tractors may be used to plant and harvest biomass. The fuel requirements of the tractors are certainly part of E, but is the energy expended in manufacturing the tractors also part of E Some analysts beheve that a complete study should trace all materials of constmction and fossil fuels used back to their original locations in the ground. 

Many attempts have been made to develop models which predict the behavior of materials undergoing size reduction. One proposal is that the energy expended in size reduction is proportional to the new surface formed (5). Another theory is that the energy required to produce a given reduction ratio (feed size product size) is constant, regardless of initial feed particle size (6). Practical results show, however, that both these theories are limited in their usehilness. 

The energy expended in deforming a material per unit volume is given by the area under the stress-strain curve. For example,... 

The energy required to produce a tire is only about 10 percent of that consumed while in use on an automobile overcoming rolling resistance during 40,000 miles of seiwice. The majority of the manufacturing energy expended, 60 to 70 percent, is for the mold during the vulcanization process. 

The effect of the heat losses to the inlet on the thermal states of the micro-channel depends mainly on the meniscus position, which is determined by the flow parameters. To characterize this effect, the coefficient of efficiency is introduced it may be defined as the ratio of the energy expended to the liquid vaporization and the total energy supplied to the micro-channel. 

Energy expended by living cells for maintenance is expressed quantitatively in appropriate units, for example kJ Kg s, and in animals it is largely provided as ATP. In this chapter, we outline how this is achieved, although our thermodynamic treatment lacks formal rigor. Further information on classical thermodynamics is given in textbooks of physical chemistry. 

Fig. 8. Sustained damage in Daucus carota suspensions, as a function of total energy expended, under laminar flow conditions in a Couette viscometer. Redrawn from Dunlop et al. (1994) Effect of fluid shear forces on plant cell suspensions. Chem Eng Sci 49 2263 - 2276, with permission of Elsevier Science...

Fig. 9. Sustained damage in Morinda citrifolia [54,59] and Damns carota [57] suspensions, as a function of total energy expended under turbulent flow conditions in capillary [54], jet [59] and viscometric devices [57]...

The assumption is normally made that the feed value of grass to the outdoor pig is equalised by the extra energy expended in walking... 

Reabsorption of Na+ ions is an active process 80% of the total energy expended by the kidneys is used for sodium transport out of the tubular epithelial cell. 

It is worth to report preliminarily the conclusions of a research conducted in Canada by Clements et al. (1995), who found no significant relationship between the yields for a com-soybean-winter wheat rotation and the energy expended for the frequency and depth of cultivations, which implies that with intensive cultivations there is ample room for energy saving and input reduction. 

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