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efficiency.

1 In business and industry, see industrial managementindustrial management,
term applied to highly organized modern methods of carrying on industrial, especially manufacturing, operations. The Rise of Factories
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; productivityproductivity,
in economics, the output of any aspect of production per unit of input. It is a measure of the output of a worker, machine, or an entire national economy in the creation of goods and services to produce wealth.
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. 2 In physics, seemachinemachine,
arrangement of moving and stationary mechanical parts used to perform some useful work or to provide transportation. From a historical perspective, many of the first machines were the result of human efforts to improve war-making capabilities; the term engineer
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; workwork,
in physics and mechanics, transfer of energy by a force acting to displace a body. Work is equal to the product of the force and the distance through which it produces movement.
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.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Efficiency

 

a parameter characterizing the effectiveness of a system, device, or machine in converting or transmitting energy; it is defined as the ratio of the usefully consumed energy to the total energy received by a system. It is usually denoted as η = Wuse/ Wtot- In electric motors the efficiency is the ratio of the mechanical work (useful work) performed to the electric power received from a source; in heat engines it is the ratio of the useful mechanical work to the amount of heat expended; in electric transformers it is the ratio of the electromagnetic energy produced in the secondary winding to the energy consumed by the primary winding.

In calculating efficiency, various forms of energy and mechanical work are expressed in the same units based on the mechanical equivalent of heat and other similar relationships. Because of its generality the concept of efficiency makes possible the comparison and evaluation of such dissimilar systems as atomic reactors, electric generators and motors, steam power plants, semiconductor devices, and biological substances from a single point of view.

Because of the unavoidable energy losses caused by friction, heating of surrounding bodies, and so on, the efficiency is always less than 1. Therefore, it is expressed in fractions of the energy consumed—that is, in the form of a proper fraction or percentages—and is a dimensionless quantity. The efficiency of steam power plants reaches 35-40 percent; that of internal-combustion engines, 40-50 percent; that of high-power dynamos and generators, up to 95 percent; and that of transformers, up to 98 percent. The efficiency of the process of photosynthesis is usually 6-8 percent; and for chlorella it attains 20-25 percent. By virtue of the second law of thermodynamics the upper limit of the efficiency of heat engines is determined by the characteristics of the thermodynamic cycle (a cyclic process) performed by the working substance. The Carnot cycle has the highest efficiency.

A distinction is made between the efficiency of one stage of a machine or installation and the efficiency that characterizes the entire energy conversion chain in a system. Efficiency of the first type may be mechanical, thermal, and so on, depending on the nature of the energy conversion. The second type includes the total, economic, and technical forms of efficiency. The total efficiency of a system is equal to the product of the partial or stage efficiencies.

In the technical literature efficiency is sometimes defined in such a manner that it can be greater than 1. Such a situation occurs if, in the determination of efficiency by means of the ratio Wuse/Wcon, the term Wuse is the useful energy obtained at the “output” of a system and Wcon is not all the energy put into the system but rather only the part that brings about the actual consumption. For example, during the operation of semiconductor thermoelectric heaters (heat pumps) the consumption of electric power is less than the amount of heat produced by the thermoelement. The excess energy is drawn from the environment. In this case, although the true efficiency is less than 1, the efficiency in question ö = Wuse/Wcon can be greater than 1.

REFERENCES

Artobolevskii, I. I. Teoriia mekhanizmov i mashin, 2nd ed. Moscow-Leningrad, 1952.
Obshchaia teplotekhnika, 2nd ed. Edited by S. la. Kornitskii and la. M. Rubinshtein. Moscow-Leningrad, 1952.
Obshchaia elektrotekhnika. Moscow-Leningrad, 1951.
Vukalovich, M. P., and I. I. Novikov. Tekhnicheskaia termodinamika, 4th ed. Moscow, 1968.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

efficiency

[ə′fish·ən·sē]
Abbreviated eff.
(chemistry)
In an ion-exchange system, a measurement of the effectiveness of a system expressed as the amount of regenerant required to remove a given unit of adsorbed material.
(engineering)
Measure of the degree of heat output per unit of fuel when all available oxidizable materials in the fuel have been burned.
Ratio of useful energy provided by a dynamic system to the energy supplied to it during a specific period of operation.
(nucleonics)
The probability that a count will be produced in a counter tube by a specified particle or quantum incident.
(physics)
The ratio, usually expressed as a percentage, of the useful power output to the power input of a device.
(statistics)
An estimator is more efficient than another if it has a smaller variance.
An experimental design is more efficient than another if the same level of precision can be obtained in less time or with less cost.
(thermodynamics)
The ratio of the work done by a heat engine to the heat energy absorbed by it. Also known as thermal efficiency.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

Efficiency

The ratio, expressed as a percentage, of the output to the input of power (energy or work per unit time). As is common in engineering, this concept is defined precisely and made measurable. Thus, a gear transmission is 97% efficient when the useful energy output is 97% of the input, the other 3% being lost as heat due to friction. A boiler is 75% efficient when its product (steam) contains 75% of the heat theoretically contained in the fuel consumed. All automobile engines have low efficiency (below 30%) because of the total energy content of fuel converted to heat; only a portion provides motive power, while a substantial amount is lost in radiator and car exhaust.

McGraw-Hill Concise Encyclopedia of Engineering. © 2002 by The McGraw-Hill Companies, Inc.

efficiency

The ratio of output to input or the ratio of work done to the effort put in. Unless specifically stated otherwise, it means efficiency with respect to power. The efficiency of any device refers to a physical quantity that may be stored, transferred, or transformed by the device.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved
References in periodicals archive ?
However, farm size was found to be significantly negative to technical, allocative and cost efficiencies from the OLS regression, indicating that small farms were more efficient than larger ones.
These efficiencies can be further explained by comparing efficiency with unit cost.
The market size does not have any impact on the efficiencies and the average wage has a negative sign which implies the positive impact on the efficiency scores and it shows that labor is fully able to perform in the favor of technical efficiency due to the well knowledge, more competent and skilled staff.
(31) Referred to as the "total welfare" (32) standard or "aggregate economic welfare" (33) standard (and sometimes called the "efficiency" or "total surplus" standard, (34) following this approach weight is given solely to allocative efficiency and thus whether efficiencies benefit consumers or benefit producers is considered irrelevant.
In this study, five types of efficiencies including cost, scale, allocative, income and technical efficiencies were estimated under constant returns to scale (CRS) and variable returns to scale (VRS) by applying DEA.
In the assessment of productive efficiencies, cost and allocative efficiencies have also gained prominence.
One could also interpret the formulation of the problem for calculating the lower and upper bound efficiencies using the leader-follower concept in game theory.
Consequently thermal and mechanical efficiencies could become tools for the management of machines within industry, resulting in an efficient control of work.
The WIMES specification lays down minimum full load efficiencies for 2 & 4 pole electric motors in the ranges 110-400kw and 6 & 8 pole motors in the range 5.5-315kw as well as minimum requirements for power factors and 3/4 load efficiency values.
Both The Solaire and The Verdesian utilize natural materials and sophisticated technologies to optimize resident comfort, maximize operational efficiencies and enhance indoor air quality, while conserving natural resources.
Previous efforts involved using federal grant money to hire four students to brainstorm energy efficiencies. One semester, the crew calculated Tulane's greenhouse emissions, as well as did a hilarious study of energy use in one four-bedroom student apartment.