Energy equivalencies, conversion factors

Energy and work are interchangeable, and various terms and conversion factors are in common usage throughout the world today. These conversion factors are equivalencies unrelated to operational efficiencies because practical energy and work conversions are never 100% efficient. 

The effect of ionising radiation is described in Section 4.2. Most often, accelerated tests are carried out using gamma radiation from an isotope source or an electron beam from an accelerator. Radiation from nuclear reactors can also be used but will be a mixed radiation which may or may not be suitable for the simulation. The penetration of an electron beam is inherently limited which means that only relatively thin samples can be treated. Hence, gamma irradiation is the more versatile technique. With thin samples, such that penetration limits are not a problem, there are conversion factors to approximately equate the various radiations and energies to an equivalent gamma dose. 

Ellipsoid of inertia, 198-202,439-440 Emission of radiation spontaneous, 121-122 stimulated, 118, 120,122,135-139 Energy conversion factors, 468 Energy-localized orbitals, 69, 103-104 Equilibrium frequencies, 147, 262 Equivalent representations, 400 Ethane ... 

This set of equations connects Planck s photon energy Ep with Einstein s mass/en-ergy equivalence, with Boltzmann s kinetic energy, with the kinetic energy of a particle and with the kinetic energy of an electron in an electric field of a voltage U of 1 V. The most important conversion factors used in photochemistry and photophysics are collected in Tab. 3-2. 

Two SI units refer to doses of radioactivity and these are used when calculating exposure levels for a particular source. The sievert (Sv) is the amount of radioactivity giving a dose in man equivalent to 1 gray (Gy) of v-rays 1 Gy = an energy absorption of 1 Jkg. The dose received in most biological experiments is a negligible fraction of the maximum permitted exposure limit. Conversion factors from older units are given in Table 35.3. 

The heat transfer was originally measured in units of calories, where one calorie was defined as the quantity of energy required to raise one gram of pure water from 14.5 to 15.5 °C at one atmosphere. This definition has been supplanted by the introduction of the joule, which represents the energy specified by the conversion factor 1 cal = 4.184 joules. One joule is also equivalent to the energy developed in a circuit by an electric current of one ampere flowing through a resistance of one ohm (driven by a potential difference of one volt) in one second. 

The SI is used throughout this book, as explained in the Preface. The system is reviewed in this appendix. Definitions and sufficient conversion factors are presented to enable the reader to understand the system, and to convert SI units to other common energy units used in the United States. Additional information is presented on the equivalencies of a few common U.S. energy units. 

The SI unit of heat and energy is the joule (J). One joule is the equivalent of 0.2390 calories, or one calorie equals 4.184 joules. Table 16-1 shows the relationships among calories, nutritional Calories, joules, and kilojoules (kJ) and the conversion factors you can use to convert from one unit to another. 

Table 4.12 Estimated total reserves of fossil fuels (after World Energy Council 2002). Approximate conversion to tonnes of oil equivalent based on energy equivalence factors of 1.07 for natural gas liquids (condensate), 0.9 for heavy oils, 0.7 for hard coals, 0.47 for brown coals, 0.23 for peat and 0.861 per 103m3 for gas (1 tonne crude oil = c.7.3 barrels = c.l.lbm3)...

Conversion factor. A common conversion factor between exposure, absorbed dose, and dose equivalent is 1 R = 1 rad = 1 rem. This is an estimate that for radiation protection purposes is close enough (it actually over estimates the dose and therefore is a conservative estimate). The actual conversion is 1 R = 0.96 rem in tissue. Note that this method works only where the roentgen is defined - for photons of energy less that 3 MeV. When dealing with particulate radiation other methods must be used. 

In practice, the instruments are properly calibrated to read directly Sv (or rem), or Gy (or rad). For some neutron detection instruments, the neutron flux is recorded. Then the dose equivalent is obtained after multiplying the flux by the conversion factor given in Table 16.4. Since different detectors do not have the same efficiency or sensitivity for all types of radiation and for all energies, there is no single instrument that can be used for all particles (a, y, n) and all energies. 

Finally, the world literature on energy production and consumption is plagued by a proliferation of measurement units. Variously, data are presented in terms of the International System of Units (SI, e.g., metres, pascals, joules), traditional industry-based units e.g., barrels of oil, kilowatt hours of electricity, million tonnes of oil equivalent) and, especially in the USA, Imperial units e.g., miles, British thermal units of heat, quads of energy, cubic feet of natural gas, bars of pressure). For the expression of time, however, units of days and years are generally more appropriate than the SI unit (seconds) in this field. In order to assist readers in translating units into those with which they are familiar, a set of conversion factors has been included. 

Einstein theory for mass-energy equivalence n. The equivalence of a quantity of mass m and a quantity of energy E by the formula E = mc. The conversion factor is the square of the velocity of light. Serway RA, Faugh JS, Bennett CV (2005) College physics. Thomas, New York. 

Mechanical equivalent of heat n. A conversion factor that transforms work or kinetic energy into heat. Probably the best known one is 788ft-lb per British thermal unit others are 2545 Btu per horsepower-hour, 4.186 X lO ergs/cal, and3413Btu/kWh. In SI there is no need for such factors because work, heat, and electrical energy are all measured in joules (IJ = ImN = IWs). 

It is often necessary to convert the adopted value of a fundamental constant to another (SI or non-SI) unit. Useful conversion factors for energy equivalent quantities can be derived using the following relations ... 

This energy can be expressed as TNT equivalent mass by using the adequate energy conversion factor (approximately 1,120 cal per gram of TNT),... 

Though Sadi Carnot used the caloric theory of heat to reach his conclusions, his later scientific notes reveal his realization that the caloric theory was not supported by experiments. In fact, Camot understood the mechanical equivalence of heat and even estimated the conversion factor to be approximately 3.7 joules per calorie (the more accurate value being 4.18 J/cal) [1-3]. Unfortunately, Sadi Carnot s brother, Hippolyte Camot, who was in possession of Sadi s scientific notes from the time of his death in 1832, did not make them known to the scientific community until 1878 [3]. That was the year in which Joule published his last paper. By then the equivalence between heat and work and the law of conservation of energy were well known through the work of Joule, Helmholtz, Mayer and others. (It was also in 1878 that Gibbs published his famous work On the Equilibrium of Heterogeneous Substances). 

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