Total energy content

Where gas or oil appliances are used for heating and installed within the heated space, between 70 per cent and 90 per cent of the total energy content of the fuel input will be converted into useful heat. Table 27.15 gives particulars of some gas-fired equipment types and Table 27.16 gives similar details for some oil-fired heaters. The first three types of equipment detailed in Table 27.15 and the first two in Table 27.16 are usually used for local warming of individuals rather than to provide a particular temperature throughout the space. 

An elementary solid, such as silver, is regarded as composed of atoms oscillating about fixed centres. The total energy content is therefore partly kinetic and partly potential. Since the solid has a finite compressibility, the atoms may be supposed to be maintained at small distances apart by forces they exert upon one another, and these may be resolved into two sets, one of which opposes a closer approximation of the atoms, and the other tends to draw the latter together. Both are functions of the distance between the atoms, and for a given distance are equal, since the form of the body is altered by external forces alone. 

The potential energy is equal to this, and the total energy content is therefore, per mol... 

The factor Dg can either be determined from the dissociation energy and the ground state vibration energy or from thermodynamic data. The heat of formation of H atoms from H2 molecules can be found in the literature, but some care should be exercised in considering the total energy content of H atoms and H2 molecules under standard conditions. 

Put simply, this means that the total energy contained within the fluid system must always be constant. Therefore, as the kinetic energy (velocity) of the fluid increases, the potential energy (pressure) must reduce by an equal amount in order to ensure that the total energy content remains the... 

The total energy content (E) of an aqueous polysaccharide dispersion is stated in the general equation... 

Cf. V 23, Section 6. In the case of sinusoidal oscillations the time average of the potential energy is equal to that of the kinetic energy. The theorem of equipartition of kinetic energy therefore determines also the total energy content for harmonic oscillators. 

Many devices such as turbines, compressors, boilers, condensers, and heat exchangers operate for long periods of time under the same conditions, and they are classified as steady flow devices. (Note that the flow field near the rotating blades of a turbomachine is of course unsteady, but we consider the overall flow field rather tlian the details at some localities when we classify device.s.) During steady flow, the fluid properties can change from point to point within a device, but at any fixed point they remain constant. Therefore, the volume, the mass, and the total energy content of a steady-flow device or flow section remain constant in steady operation. 

A typical American diet contains about 40% of its total energy content as fat. About half this energy is in the form of saturated fatty acids, one-fourth as monounsatu-rated fatty adds, and one-fourth as polyunsaturated fatty adds (PUFAs) (Ginsberg et dl., 1990). The quantity and nature of dietary fats carx influence the lex. d of plasma cholesterol. A reduction in total fat from the typical 40% of energy intake to 30% can result in a decrease in plasma cholesterol. 

Photolnltlator" Is a compound which absorbs light and Is excited by It to a higher energy state having a total energy content In excess of that required to effect a homolytlc scission of some bonds In pol3nner molecule to form free radicals, which promote secondary reactions. 

ISe. Classical Calculation of Heat Capacities.— For a diatomic molecule two types of rotation are possible, as seen above, contributing RT per mole to the energy. Since there are two atoms in the molecule, i.e., n is 2, there is only one mode of vibration, and the vibrational energy should be RT per mole. If the diatomic molecules rotate, but the atoms do not vibrate, the total energy content E will be the sum of the translational and rotational energies, i.e., RT + RT = RT, per mole hence,... 

It will be observed from equations (16.8) and (16.9) that the energy and heat capacity of a gas depend on the logarithm of the complete partition function. Since the latter is equal to the product of the factors for the several forms of energy, the total energy content and heat capacity of the molecules will be equal to the sum of the contributions obtained by inserting the appropriate partition functions in the aforementioned equations. Thus, from equation (16.12),... 

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