Thermodynamic energy

The chemical energy generated by the combustion of energetic materials is converted to thermodynamic energy used for propulsion and explosion. As described in the preceding sections of this chapter, the amount of stored chemical energy is 

Though the thermodynamic energies of propellants and explosives are not determined by the thermodynamic energies of their individual components, it is important to recognize the thermochemical properties through the thermodynamic energy of each component. Table 2.7 shows Tg, Mg, 0, and the combustion products of the major components used in propellants and explosives, as obtained by computations with a NASA program.  

1 Dickerson, R. E., Molecular Thermodynamics, W. A. Benjamin, New York (1969), Chapter 5. 

3 Sarner, S. E., Propellant Chemistry, Re-inold Publishing Corporation, New York (1966), Chapter 4. 

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It should be stressed that although these symmetry considerations may allow one to anticipate barriers on reaction potential energy surfaces, they have nothing to do with the thermodynamic energy differences of such reactions. Symmetry says whether there will be symmetry-imposed barriers above and beyond any thermodynamic energy differences. The enthalpies of formation of reactants and products contain the information about the reaction s overall energy balance. 

Membra.ne Diffusiona.1 Systems. Membrane diffusional systems are not as simple to formulate as matrix systems, but they offer much more precisely controlled and uniform dmg release. In membrane-controlled dmg deUvery, the dmg reservoir is intimately surrounded by a polymeric membrane that controls the dmg release rate. Dmg release is governed by the thermodynamic energy derived from the concentration gradient between the saturated dmg solution in the system s reservoir and the lower concentration in the receptor. The dmg moves toward the lower concentration at a nearly constant rate determined by the concentration gradient and diffusivity in the membrane (33). 

In summaiy, the first law of thermodynamics. Equations la and lb, states that energy is conserved and the energy associated with heat must be included as a form of energy. No process i f is possible if it violates the first law of thermodynamics energy is always conserved in our world as dictated by Equation lb. If Equation lb is applied to an adiabatic process, then because Q = 0 the first part, Equation la is recovered, but one still needs both parts of the first law to define the quantities. 

Thermodynamic energy terms (and equilibrium constants) may differ for compounds containing different isotopic species of an element. This effect is described in theoretical detail by Urey (1947), and applications to geochemistry are discussed by Broecker and Oversby (1971) and Faure (1977). A good example is the case of the vapor/liquid equilibrium for water. The vapor pressure of a lighter isotopic species, H2 0, is higher relative to that of heavier species, (or HD O), and others. 

Normally in chemistry one does not expect reaction rates or sequences to follow thermodynamic energy gain. Rather, they are dictated by... 

The sarcolemmal Na/K pump plays an imp>ortant, although indirect role in the regulation of cellular calcium homeostasis. The transmembrane Na gradient is maintained by the activity of the Na/K pump and the thermodynamic energy of this gradient in turn drives the Na/Ca exchange mechanism (Sheu and Fozzard, 1982 Barry and Bridge, 1993). Thus, the intracellular Ca concentration is closely related to intracellular Na and the activity of the Na/K pump (Bers and Ellis, 1982). 

The use of these expressions is effectual only in cases where there is no extensive deviation in the system behavior due to charge transfer overpotential or other kinetic effects.(l) The calculated threshold or thermodynamic energy requirement (2 ) (AG in the previous equation) is often much lower than actually encountered, but is still useful in estimating an approximate or theoretical minimum energy required for electrolysis. Part of the difficulty in applying thermodynamics to many systems of industrial interest may reside in an inability to properly define the activities or nature of the various species involved in the... 

The difficulties in relating the calculated thermodynamic energy of decomposition (—AU) to that occurring in practice are discussed, and values of the experimentally observed energies of decomposition for some characteristic molecular structures are tabulated in comparison with the calculated values. A second table gives the range of decomposition energies which have been measured by DSC for... 

Since that time much has happened to improve both the scientific understanding of, and commercial interest in, this process. The basics of how liquid Ga-Al alloys split water are now understood. The liquid Ga-Al alloy has two properties that work together to split water. First, A1 itself has enough thermodynamic energy to split water. The oxidation of A1 to alumina,... 

The chemical thermodynamic energy scale of ions described in this section is not the same as the conventional energy scale of hydrated ions in aquatic electrochemistry (Refer to Sec. 6.4.) the conventional scale is referred to the ion level of hydrated proton of unit activity. 

If we set at a value of zero according to the conventional chemical thermodynamic energy scale, the standard chemical potential of a hydrated proton,, is given by Eqn. 6-24 ... 

Earlier, I stated the First Law of Thermodynamics energy is conserved. If we apply the First Law to the case of body weight control, we have the following equation ... 

First Law of Thermodynamics energy is conserved quantitatively, AE = q — w, where q is heat added to the system and w is work done by the system. 

The effective work done by a gun propellant is the pressure force that acts on the base of the projectile. Thus, the work done by propellant combustion is expressed in terms of the thermodynamic energy, f, which is represented by... 

Since the energetics of nitropolymer propellants composed of NC-NG or NC-TMETN are limited due to the limited concentration of oxidizer fragments, some crystalline particles are mixed within these propellants in order to increase the thermodynamic energy or specific impulse. The resulting class of propellants is termed composite-modified double-base (CMDB) propellants . The physicochemical properhes of CMDB propellants are intermediate between those of composite and double-base propellants, and these systems are widely used because of their great potential to produce a high specific impulse and their flexibility of burning rate. 

Triple-base propellants are made by the addition of crystalUne nitroguanidine (NQ) to double-base propellants, similar to the way in which nitramine is added to CMDB propellants as described in the preceding section. Since NQ has a relatively high mole fraction of hydrogen within its molecular structure, the molecular mass of the combustion products becomes low even though the flame temperature is reduced. Table 4.13 shows the chemical composition, adiabatic flame temperature, and thermodynamic energy,/ as defined in Eq. (1.84), of a triple-base propellant at 10 MPa (NC 12.6% N). 

Fig. 4.26 Thermodynamic energies of singie-, doubie-, and triple-base propellants.

Figure 4.26 shows the thermodynamic energy,/ as defined in Eq. (1.84), of singlebase, double-base, and triple-base propellants as a function of the combustion temperature, Tg. Though the/values of double-base propellants are high, Tg is also high. In order to suppress gun erosion, Tg needs to be low. Triple-base propellants are thus formulated to reduce erosion while maximizing the /value. 

It can be seen that the pressure in a closed chamber is raised by an increase in 0, even when the combushon temperature is low as long as the molecular mass of the reaction products is reduced. In other words, 0 indicates the work done by the combushon of pyrolants and is simply evaluated by the thermodynamic energy 0 defined in Eq. (10.6). 

The low threshold energies for the production of D( S), 0( P), and 0( D2) show the importance of valence excited states in the BSD of neutral fragments [47]. The pathway for D( S) desorption probably involves D O D -I- OD. Ffowever, the thresholds for producing 0( P2) and 0( D2), which are the same within experimental error, are lower than the 9.5-and 11.5-eV thermodynamic energies required to produce 0( P2) + 2D( S) and 0( D2) + 2D( S), respectively. The low threshold values therefore indicate that the formation of 0( P2) and 0( D2) must occur by a pathway which involves simultaneous formation of D2. Kimmel et al. have in fact reported [46] a threshold for the production of D2 from D2O ice at — 6 to 7 eV, which supports this conclusion. Above the ionization threshold of amorphous ice, these excited states can be formed directly or via electron-ion recombination. 

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