Thermodynamic energy release

Box 1.6 Activation energy versus thermodynamic energy release... 

CHETAH-The MSTM Chemical Thermodynamic and Energy Release Evaluation Program, ASTM Data Series Pubheation DS 51, American Society for Testing Materials, Philadelphia, 1974, original, updated. 

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). 

Downey et al. 1993. CHETAH 7.0 Reference Manual, The ASTM Computer Program for Chemical Thermodynamic and Energy Release Evaluation. 

The energy release rate (G) represents adherence and is attributed to a multiplicative combination of interfacial and bulk effects. The interface contributions to the overall adherence are captured by the adhesion energy (Go), which is assumed to be rate-independent and equal to the thermodynamic work of adhesion (IVa)-Additional dissipation occurring within the elastomer is contained in the bulk viscoelastic loss function 0, which is dependent on the crack growth velocity (v) and on temperature (T). The function 0 is therefore substrate surface independent, but test geometry dependent. 

The released energy might result from the wanted reaction or from the reaction mass if the materials involved are thermodynamically unstable. The accumulation of the starting materials or intermediate products is an initial stage of a runaway reaction. Figure 12-6 illustrates the common causes of reactant accumulation. The energy release with the reactant accumulation can cause the batch temperature to rise to a critical level thereby triggering the secondary (unwanted) reactions. Thermal runaway starts slowly and then accelerates until finally it may lead to an explosion. 

American Society for Testing and Materials (ASTM) (1994). CHETAH, Version 7-0 The ASTM Computer Program for Chemical Thermodynamic and Energy Release Evaluation. ASTM Data Series DS 51B. Philadelphia, PA American Society for Testing and Materials. 

The energy released from the breakdown of ATP has been used to drive an unfavorable process. A reaction (the formation of XY) that would not have occurred spontaneously has taken place. Of course, the amount of energy required for the formation of one molecule of XY must be less than the ainount released when one ATP is broken down, otherwise the system would have gained total energy during the coupled reaction, and violated the first law of thermodynamics. 

The oxidation of hydrogen to water (Hj -t- i Oj -> HjO) is thermodynamically spontaneous and the energy released as a result of the chemical reaction appears as heat energy, but the decomposition of water into its elements is a non-spontaneous process and can be achieved only by supplying energy from an external source, e.g. a source of e.m.f. that decomposes the water electrolytically. Furthermore, although the heat produced by the spontaneous reaction could be converted into electrical energy, the electrical... 

Why Do We Need to Know This Material The laws of thermodynamics govern chemistry and life. They explain why reactions take place and let us predict how much heat reactions release and how much work they can do. Thermodynamics plays a role in every part of our lives. For example, the energy released as heat can be used to compare fuels, and the energy resources of food lets us assess its nutritional value. The material in this chapter provides a foundation for the following chapters, in particular Chapter 7, which deals with the driving force of chemical reactions. 

Fig. 16-7 Changes in concentration of metabolites in sediment. The reaction order follows the sequence dictated by thermodynamics (i.e., the most energy releasing reactions occur first). (Modified from Froe-lich et al, 1979.)...

The CHETAH programme is the most popular process of quantitatively estimating the risks related to the instability of a compound. It stands for Chemical Thermodynamic and Energy Release Program. This program was developed by the National Institute of Standards (N1ST)2. The 7-0 version is not distributed in France. 

Furthermore, it was found that I I2Si=S is thermodynamically stable compared with H2Si=0. In an attempt to assess the strength of a silicon-sulfur double bond, a comparison was made of the hydrogenation energies released upon addition of H2... 

When one considers the potential high-energy release on rupture of a carborane unit, together with the thermodynamic stability of combustion products, it is hardly surprising that there is a body of literature that reports on the use of carbo-ranes within propellant compositions. Their use in energetic applications is to be expected when the enthalpy of formation (AH/) data for the products of combustion for boron are compared to those of carbon. Thermodynamic data for the enthalpy of formation of o-carborane and of typical boron and carbon combustion products is shown in Table 4. Measurements of the standard enthalpy of combustion32 for crystalline samples of ortho-carborane show that complete combustion is a highly exothermic reaction, AH = — 8994 KJmol. ... 

The ASTM Chemical Thermodynamic and Energy Release Evaluation Programme, Version 4.4, 2nd Edn (ASTM Data Series Publication 51 A), Davies C. A. etal., Philadelphia, ASTM, Appendix V. Upgrades continue to be issued (1998)... 

The thermodynamic drives cited are the energy released instantaneously by the metabolic reaction, at the moment reaction commences. The drives tell whether the reaction can proceed, and whether it can supply enough energy for a cell to conserve energy by synthesizing ATP, as discussed in Section 7.4. The values, however, do not describe how much energy microbes can extract from a fluid, and hence how much microbial growth the fluid can sustain. 

Following through the chart in Figure 3.24, the thermodynamics, impact sensitivity, and thermal analysis are defined. If the energy release potential calculated via CHETAFI is higher than 700 kcal/kg, the reaction system is considered a definite hazard. 

Seaton, W. H., E. Freedman, and D. N. Treweek, "CHETAH The ASTM Chemical Thermodynamic and Energy Release Potential Evaluation Program," American Society for Testing and Materials, Philadelphia, PA (1974). 

Thermodynamic cycles are a useful way to understand energy release mechanisms. Detonation can be thought of as a cycle that transforms the unreacted explosive into stable product molecules at the Chapman-Jouguet (C-J) state,15 which is simply described as the slowest steady-state shock state that conserves mass, momentum, and energy (see Figure 1). Similarly, the deflagration of a propellant converts the unreacted material into product molecules at constant enthalpy and pressure. The nature of the C-J state and other special thermodynamic states important to energetic materials is determined by the equation of state of the stable detonation products. 

Even in smaller cars that use less petroleum, most of the energy released in combustion is wasted and only 12-15% is finally applied to move the car. The rest is lost due to the thermodynamic inefficiency of the en-... 

CHETAH Chemical Thermodynamic and Energy Release Program... 

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