Available energy methods

A wide variety of procedures have been developed to evaluate the performance of explosives. These include experimental methods as well as calculations based on available energy of the explosives and the reactions that take place on initiation. Both experimental and calculational procedures utilize electronic instmmentation and computer codes to provide estimates of performance in the laboratory and the field. 

In the case of thick-walled HP vessels, the strain energy in the vessel shell can contribute to the available energy, but for vessels below about 20 MN/m (200 barg) it is negligible and can be ignored. If a MoUier chart for the gas is available, the adiabatic energy can be measured directly. This is the preferred method, but in many cases the relevant chart is not available. 

To compare the values of steam at various pressures for design studies or accounting once the plant is built, the AB method is useful. The maximum available energy in a working fluid can be determined from... 

For BLEVEs or pressure vessel bursts that take place far from reflecting surfaces, the above method may be used if a few modifications are made. The blast wave does not reflect on the ground. Thus, the available energy E is spread over twice the volume of air. Therefore, instead of using Eq. (6.3.15), calculate the energy with... 

Numerical optimizations are available for methods lacking analytic gradients (first derivatives of the energy), but they are much, much slower. Similarly, frequencies may be computed numerically for methods without analytic second derivatives. 

For sake of comparison, in all studied cases, we run calculations for those geometries and basis sets with a FCI (or near FCI) available. The methods we deal with are CCSD, CAS-SDCI, (SC)2CAS-SDCI and ec-CCSD corrected from both CAS-SDCI and (SC) CAS-SDCI. The performance of the methods is examined from two aspects the total energy and the quality of the potential energy surface (PES), being this quality measured by the so-called non-parallelity error (NPE). For a given set of calculations in a dissociative curve, the NPE is defined as the difference between the maximal and minimal deviation from the exact FCI PES. 

Cook (Ref 17, p 36) designates the available energy as A, and states that this property, as well as the heat of explosion Q, and the ratio A/Q are the important quantities determining the total blast or "avaiable work potential or "available energy . The theory is presented in Chapter 11 of Ref 17, pp 265ff and is considered more reliable than experimental procedures, at least for CHNO expls. The experimental procedures referred to by Cook for determination of (A) include Trauzl Block Test and Ballistic Mortar Test. New methods have been proposed, such as determination of peak pressure or/and total energy ... 

Similar studies have been carried out by Cook who came to the conclusion that ballistic mortar is not a reliable method for determining field strength of HE s. Nevertheless, the maximum available work (A) in the mortar can be predicted quite accurately by the use of equation 11.8 given on p 268-L of Ref 17 and equation 11,12 given on p 273-R of Ref 17 [See also Detonation (and Explosion), Impetus and Available Energy in ]... 

IEC 47, 1794(1955) (Detailed discussion on Trauzl block method) 15) J.F. Roth, Explosivst 1957, 161-76. PicArsn Translation No 30, by Dr G.R. Loehr (1959) (Ballistic methods for measuring expl power and deton shock) 16) Dunkle s Syllabus (1957-1958), p 257 (Discussion on expression nRTy misnamed "power or "explosive force , whereas a better name is "impetus ) [See "Detonation (and Explosion), Impetus and Available Energy in]... 

Microwave Method) 32—35 (Meas of Deton Press) 35—36 (High Speed Photography) 36—37 (Available Energy) 37—38 (Temp of Deton) 38—39 (Impact Sensitivity) 39—41 Thermal Decomposition) 41 (Miniature Charge Techniques) 42 (Charge Preparation)... 

Suppose that such electronic structure results had not been available, and that we had used instead the simplest bond-dissociation-energy method of estimating A Hj. The B.D.E for C-H bonds in the hydrocarbon series is [32] as 415 kJ/mole. Using the known heats... 

Undoubtedly, the most general conclusion to be drawn from this overview of recent TDDFT calculations on transition-metal complexes is that this technique, compared to other available theoretical methods, provides state-of-the-art results for excitation energies. We stress that in order for this to be a valid statement, there are two points that should receive due attention the applied functional, and the geometry of the system. 

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