Explosion thermal effects

The above two equations showed the relationship of explosion gas with constant volume to that with constant pressure. In the design calculation of explosive thermal effects, some further simplifications can be made based on the specific circumstances. 

This value is the constant-volume explosion thermal effect of a mixture of ammonium nitrate (11.35 mol) and TNT (1 mol). 

Nonionizing radiation E-1 Fire—Thermal effects in combination with combustible/flammable material E-2 Explosion—Thermal effects in combination with explosive material E-4 Direct exposure—Worker injury Other—May interfere with equipment operation... 

In addition to the many different forms of boiler section ferrous corrosion already described, several other less common types occasionally develop. In particular, corrosion processes may evolve that are interrelated with stress, deposition, and/or high temperatures (thermal effect corrosion), and together these may lead to metal fatigue (metal fatigue corrosion), metal failure, and even more serious problems such as the risk of a boiler explosion. 

Whenever the operation to be performed involves the potential to cause the initiation of the propellant, explosive or pyrotechnic (PEP) component(s) of a munition item, the APE is either operated by remote control, with the operator behind a protection wall or barrier, or it is enclosed in a protective barricade or operational shield. Barricades or operational shields are designed to protect personnel and assets from the effects of blast overpressures, thermal effects or fireball, and fragments result from the initiation of PEP components, such as the fuze, primer, propelling charge, burster, etc. 

Since thermal effects and irreversibility are involved in an explosion, this equation r resents a limiting or maximum value for the explosion energy. 

The heat of detonation therefore is, like the heat of explosion, a function of the chemical energy of the explosive. In fact, the two heats differ only by the thermal effect, at standard temperature, of the shift in composition of the product mixture between (Tj) and (Tv). This depends on the... 

There is a great deal of evidence that most explosive sensitivity phenomena are understandable in terms of the thermal decomposition of the explosive involved. Some of the early work on the interpretation of impact and friction sensitivity of explosives in terms of thermal effects is excellently summarized by Bowden Yoffe (Ref 1). More recent studies which also include investigations of irradiation of explosives by nuclear particles and ionizing radiations are also reviewed by these authors (Ref 2), and by Bowden (Ref 7)... 

This section presents some historical examples of spontaneous ignition. A more technical discussion of spontaneous ignition will be given under Thermal Explosion, Catalytic Effects in a future Vol... 

Cd azides, Ag acetylide and nitrogen iodide) by electrons, neutrons, fusion products and X-rays. All these substances were exploded by an intense electron stream but it was shown that this was due to a thermal effect. Fission products exploded nitrogen iodide but in the other substances some changes within the crystals took place but no explosions. The experiments showed that, in general, the activation of a small group of adjacent molecules was not enough to cause explosion... 

Underground literature explosive Produces high-temperature thermal effects Oxidizer Fuel... 

Produces high-temperature thermal effects Primary high explosive Low explosive, Main component in smokeless powders, lED fiUer Primary high explosive Primary high explosive Nerve agent... 

A new insensitive, cast-cured PBX called -135, has been developed in order to meet the requirements of US Navy s Insensitive Munitions Advanced Development Programfor High Explosives (IMAD/HE). PBXIH-135 has enhanced internal blast performance, improved non-vulnerability and penetration survivability characteristics compared with PBXN-109. Thermobaric explosives are required to defeat hard and deeply buried structures. PBXIH-135 thermobaric explosive which not only offers effective blast and thermal effects, but is also extremely insensitive to factors responsible for accidental detonation during transit or storage, may also be used for this purpose. 

The calculated thermal effect in this reaction (ca. 1250kcal/kg) would fall between those of the explosive decomposition of nitroglycerine and guncotton, and the calculated temperature would be ca. 2500°C. 

Recent developments of novel explosive materials have concentrated on reducing the sensitivity of the explosive materials to accidental initiation by shock, impact and thermal effects. The explosive materials, which have this reduced sensitivity, are call Insensitive Munitions, (IM). Although these explosive materials are insensitive to accidental initiation they still perform very well when suitably initiated. Examples of some explosive molecules under development are presented in Table 1.5. A summary of the significant discoveries in the history of explosives throughout the world is presented in Table 1.6. 

The large thermal effect entitles this substance to be regarded as a very powerful explosive. Its sensitiveness to shock is barely less than that of nitroglycerine, as it explodes under the impact of a 2 kg weight dropped from a height of 7-10 c l. 

Thus the substance is one of the strongest explosives known, and a composition made from 75% of nitroglycerine and 25% of nitrodiglycerine gives practically the same thermal effect as that caused by pure nitroglycerine. 

The thermal effect from exploding methyl nitrate (1609-1612 kcal/kg) is 1% higher than that developed by the explosion of nitroglycerine according to equations ... 

Merzhanov et al (Ref 3) also made an investigation of the thermal explosion of Dinitrohy-droxydiethylnitramine (mp 52.5°) and of Tetryl (mp 130°) in the liq phase under conditions where the reaction zone was free of temp distribution and the entire thermal gradient was at the walls of the container. The method exptl setup were the same as previously used by the authors (Ref 1). The activation energy, thermal effect critical temp were reported for both expls (Ref 6)... 

This paper is a continuation of a series of theoretical studies carried out at the Institute of Chemical Physics which seek to give a description of various phenomena of combustion and explosion under the simplest realistic assumptions about the kinetics of the chemical reaction. A characteristic feature of the specific rate (rate constant) of chemical combustion reactions is its strong Arrhenius-like dependence on the temperature with a large value of the activation heat, related to the large thermal effect of the combustion reaction. 

The reader is urged to read Initiation of Explosives by Impact in Vol 7,135-R ff of this Encycl, Whereas that article dealt principally with the testing of expls, we shall want to include propints in the discussion. There is probably no subject in hazards analysis which is so actively studied as the role of impact, shock and thermal effects on the safety of expls and proplnts and which is as poorly understood. We have alluded to this incomplete state of theoretical development in the section of this article on Application of Computer Programming... 

Thermal Effects of Impact. See under Impact, Initiation of Explosion by in Vol 7,I35-L ff... 

The editor has encountered numerous studies of laser ignition, usually of explosives. These demonstrate that the ignition is normally a thermal effect, caused by heating solid particles, not photochemical, and thus the MIE is not lower than other methods. This may not obtain if the light be of a frequency (visible or uv) sufficient to excite the early steps of the explosion reaction, as, for example, photodissociation of halogens to the atomic radicals which are the start of their explosive reactions with fuels. 

First, different typologies of nonideal batch reactors are considered. In particular gas-liquid reactors are discussed, which may be used for different industrial applications (e.g., reactions of oxidation) and are often encountered in the case of gassy reactions (i.e., liquid-phase reactions which do not produce significant thermal effects but in which the production of gaseous products may lead to explosions). 

In this case, the fast increase of concentration of radicalic species can result in the loss of control of the reaction (runaway) and in the explosion of the system. This radicalic runaway may be strongly enhanced by linked thermal effects that are discussed in more details in Chap. 4. 

Steam curtains are best used for diluting heavier-than-air releases of flammable vapors, not toxic materials. For flammable materials the level of dilution with air that has to be obtained is the lower explosive limit toxic materials could require dilution to <100 ppm range. Moreover, while steam curtains can provide the thermal effects that will help disperse flammable material, they hinder the absorption effects needed for toxic materials, especially materials that are water-soluble. 

Electrical components which could ignite a hazardous atmosphere either by sparking, arcing or by thermal effects, e.g. the contacts of relays, semiconductors, the windings of transformers or solenoids, can be explosion protected by enclosing them in a compound to avoid immediate contact with the environmental atmosphere. 

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