Adiabatic self-heating test

Figure 1. The whole self-heating process up to the thennal explosion of2 em of a chemical of the Tl) type charged in the open-cup cell, or confined in the closed cell, in accordance with the self-heating property of the chemical, and subjected to the adiabatic self-heating test started from a Tj.

The above approach, i.e., the heat generation data by the adiabatic self-heating test, or by the adiabatic oxidatively-heating test, and, the heat transfer data by experimental measurements, has been adopted throughout a series of studies described herein in order to calculate the 7 for a chemical of the TD type, including every gas-permeable oxidatively-heating substance, having an arbitrary shape and an arbitrary size, placed in the atmosphere under isothermal conditions. 

It has been ascertained, as to the value of A T, that, when the value of In t is plotted against that of l/T on several values of A T, with reference to a self-heating process, in the early stages, of 2 cm of a certain chemical of the TD type subjected to the adiabatic self-heating test started from a T several straight lines, which are almost parallel with one another, are obtained. 

The differential equations, in which one of the unknown variables, e.g., temperature, enters in a nonlinear manner, i.e., as an exponential function, while its derivative enters in a linear form, are often dealt with in the thermal explosion theory. Such an equation is called quasilinear in mathematics [21]. For instance, we have assumed in Eq. (50) presented in Section 2.5 that the value of dTIdt remains virtually constant while the self-heating process of 2 cm of a chemical of the TD type, subjected to the adiabatic self-heating test, is in the early stages. 

Thirdly, let us assume that the coefficient, a, i.e., EIR K, of Eq. (44) holding for the individual self-heating processes, in the early stages, of 2 cm each of the ten organic liquid peroxides charged each in the open-cup cell and subjected each to the adiabatic self-heating test, takes a mean and constant value of 14,000 K, on comparing the values of a presented Table 8 in Subsection 5.7.1. 

And lastly, let us assume that, at the time when the adiabatic self-heating test was started from a T, of 60 °C for 2 cm of an organic liquid peroxide charged... 

Then, according to the result of the calculation given in Table 2, at the time when the adiabatic self-heating test started from the T,. is interrupted, i.e., at the time when the temperature of the peroxide has increased by 1.25 K from the the rate of increase in temperature of the peroxide will be about 1.346 (= 1.15 X 1.1701) K/h. 

When the rate of increase in temperature of 2 cm of the chemical subjected to the adiabatic self-heating test started from a T, has varied or has accelerated from 1.15 up to 1.346 K/h after the lapse of one hour, we may assume that the rate has remained, in fact, at a mean, and almost constant, value of 1.25 (1.15 + 1.346)/2 K/h during this one hour. 

The linearity, of this order, of the self-heating process or curve, of 2 cm of a chemical of the TD type subjected to the adiabatic self-heating test started from a Ts, recorded for the time, A t, required for the temperature of the chemical to increase by the definite value of AT of. 25 K from the r is exemplified by a digital record of the self-heating process, which is presented in Table 5 in Section 4.7, of 2 cm of 99 % tert-butyl peroxybenzoate (TBPB) charged in the open-cup cell and subjected to the adiabatic self-heating test started from a nominal T, of 76 °C, for the time, At, required for the temperature of TBPB to increase by the definite value of AT of. 25 K from the nominal T. ... 

Both liquid and powdery chemicals of the TD type are, however, the same to the effect that their exothermic decomposition reactions are accompanied with no phase transition. Therefore, when charged in the open-cup cell, or confined in the closed cell, in accordance with the self-heating property of the chemical, and subjected to the adiabatic self-heating test started from a r, 2 cm each of a liquid chemical, or a powdery chemical, of the TD type continues to self-heat over the at a very slow, but virtually constant, rate depending on the value of Ts in accordance with the Arrhenius equation, after its having been warmed up to the Ts. 

In the last analysis, self-heating chemicals are classified into the two large groups, the TD and the AC type, but in fact they are subdivided into the following four groups in all, in accordance with the difference in the selfheating process which, when subjected to the adiabatic self-heating test started from a T, 2 cm each of them each show, or, in accordance with the difference in the characteristic temperature, i.e., the Tc or the SADT, to express each individual thermal instability, as presented in Table 3. 

Group in. Powdery chemicals to each of which neither of the two equations of the thermal explosion theory can be applied to calculate the Tc. When confined in the closed cell and subjected to the adiabatic self-heating test started from a 7 2 cm of a powdery chemical of this group warms slowly up to the 7j, but the temperature remains near the F, until the chemical has finished melting. Once, however, the chemical finishes melting in the course of time, an apparently sudden quasi-autocatalytic reaction of the resultant liquefied chemical starts [25]. 

Detailed procedure to perform the adiabatic self-heating test, which is started from a J for 2 cm of a chemical of the TD type confined in the closed cell, for the time, A t, required for the temperature of the chemical to increase by tbe definite value of T of 1.25 K from the T,... 

The temperature of the air bath, i.e., the nominal T, of the run, is set at a proper value by means of the temperature dial on the air bath on the basis of the self-heating property of the chemical tested to give estimated rates of increase in temperature of 1.25 K/h in the adiabatic self-heating test. 

The whole procedure to perform the adiabatic self-heating test by means of the closed cell is explained in detail in Chapter 6, in connection with the procedure to calculate the T for a powdery chemical of the TD type, having some one of several specific shapes including the class A geometries as well as an arbitrary size, confined in a fiber drum, and placed in the atmosphere under isothermal conditions. 

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