TABLE OF CONTENTS The deflagration of a flammable gas mixture in a closed vessel is important in itself and in relation to venting of the vessel. It is closely related to the combustion of a flammable dust mixture in a vessel. Quantification requires the measurement of flame speed and burning velocity. The two parameters of main interest in explosion in a closed vessel are the maximum pressure P m and the rate of pressure rise, particularly the maximum rate (d P/d t) max.
As described in Section 17.5, for a deflagration at constant volume, in a sphere, the maximum explosion pressure is
where n is the number of moles in the gas mixture, P is the absolute pressure, T is the absolute temperature and the subscripts 1 and 2 denote the initial and final state, respectively. The determination of the maximum pressure therefore involves the calculation of the final temperature.
Combustion in a closed vessel is a constant volume process. The heat of reaction and the gas specific heats applicable to it are those at constant volume. The relevant thermodynamic quantity is the internal energy. Thus, the final temperature should be obtained by equating the internal energy of the products to the internal energy of the reactants and the heat of reaction at constant volume.
The computation of the final temperature is frequently done making the incorrect assumption of constant pressure conditions. The problem is...
