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2 Mechanics and Mechanical Engineering

2 2004

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Unsteady emptying of a pressure vessel

El-Naggar B. B., Kholeif I. A.

Mechanics and Mechanical Engineering

2004

Vol. 7, nr 2

121-125

In this paper the problem of the unsteady emptying of a pressure vessel is solved by integrating the equations representing conservation of mass and energy in adiabatic expansion numerically for air where the adiabatic index γ = 1.4, two unknown functions are determined namely; the pressure and temperature inside the bottle. The ambient pressure and temperature are assumed constants and are used for non-dimensionalization. The area of the orifice is considered a constant throughout the whole expansion.

Correction of the diffusion equation

Kholeif I. A., El-Naggar B. B.

Mechanics and Mechanical Engineering

2004

Vol. 7, nr 2

99-107

A test problem is investigated and indicate that the conventional foundation of Fick's law and the resulting diffusion equation admit mass transfer at relatively high velocity. This contradicts nature and two independent corrections are made: 1. The front beyond which matier cannot reach; advances with a characteristic speed dependent on the diffusing substance and the medium; 2. Relativistic type correction in which time dilation and length contraction is taken in consideration. In both cases solutions are obtained and discussed.