Thank you for receiving me in this forum.

Need help to determine the time required to drain a pressurized tank.

It's a 5 cubic meters tank, with air at 100 psi and need to drain to atmosphere through a 12 mm orifice.

Problem is that the tank pressure will be gradually reduced as it is being drained, so I assume the flow is being reduced, and cannot find the rationale (formula) to determine the time used to fully drain the tank (to 0 psi).

Thank you for the help.

Sergio