The flash unit operation separates vapor and the remainder of the flow. It has one inlet, and two or three material outlets.
A pressure drop can be specified, or the outlet pressure can be specified. Equilibrium calculations are done at the outlet pressure, i.e. after a pressure drop.
If the three-phase flash option is selected, vapor will exit through the first outlet, the lightest liquid will go through the second outlet. This will happen in case multiple liquids are present, or nothing will go through the second outlet. All remaining phases will go through the third outlet.
If the three-phase flash option is not selected, vapor will exit through the first outlet, and all remaining phases will exit through the second outlet.
Either temperature must be specified, or heat duty must be specified. Heat duty can be specified directly, or via an energy inlet stream. If heat duty is not specified via an energy inlet stream, an energy outlet stream can be connected that will receive a value for the heat duty for the flash.
The flash calculation is performed using the thermodynamics that apply to the inlet port.
By default, outlet streams are flashed using a PVF flash, unless:
- the TP flash option is selected,
- there is zero flow through that outlet,
- either the total vapor flow is zero, or the total remaining flow is zero (in which case the system is sub cooled or super heated).
In the above cases, the outlet will be flashed using a TP flash.