FlashTank is not locally balanced

[valentind-met]

FlashTank is not locally balanced, possibly because of outlet connectors.

[AndreaBartolini]

I see the following potential issues that require some analysis and/or model modification (if necessary) by Metroscope:

1. the instantiated model IsoPFlowModel is balanced because the input variable W_input has been added and put in relation with the variable W by means of the equation W = W_input. This is generally correct, the point is that the input variable W_input has no binding equation in the FlashTank model that instantiates the IsoPFlowModel model, and this is not correct because only the input variables at top-level can be left without binding,

2. probably the cause of the local unbalancing of the model is related to 1) plus the balance equation steam_phase.W + liquid_phase.W = 0 at the top-level;

[casella]

Result of today's meeting with @pepmts, @casella, and @AndreaBartolini: the current structure of the model is not adequate, because the structure of the physical system does not have two parallel branches, but rather a single control volume.

It is suggested to directly write the mass and energy balance equations for such a volume (possibly in a generic base class) and then add the two extra equations fixing the saturated liquid and vapour enthalpies at the outlet ports.

[pierre-eliep-met]

This discussion also made us realize that the steam dryer was not locally balanced

[pierre-eliep-met]

@casella and @AndreaBartolini I have some difficulties in #297, the model is still not locally balanced but I don't know why, can you have a look there ?