Isobaric dynamic mass balance

In the volumes (and derived components) dynamic_mass_bamancecan be set to:

• false → BQ=0: inflows equal outflows.
• true → BQ=V*der(rho) : the inflow/outflow inbalance compensate compression/dilation.

In ThermoSysPro the der(rho) term is generally decomposed in the ddph*der(P) (isenthalpic) and ddhp*der(h) (isobaric) terms.

I'am wondering whether an intermediate choice to take into account only the isobaric term, aka the thermal dilatation, would be a good enhancement for the library. I think this would make sense at least for liquid water for a couple of reasons:

• Liquid water is generally considered as incompressible (ddph~0).
• Variations of h travel slowly (transported by the mass flow) compared to Pvariations: it should be easier to solve the isobaric term only than the whole equation.

This could be useful for example to model the thermal dilatation in the primary circuit of a PWR ( @viola.ferrara).

changed milestone to %ThermoSysPro v4.x

added enhancement init labels

We have some discussion today with users of the ThermoPower library (Polimi). They have the same decomposition of the density derivative in the two terms; however, ddph is set to zero if the flow is monophasic. @viola.ferrara should test something on this issue (e.g. simplified_mass_balance=true) in the next days.

assigned to @giorgio.simonini

mentioned in issue #88