Link mass and energy balances
In the mass balance equation, the BQ term (right size) is equal to der(M) (left side) which is then decomposed as a function of P and h and the derivative of density to these states: ddph and ddhp (see also #80).
In the energy balance equation, the left side is der(uM) which is then decomposed, once again, as a function of Pand h which use the same properties ddhp and ddph.
I am wondering whether it would increase numerical efficiency to better link the two equations instead of resolve two times the same terms:
der(uM)=Mder(u)+uder(M)=Mder(u)+uBQ
.