Mixing volume with a heat port.
This model is identical to AixLib.Fluid.MixingVolumes.BaseClasses.PartialMixingVolume, except that it has a heat port.
Note that this model is typically only used to implement new component models that
have staggered volumes.
In contrast to
AixLib.Fluid.MixingVolumes.MixingVolume, it does
not set initialize_p to final in order
for this model to be usable in staggered volumes which require one
pressure to be set to initialize_p = not Medium.singleState
and all others to false.