.StreamConnectors.Sources.MassFlowBoundary_h .StreamConnectors.Sources.MassFlowBoundary_hNote that it is not necessary to specify if the boundary component is a source or a sink. The enthalpy is only relevant when the component acts as a source, i.e. when the mass flow leaves the component.
However, if you look in the equation section you'll se that the default direction of the mass flow is out of the component.