Enthalpy is integrated when its checkbox (E&M) indicates "v". Note that the area of integration can be performed in all media or in the chosen media depending on the state of the checkbox "Pdiss in dense regions only".
Calculate Time Integral is used to calculate the enthalpy by integration of the dissipated power over time. It can be turned on when one of the components: Pdiss/Pdens/PdissE/PdissM is chosen. This option is useful when we want to calculate the energy dissipated over the entire duration of a pulse of limited duration regardless of its spectral content.