Accurate modeling of thermal-hydraulic transients in a joint + conductor system, e.g., in the analysis of the test program of the ITER Model Coils (CSMC and TFMC) requires a major extension of existing codes. The two-fluid MITHRANDIR code has been upgraded accordingly to version 2.1 and it can now deal with variable geometry and materials along the hydraulic path. A limited validation of the extended quasi one-dimensional model is presented against data we obtained in dedicated thermal-hydraulic tests on the Full Size Joint Sample (FSJS). Taking into account experimental uncertainties the agreement between prediction and measurement can be considered good.