Three different pressurized subcooled water cooling options [hypervapotron, mini-channels (MCs), and meander flow drivers] for a full-size gyrotron cavity are developed and analyzed using the commercial computational fluid dynamics code STAR-CCM+, to guarantee a pressure drop below the maximum acceptable, and the compliance with manufacturing constraints. The full-size designs are then transposed to corresponding mock-ups to identify the most suitable candidate for an experimental test. The conjugate multiphase heat transfer problem is solved in the three mock-up geometries, aimed at comparatively assessing their thermal performance at increasing heat load on the target up to 24 MW/m ² . The most promising option for an effective cooling of the cavity results to be the mini-channels.