The Friction Stir Channelling (FSC) is a novel advanced solution for producing internal closed channels along any desired path with a constant or continuously modified shape along the path in a single manufacturing step. The channels are formed by continuous extraction of part of the stirred processed material into external flash. In this work, the performance of channels with the same shape and dimensions but produced by FSC and milling respectively, are compared using an experimental calorimeter setup with a focus on the influence of the geometrical features of the channels on the thermal efficiency. The investigation is implemented in a plate of AA5083-H111, with a thickness of 10 mm. The material properties of the channels produced by FSC are investigated with a microhardness field and optical microscopic analysis, assessing the thermomechanically processed and heat affected zones. The mechanical resistance of the channels produced by FSC is evaluated with an application of internal pressure up to 380 bar. The results show that the FSC enhanced the heat transfer by about 45 % compared with smoother milled channels. The optical microscopy shows evidence of a good consolidation of the solid state joining mechanisms activated during the FSC, with a small reduction of the hardness around the channel in the stirred zone and heat affected zone, being assisted by a harder top region at the ceiling of the channel.