Additive manufacturing of metal alloys allows to create completely new designs for components that require to be actively cooled, such as gas turbines. The parts can now be printed with an uniform and distributed pattern of internal microchannels, leading to a better heat exchange. These channels, however, present a roughness pattern different from the one observed on conventionally manufactured channels, and this changes the flow behaviour in terms of pressure drop and heat exchange performance. This thesis aims to study the different behaviour of AM-manufactured channels and the impact that their relative roughness has on two adimensional parameters: Darcy friction factor for the pressure losses and Nusselt number for the heat exchange performance.