Browsing by Author "Fos Mira, Ignacio"

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    Modelling of thermal management by hybrid channeling
    (2018-06-11) Fos Mira, Ignacio; Karvinen, Heikki; Insinööritieteiden korkeakoulu; Vilaça da SIlva, Pedro
    Friction Stir Welding was born as a technique to join dissimilar metals overcoming the different physical properties. The join is made in a solid state with non-consumable tools, becoming environmentally friendly. The microstructure of the new regions created during FSW shown enhanced properties too interesting for a new technique to appear, Friction Stir Processing. Based on same principles as FSW, FSP performs on metals proceeding to a microstructure refinement and so surface properties. Nevertheless, when the parameters during FSP are improperly settled, some defects emerge in the weld zone. Most outstanding one developed Friction Stir Channeling, a technique which manufactures internal closing channels by a developed tool. One step further, Hybrid Friction Stir Channeling combines, in a simultaneous action, the production of internal channels with the join of different components. This investigation is focused on the study of the parameters involved in the proper performance and functioning of HFSC prototypes for thermal management. The adequate knowledge of these parameters leads to an optimization of HFSC application for heat removal. This dissertation considers three parameters as most relevant ones: channel roughness, thermal bridge by the weld zone and coolant velocity and temperature. Acquired knowledge about the behavior in different configurations determined by these parameters is later applied in the simulation of prototypes proposed for thermal management. Each prototype differs from others in geometry, boundary conditions, heat sources, channel path and application. The influence of each parameter was simulated within different models. Results showed how the increase of the contact area and turbulence in the flow propitiated by roughness aid the heat transfer mechanism significantly improving heat removal. Contact surfaces are not fully contacted due to surface roughness and waviness, where the peaks leave gaps filled by air. Air low thermal conductivity act as a barrier for heat transfer. Weld zone, composed of a continuous material, avoids this resistance and aids the heat to flow through the weld zone. Easiness in heat flow means greater conduction to the coolant and lower maximum temperatures. Coolant velocity has limitations because of pump requirements and frictional losses. The higher the inlet velocity, the higher heat removal. Nonetheless, excessive velocities do not result in excellent efficiencies. There is a point from which the gain in heat removal is too deficient compared with the increase needed in the flow.