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Cryogenic liquid propellants are used in liquid rocket engines to obtain high specific impulse. The flow rates are controlled by turbopumps that deliver liquid propellant to the engine at high pressure levels. Due to the very low saturation temperature of the cryogenic propellant, in the first phases of the transient operation, in which the engine is at ambient temperature, its surfaces are subject to boiling conditions. The effect of boiling on the heat transfer between the solid and the fluid needs to be well characterized in order to correctly predict the cryopump metal temperature temporal evolution and the necessary amount of propellant. With the aim of benchmarking numerical tools against experimental data, a representative test case was chosen. This consists of a stator-rotor-stator spinning disc reactor studied under single-phase and two-phase heat transfer conditions. The numerical approaches used are represented by a 1D network solver, where the pressure drop and heat transfer are calculated by correlations, and Computational Fluid Dynamics (CFD) simulations, carried out with ANSYS Fluent. Both the numerical tools returned a reasonable agreement in single-phase conditions, also thanks to the use of adequate correlations in the flow network solver and typical conditions for the CFD simulations. Two-phase conditions on the contrary are more challenging, with underpredictions up to 20% and 80%, respectively. The issues are ascribable to the use of correlations that are inadequate to capture the two-phase phenomena occurring in the srs reactor and numerical limitations in the actual implementation of the boiling model in the CFD solver.

Cryogenic liquid propellants are used in liquid rocket engines to obtain high specific impulse. The flow rates are controlled by turbopumps that deliver liquid propellant to the engine at high pressure levels. Due to the very low saturation temperature of the cryogenic propellant, in the first phases of the transient operation, in which the engine is at ambient temperature, its surfaces are subject to boiling conditions. The effect of boiling on the heat transfer between the solid and the fluid needs to be well characterized in order to correctly predict the cryopump metal temperature temporal evolution and the necessary amount of propellant. With the aim of benchmarking numerical tools against experimental data, a representative test case was chosen. This consists of a stator-rotor-stator spinning disc reactor studied under single-phase and two-phase heat transfer conditions. The numerical approaches used are represented by a 1D network solver, where the pressure drop and heat transfer are calculated by correlations, and Computational Fluid Dynamics (CFD) simulations, carried out with ANSYS Fluent. Both the numerical tools returned a reasonable agreement in single-phase conditions, also thanks to the use of adequate correlations in the flow network solver and typical conditions for the CFD simulations. Two-phase conditions on the contrary are more challenging, with underpredictions up to 20% and 80%, respectively. The issues are ascribable to the use of correlations that are inadequate to capture the two-phase phenomena occurring in the srs reactor and numerical limitations in the actual implementation of the boiling model in the CFD solver.

In this thesis work, it has been studied the effect of carbonaceous nanomaterials like graphene and nanotubes on GC electrodes, in various configurations, to perform the synthesis of the layered double hydroxide of nickel and aluminium. The potentiodynamic electrodeposition was found more efficient as to Ni centres electroactivity and more reproducible than potentiostatic or galvanostatic electrodeposition. It has been performed a structural characterization by means of XRD analysis (which confirmed the typical hydrotalcitical pattern) and a morphological characterization by means of SEM analysis, from which it was observed a homogeneous and well adherent coating, except for the bilayer configurations. It was carried out an electrochemical characterization to evaluate the electroactive surface area, that was found to be significantly increased in the presence of graphene, and the charge transfer resistance, that was lower when the nanomaterials were present. The modified electrodes were then tested in practical applications like the glucose determination and the oxygen evolution reaction.

In this thesis work, it has been studied the effect of carbonaceous nanomaterials like graphene and nanotubes on GC electrodes, in various configurations, to perform the synthesis of the layered double hydroxide of nickel and aluminium. The potentiodynamic electrodeposition was found more efficient as to Ni centres electroactivity and more reproducible than potentiostatic or galvanostatic electrodeposition. It has been performed a structural characterization by means of XRD analysis (which confirmed the typical hydrotalcitical pattern) and a morphological characterization by means of SEM analysis, from which it was observed a homogeneous and well adherent coating, except for the bilayer configurations. It was carried out an electrochemical characterization to evaluate the electroactive surface area, that was found to be significantly increased in the presence of graphene, and the charge transfer resistance, that was lower when the nanomaterials were present. The modified electrodes were then tested in practical applications like the glucose determination and the oxygen evolution reaction.