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In this work, a pipe provided with twisted tape inserts is analyzed. This system allows a significant increase of convective heat transfer coefficient by introducing a swirl motion which determines greater heat removal from the solid surface, by improving the fluid mixing. The analysis performed in this paper focuses on the evaluation of the thermal and flow quantities for a pipe of a shell and tube heat exchanger, previously optimized through a design software widely used in the petrochemical industry. The thermo and fluid dynamics analysis were performed by using a commercial CFD software (Fluent TM ). After performing the necessary computational checks for the acceptance of the results provided by the solver, a pitch parameterization was performed through a finite volume simulation. In this way the behaviour of a highly viscous fluid was studied, whose thermo-physical characteristics are highly variable with temperature. Furthermore, using water as fluid, the behaviour of the pipe provided with inserts was investigated by varying the Reynolds number, through mass flow rate variation. To verify the correctness of the results, they were compared in both cases with correlations in the literature.

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In the present work, the law of motion of reflectors for a concentrating solar Linear Fresnel plant is geometrically analyzed. Firstly, a method for optimally distributing the primary reflectors on the ground is proposed. Furthermore, the mathematical procedure used to identify the law of motion that the mirrors must follow to reflect solar radiation on the absorber tube is presented. To make better use of the surface area occupied by the plant it is necessary to distance the rows of mirrors adequately so that the effects of shading and blocking between the same can be reduced. Avoiding these phenomena allows the initial costs of the plant to be reduced since the reflective material is not used in excess, thus allowing exploitation of the entire reflective surface available. In the work, using spherical trigonometry concepts, the motion law equation of the mirrors is detected. It allows the angle that they must assume in every moment of the day to be established and it has an entirely general valence: it can be applied to each plant according to its constructional characteristics and to each type of orientation. Finally, a comparison is carried out in which the main tracking differences between the plants oriented North-South and East-West are analyzed.