6A model is developed for an existing organic Rankine cycle (ORC) utilizing a low temperature geothermal source. The model is implemented in Aspen Plus ® and used to simulate the performance of the existing ORC equipped with an air-cooled condensation system. The model includes all the actual characteristics of the components. The model is validated by approximately 5000 measured data in a wide range of ambient temperatures. The net power output of the system is maximized. The results suggest different optimal operation strategies based on the ambient temperature. Existing literature claims that no superheat is optimal for maximum performance of the system; this is confirmed only for low ambient temperatures. For moderate ambient temperatures (T amb ≥ 1.7 ) superheat maximizes net power output of the system. The value of the optimal superheat increases with increasing ambient temperature.The optimal operation boosts the total power produced in a year by 9%. In addition, a simpler and semi-analytic model is developed that enables very quick optimization of the operation of the cycle. Based on the pinch condition at the condenser, a simple explicit formula is derived that predicts the outlet pressure of the turbine as a function of mass flow rate of working fluid.

No abstract

Among the various fuel cell (FC) systems, molten carbonate fuel cells (MCFC) are nowadays one ofthe most promising technologies, thanks to the lower specißc costs and a very high electrical efficiency (net low heating value (LHV) electric efficiency in the range 45%-50% at MWei scale using natural gas as fuel). Despite this high performance, MCFC rejects to the ambient almost half of the fuel energy at about 350^00° C. Waste heat can be exploited in a recovery Rankine cycle unit, thereby enhancing the electric efflciency ofthe overall system. Due to the temperature ofthe heat source and the relatively small power capacity of MCFC plants (from few hundred kW^i to ¡OMW^i), steam Rankine cycle technology is uneconomical and less efficient compared to that of the organic Rankine cycle (ORC). The objective of this work is to verify the practical feasibility ofthe integration betn'een a MCFC system (topping unit) and an ORC turbogenerator (bottoming unit). The potential beneflts ofthe combined plant are assessed in relation to a commercial MCFC stack. In order to identify the most suitable working fluids for the ORC system, organic substances are considered and compared. The figure of merit is the maximum net power ofthe overall system. Finally, the economical beneflts of the integration are determined by evaluating the levelized cost of electricity (LCOE) of the combined plant, with respect to the standalone MCFC system. In order to assess the economic viability of the bottoming power unit, two cases are considered. In the flrst one, the ORC power output is approximately 500 kW^¡; in the latter, about I h/TW^i. Results show that the proposed solution can increase the electrical power output and efficiency of the plant by more than 10%, well exceeding 50% overall electrical efficiency. In addition, the LCOE of the combined power plant is 8% lower than the standalone MCFC system.

The aim of this work is to analyze the stress and the strain fields in the brake caliper mounts of front motorbike suspensions produced by the braking action. First of all, some formulae useful to evaluate the maximum braking force in function of the vehicle features (e.g., total mass, centre of gravity position, tyre dimension, and brake disk diameter) have been developed. A mathematical model useful to calculate the axial, the bending, and the torque stresses on the braking caliper mounts has been then defined. The model has been developed by comparing the theoretical results with those obtained by some numerical analyses, based on the finite element method. An ad hoc test equipment has been, finally, designed and manufactured in order to define and analyze experimentally the strength of different types of brake caliper mounts and, at the same time, to verify the proposed model.

No abstract