L. Barelli

Development of an Innovative Defrosting System for Commercial Chiller Evaporators Through Piezoelectric Elements Application

The present study relates to the design of an innovative defrosting system for commercial chiller evaporators. This system is based on piezoelectric plates connected to the evaporator fins and driven at ultrasonic frequencies by a suitable electronic circuit. The operational frequency of piezoelectric elements is chosen to be close to the first harmonics of the fin resonance frequency in the ultrasonic range. The electronic driving system supplies the electric voltage required at the operational frequency starting from the PVM 0–5V signal output of a microcontroller. Moreover, the measurement of the absorbed current is acquired by the microcontroller as feedback to tune the operational frequency at the variation of the fin mass due to frost deposit and detachment. Experimental results show that the approach inhibits the frost deposit during chiller operation, increasing the period between two consecutive defrosting phases which currently is typically no greater than 6 hours. This is an important result considering that while defrosting the chiller must be shut off, depending on the defrosting methods applied, with negative effects on the goods being preserved. The system was developed in collaboration of ISA S.p.A and patented [1].Copyright

Analysis and validation of a biogas hybrid SOFC/GT emulator

MicroGrids (MGs) are one of the most useful and efficient ways to integrate the renewable energy technologies in the rural area, which has an often unused renewable resource: the organic waste. The biogas produced by the transformation of this primary energy resource can be valorised in a MG using a hybrid system based on a Solid Oxide Fuel Cell (SOFC) and a Gas MicroTurbine (GT) to obtain a high electrical efficiency. However, the demonstrators of this type of system are very few and the experimental data are rare. To approach the operation of a real system, the design and validation of hybrid SOFC/GT emulator have been proposed. The emulator will be then integrated into a rural MG in order to prove its contribution to the power quality and stability in the context of weak rural grids.

Fuzzy Logic Regulator for the Performance Improvement and the Energy Consumption Reduction of an Industrial Chiller

Nowadays producers of household and industrial appliances need to optimize the efficiency of their products to diminish electric consumptions. In the case of refrigerators, the compressor is the component characterized by the highest electric absorption. The aim of the present study is to develop a compressor control algorithm for an industrial chiller to improve the performances and reduce the energy consumption. Results obtained by the authors in previous studies, encourage to the implementation of the fuzzy logic for regulator design. In particular a refrigerator for pastry shop was considered as the object of the study. A fuzzy controller was developed for the particular application by software simulation. The controller has greater performances of the PID and optimal linear regulators designed by the author for the same system. Subsequently a fuzzy adaptive procedure was defined to generalize the control algorithm, and allow the implementation of the controller to different refrigerators.Copyright

Radial Turbines Diagnosis in Turbocharging Application

The main purpose of this work is the development of a diagnostic procedure for radial turbines installed on internal combustion engine turbochargers. The study is part of a wider research activity regarding the development of diagnostic systems dedicated to cogenerative engine. The proposed procedure is able to formulate a judgment about the turbines efficiency through the real-time evaluation of an effective performance index, only on the basis of pressure measurements across the turbine. Such diagnostic procedure was developed in reference to experimental data gathered in two acquisition campaigns performed before and after a consistent maintenance intervention on engine turbines. The first part of the work approaches turbine failures issues, while in the second one experimental results are presented and analyzed. Finally, the study deals with the definition of some turbine health state indices and their test in reference to the experimental data cited above. A particular index was validated as useful to be implemented in a diagnostic procedure for detection of turbine degradation.

Performance Improvement of an Industrial Chiller Through the Optimization of the Control Logic

According to the tasks agreed within the Kyoto protocol, in terms of CO2 emissions reduction, the European Community is promoting energy saving. The introduction of energetic classification for electrical household appliances, makes consumption as a parameter of choice for consumers and thus represents a relevant tool for the promotion of energy saving. Therefore the interest in the evaluation and minimization of electric consumption for industrial appliances is also evident. The aim of the present study is to investigate alternative control solutions to improve the performance and diminish the energy consumption of an industrial chiller. This was carried out through software modeling of the system and experimental validation of the best performing solutions. Simulated trends show good agreement with experimental data and allow the definition of a suitable PID controller that performs good temperature regulation while slightly reducing energy demand. Further ameliorations were considered and preliminary results are shown both for optimal control and neural modeling of the chiller. Results obtained encourage to continue in the development of better performing regulators, also through neuro–fuzzy logic control.Copyright