TECHNICAL PERFORMANCE ANALYSIS OF A CO2 BASED COOLING CYCLE WITH WORK RECOVERY THROUGH EXPANDER

This Thesis presents a comprehensive study on the design, optimization, and analysis of a cooling cycle system aimed at achieving enhanced efficiency and sustainability by the usage of carbon dioxide as refrigerant and the implementation of a free piston expander (FPE) in the cycle. Two different companies collaborate on this project, the first one SCM Frigo S.p.A. where the tests were carried out, the second one is Turboalgor which has recently registered a second patent for a technology that allows significant energy savings in transcritical CO2 refrigeration systems. This prototype is made up of two main components, the first one is a free piston expander (FPE) that converts the energy of high-pressure flash gas, coming from the receiver, into mechanical energy. This energy is then reused to pre-compress the refrigerant fluid coming from the evaporator before entering the main compressor. The second one is the fluid control unit (FCU) that allows to move the piston with a defined frequency to maximize its performance. To validate the assumption of the improving of the energy saving, a FPE implemented cooling machine is run and the principal variables are monitored in order to calculate the main energy parameters of the cycle. Then, these parameters are compared to the ones obtained with a simulation software belonging to a FPE non-implemented cooling machine. The comparison underlines how the implementation of this component wellaffect the energy consumption, namely how it considerably helps in saving energy, going up to 25% of energy saving.