The optimization of industrial refrigeration systems for the fruit and vegetable sector

The thesis focuses on refrigeration plants design criteria to define the optimal technological solutions for fruit and vegetable cold storage, aiming to improve both the system energy efficiency and the final product quality. The study has been carried out through a combination of industrial-scale test using real-time system monitoring in the cold rooms available in the UNIBAS-MAClab and in local packing house. The collected data was used to validate the simulation model developed. In the first phase, tests were carried out in an industrial cold storage facility (in the packing house), where temperature and humidity were continuously monitored under evaporation conditions vary according to the test protocol. Results showed that, with a direct expansion system and a temperature difference (ΔT) of about 5 °K between the air and the evaporator surface, it is possible to maintain the relative humidity in the range 91–93%, which minimizes product dehydration while ensuring efficient energy use. The second phase, initiated in the MACLAB and subsequently extended to the industrial cold room, focused on the monitoring and analysis of key refrigeration parameters — including pressures, temperatures, and power consumption — to evaluate the system’s real-time performance and stability. Based on these observations, an intelligent defrost control strategy was developed and benchmarked against conventional time-based methods. The proposed approach achieved up to a 70% reduction in defrost cycles, leading to lower energy consumption and improved overall system efficiency. A MATLAB simulation model was also developed to estimate fruit and vegetable weight loss under various thermo-hygrometric conditions, supporting predictive evaluation of storage performance. Finally, an energy analysis was performed to evaluate the impact of inverter-driven components on system performance. The use of inverters for the compressor, condenser fans, and evaporator fans led to energy savings of up to 34%, with corresponding reductions in CO₂ emissions and operating costs. Overall, the results demonstrate that an integrated, data-driven approach combining experimental testing, smart control strategies, and dynamic modeling can significantly enhance the efficiency, reliability, and sustainability of refrigeration systems used in the fruit and vegetable cold storage sector.