Comparison between microchannels and fin&tube heat exchanger on a R290 reversible air-to-water heat pump: performance, defrosting and refrigerant charge analysis

The current global efforts to increase energy efficiency and environmental sustainability have highlighted the need for innovative technologies to reduce greenhouse gas emissions and minimize energy consumption. International policies aim at reducing the consumption of fossil fuels by promoting the generation and use of electricity through cleaner technologies. Among these, heat pumps have emerged as a key solution for both residential and industrial applications. By efficiently transferring thermal energy from one environment to another and utilizing renewable energy sources such as ambient air, groundwater or geothermal heat, heat pumps have become a crucial element in modern heating and cooling systems. Despite their high efficiency and sustainability, heat pumps are now facing stricter regulations, particularly regarding the refrigerants used in their operation. This thesis examines the feasibility of integrating a newly designed microchannel heat exchanger (MCHX) as the source heat exchanger in an air-to-water reversible heat pump using propane as refrigerant. The adoption of this kind of heat exchangers aims at significantly reducing the refrigerant charge required by the system. The methodology employed in this work includes both simulations and experimental tests, enabling a comparison between the obtained results and the verification of the simulation software. The findings indicate the effectiveness of microchannel technology, resulting in a significant reduction in the refrigerant charge. The newly designed distribution system proved to be effective, and the redesigned fins exhibit lower water retention, leading to improved performance during the frosting and defrosting cycles. Nevertheless, there is still room for further optimization in the future.