Analysis and optimization of water-loop systems with low-GWP multipurpose heat pumps
Heat pumps are among the most promising technologies to reduce greenhouse gas emissions, especially when combined with low-GWP refrigerants. In this context, the combination of heat pumps and water loops for heat dissipation and valorization has recently gained interest. This study evaluates the performance of heat pumps employing different refrigerants (R454B and R290) within the water-loop system of a supermarket in London, where a water loop is used for heat dissipation from refrigerated counters. The water loop operates at a nominal flow rate of 11.5 l/s and a supply temperature of 18 °C. Peak heat loads reach 95 kW in winter and 270 kW in summer. The existing setup includes a dry cooler, two R454B reversible air-to-water heat pumps, and an R454B water-to-water heat pump active in winter for building climatization by exploiting the water-loop heat. Two retrofit scenarios are compared. The first configuration includes the pre-existing dry cooler, two R290 air-to-water heat pumps and an R290 multipurpose heat pump, which is able to release the condensation heat either to air or to water for building climatization. The second solution involves only R290 multipurpose heat pumps, used to thermally stabilize the water loop, satisfying the building heating demand. In order to compare the different solutions, energy analyses are performed through hourly simulations. Results show that both retrofit alternatives outperform the current system in terms of energy efficiency, environmental impact, and economic feasibility, with the second configuration offering the best overall performance (seasonal efficiency up to +20% of the current setup). The study demonstrates the viability of the proposed system and suggests directions for further technological development of water loops with multipurpose heat pumps using natural refrigerants in commercial, industrial, and district heating/cooling applications