Modelling vapour compression cycles with R744 for residential heat pumps adapted to the Spanish climate

R744 heat pumps appear as an ideal solution to produce heating, cooling and domestic hot water (DHW). The transcritical cycle has the potential to produce high temperature hot water simultaneously with other demands as heating or air conditioning, however the low trans-critical temperature of CO₂ is a natural limitation for applications in warmer climates. R744 heat pumps are now used in Nordic countries, but they are still a challenge for hotter climates, for which there are R&D efforts to enhance their COP. Among the technologies to implement, ejectors appear to improve the cycle performance in percentages that go from 10 to 20%, according to previous works from the literature. This paper details the study of residential heat pumps with R744 to produce combined heating/cooling and DHW under different climatic conditions that occur in Spain. The COP for R744 heat pumps supplying combined heating/cooling and DHW demand is improved by implementing ejectors, however the improvement is not as high as stated in other research studies