Experimental investigation on the performance of a propane (R290) heat pump working with a vapor injection compressor

Heat pumps are recognized as a crucial technology in the transition toward sustainable energy systems, in line with European Union policies aimed at reducing carbon emissions and improving energy efficiency. The main challenge for the installation of air-source heat pumps (ASHP) in cold regions is their loss in performance at low ambient temperatures. Vapor injection technology has emerged as a promising solution to improve heat pump efficiency under such conditions. This thesis discusses the testing of a heat pump prototype featuring vapor injection, utilizing propane as the refrigerant and a twin-rotary compressor, a configuration for which the available research is currently limited. Natural refrigerants such as propane are gaining popularity due to their low Global Warming Potential (GWP) and ozone depletion potential (ODP). The new configuration was tested under a variety of operating conditions, with particular focus on low air temperatures, to assess performance improvements resulting from vapor injection. The heating capacity and the calculated COP increased for all injection tests, compared to those without injection. As expected, the highest gains were observed at higher pressure ratios. The compressor discharge temperature showed both positive and negative variations, making it difficult to establish a clear relationship with the injection. In cooling mode, the cooling capacity and EER also showed increases for all injection tests. Further research may focus on modeling vapor injection systems to predict their performance across a wider range of conditions, as well as on developing new configurations applicable to commercial solutions optimized for operation in cold regions.