Numerical performance of a water source transcritical CO2 heat pump with mechanical subcooling

In order to improve their efficiency, transcritical CO2 heat pumps need resort the use of a subcooling method. Among different methods, dedicated mechanical (DMS) systems and internal exchangers (IHX) are currently more promising technologies. This paper presents numerical study water source pump during hot generation using methods. Ten configurations, including both, IHX DMS, separately combined in layouts, some them not studied previously, analyzed numerically under same operating conditions compare performance. A description model is presented: compressors modeled performance curves provided by manufacturers, expansion valves as isenthalpic, deriving correlations for evaporation/condensation pressure transfer rate obtained 1D cell-by-cell discretization method previously applied all exchangers. Results presented heating show that most configurations analyzed, DMS does system compared base with IHX. There only an improvement efficiency two those which main cycle coupled flowing first through evaporator auxiliary then gas cooler cycle. Specifically, IHX, configuration provides best results (Conf. F* according nomenclature used this work) gives average improvements around 26% almost 160% capacity, while optimum reduced 12%. Even more, other authors (indirect without Conf. F improves 8.5%, decrease total capacity lower than 1% similar pressure. The also compressor way distributed among have important influence on system, although depends studied. For F*), when (55% comes from cycle), mostly heated (85% flow condenser cycle, 15% cycle).