Continuous tuning of ejector parameters via zeotropic component migration for optimising high-temperature heat pump

As the temperature lift increases, heat pump performance declines due to rising throttling losses in expansion valves. Ejectors present a promising alternative, enabling power recovery from the throttling process. However, fixed-geometry ejectors suffer performance degradation under off-design conditions. Here we propose leveraging the component migration characteristics of zeotropic refrigerants to continuously adjust critical ejector parameters by modulating the quality. This approach enables optimal performance across varying conditions without mechanical modifications. A vapor-injection heat pump cycle incorporating a component-adjustable ejector with three tunable parameters is developed. The concept of equivalent ejector efficiency was introduced, and the adjustment capability of typical high-temperature refrigerant mixtures was investigated, such as mixtures of butane (R600) and synthetic refrigerants (R245fa). Results show that, at a nominal heating capacity of 100 kW, R600/R245fa achieves a lower adjustable limit of -5%, compared to -2% for R1224yd(Z)/R1233zd(E) (synthetic refrigerant mixtures). These findings demonstrate the feasibility of efficient operation of fixed-geometry ejectors under variable conditions. The proposed system and regulation strategy offer a promising design alternative for industrial high-temperature heat pump applications.