Experimental investigation on a modified lightweight ejector-enhanced mechanical humidity control system with low-GWP refrigerant

This study experimentally investigates a modified ejector-enhanced mechanical dehumidification system (EMDS) designed to overcome limitations of conventional systems, such as the use of high-GWP refrigerants and significant throttling losses. The system employs environmentally friendly R290 (GWP = 0.02) combined with compact heat exchangers (5 mm finned-tube evaporator and microchannel condensers) to minimize refrigerant charge. A key innovation is the integration of an ejector to recover part of expansion work, which provides a pressure lift of up to 80 kPa. This pressure-boosting effect enables dual-temperature condensation, effectively reducing the average condensing temperature and enhancing system efficiency. Specifically, the ejector is placed at the outlet of the high-temperature condenser. The two-phase refrigerant at the high-temperature condenser outlet is used as the main fluid to drive the ejector and to entrain the vapor-phase refrigerant from the vapor-liquid separator at the outlet of the low-temperature condenser. Experiments comparing three operational layouts (single condenser, dual condenser, and ejector modes) under standard conditions demonstrate the superior performance of the ejector mode. The ejector layout achieved significant improvements in dehumidification capacity ( DC ) and energy factor ( EF ) across various temperature and humidity conditions, with performance enhancements exceeding 20% compared to the single condenser mode. Furthermore, optimization of the electronic expansion valve opening further improved performance. The results confirm that the ejector's work recovery and pressure lift mechanism are central to improving energy efficiency, highlighting the system's important engineering significance for advancing low-carbon dehumidification technologies.