Synergistic regulation of thermal effect-solution recirculation on liquid desiccant air dehumidification in extreme hot-humid climates

High temperatures, humidity, and solar radiation are typical climate characteristics of regions with extreme hot and humid climates, as well as isolated islands. The control of the thermal environment in buildings often relies on air conditioning and refrigeration systems. Therefore, exploring efficient systems and operational modes is crucial for the development of these areas. This paper presents an analytical model for an internal cooling/heating liquid desiccant dehumidification system to explore the synergistic regulation effect of thermal effect (improved mass transfer due to enhanced heat transfer) and solution recirculation. Furthermore, the system integrated solution recirculation in four modes, which allowed for the independent control of dehumidification and regeneration mass flow rates, thereby optimizing performance. Experimental data were then used to verify the proposed model. Additionally, a parametric analysis of system performance was conducted to investigate the effects of the solution recirculation ratio and ambient air parameters. Subsequently, a comparison was made with the adiabatic system to prove the positivity of the synergistic effect of thermal effect - solution recirculation. The proposed system demonstrated a significantly improved energy effectiveness ratio (EERsys) under standard operating conditions compared to the conventional system. The maximum EERsys values of the four modes (NR: no recirculation; DR: only dehumidification recirculation; RR: only regeneration recirculation; DRR: both dehumidification and regeneration recirculation) were 0.221, 0.397, 0.284, and 0.329, respectively, with a maximum improvement rate of 48.9 % owing to solution recirculation. This system is adaptable to varying environmental conditions, particularly excelling in high-temperature environments with stable performance and minimal fluctuations in air temperature and humidity. In addition, comparative analysis with a conventional cross-flow liquid desiccant system revealed notable improvements, with moisture removal rate per unit of energy consumption (MPE) increasing by 388.9 %, 369.2 %, and 239.1 % in DR, RR, DRR mode, respectively. This research emphasizes the energy-saving potential and adaptability of the internally cooled/heated liquid desiccant dehumidification system, offering valuable insights for optimizing recirculation strategies in extreme hot and humid climates and isolated island areas.