Experimental and numerical investigation of a novel hybrid deep-dehumidification system using liquid desiccant

Abstract

Desiccant-based hybrid air-conditioning systems have recently become popular owing to a reduction in their energy consumption. In addition to the dehumidification process, regeneration is a necessary process in a hybrid system, and in all previous studies the regenerator (REG) has been separated from the liquid desiccant dehumidifier (DEH), which implies the need for a complex duct configuration and a large equipment space. In the present study, a novel hybrid liquid desiccant–heat pump air-conditioning system combined with a cooling coil is proposed for deep dehumidification with a supply air humidity ratio of below 5 g/kg, where the REG, condensing DEH (cooling coil), and liquid desiccant DEH are cascaded. This system not only maintains the energy performance advantages of hybrid systems over conventional systems, it also simplifies the layout of the entire system and guarantees a compact system structure, particularly for buildings with an existing central air-conditioning–chilled-water system. Using the proposed system, a coefficient of system performance (COPsys) of 2.4–3.2 has been obtained experimentally with an supply air humidity ratio of 2.1–4.5 g/kg. Despite the compact system structure, when the air is processed from 30 °C and 20 g/kg to 4 °C and 3.6 g/kg, the proposed system achieves a superior COPsys of 3.3 with an improvement of 13.8% when compared with a conventional liquid desiccant dehumidification system.