Experimental study for practical application of liquid-desiccant air-conditioning system using hollow-fiber permeable membranes

Dehumidification is essential in air conditioning during hot and humid summers. A liquid- desiccant air-conditioning system using hollow-fiber permeable membranes can be an effective solution. This system dehumidifies humid air by indirectly contacting it with a liquid desiccant that flows through multiple hollow-fiber membrane units. Several experiments were conducted to evaluate the feasibility of the system. The experiments simulated this system and measured the absolute humidity changes in the air before and after passing through the membrane units. In the experiments using a single membrane unit, the dehumidification and regeneration performances were tested for various membrane types and concentrations of the desiccant solution (in this case, a lithium chloride solution). The results revealed that the membrane type affected the absolute performance values and clarified the dehumidification behavior at various concentrations. Appropriate adjustment of the desiccant solution concentration may contribute to the enhancement of system efficiency. In the experiments using multiple membrane units, the absolute humidity difference reached a maximum of approximately 9 g/kg’. This result approaches the target dehumidification level necessary to guide Japanese summer outdoor air into the comfort zone for humidity, which indicates the significant potential for a practical system.