Enhancing the dehumidification performance of LiCl solution with surfactant PVP-K30

Adding additives into liquid desiccant cooling system (LDCS) can enhance its mass transfer performance. However, the additives proposed by previous researchers are volatile and odorous which is a great threat to the indoor air quality. Therefore, this study introduced a new kind of non-volatile, odorless and nontoxic additive, i.e. polyvinyl pyrrolidone (PVP-K30), into LDCS for better dehumidification performance. Comparative studies were carried out to investigate the dehumidification performance of LiCl solution with and without the additive PVP-K30. The mass fraction PVP-K30 was chosen to be 0.4%. The results show that the dehumidification rate and dehumidification effectiveness have an average relative increment of 22.7% and 19.9% respectively with the addition of surfactant. The enhancement is attributed to the reduction of surface tension of liquid desiccant which is demonstrated by the decrement of contact angle from 58.5° to 28.0°. Correspondingly, the wetting ratio of desiccant falling film on plate has a relative increment of 16.9% from 82.7% to 96.7%, and the film thickness of falling film decreases from 0.681 mm to 0.583 mm. To sum up, the adding of additive PVP-K30 into LDCS provides an effective and practical way to enhance the vapor absorption performance in an absorber and so does the system efficiency.