Numerical exploration of performance enhancement in falling film liquid desiccant cooling system using additive materials

Abstract

ABSTRACT Liquid desiccant dehumidification has garnered significant attention due to its numerous benefits. This study focuses on enhancing the efficiency of liquid desiccant dehumidification through the use of modified solutions, particularly by incorporating polyvinyl pyrrolidone (PVP) as an additive. PVP is a nonvolatile, odorless, and nontoxic surfactant that was selected to enhance the dehumidification performance of the liquid desiccant system. Computational fluid dynamics was employed to investigate the dehumidification performance of falling film liquid desiccant systems. The study aims to assess the impact of PVP, solution parameters, and moist air conditions (humidity concentration, temperature, and flow rate) on dehumidification effectiveness. The specific objectives of the numerical simulation include analyzing performance metrics such as dehumidification rate and effectiveness to evaluate the enhancement in the falling film liquid desiccant cooling system. The selection of lithium chloride (LiCl) as the base solution and PVP as an additive at 0.4 wt% is highlighted as a key aspect of the study. The findings indicate that PVP significantly improves dehumidification effectiveness by reducing the contact angle of liquid solution on the surface plate and increasing the surface wetting ratio, thereby enhancing moisture transfer capacity. Optimal dehumidification performance is achieved with the combination of LiCl and PVP at the specified concentration. The study reveals that increasing solution or air inlet temperature reduces the dehumidification rate, while raising solution or air inlet concentration, velocity, or air humidity strengthens the dehumidification process. Additionally, the efficacy of dehumidification increases with solution velocity but decreases with solution intake concentration or air velocity. Overall, the results demonstrate an average relative increase of 21.6% in dehumidification rate and 17.4% in dehumidification effectiveness, underscoring the effectiveness of PVP in enhancing vapor absorption capability and overall system efficiency in Liquid Desiccant Cooling systems (LDCs). This enhancement is attributed to the reduction in surface tension of the liquid desiccant, as evidenced by the decrease in contact angle from 58.6° to 28.9°.