Performance evaluation of PVA-LiCl coated heat exchangers for next-generation of energy-efficient dehumidification

Abstract

The conventional vapor-compression air-conditioner operates with low efficiency because of the intrinsic coupling between sensible and latent cooling. Its efficiency can be improved via employing solid desiccant coated heat exchangers (DCHEs). Dehumidification performance of a DCHE is influenced by the nature of the selected desiccant material. The key attributes of a desiccating material include higher sorption capacity and faster kinetics coupled with its ability to regenerate at a low temperature. In this paper, we developed different concentrations of composite polymer desiccant with polyvinyl alcohol (PVA) and lithium chloride (LiCl). Experiments on isotherms indicated that the composite PVA with a greater concentration of LiCl displayed superior sorption capacity; however, due to the occurrence of deliquescence phenomenon, the most effective concentration of LiCl was observed to be 50w%. The equilibrium sorption capacity of PVA-LiCl (50w%) was 177.2% in contrast to only 28% for silica gel. Further, kinetics revealed that silica gel would take twice the time to adsorb an equivalent amount of water vapor as absorbed by composite polymer desiccant. Our experimental findings on dehumidification performance and process efficacy revealed that the use of composite PVA on DCHEs yielded about 20–60% improvement in moisture removal capacity and thermal coefficient of performance. Lastly, energy analysis indicated that the novel composite polymer DCHE enabled high moisture removal rate even at lower regeneration temperature and recorded a significant saving of 54% in specific power consumption.