Experimental performance evaluation of a composite superabsorbent polymer coated heat exchanger based air dehumidification system

Abstract

Decoupling sensible and latent cooling loads by using desiccant coated heat exchangers (DCHEs) is an effective way to promote air-conditioners’ energy efficiency. At the moment, there is still room for existing DCHEs to improve because of the restricted adsorption capacity of the desiccants used and the requirement of higher regeneration temperatures. In this paper, we have developed a composite polymer desiccant comprising a hydrophilic superabsorbent polymer and a hygroscopic salt. We have conducted a series of experiments to evaluate its static and dynamic sorption characteristics. The new composite desiccant showed up to 12 times improvement in the isothermal water sorption capacity and yielded 2.1 times enhancement in sorption rate when it was benchmarked with desiccants such as silica gel, zeolites, and metal-organic frameworks. Dynamically, the new DCHE was able to regenerate effectively between 40 and 50 °C in contrast to the previous requirement of 70–90 °C. Also, due to its excellent water retention capacity, the cooling water could be maintained at temperatures lower than the air’s dew point without any issue of deliquescence. Further, it could operate with cycle times of 10 min vis-à-vis earlier DCHE systems that were confined to 20–300 s. Lastly, we studied the energy savings potential of incorporating the composite polymer based DCHE to a chiller system. Key results indicated that for a fully fresh air configuration, energy savings up to 50% can be achieved. On the other hand, with 70% return air recirculation, DCHE has the potential to reduce 20% of the electrical energy consumed by the chiller.