Exergy analysis of dehumidification systems: A comparison between the condensing dehumidification and the desiccant wheel dehumidification

This paper presents a framework of exergy analysis to evaluate the performance of the condensing dehumidification and the desiccant wheel dehumidification. The performance of two dehumidification methods are compared for pure dehumidification purposes based on proposed dehumidification systems that undertake only the latent load. An air-source heat pump is adopted in the dehumidification systems to serve as the cold and heat source. Based on thermodynamic perfectibility theory and the laboratory experiment of the desiccant wheel, the power requirements and exergy efficiency of the two dehumidification methods are analyzed and compared under 17 sets of operating conditions. The coefficient of performance of the heat pump in the condensing dehumidification system is 2-3 times higher than in conventional air-conditioning systems. Environmental factors that influence the performance of each dehumidification method are identified. The performance of condensing dehumidification is affected mostly by the humidity ratio of indoor air, whereas the outdoor air temperature has a minor impact. The humidity ratio difference between indoor and outdoor air is the most influential factor in the desiccant wheel dehumidification, followed by the outdoor air temperature. Under the operating conditions examined in the present study, the condensing dehumidification shows 3-4 times higher exergy efficiency than the desiccant wheel dehumidification. Therefore, the condensing dehumidification should be preferred over the desiccant wheel dehumidification for typical indoor dehumidification applications.