Humidity control in confined building spaces using a liquid desiccant dehumidifier

This dissertation investigates the application of a liquid desiccant dehumidifier system in confined building spaces. The proposed dehumidifier system controls the humidity ratio of the confined space when a large amount of moisture is released, and uses ambient space air for regeneration when the spaces produce no moisture. The generated moisture air during the regeneration period can be discharged through continuous exhaust ventilation. In the dissertation, the physical system design is described and dehumidifier performance models and CFD models are integrated and developed. Numerical simulations were conducted to compare the results of a conventional ventilation system and a dehumidifier system. The results of the simulations show that the dehumidifier system reduced moisture condensation by 24.0% over a conventional exhaust ventilation system. It was also found that the configurations of the confined space and dehumidifier, e.g., the locations of the inlet air, exhaust air and moisture source, significantly impacted the space air humidity ratio and temperature distributions. The theoretical analysis in the feasibility investigation suggests that an optimal dehumidifier system reduces moisture condensation and saves energy. Thus, the system optimizations are achieved by three approaches: optimal dehumidifier design parameters, improved dehumidifier location, and optimal regeneration period. The results of the optimizations show that an improved dehumidifier location can reduce moisture condensation by 33.1% over the original dehumidifier location in the feasibility investigation. In addition, use of an optimal reheat desiccant temperature can reduce the regeneration period by 16.0% and the total performance period by 12.5%. Yearly energy consumption and cost were compared between a base ventilation system and an optimal dehumidifier system for a bathroom in a hotel at two locations of Miami and Omaha. The comparisons were conducted for both systems with the same amount of accumulated condensation on the surfaces of the space. The total yearly electricity energy consumption in an optimal dehumidifier system can be saved by 63.7% in Omaha and 65.2% in Miami. The heating consumption can be saved by 66.7% in Omaha and 66.7% in Miami. The average yearly energy cost saving is around 65.5%