Heat and mass transfer of composite desiccants for energy efficient air dehumidification: Modelling and experiment

• Heat and mass transfer model dynamics of composite desiccants.
• Model is validated against experimental observations of different desiccants.
• Experiments performed on moisture adsorption, regeneration and pressure drop.
• Energy index indicated composite desiccants outperformed silica gel by 11%.

Desiccant dehumidification technology provides a method of drying air before it enters a conditioned space. When combined with conventional cooling systems, desiccant dehumidification provides an energy-efficient way of supplying thermal comfort air. This paper presents a combined experimental–analytical study on the heat and mass transfer dynamics of composite desiccants during air dehumidification. The composite desiccants are silica gel–calcium chloride, silica gel–lithium chloride, and silica gel–polyvinyl alcohol (PVOH). The derived model is validated against experimental observations of different desiccant types with silica-gel as the host desiccant. Predictions are shown to agree well with extensive experimental measurements conducted using an in-house experimental setup as well as data published in the literature. Experiments were conducted on several promising composite desiccants. The effects of process air velocity, inlet air temperature and humidity on moisture removal capacity, regeneration rates and the associated pressure drops were investigated. Relying on a holistic energy performance index, desiccant coefficient of performance (DCOP), results have indicated that the moisture removal capacity, regeneration rates and the associated pressure drops of composite desiccants outperformed that of pure silica gel by at least 11%.