Investigation of a liquid desiccant system for air dehumidification working with an ionic liquid in a two-stage refrigeration system for cold stores.

Electrically-driven compression chillers are the commonly used technology for cooling and dehumidifying air. Open sorption systems are an alternative to conventional air dehumidification technology. The separation of the cooling of the air and the air dehumidification by a combination of a closed absorption chiller for cooling and a thermally-driven open sorption system for dehumidification bears the potential to reduce primary energy consumption because part of the heat rejected from the closed absorption refrigeration cycle can be used to drive the dehumidification cycle in a two-stage process. The desiccant must achieve a high vapour pressure depression at the available driving temperature level of the heat rejected from the closed absorption refrigeration system in order to reach a low absolute air humidity which is required for low temperature refrigeration in order to avoid frost. Ionic liquids may fulfill this and other requirements since to a certain extent the vapour liquid equilibrium can be designed according to the boundary conditions of the respective application. In the paper at hand, the experimental results of a liquid desiccant system for air dehumidification working with an ionic liquid designed for an application down to -20°C for cold stores are presented. The system under investigation has been built up at the TU Berlin. The experiments presented here focus on the dehumidification capacity of the system.