Desorption characteristics of a lab-scale tube-bundle heat and mass transfer unit
Abstract
Thermal energy storages tackle the load shift and can balance the availability of supply and demand. Types of storages are sensible, latent and thermo-chemical. The selection of the storage materials – and thus the storage type - is one of the key tasks and depends on the time length of energy storage as well as on power and capacity demand. Because of their high potential energy density and thus their low volume, absorption storages are under investigation. Regarding their heat and mass transfer coefficient for charging and discharging, tube-bundles are an option to form falling films and keep the flexibility of multiuse as absorber, desorber, evaporator and condenser. In this paper, the application of a tube-bundle heat and mass exchangers (HMX) and its characteristics in the charging process step for liquid sorbate i.e. desorption of water (vapor) is presented. The sorbent-sorbate combination is aqueous sodium hydroxide and a concentration difference of 20 wt.% is aimed to reach a high energy storage density. The characterization of different HMX versions in desorption modus are presented in this paper. Even if the best performing HMX versions are not the same in absorption and in desorption modus, it was found that some adaptations could lead to a HMX working decently in both modus.