Experimental Investigation of a Falling Film Horizontal Tube Bundle Absorber for Thermal Absorption Storage with H2O/LiBr
Abstract
Compared to state-of-the-art sensible and latent heat storage techniques, thermal absorption storage systems can theoretically achieve a significantly higher energy storage density, which increases with the concentration difference between diluted and concentrated sorbent solution. In the absorption process, the concentration difference can be increased by reducing the sorbent volume flow at the absorber. From first principles, this causes a reduction of the absorbed water vapor and therefore also of the heat removed from the absorber. Furthermore, a low sorbent volume flow can reduce the wetting of the absorber surface, which leads to a further reduction of the absorbed water vapor. Therefore, in the scope of developing a novel absorption cold storage process with H2O/LiBr, we experimentally investigated the impact of reducing the salt solution volume flow on the mass and heat exchange on a falling film horizontal tube bundle absorber. In the experiments, we stepwise reduced the specific salt solution volume flow distributed over the absorber from 100 l/(h∙m) to 20 l/(h∙m) and determined the mass and heat transferred. We thereby experimentally quantified the dependence of the specific salt solution volume flow on the concentration difference and the area-specific heat flow for the tested absorber. The results indicate that reducing the specific salt solution volume flow is an effective way to significantly raise the concentration difference on a falling film horizontal tube bundle absorber. Hence, this absorber type seems to be suitable for thermal absorption storage systems with H2O/LiBr.