Impact of micromixing on performance of a membrane-based absorber

In this study, microstructures are employed to manipulate thermohydraulic characteristics of the lithium bromide (LiBr) solution flow in a membrane-based absorber in order to enhance the absorption rate. In a membrane-based absorber, the liquid absorbent is constrained between a solid wall and a highly permeable membrane, thus facilitating manipulation of the flow properties. Recent numerical studies have shown that transport mode in a laminar flow can be changed from diffusive to advective via the implementation of surface microstructures on the flow channel walls. Here, we experimentally evaluate the enhancement in absorption rate caused by the introduction of microstructures on the solution flow channel wall of a membrane-based absorber. The experiments are conducted in a fully instrumented membrane-based absorption refrigeration system. The geometry and dimensions of the microstructures are based on the optimal values determined in our previous numerical studies. Absorption rates as high as that of a 100-μm-thick solution film (in the absence of wall features) is achieved but at two orders of magnitude less pressure drop. The achievement of a high absorption rate at a relatively low solution pressure drop in the proposed approach enhances the prospect of developing large-scale membrane-based absorbers.