A novel spherical micro-absorber for dehumidification systems

Abstract

In this work, a novel design concept for absorbers used in dehumidification systems is proposed to overcome the practical challenges of the conventional packed-column absorbers. In the proposed design, spherical micro-absorbers (microcapsules) that contain a liquid LiBr desiccant inside a semi-permeable polymeric membrane shell are produced by using a custom-built microfluidic technique. The produced microcapsules are capable of containing the salt during crystallization. The X-ray diffraction analysis has confirmed that the observed crystals in the microscopes images were indeed for the encapsulated (LiBr) salt. Due to the indirect contact between the liquid desiccant and the process air, problems such as solution carryover and corrosion associated with packed-column absorbers can be eliminated. The collected sorption data show that the spherical microcapsules offer a high sorption capacity of 1 gw/gdry under 80% relative humidity. The proposed microcapsules offer surface-to-volume ratios between 6,000–12,000 m2/m3, which is up to two orders of magnitude higher than the conventional packed-column absorbers (200–600 m2/m3). The produced micro-absorbers can withstand a compression force up to 2 × 105 their weight, elastically expanded during the absorption process without rupture, and did not show a leakage or a reduction in capacity even after an accelerated test of 200 sorption-desorption cycles.