Parametric and comparative study on enhanced microchannel membrane-based absorber structures for compact absorption refrigeration

Novel and simple enhancement structures are proposed to improve the absorption characteristics of flat membrane-based absorbers. Firstly, a parametric study is conducted to elucidate the effect of membrane parameters on the absorption process using a two-dimensional CFD model. Results indicate that the most critical membrane parameter affecting the absorption rate is the membrane porosity compared with the membrane thickness and pore diameter. The recommended membrane porosity, pore diameter, and thickness are 0.8, 1 μm, and 60 μm, respectively. Then, a comparative study on the proposed enhancement structures is carried out. Results demonstrate that inclined groove induces solution swirling while increasing the effective heat transfer areas, and thus the absorption performance is significantly improved at lower solution pressure drops. Flow visualization shows that two counter-rotating vortices are generated inside HG (herringbone groove) and SHG (staggered herringbone grove) structures, and the longitudinal swirling flows are induced inside IG (inclined groove) and SIG (staggered inclined groove) structures. Comparisons indicate that the HG structure improves the absorption rate by 1.62 times, reducing the solution pressure drop by 19.01%. These changes from the IG structure are 1.56 and 20.77%, respectively. Therefore, the IG and HG structures are recommended.