Experimental performance comparison of three flat sheet membranes operating in an adiabatic microchannel absorber

Abstract

A microchannel absorber working adiabatically with the H2O-LiBr pair was tested experimentally using three different nanofibrous flat membranes separating the vapour from the solution. Pore diameters of the membranes were 1 and 0.45 μm, and thicknesses vary from 25 to 175 μm. The experimental absorption rates varied from 1.5 · 10−3 to 2.6 · 10−3 kg/m2 s varying linearly with the solution mass flow rate circulating through the channels. The reduction in pore diameter from 1 μm to 0.45 μm induced the need for higher pressure potential or solution mass flow rate to obtain similar performance. Relationships between changes in diameter pore and membrane thickness from previous models were used to quantify the effect of these membranes characteristics on the absorption ratio. The analytical results compared well with our experiments. In the present design, the solution film thickness was 150 μm and the solution mass transfer resistance dominated the process. The experimental overall resistances, compared with calculated values from correlations used in previous models, showed differences below 30%.