22 May 2008

CHARACTERISTICS OF THE MEMBRANE UTILIZED IN A COMPACT ABSORBER FOR LITHIUM BROMIDE/WATER ABSORPTION CHILLERS


This study aims at investigating experimentally and analytically the characteristics
and properties of a membrane contactor utilized to design compact absorbers for lithium
bromide/water absorption chillers. The main focus of this study are the factors that influence
the water vapor transfer flux into a lithium bromide/water solution in confined narrow
channels under vacuum conditions, as well as the properties limits for utilization in compact
absorber design. The results indicate that the desired membrane characteristics for this
application are as follows: high permeability to water vapor, hydrophobic to the aqueous
solution with high liquid entry pressure to avoid wettability of the membrane pores and no
capillary condensation of water vapor to avoid blocking of the pores. For practical use, this
membrane should have a thin hydrophobic microporous active layer with a thickness up to
60 µm, mean pore sizes around 0.45 µm and a porosity of up to 80%. The active layer
should be attached to a porous support layer to meet the strength requirements needed for
practical use in the absorber of lithium bromide water absorption chillers.