Comparative studies on two types of adiabatic membrane-based absorbers/desorbers in absorption chiller

This study compares two types of compact and efficient absorbers and desorbers—plate frame membrane (PFM) and hollow fiber membrane (HFM)—for use in absorption chillers. Experiments were conducted to determine the mass transfer coefficients and fraction factors necessary for accurate modeling. Under identical hydraulic diameters, PFM modules consistently exhibit higher absorption and desorption rates than HFM modules with smaller solution pressure drops. A detailed analysis of the geometric effects on sorption rates and pressure drops reveals that smaller channel widths, channel heights, tube diameters, and higher channel/tube numbers enhance sorption rates but also increase pressure drops. Using MATLAB's optimization toolbox, the optimal geometries for maximizing volumetric cooling capacity were identified: 1175 kW/m³ for the PFM absorber (PFMA), 3510 kW/m³ for the HFM absorber (HFMA), 1994 kW/m³ for the PFM desorber (PFMD), and 4106 kW/m³ for the HFM desorber (HFMD). The absorption and desorption processes along the module length were also compared, showing that 80 % of these processes occur within the first 40 % of the module length and are completed within 80 % of the module. This research provides a comprehensive comparison of two adiabatic membrane-based absorbers and desorbers, facilitating the optimization and development of compact and efficient absorption chillers.