Heat and mass transfer performance comparison of various absorbers/desorbers towards compact and efficient absorption heat pumps
Abstract Absorption heat pump (AHP) is significant for renewable/waste energy utilization to alleviate the energy crisis. Compact and energy-efficient AHP is essential for wider applications, and absorbers and desorbers play critical roles. To select the best-performing components for this purpose, heat and mass transfer characteristics are compared for different kinds of absorbers/desorbers, including microchannel membrane-based heat exchanger, plate heat exchanger, falling-film horizontal tube, and falling-film vertical tube. Heat and mass transfer models for each absorber/desorber have been established with validated accuracies. A wide range of geometrical parameters of absorbers/desorbers have been considered to obtain the variations of heat and mass transfer rates of each kind of absorber/desorber. Results indicate that the heat transfer coefficient and sorption rate (absorption/desorption) show a decreasing trend as the volume increases for all absorbers/desorbers. The microchannel membrane-based structure yields overwhelming heat and mass transfer performance in both absorbers and desorbers. The maximum heat transfer coefficient and sorption rate are up to 8.6 kW m−2 K−1 and 0.0150 kg m−2 s−1 for the microchannel membrane-based absorber and 4.2 kW m−2 K−1 and 0.0225 kg m−2 s−1 for the microchannel membrane-based desorber. This work provides a thorough comparison among various absorbers and desorbers and identifies their heat/mass transfer rate domains, facilitating structural design towards compact and efficient AHPs.