Absorption characteristics of falling film LiBr (lithium bromide) solution over a finned structure

• A flat plate absorber design with significantly high performance is presented.
• Absorption rates as high as two times that of prior studies are achieved.
• Effect of operating conditions on the absorber performance is extensively investigated.

In this study, an absorber design suitable for the plate-and-frame absorber configuration is introduced. The design utilizes a fin structure installed on a vertical flat plate to produce a uniform solution film and minimize its thickness and to continuously interrupt the boundary layer. Using numerical models supported by experiments employing dye visualization, the suitable fin spacing and size and surface wettability are determined. The solution flow thickness is measured using the laser confocal displacement measurement technique. The new surface structure is tested in an experimental absorption system. A significantly high absorption rate (6 × 10−3 kg/m2s at a pressure potential of 700 Pa) is achieved in comparison with the conventional absorption systems. The effect of absorber water vapor pressure, solution flow rate, solution inlet concentration, cooling water inlet temperature and solution inlet temperature on the absorption rate is investigated. The proposed design provides a potential framework for development of highly compact absorption refrigeration systems.