Design and Analysis of the Absorber Component in Waste-Heat-Driven Diffusion Absorption Refrigeration Systems

The diffusion absorption refrigeration (DAR) cycle can provide refrigeration in remote locations using waste-heat or other low-grade-thermal input. Unlike conventional absorption systems, the DAR cycle receives no mechanical input, so all flows must be driven by passive mechanisms. Further, a third inert gas is employed to allow refrigerant expansion since conventional throttling devices impart large pressure drops. Thus, DAR absorber design is challenging due to increased mass transfer resistance from the inert gas, multiple outlet flow paths for the inert gas and solution, and limited (passive) external cooling. In the present study, a detailed, coupled heat and mass transfer model is developed for a counter-flow serpentine-tube DAR absorber. The model is applied to the analysis of an absorber for a small-scale refrigeration system with a 36 W cooling capacity. Studies are conducted to investigate the effect of key configuration and operational parameters on absorber performance, and guidelines are provided for component and system design.