Design of an ejector-absorption heat pump based on entropy generation minimization

This paper presents the design method for an ejector-absorption heat pump based on entropy generation minimization (EGM). This cycle is driven by low-temperature waste heat below 90 °C. A cycle model of the ejector-absorption heat pump with an ammonia-water mixture as the working fluid has been constructed. The required model parameters to represent the thermodynamic and geometric characteristics were determined from an experimental study. Cycle simulation specifies the dominant locations of irreversibility and operability. Parametric analysis is performed to investigate the effects of the geometry of the cycle components on entropy generation. This study considers the entropy generation from two components: one associated with the frictional pressure drop and the other including heat transfer in each heat exchanger. The geometric parameter for each component is set based on the results of the parametric analysis. The performance of the designed heat pump is evaluated by its modified coefficient of performance (COP) based on the primary energy consumption. The results show that the dominant entropy generation occurs in the solution heat exchanger and absorber, and the design using EGM produces an improved COP. The results of the sensitivity analysis for the overall unit size of the designed heat pump are also shown.