Entransy based heat exchange irreversibility analysis for a hybrid absorption-compression heat pump cycle

Abstract

Thermally-coupled hybrid absorption-compression heat pump cycle could achieve large temperature lift and high output temperature, which is promising for the decarbonization of industrial heat demand. However, the cycle also has many heat exchange processes, resulting in irreversible losses in different components and performance degradation. In this study, entransy dissipation is used for the heat exchange irreversibility analysis of different components in the cycle. Heat and mass transfer model and entransy dissipation model for combined heat and mass transfer components such as absorber and generator are proposed. By comparing with the exergy loss, it proved that the entransy dissipation calculation model is reasonable. In addition, the T-Q diagram obtained by entransy dissipation analysis visually illustrates the heat exchange processes in each heat exchange component, which shows that entransy dissipation analysis has the characteristics of focusing on heat exchange, process-oriented and visualization. Results of entransy dissipation analysis are then used to guide the heat exchange enhancement of different components, thus optimizing the performance of whole heat pump cycle. Reducing the heat exchange irreversibility in internal heat recovery part can obtain the maximize improvement on COP by 3.92 %. The effect of thermal coupling temperature on exergy based and entransy based parameters of the heat pump cycle is investigated. The entransy increment states the optimal coupling temperature as 73.9 °C, in agreement with the COP and exergy analysis results. Therefore, from entransy dissipation to entransy increment, entransy analysis is expected to be a powerful tool to guide from the heat transfer optimization to the thermodynamic system optimization.