Graphical analysis on internal heat recovery of a single stage ammonia–water absorption refrigeration system

•The graphical method is intuitional to identify the system construction and energy target.•The optimal cycle with maximum internal heat recovery is verified.•Saturated feed condition is the optimum on maximizing internal heat recovery.•Reducing the size of the pocket of BGCC is beneficial to internal heat recovery.•Rectification heat recovery is not necessary in a GAX cycle.

The internal heat recovery has great influence on the performance of an ammonia water absorption refrigeration system. This paper presents an intuitional graphical analysis to identify the characteristics of different cycles with different internal heat recovery strategies and to find out the key points which have significant influence on internal heat recovery. The different cycles can be illustrated clearly in a temperature–heat load diagram with the system construction and the energy target so that the better one can be obtained. And the optimal one can be verified from the comparison. The feed condition and the size of the pocket of the background process are regarded as the key points of internal heat integration for the reduction of the system heat input. The results show that saturated feed condition is the optimal feed condition due to the minimum irreversible loss of heat and mass transfer and reducing the heat flow rate in the pocket of the background process contributes to the heat integration between the column and background processes. The two key points on internal heat recovery can be the operating direction on internal heat recovery for system performance improvement.