Thermodynamic analysis on an ammonia water absorption-resorption system for heat pump application.

Ammonia water absorption-resorption system employs a desorber and a resorber replacing the evaporator and the condenser in a conventional single stage absorption system. It is advantageous on heat pump applications due to the large temperature glide of the absorption process for better heat matching. Moreover, the high system pressure is reduced so that the cost of fabrication and maintenance can be lowered. The coupling of the system pressure and the solution concentration makes the system flexible to be operated. This paper presents a thermodynamic analysis on the system. The operating features are given to show the performance and the heat matching. In order to improve the performance, a pinch analysis is carried out for better internal heat recovery strategy. A case study is conducted under the operating conditions of producing hot water of 45oC and the ambient temperature of 10oC while the driving hot water approximates 100oC. The minimum heat input is calculated by problem table and the system configuration is constructed by grid method. The performance can be improved by 18.8% compared to a conventional absorption-resorption system. Although the configuration is complicated, it provides an insight of the optimal system with maximum internal heat recovery.