A new combined cooling and power system based on ammonia-water absorption refrigeration cycle: Thermodynamic comparison and analysis

Abstract

In this paper, a new combined cooling and power (CCP) system, based on ammonia-water absorption refrigeration cycle, is proposed to utilize low-temperature heat sources effectively. The system is characterized by that an ejector is introduced to lower the turbine back pressure by the evaporated ammonia vapor used for cooling, and is appropriate for the working scenarios needing much cooling capacity but bits of electricity. The system mathematical models are set up in detail, based on which the data of the system design working condition are obtained by numerical simulation. The results show that the net power output of the proposed system is 13% more than that of a similar system without ejector and moreover the system thermal efficiency could approach 45%. By performance comparison with a cascade-type CCP system, the proposed system shows the advantages of simple structure and good economy. Finally a thermodynamic parameter analysis is carried out to investigate the effects of five parameters on the system performance. The results show that there is an optimal rectification column pressure leading to the maximal net power output. The increases of rectification column pressure, turbine back pressure and evaporation temperature have negative effects on cooling capacity and thermal efficiency of the system, while the increase of absorber pressure has positive effects on the two indicators. Especially for the increase of ammonia-weak solution temperature of rectification column bottom, all the system performance experiences a process of increasing sharply, increasing slowly and decreasing slightly.