Proposal and thermodynamic assessment of a new ammonia-water based combined heating and power (CHP) system

In this paper, a new ammonia-water based combined heating and power (CHP) system that combines a superheated Kalina cycle and a compression heat pump cycle is proposed to provide power and hot air simultaneously for users. In the system, large amounts of energy remained in the ammonia-poor liquid exhausted from the separator of Kalina cycle is recovered by the compression heat pump cycle. Firstly the superiority of superheated Kalina cycle to basic Kalina cycle is demonstrated in order to introduce the proposed CHP system. Then the mathematical models of the CHP system are established for simulation and analysis. An exergy loss analysis for the system under a preliminary design operation condition shows that the largest two parts of exergy destructions of equipment occur in vapor generator and heat supplier. Finally a thermodynamic parameter analysis is carried out and the results reveal that there exists an optimal high pressure of system that yields the maximal system exergy efficiency. Within certain ranges, lower middle pressure of system and separation temperature, higher low pressure of system and ammonia mass fraction of basic solution, would reach higher system exergy efficiencies. The turbine inlet temperature just has a little effect on the system exergy efficiency.