Thermoeconomic analysis of a new combination of ammonia/water power generation cycle with GT-MHR cycle and LNG cryogenic exergy

Abstract

This paper deals with a thermoeconomic analysis of a new combination of ammonia/water power generation cycle and Turbine-Modular Helium Reactor (GT-MHR) cycle and liquefied natural gas (LNG) cryogenic exergy. In the proposed power generation system, the GT-MHR waste heat is considered as heat source as well as cryogenic exergy of LNG as thermal sink. Parametric study is performed to investigate the effects of key parameters. Also, a comparative study is conducted for proposed system with the same combined cycle without LNG cryogenic exergy. The results show that minimum temperature difference in the evaporator, ΔTEV, has the greatest effect on the energy and exergy efficiencies as well as total cost rate in comparison to other key parameters. For the proposed system, an increase in ΔTEV from 20K to 30K, leads to a reduction of 2.8% and 3.4%in both energy and exergy efficiencies and total cost rate, respectively. The results also show that the temperature and pressure of ammonia/water solution exiting the evaporator have the negligible effects on energy and exergy efficiencies. Also, ammonia concentration of solution entering the separator, has the greatest effect on the product cost. Moreover, a multi-objective optimization is performed to obtain optimal values of design parameters.