Thermoeconomic Multi-objective Optimization of an Ammonia-Water Power/Cooling Cycle Coupled with a HCCI Engine

Two different multi-objective optimization scenarios are carried out to determine the best design parameters of a bottoming cycle of a trigeneration system with a HCCI engine as prime mover. For the first scenario, the objective functions which are utilized in the optimization study are exergy efficiency and the sum of the unit costs of the system products. The system cost criteria is minimized, while the cycle exergy efficiency is maximized using an evolutionary algorithm. Exergy efficiency increases about 16.34%, and the reduction in the unit costs of the system products is about 10%. However, it is found that cooling capacity of the system is reduced about 83%. For the second scenario, the objective functions are considered to be the sum of the unit costs of the system products, net power generation, and exergy flow rate of refrigeration output. Employing the second scenario improves both power generation and cooling capacity of the system. The increase in exergy efficiency is about 5.61%. These are achieved with even a slight reduction in the system cost criteria.