| As a form of energy consumption that can effectively improve the energy utilization rate,Combined cooling heating and power(CCHP)system has developed rapidly in recent years with its advantages of energy saving and environmental protection.The newly issued national " 14 th Five-Year Plan " clearly proposes to speed up the construction of distributed energy system in central and eastern China.As an efficient distributed energy system,CCHP system will also be developed in the future Fully.However,most of the evaluation and optimization objectives of CCHP system are based on the first law of thermodynamics,and the research based on the second law of thermodynamics,especially the entropy analysis of the system,is relatively less,and these studies are static analysis of the system.Therefore,this work is carried out about the exergy analysis and the entropy analysis of the CCHP system using gas turbine based on the transient simulation.The energy consumption of the system is analyzed in the transient operation state,and the direction for the optimization of the CCHP system is provided.Firstly,the CCHP system with gas turbine as power is constructed,and the mathematical model of the main equipment in the system is established,so as to lay the foundation for the enexgy analysis and the entropy analysis.Secondly,the analytical model of the CCHP system and its main equipment is established,and the entropy generation calculation model of each equipment is established with simplified method on equipment by using the improved entropy generation calculation method.At the same time,we verify the effectiveness of the improved entropy generation calculation method and the established entropy generation calculation model.Finally,based on the exergy analysis and entropy generation model,the CCHP system under different operation modes are simulated and analyzed,and the differences between the simulation results and the primary energy rate(PER)of the system are compared.The results show that the simulation results of system exergy efficiency,entropy generation and PER are consistent based on the equipment characteristics and building load characteristics of the CCHP system established in this paper.The simulation results show that the operation mode of "determining heat based on power" is better than that of " determining power based on heat ".The calculated results of system exergy efficiency are far less than the calculated results of PER.This phenomenon shows that the evaluation method based on the second law of thermodynamics can reveal the level of energy utilization betterly.The simulation results of exergy loss and entropy production basically meet the Gouy Stodola relationship,which proves that the exergy analysis and entropy production calculation models established in this paper are effective.The results of exergy analysis show that the reasonable utilization of energy is low,and there is great potential to improve the degree of energy utilization;The entropy generation of adiabatic combustion is greater than that of power generation in the entropy generation model of gas turbine.In the waste heat boiler,the entropy generation of exhaust gas is the largest.The entropy generation of heat exchange process is the second,and the entropy generation of heat loss is the smallest.In Li Br absorption chiller,the entropy production in condenser is greater than that in evaporator and generator.For the entropy generation of flue gas / hot water heat exchanger,the entropy generation caused by exhaust gas is the largest.In summary,the entropy generation calculation model of each equipment established in this paper can greatly simplify the entropy generation calculation process of CCHP system,and has good application prospect.The simulation results of exergy analysis and entropy analysis of CCHP system can reveal the level of energy utilization and provide more reasonable and effective guidance for energy system optimization. |
