دانلود رایگان مقاله تجزیه و تحلیل ترمودینامیکی چرخه ترکیبی خنک کننده و قدرت رانده

Abstract

This paper investigates a Kalina-based combined cooling and power (CCP) cycle driven by low-grade heat source. The proposed cycle consists of a Kalina cycle and an absorption refrigeration cycle. By establishing the mathematical model, numerical simulation is conducted and parametric analysis is performed to examine the effects of five key parameters on the thermodynamic performances of Kalina-based CCP cycle. A performance optimization is conducted by genetic algorithm to obtain the optimum exergy efficiency. According to parametric analysis, an optimum expander inlet pressure can be achieved; exergy efficiency increases with expander inlet pressure and concentration of ammonia-water basic solution, but exergy efficiency decreases when terminal temperature difference of high-temperature recuperator and low-temperature recuperator increases. Refrigeration exergy increases with expander inlet pressure and decreases as expander inlet temperature and concentration of ammonia-water basic solution rise. However, the refrigeration exergy keeps constant as the terminal temperature difference of high-temperature recuperator and low-temperature recuperator vary. Furthermore, the optimized Kalina-based CCP cycle is compared with a separate generation system which is also optimized. The optimization results show that the exergy efficiency and net power output of Kalina-based CCP are higher than those of separate generation system.

5. Conclusion

In this paper, a Kalina-based CCP cycle driven by low-grade heat source is analyzed. By establishing mathematical model, a simulation is conducted to perform parametric analysis. Five key parameters including expander inlet pressure, expander inlet temperature, concentration of ammonia-water basic solution, terminal temperature difference of HTR and terminal temperature difference of LTR are selected to explore their effects on the thermodynamic performances of Kalina-based CCP cycle. According to the parametric analysis, an optimization is conducted by Genetic Algorithm to search for optimum exergy efficiency. Moreover, a comparison between Kalina-based CCP cycle and separate generation system is conducted under the optimum condition. The main conclusions are summarized as follows: (1) Exergy efficiency increases with expander inlet temperature and concentration of ammonia-water basic solution; exergy efficiency decreases as the terminal temperature difference of HTR and LTR increases. An optimum expander inlet pressure can be achieved to maximize exergy efficiency. (2) Refrigeration exergy is positively correlated with mass flow rate of refrigerant. The mass flow rate of refrigerant rises with expander inlet pressure, which leads to an increase in refrigeration exergy. As the expander inlet temperature and concentration of ammonia-water basic solution increases, the mass flow rate of refrigerant and refrigeration exergy decline simultaneously. The terminal temperature difference of HTR and LTR are irrelevant with refrigeration exergy. (3) Comparing the optimization results of Kalina-based CCP cycle and separate generation system, Kalina-based CCP cycle has higher exergy efficiency and generates more net power output than separate generation system does on the condition that the Kalina-based CCP cycle and separate generation system produce the same amount of refrigeration exergy. (4) Exergy analysis of Kalina-based CCP cycle at the optimum condition illustrates that the HRSG contributes most exergy destruction to the cycle, which is the largest source of overall cycle inefficiency. And expander and condenser I destroy second largest amount of exergy. The exergy destruction of absorption refrigeration cycle is relatively small on account of small mass flow rate of working fluid.