Recovery Of Low-temperature Waste Heat By Optimization Of Ejector Cold-Power Cogeneration System With Binary Non-azeotropic Mixtures

There are a lot of low-temperature heat resources in architectural material industry, metallurgical industry, chemical industry, light industry and so on. Recycling these waste heat is an important means to solve our energy shortage and environmental pollution problems. With the development of the low grade energy utilization technology, ejector cold-power cogeneration system has been put forward to meet the demands of cold and electric. At present, many scholars focused on studied the thermodynamic performance and economic performance of the pure refrigerant system. However, for improving the performance of the system and meeting the actual needs of the project, the research of multi-objective optimization for the system with non azeotropic mixed refrigerants will be more significance.Based on the considerations stated above, the theoretical research on the jet refrigeration cycle system using the pure working fluid and non azeotropic mixed refrigerants was carried out. In the cycle system the low temperature flue gas waste heat selected as the heat source. For the given heat source temperature of the system, the factors affecting the thermodynamic performance and economic performance of the system were studied and analyzed, and the influence of work fluids parameters and operating parameters on the performance of the system was studied and calculated. Finally, according to the thermodynamic performance and economy of the system, the working conditions of the system are optimized. The research contents are as follows:The refrigerating capacity, thermal efficiency, corrected thermal efficiency and exergy efficiency are taken into account when optimum the combined cycle. According to the first and second low of thermodynamic, the thermodynamic performance of the system were studied. Considering the characteristics of the heat source and the system, R141 b, R245 fa, R600, R600 a, R601 and R601 a six kinds of organic substance are chosen to be the work fluids. Through the research and comparison, the optimal work fluid of the system is obtained. The results show that R245 fa has the highest refrigerating capacity, R600 and R600 a have the highest thermal efficiency and exergy efficiency. Under the same operating conditions, non-azeotropic refrigerants R245 fa and R601 a with different mass ratio are conducted. The results show that R245fa/R601a(0.4/0.6) has a better thermodynamic performance than other fluids. And the research of the system components’ exergy loss show that the ejector and steam generator are the major loss of the exergy.The APR and LEC is introduced as the evaluation criteria to discuss the system economic performance. The results show that with the increasing proportion of R245 fa in the mixture, the economic performance of the system is more excellent, so the economic performance of pure working fluid R245 fa is optimal. Under different optimization indexes, the optimal working fluids and the optimal operating conditions of the system are different, so the multi-objective optimization is carried out. Through the careful analysis of the system, the R245fa/R601a(0.7/0.3) and R245fa/R601a(0.6/0.4) are the optimal working fluids of the system. Meanwhile, the optimal working condition of multi-objective is the generating temperature 383 K, the condensing temperature 301 K, and the evaporating temperature 282 K.