A detailed model of three-dimensional computational fluid dynamics(CFD)on a finned-tube CO_(2)gas cooler has been developed and validated.The model is then applied to investigate the effect of uniform and mal-distribu...A detailed model of three-dimensional computational fluid dynamics(CFD)on a finned-tube CO_(2)gas cooler has been developed and validated.The model is then applied to investigate the effect of uniform and mal-distribution inlet airflow profiles on the coil performance.The airflow mal-distribution velocity profiles include linear-up,linear-down and parabolic while the effected coil performance parameters contain airside pressure drop,average airside heat transfer coefficient,approach temperature and coil heating capacity.The model also enables to predict the CO_(2)refrigerant temperature profile along the coil pipes from refrigerant inlet to outlet at different operation conditions.The simulation results reveal that different types of inlet airflow velocity profiles have significant effects on the gas cooler performance.The uniform airflow velocity profile case shows the best thermal performance of gas cooler.Compared with the cases of linear-up and parabolic air velocity profiles,the linear-down airflow profile can influence more on the coil heat transfer performance.Due to the thermal conduction between neighbour tubes through coil fins,reversed heat transfer phenomenon exists which can be detected and simulated by the CFD model.It is predicted that the linear-down airflow profile can increase greatly the reversed heat transfer phenomenon and thus lead to the highest approach temperature and the lowest heating capacity amongst these four types of airflow profiles.The research method and outcomes presented in this paper can have great potentials to optimize the performance of a CO_(2)gas cooler and its associated refrigeration system.展开更多
The EGR (exhaust gas recirculation) technique can greatly reduce the NOx emission of diesel engines, especially when an EGR cooler is employed. Numerical simulations are applied to study the flow field and temperature...The EGR (exhaust gas recirculation) technique can greatly reduce the NOx emission of diesel engines, especially when an EGR cooler is employed. Numerical simulations are applied to study the flow field and temperature distributions inside the EGR cooler. Three different models of EGR cooler are investigated, among which model A is a traditional one, and models B and C are improved by adding a helical baffle in the cooling area. In models B and C the entry directions of cooling water are different, which mostly influences the flow resistance. The results show that the improved structures not only lengthen the flow path of the cooling water, but also enhance the heat exchange rate between the cool and hot media. In conclusion we suggest that the improved structures are more powerful than the traditional one.展开更多
基金the support received from GEA Searle and Research Councils UK(RCUK)for this project.
文摘A detailed model of three-dimensional computational fluid dynamics(CFD)on a finned-tube CO_(2)gas cooler has been developed and validated.The model is then applied to investigate the effect of uniform and mal-distribution inlet airflow profiles on the coil performance.The airflow mal-distribution velocity profiles include linear-up,linear-down and parabolic while the effected coil performance parameters contain airside pressure drop,average airside heat transfer coefficient,approach temperature and coil heating capacity.The model also enables to predict the CO_(2)refrigerant temperature profile along the coil pipes from refrigerant inlet to outlet at different operation conditions.The simulation results reveal that different types of inlet airflow velocity profiles have significant effects on the gas cooler performance.The uniform airflow velocity profile case shows the best thermal performance of gas cooler.Compared with the cases of linear-up and parabolic air velocity profiles,the linear-down airflow profile can influence more on the coil heat transfer performance.Due to the thermal conduction between neighbour tubes through coil fins,reversed heat transfer phenomenon exists which can be detected and simulated by the CFD model.It is predicted that the linear-down airflow profile can increase greatly the reversed heat transfer phenomenon and thus lead to the highest approach temperature and the lowest heating capacity amongst these four types of airflow profiles.The research method and outcomes presented in this paper can have great potentials to optimize the performance of a CO_(2)gas cooler and its associated refrigeration system.
文摘The EGR (exhaust gas recirculation) technique can greatly reduce the NOx emission of diesel engines, especially when an EGR cooler is employed. Numerical simulations are applied to study the flow field and temperature distributions inside the EGR cooler. Three different models of EGR cooler are investigated, among which model A is a traditional one, and models B and C are improved by adding a helical baffle in the cooling area. In models B and C the entry directions of cooling water are different, which mostly influences the flow resistance. The results show that the improved structures not only lengthen the flow path of the cooling water, but also enhance the heat exchange rate between the cool and hot media. In conclusion we suggest that the improved structures are more powerful than the traditional one.
