To improve the coefficient of performance （COP） of CO2 transcritical reverse cycle and determine the most efficient cycle, comparison analysis on （single-and） two-stage CO2 transcritical cycles with internal heat ...To improve the coefficient of performance （COP） of CO2 transcritical reverse cycle and determine the most efficient cycle, comparison analysis on （single-and） two-stage CO2 transcritical cycles with internal heat exchanger （IHX） or expander is presented adopting the principle of thermodynamics. Results indicate that the COP of four cycles,namely single-stage compression with IHX （SI）, single-stage compression with expander （SE）, two-stage compression with IHX （TI） and two-stage compression with expander （TE）, can be ranged as TE>SE>TI>SI. It presents that adopting an expander to recover expansion power is the primary method to improve the COP of CO2 transcritical reverse cycle if the efficiency of the expander is up to a certain value. Under supposed operating condition, where the outlet temperature of gas cooler is 35 ℃ and the evaporating temperature is 5 ℃, the COP of TE cycle is about 4200 higher than that of SI cycle when the expander efficiency is 0.6 and the degree of superheat of IHX is 15 ℃. Therefore TE cycle is the most recommendatory one and it is better to adopt TE in those high-cooling capacity systems because its technology cost will be higher.展开更多
文摘To improve the coefficient of performance （COP） of CO2 transcritical reverse cycle and determine the most efficient cycle, comparison analysis on （single-and） two-stage CO2 transcritical cycles with internal heat exchanger （IHX） or expander is presented adopting the principle of thermodynamics. Results indicate that the COP of four cycles,namely single-stage compression with IHX （SI）, single-stage compression with expander （SE）, two-stage compression with IHX （TI） and two-stage compression with expander （TE）, can be ranged as TE>SE>TI>SI. It presents that adopting an expander to recover expansion power is the primary method to improve the COP of CO2 transcritical reverse cycle if the efficiency of the expander is up to a certain value. Under supposed operating condition, where the outlet temperature of gas cooler is 35 ℃ and the evaporating temperature is 5 ℃, the COP of TE cycle is about 4200 higher than that of SI cycle when the expander efficiency is 0.6 and the degree of superheat of IHX is 15 ℃. Therefore TE cycle is the most recommendatory one and it is better to adopt TE in those high-cooling capacity systems because its technology cost will be higher.
