To improve energy conversion efficiency, optimization of the working fluids in organic Rankine cycles(ORCs) was explored in the range of low-temperature heat sources. The concept of unit-heat-exchange-area(UHEA) net p...To improve energy conversion efficiency, optimization of the working fluids in organic Rankine cycles(ORCs) was explored in the range of low-temperature heat sources. The concept of unit-heat-exchange-area(UHEA) net power, embodying the cost/performance ratio of an ORC system, was proposed as a new indicator to judge the suitability of ORC working fluids on a given condition. The heat exchange area was computed by an improved evaporator model without fixing the minimum temperature difference between working fluid and hot fluid, and the flow pattern transition during heat exchange was also taken into account. The maximum UHEA net powers obtained show that dry organic fluids are more suitable for ORCs than wet organic fluids to recover low-temperature heat. The organic fluid 1-butene is recommended if the inlet temperature of hot fluid is 353.15-363.15 K or443.15-453.15 K, heptane is more suitable at 373.15-423.15 K, and R245 ca is a good option at 483.15-503.15 K.展开更多
With the increased use of natural gas,it is valuable to study energy recovery ratio in the natural gas pressure reduction stations(PRSs).This paper focused on recovering the energy in PRSs as well as low-grade waste h...With the increased use of natural gas,it is valuable to study energy recovery ratio in the natural gas pressure reduction stations(PRSs).This paper focused on recovering the energy in PRSs as well as low-grade waste heat by a coupled power generation system(CPGS).The CPGS integrates a natural gas expansion(NGE)subsystem and an organic Rankine cycle(ORC)subsystem driven by low-temperature waste heat.Firstly,a comparative analysis is carried out between the separated natural gas expansion system and the separated ORC system.Then,the effects of heat source conditions,upstream pressure of natural gas and the isentropic efficiency of the natural gas expander are investigated.At last,working fluids selection is conducted with respect to two different pressure ranges of natural gas.The results show that there is an optimal temperature and mass flow rate of the heat source that maximizes the system exergy efficiency.With the increase of the upstream pressure of natural gas,the net power output and waste heat recovery factor increase while the system exergy efficiency has an optimal point.Furthermore,the isentropic efficiency of the natural gas expander has a great influence on the net power output of the system.展开更多
基金Projects(U0937604,50876116)supported by the National Natural Science Foundation of ChinaProjects(2010QZZD0107,2014zzts192)supported by the Fundamental Research Funds for the Central Universities of China
文摘To improve energy conversion efficiency, optimization of the working fluids in organic Rankine cycles(ORCs) was explored in the range of low-temperature heat sources. The concept of unit-heat-exchange-area(UHEA) net power, embodying the cost/performance ratio of an ORC system, was proposed as a new indicator to judge the suitability of ORC working fluids on a given condition. The heat exchange area was computed by an improved evaporator model without fixing the minimum temperature difference between working fluid and hot fluid, and the flow pattern transition during heat exchange was also taken into account. The maximum UHEA net powers obtained show that dry organic fluids are more suitable for ORCs than wet organic fluids to recover low-temperature heat. The organic fluid 1-butene is recommended if the inlet temperature of hot fluid is 353.15-363.15 K or443.15-453.15 K, heptane is more suitable at 373.15-423.15 K, and R245 ca is a good option at 483.15-503.15 K.
基金Project(21506257)supported by the National Natural Science Foundation of ChinaProject(2019zzts535)supported by the Fundamental Research Funds for the Central Universities,China
文摘With the increased use of natural gas,it is valuable to study energy recovery ratio in the natural gas pressure reduction stations(PRSs).This paper focused on recovering the energy in PRSs as well as low-grade waste heat by a coupled power generation system(CPGS).The CPGS integrates a natural gas expansion(NGE)subsystem and an organic Rankine cycle(ORC)subsystem driven by low-temperature waste heat.Firstly,a comparative analysis is carried out between the separated natural gas expansion system and the separated ORC system.Then,the effects of heat source conditions,upstream pressure of natural gas and the isentropic efficiency of the natural gas expander are investigated.At last,working fluids selection is conducted with respect to two different pressure ranges of natural gas.The results show that there is an optimal temperature and mass flow rate of the heat source that maximizes the system exergy efficiency.With the increase of the upstream pressure of natural gas,the net power output and waste heat recovery factor increase while the system exergy efficiency has an optimal point.Furthermore,the isentropic efficiency of the natural gas expander has a great influence on the net power output of the system.
