The organic Rankine cycle(ORC)is a popular technique used in the utilization of low-grade thermal energy.Among wet,dry,and isentropic organic working fluids,the latter two types are more appropriate for ORC systems.In...The organic Rankine cycle(ORC)is a popular technique used in the utilization of low-grade thermal energy.Among wet,dry,and isentropic organic working fluids,the latter two types are more appropriate for ORC systems.In this paper,the definition of turning point on saturated vapor curve of dry fluid and isentropic fluid was given according to the shape of the saturated curve of working fluids in a T-s diagram.On this basis,the model of near-critical region triangle was established.Using this model,the thermodynamic performance of 57 kinds of dry and isentropic organic working fluids in ORC was evaluated.The performance includes the relation between turning point temperature and cycle thermal efficiency,the relation between near-critical region triangle area and cycle thermal efficiency,the relation between near-critical region triangle area and exergy at turning point temperature,the relation between near-critical region triangle area and reciprocal value of slope of saturated vapor curve.Moreover,working fluid selection was also conducted in terms of heat source type.It was found through theoretical analysis results that the popular R123 is an acceptable choice especially for the utilization of closed type heat source.Considering it will be phased out in near future,then cis-butene,butane,trans-butene,and isobutene are worth studying as its successor.Dodecane is worthy of attention and further research and it can be a good choice for utilization of open type heat source.展开更多
In the present study,the thermodynamic and economic performance of a combined thermodynamic cycle formed by an ORC and a Kalina cycle,which can simultaneously recover waste heat of exhaust gas and cooling water of mar...In the present study,the thermodynamic and economic performance of a combined thermodynamic cycle formed by an ORC and a Kalina cycle,which can simultaneously recover waste heat of exhaust gas and cooling water of marine engine,has been analyzed.Two typical marine engines are selected to be the waste heat source.Six economic indicators are used to analyze the economic performance of this combined thermodynamic cycle system with different marine engine load and under practical comprehensive operating condition of marine engine.The results of the present study show that the combined thermodynamic cycle system with R123 as organic working fluid has the best performance.The system with cis-butene has the worst economic performance.Under practical comprehensive operating conditions of ships,R123 has the shortest Payback Periods,which are 8.51 years and 8.14 years for 8 S70 ME-C10.5 engine and 5G95 ME-C10.5 engine,respectively.Correspondingly,payback Periods of Cyclopentane are 11.95 years and 11.90 years.The above values are much shorter than 25 years which are the lifetime of a marine ship.Under practical comprehensive operating conditions of ships,the combined cycle system can provide output power which is at least equivalent to 25%of engine power.Considering that R123 will be phased out in near future,cyclopentane may be its good successor.Cyclopentane can be used safely by correct handling and installing according to manufacturer's instructions.展开更多
In this work,the effects of electric field on the microstructure and transport property of[bmim][Tf_(2)N]were simulated by molecular dynamics method to provide regulating strategy of required ionic liquid.The simulati...In this work,the effects of electric field on the microstructure and transport property of[bmim][Tf_(2)N]were simulated by molecular dynamics method to provide regulating strategy of required ionic liquid.The simulation results showed that[bmim]^(+) and [Tf_(2)N]^(–)move slowly along the positive and negative direction of the electric field,respectively,and anions and cations are still arranging alternatively under weak electric field which has slight influence on the electrostatic force in[bmim][Tf_(2)N].When the electric field is strong,it has significant influence on the electrostatic force of[bmim][Tf_(2)N],which results the aggregation of[bmim]^(+) and [Tf_(2)N]^(–) and the appearance of large hole inside[bmim][Tf_(2)N].In addition,with the increase of electric field intensity,the density of[bmim][Tf_(2)N] increases,which means the free volume inside[bmim][Tf_(2)N]become smaller.Meanwhile,the thermal conductivity and viscosity exhibit anisotropy.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51506001)Beijing Municipal Education Commission(KM201710005029)National Key R&D Program of China(Grant No.2016YFE0124900)
文摘The organic Rankine cycle(ORC)is a popular technique used in the utilization of low-grade thermal energy.Among wet,dry,and isentropic organic working fluids,the latter two types are more appropriate for ORC systems.In this paper,the definition of turning point on saturated vapor curve of dry fluid and isentropic fluid was given according to the shape of the saturated curve of working fluids in a T-s diagram.On this basis,the model of near-critical region triangle was established.Using this model,the thermodynamic performance of 57 kinds of dry and isentropic organic working fluids in ORC was evaluated.The performance includes the relation between turning point temperature and cycle thermal efficiency,the relation between near-critical region triangle area and cycle thermal efficiency,the relation between near-critical region triangle area and exergy at turning point temperature,the relation between near-critical region triangle area and reciprocal value of slope of saturated vapor curve.Moreover,working fluid selection was also conducted in terms of heat source type.It was found through theoretical analysis results that the popular R123 is an acceptable choice especially for the utilization of closed type heat source.Considering it will be phased out in near future,then cis-butene,butane,trans-butene,and isobutene are worth studying as its successor.Dodecane is worthy of attention and further research and it can be a good choice for utilization of open type heat source.
基金funded by the National Natural Science Foundation of China(Grant No.51506001)Beijing Municipal Education Commission(KM201710005029)。
文摘In the present study,the thermodynamic and economic performance of a combined thermodynamic cycle formed by an ORC and a Kalina cycle,which can simultaneously recover waste heat of exhaust gas and cooling water of marine engine,has been analyzed.Two typical marine engines are selected to be the waste heat source.Six economic indicators are used to analyze the economic performance of this combined thermodynamic cycle system with different marine engine load and under practical comprehensive operating condition of marine engine.The results of the present study show that the combined thermodynamic cycle system with R123 as organic working fluid has the best performance.The system with cis-butene has the worst economic performance.Under practical comprehensive operating conditions of ships,R123 has the shortest Payback Periods,which are 8.51 years and 8.14 years for 8 S70 ME-C10.5 engine and 5G95 ME-C10.5 engine,respectively.Correspondingly,payback Periods of Cyclopentane are 11.95 years and 11.90 years.The above values are much shorter than 25 years which are the lifetime of a marine ship.Under practical comprehensive operating conditions of ships,the combined cycle system can provide output power which is at least equivalent to 25%of engine power.Considering that R123 will be phased out in near future,cyclopentane may be its good successor.Cyclopentane can be used safely by correct handling and installing according to manufacturer's instructions.
基金the National Natural Science Foundation of China(No.51976167 and No.41941018)。
文摘In this work,the effects of electric field on the microstructure and transport property of[bmim][Tf_(2)N]were simulated by molecular dynamics method to provide regulating strategy of required ionic liquid.The simulation results showed that[bmim]^(+) and [Tf_(2)N]^(–)move slowly along the positive and negative direction of the electric field,respectively,and anions and cations are still arranging alternatively under weak electric field which has slight influence on the electrostatic force in[bmim][Tf_(2)N].When the electric field is strong,it has significant influence on the electrostatic force of[bmim][Tf_(2)N],which results the aggregation of[bmim]^(+) and [Tf_(2)N]^(–) and the appearance of large hole inside[bmim][Tf_(2)N].In addition,with the increase of electric field intensity,the density of[bmim][Tf_(2)N] increases,which means the free volume inside[bmim][Tf_(2)N]become smaller.Meanwhile,the thermal conductivity and viscosity exhibit anisotropy.
