A systematic strategy for retrofit of the multi-period heat exchanger network （HEN） on the basis of the multi- objective optimization is developed. In this three-stage procedure, a simplified multi-objective optimiz...A systematic strategy for retrofit of the multi-period heat exchanger network （HEN） on the basis of the multi- objective optimization is developed. In this three-stage procedure, a simplified multi-objective optimization model of the multi-period lIEN is first established and then solved to target the retrofit, aiming to minimizing the total annual cost and total annual CO2 emissions. The obtained Pareto front represents series of retrofit targets under different emission limitations, from which the most desirable one can be selected. The matching of the existing and the required heat exchangers is further implemented to finalize the retrofit, which will meet the practical retrofit requirements and matching restrictions. The application of the proposed procedure is illustrated through a case study of a HEN in a vacuum gas oil hydro-treating unit.展开更多
The energy efficiency monitoring is an essential precondition for ground source heat pump system's controlling and energy saving operation. Based on the data monitoring applied in the school building, this work is...The energy efficiency monitoring is an essential precondition for ground source heat pump system's controlling and energy saving operation. Based on the data monitoring applied in the school building, this work is focused on the parameters acquisition and operation analysis of the GSHP system in Tangshan. Results show the average COPs(coefficient of performance) are2.85 and 2.70 in summer and winter, respectively, and heat(cold) unbalance underground existed after whole year operation. The analysis of data also indicates that the direct borehole air-conditioning saved some power consumption obviously in the early stage of summer and energy saving of the GSHP system depended remarkably on its operation and management level. Besides the observation points of ground temperature are laid for a large-scale GSHP system, and the hydraulic balance of the pipes group needs to be concerned specially in safeguarding better reliability.展开更多
The impedance matching is crucial for continuous wave operation of ion cyclotron resonance heating（ICRH） antennae with high power injection into plasmas.A sudden increase in the reflected radio frequency power due t...The impedance matching is crucial for continuous wave operation of ion cyclotron resonance heating（ICRH） antennae with high power injection into plasmas.A sudden increase in the reflected radio frequency power due to an impedance mismatch of the ICRH system is an issue which must be solved for present-day and future fusion reactors.This paper presents a method for theoretical analysis of ICRH system impedance matching for a triple liquid stub tuner under plasma operational conditions.The relationship of the antenna input impedance with the plasma parameters and operating frequency is first obtained using a global solution.Then,the relations of the plasma parameters and operating frequency with the matching liquid heights are indirectly obtained through numerical simulation according to transmission line theory and matching conditions.The method provides an alternative theoretical method,rather than measurements,to study triple liquid stub tuner impedance matching for ICRH,which may be beneficial for the design of ICRH systems on tokamaks.展开更多
The increasing penetration of non-programmable renewable sources poses new challenges to the stability and reliability of electric power systems.Particularly,as traditional ancillary services from thermoelectric power...The increasing penetration of non-programmable renewable sources poses new challenges to the stability and reliability of electric power systems.Particularly,as traditional ancillary services from thermoelectric power plants are declining,new flexible actors are needed.This work investigates the potential of a residential house heated by a heat pump to offer flexibility services to the electric grid by leveraging its thermal inertia.An optimisation model is developed to schedule the heat pump operations while minimising the daily electricity costs,providing upward reserve(i.e.reducing consumption when requested)and ensuring occupants thermal comfort.The building thermal behaviour is modelled using a 7R4C network based on a thermo-electric analogy.The developed model is applied to a refurbished single-family house,equipped with an air source heat pump and radiant floor heating system,during a typical winter day.Then,five sensitivity analyses are performed to assess the impact of weather conditions,building age,heating system,electricity pricing,and heat pump type.The base case results show that offering upward reserve primarily shifts the heating consumption throughout the day without large variations in the overall energy use,preserving thermal comfort and with potential economic benefits.However,the sensitivity analyses show a reduced profitability linked to mid-season days,building with lower thermal inertia,lack of heat pump inverter control and time-varying electricity tariffs.In conclusion,results confirm that building-energy systems can provide flexibility services by leveraging their thermal inertia,but economic convenience is highly context-dependent.展开更多
Based on Perelman’s entropy monotonicity,uniform logarithmic Sobolev inequalities along the Ricci flow are derived.Then uniform Sobolev inequalities along theRicci floware derived via harmonic analysis of the integra...Based on Perelman’s entropy monotonicity,uniform logarithmic Sobolev inequalities along the Ricci flow are derived.Then uniform Sobolev inequalities along theRicci floware derived via harmonic analysis of the integral transform of the relevant heat operator.These inequalities are fundamental analytic properties of the Ricci flow.They are also extended to the volume-normalized Ricci flow and the Kähler-Ricci flow.展开更多
基金Supported by the National Natural Science Foundation of China(21376188,21676211)
文摘A systematic strategy for retrofit of the multi-period heat exchanger network （HEN） on the basis of the multi- objective optimization is developed. In this three-stage procedure, a simplified multi-objective optimization model of the multi-period lIEN is first established and then solved to target the retrofit, aiming to minimizing the total annual cost and total annual CO2 emissions. The obtained Pareto front represents series of retrofit targets under different emission limitations, from which the most desirable one can be selected. The matching of the existing and the required heat exchangers is further implemented to finalize the retrofit, which will meet the practical retrofit requirements and matching restrictions. The application of the proposed procedure is illustrated through a case study of a HEN in a vacuum gas oil hydro-treating unit.
基金Project(2012BAJ06B04)supported by"12th Five-Year Plan"National science and Technology,ChinaProject(2014-228)supported by Department of Housing and Urban Rural Development of Hebei,China
文摘The energy efficiency monitoring is an essential precondition for ground source heat pump system's controlling and energy saving operation. Based on the data monitoring applied in the school building, this work is focused on the parameters acquisition and operation analysis of the GSHP system in Tangshan. Results show the average COPs(coefficient of performance) are2.85 and 2.70 in summer and winter, respectively, and heat(cold) unbalance underground existed after whole year operation. The analysis of data also indicates that the direct borehole air-conditioning saved some power consumption obviously in the early stage of summer and energy saving of the GSHP system depended remarkably on its operation and management level. Besides the observation points of ground temperature are laid for a large-scale GSHP system, and the hydraulic balance of the pipes group needs to be concerned specially in safeguarding better reliability.
基金supported by the National Magnetic Confinement Fusion Science Program of China(Nos.2014GB108002,2013GB107001)National Natural Science Foundation of China(Nos.11205086,11205053,11375085,and 11405082)+1 种基金the Construct Program of Fusion and Plasma Physics Innovation Team in Hunan Province,China(No.NHXTD03)the Natural Science Foundation of Hunan Province,China(No.2015JJ4044)
文摘The impedance matching is crucial for continuous wave operation of ion cyclotron resonance heating（ICRH） antennae with high power injection into plasmas.A sudden increase in the reflected radio frequency power due to an impedance mismatch of the ICRH system is an issue which must be solved for present-day and future fusion reactors.This paper presents a method for theoretical analysis of ICRH system impedance matching for a triple liquid stub tuner under plasma operational conditions.The relationship of the antenna input impedance with the plasma parameters and operating frequency is first obtained using a global solution.Then,the relations of the plasma parameters and operating frequency with the matching liquid heights are indirectly obtained through numerical simulation according to transmission line theory and matching conditions.The method provides an alternative theoretical method,rather than measurements,to study triple liquid stub tuner impedance matching for ICRH,which may be beneficial for the design of ICRH systems on tokamaks.
文摘The increasing penetration of non-programmable renewable sources poses new challenges to the stability and reliability of electric power systems.Particularly,as traditional ancillary services from thermoelectric power plants are declining,new flexible actors are needed.This work investigates the potential of a residential house heated by a heat pump to offer flexibility services to the electric grid by leveraging its thermal inertia.An optimisation model is developed to schedule the heat pump operations while minimising the daily electricity costs,providing upward reserve(i.e.reducing consumption when requested)and ensuring occupants thermal comfort.The building thermal behaviour is modelled using a 7R4C network based on a thermo-electric analogy.The developed model is applied to a refurbished single-family house,equipped with an air source heat pump and radiant floor heating system,during a typical winter day.Then,five sensitivity analyses are performed to assess the impact of weather conditions,building age,heating system,electricity pricing,and heat pump type.The base case results show that offering upward reserve primarily shifts the heating consumption throughout the day without large variations in the overall energy use,preserving thermal comfort and with potential economic benefits.However,the sensitivity analyses show a reduced profitability linked to mid-season days,building with lower thermal inertia,lack of heat pump inverter control and time-varying electricity tariffs.In conclusion,results confirm that building-energy systems can provide flexibility services by leveraging their thermal inertia,but economic convenience is highly context-dependent.
文摘Based on Perelman’s entropy monotonicity,uniform logarithmic Sobolev inequalities along the Ricci flow are derived.Then uniform Sobolev inequalities along theRicci floware derived via harmonic analysis of the integral transform of the relevant heat operator.These inequalities are fundamental analytic properties of the Ricci flow.They are also extended to the volume-normalized Ricci flow and the Kähler-Ricci flow.
