Cascading faults have been identified as the primary cause of multiple power outages in recent years.With the emergence of integrated energy systems(IES),the conventional approach to analyzing power grid cascading fau...Cascading faults have been identified as the primary cause of multiple power outages in recent years.With the emergence of integrated energy systems(IES),the conventional approach to analyzing power grid cascading faults is no longer appropriate.A cascading fault analysis method considering multi-energy coupling characteristics is of vital importance.In this study,an innovative analysis method for cascading faults in integrated heat and electricity systems(IHES)is proposed.It considers the degradation characteristics of transmission and energy supply com-ponents in the system to address the impact of component aging on cascading faults.Firstly,degradation models for the current carrying capacity of transmission lines,the water carrying capacity and insulation performance of thermal pipelines,as well as the performance of energy supply equipment during aging,are developed.Secondly,a simulation process for cascading faults in the IHES is proposed.It utilizes an overload-dominated development model to predict the propagation path of cascading faults while also considering network islanding,electric-heating rescheduling,and load shedding.The propagation of cascading faults is reflected in the form of fault chains.Finally,the results of cascading faults under different aging levels are analyzed through numerical examples,thereby verifying the effectiveness and rationality of the proposed model and method.展开更多
Building energy consumption and building carbon emissions both account for more than 20%of their total national values in China.Building employing phase change material(PCM)for passive temperature control shows a prom...Building energy consumption and building carbon emissions both account for more than 20%of their total national values in China.Building employing phase change material(PCM)for passive temperature control shows a promising prospect in meeting the comfort demand and reducing energy consumption simultaneously.However,there is a lack of more detailed research on the interaction between the location and thickness of PCM and indoor natural convection,as well as indoor temperature distribution.In this study,the numerical model of a passive temperature-controlled building integrating the developed PCM module is established with the help of ANSYS.In which,the actual weather condition of Beijing city is set as the boundary conditions and the indoor natural convection is simulated with the consideration of radiation model.The effects of PCM’s thickness and location on the internal temperature field are analyzed and discussed.The results show that the room could maintain within the human comfort temperature range with the longest ratio of 94.10%and the shortest ratio of 51.04%as integrating PCM.In comparison,the value is only 26.70%without PCM.The room’s maximum temperature fluctuation can also be improved;it could be lowered by 64.4%compared to the normal condition.When the quantity of PCM is sufficient,further increasing the PCM amount results in a temperature fluctuation reduction of less than 0.1°C and does not increase the comfort time.Placing PCM on the wall induces an apparent variation in indoor temperature along the vertical direction.Conversely,placing PCM on the roof can lead to a heat transfer rate difference of up to seven times.The optimal placement of PCM depends on the difference between the environmental and phase change temperatures.If the difference is positive,placing PCM on the roof is more effective;conversely,the opposite holds.According to the results over the entire cycle,PCM application on vertical walls yields better performance.The significant difference in natural convection caused by the same thickness of PCM but different application positions,coupled with the influence of air movement on the melting and solidification of PCM,further impacts indoor temperature fluctuations and comfort.This study can provide guidance for the application location and thickness of PCM,especially for scenarios where temperature regulation is required at a specific time.展开更多
When a brazed plate heat exchanger is used as an evaporator,the working mass in the channel may undergo soli-dification,thereby hindering the refrigeration cycle.In this study the liquid solidification process and its o...When a brazed plate heat exchanger is used as an evaporator,the working mass in the channel may undergo soli-dification,thereby hindering the refrigeration cycle.In this study the liquid solidification process and its optimi-zation in a brazed plate heat exchanger are investigated numerically for different inlet velocities;moreover,different levels of corrugation are considered.The results indicate that solidificationfirst occurs around the con-tacts,followed by the area behind the contacts.It is also shown that deadflow zones exist in the sharp areas and such areas are prone to liquid solidification.After optimization,the solidification area attains its smallest value when a corrugation spacingλ=4.2 mm is considered.展开更多
The temporal and spatial characteristics of seasonal hydrogen storage will play a very important role in the coupling of multi-energy systems.This essay believes that there are several key issues worth noting in the s...The temporal and spatial characteristics of seasonal hydrogen storage will play a very important role in the coupling of multi-energy systems.This essay believes that there are several key issues worth noting in the seasonal hydrogen storage coupled multi-energy system,namely,hydrogen storage methods,coupling models,and benefit evaluation.Through research,this article innovatively divides seasonal hydrogen storage into two types:space transfer hydrogen storage technology and time transfer physical property conversion hydrogen storage technology.Then sort out the two most typical seasonal hydrogen storage multi-energy system application scenarios and their hydrogen storage unit models.Finally,it is shown that hydrogen storage methods should be selected according to different periods of time and regions,and the benefits should be evaluated before they can be used in practice.This review study is applicable to the process of coupling seasonal hydrogen storage in multi-energy systems.Hydrogen energy is used as an intermediate energy link for the selection,evaluation and modeling of the optimal selection and rational utilization.展开更多
Recovery of waste heat from boiler flue gas is an effective way to improve energy utilization efficiency.Taking a heating station heating project as an example,the existing heating system of this heating station was a...Recovery of waste heat from boiler flue gas is an effective way to improve energy utilization efficiency.Taking a heating station heating project as an example,the existing heating system of this heating station was analyzed for its underutilized flue gas waste heat and low energy utilization rate.Rankine cycle is an effective waste heat recovery method,and a steam boiler organic Rankine cycle(ORC)cogeneration waste heat utilization method is proposed.The system model simulation is constructed and verified.First,a thermodynamic model was constructed in MATLAB and five suitable work gases were selected to analyze the effects of evaporation temperature and condensation temperature on the network and thermal efficiency of the waste heat cycle power system.Secondly,the ORC model is invoked in TRNSYS to construct the improved cogeneration system,and the rationality of the remaining heat utilization methods is determined by calculating and analyzing the thermal performance,economy,and environmental protection of the improved system.The simulation results show that the system can generate about 552,000 kWh of electricity per year,and improving the energy utilization rate from 0.72 to 0.78.展开更多
Realization of CO_(2) resource utilization is the main development direction of CO_(2) reduction.The CO_(2) methana-tion technology based on microbial electrolysis cell(MEC)has the characteristics of ambient temperatu...Realization of CO_(2) resource utilization is the main development direction of CO_(2) reduction.The CO_(2) methana-tion technology based on microbial electrolysis cell(MEC)has the characteristics of ambient temperature and pressure,green and low-carbon,which meets the need of low-carbon energy transition.However,the lack of the system such as the change of applied voltage and the reactor amplification will affect the methane production efficiency.In this research,the efficiency of methane production with different applied voltages and different types of reactors was carried out.The results were concluded that the maximum methane production rate of the H-type two-chamber microbial electrolysis cells(MECs)at an applied voltage of 0.8 V was obtained to be 1.15 times higher than that of 0.5 V;under the same conditions of inoculated sludge,the reactor was amplified 2.5 times and the cumulative amount of methane production was 1.04 times higher than the original.This research can provide a theoretical basis and technical reference for the early industrial application of CO_(2) methanation tech-nology based on MEC.展开更多
Reducing CO_(2) to produce methane through microbial electrolytic cell(MEC)is one of the important methods of CO_(2) resource utilization.In view of the problem of low methanogenesis rate and weak CO_(2) conversion ra...Reducing CO_(2) to produce methane through microbial electrolytic cell(MEC)is one of the important methods of CO_(2) resource utilization.In view of the problem of low methanogenesis rate and weak CO_(2) conversion rate in the reduction process,theflowfield environment of the cathode chamber is changed by changing the upper gas cir-culation rate and the lower liquid circulation rate of the cathode chamber to explore the impact on the reactor startup and operation and products.The results showed that under certain conditions,the CO_(2) consumption and methane production rate could be increased by changing the upper gas recirculation rate alone,but the increase effect was not obvious,but the by-product hydrogen production decreased significantly.Changing the lower liquid circulation rate alone can effectively promote the growth of biofilm,and change the properties of biofilm at the later stage of the experiment,with the peak current density increased by 16%;The methanogenic rate decreased from the peak value of 0.561 to 0.3 mmol/d,and the CO_(2) consumption did not change signifi-cantly,which indicated that CO_(2) was converted into other organic substances instead of methane.The data after coupling the upper gas circulation rate with the lower liquid circulation rate is similar to that of only changing the lower liquid circulation rate,but changing the upper gas circulation rate can alleviate the decline of methane pro-duction rate caused by the change of biofilm properties,which not only improves the current density,but also increases the methane production rate by 0.05 mmol/d in the stable period.This study can provide theoretical and technical support for the industrial application scenario offlowfield regulation intervention of microbial elec-trolytic cell methanogenesis.展开更多
Microbial Electrolytic Cell(MEC)is an electrochemical reaction device that uses electrical energy as an energy input and microorganisms as catalysts to produce fuels and chemicals.The regenerative electrochemical syst...Microbial Electrolytic Cell(MEC)is an electrochemical reaction device that uses electrical energy as an energy input and microorganisms as catalysts to produce fuels and chemicals.The regenerative electrochemical system is a MEC improvement system for methane gas produced by biological carbon sequestration technology using renewable energy sources to provide a voltage environment.In response to the influence of fluctuating disturbances of renewable electricity and the long system start-up time,this paper analyzes the characteristics of two strategies,regulating voltage parameter changes and activated sludge pretreatment,on the methane production efficiency of the renewable gas electrochemical system.In this system,the methane production rate of regenerative electrochemical system is increased by 1.4 times through intermittent boosting start-up strategy;based on intermittent boosting,the methane production rate of regenerative electrochemical system is increased by 2 times through sludge pyrolysis pretreatment start-up strategy,and the start-up time is reduced to 10 days.Meanwhile,according to the simulation test results of power input fluctuation and intermittency,the stability standard deviation of its system operation is 75%of the original one,and the recovery rate is about 1 times higher.This study can provide a theoretical basis and technical reference for the early industrial application of microbial CO_(2)methanation technology based on renewable energy.展开更多
In order to comprehensively evaluate the flow and heat transfer performance of a large-size annular combustion chamber of a heavy-duty gas turbine,we carried out numerical computation and analyses on the velocity,temp...In order to comprehensively evaluate the flow and heat transfer performance of a large-size annular combustion chamber of a heavy-duty gas turbine,we carried out numerical computation and analyses on the velocity,temperature and pressure fields in the chamber with double swirlers.The mathematical model of the coupling combustion,gas flow,and heat transfer process was established.The influences of the inlet swirling strength,fuel-air ratio and temperature of the premixed gas on the multi-field characteristics and synergy were investigated on the basis of field synergy theory.The results showed that the central recirculation zone induced by the inlet swirling flow grows downstream in the combustion chamber.The velocity and temperature in the outlet section of the chamber tend to be uniform due to the upstream improved synergy.The outer swirl number of the premixed gas flow has a great influence on the comprehensive flow and heat transfer performance of the combustion chamber.The synergy angles change towards benefiting the synergy between velocity and temperature fields with the increasing swirl numbers and inlet gas temperature while the velocity-pressure synergy becomes poor.The increasing fuel-air ratio of premixed gas leads to different trends of the velocity-temperature synergy and velocity-pressure synergy.The comprehensive synergy representing the low-resistance heat transfer performance is evidently dominated mainly by the velocity-temperature synergy.展开更多
The earth to fluid pipe(ETFP)system has been widely applied to various energy engineering.The numerical model of the heat transfer process in the ETFP system with a shallow-buried horizontal or a deep-buried vertical ...The earth to fluid pipe(ETFP)system has been widely applied to various energy engineering.The numerical model of the heat transfer process in the ETFP system with a shallow-buried horizontal or a deep-buried vertical U-shape pipe adopted in practical engineering was established and the model distinctions were pointed out.The comparison of the thermal performance between the two types of ETFP system under various schemes was conducted on the basis of numerical prediction.The results showed that the thermal parameters of the ETFP system with a shallow-buried horizontal pipe were influenced by the inlet velocity and ground temperature obviously.The variation of the fluid temperature was smooth and the thermal influence zone was limited under the fixed conditions.The proper intermittent operation scheme reduced 53.1%outlet fluid temperature rising.By contrast,the fluid temperature in the ETFP system with a deep-buried vertical U-shape pipe varied dramatically with the operation conditions.The intermittent operation scheme with a relatively short interval led to a less temperature fluctuation of soil around the pipe.The intermittent scheme is beneficial to the recovery of the thermal condition of soil around the U-shape pipe.These results indicated a stark difference in thermal performance between the two types of system.The study can provide guidance for the selection and operation of ETFP system in practical heat exchange engineering.展开更多
SO2 poisoning and regeneration of Mn-Ce/TiO2 catalyst prepared by a novel co-precipitation method for low temperature selective catalytic reduction (SCR) of NOx with ammonia were investigated in this study. When 700 p...SO2 poisoning and regeneration of Mn-Ce/TiO2 catalyst prepared by a novel co-precipitation method for low temperature selective catalytic reduction (SCR) of NOx with ammonia were investigated in this study. When 700 ppm SO2 was fed in, the Mn-Ce/TiO2 catalyst had good resistance to SO2, but the deactivation of Mn-Ce/TiO2 poisoned by SO2 still occurred. The NO conversion of Mn-Ce/TiO2 (the molar ra-tio of Ce to Ti is 0.075) catalyst decreased from 92.5% to 34.6% in 13 h. Characterizations of fresh and SO2-poisoned Mn-Ce/TiO2 catalysts were carried out by Brunauer-Emmett-Teller method (BET), ion chromatography (IC), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The characterized results indicated that the deposition of sulfates and nitrates on the surface made the catalyst deactivated. Water washing, thermal regeneration and reductive regeneration were used to regenerate the deactivated Mn-Ce/TiO2. And water washing showed best performance on the regeneration of poisoned catalysts, especially with ultrasonic vibration. The Mn-Ce/TiO2 catalyst showed high stability under a series of deactivation-regeneration experiments for ten cycles.展开更多
A dual-channel solar thermal storage wall system with eutectic phase change material is studied.The full-day cooling load in summer and heating load in winter can be both decreased by this novel system.To investigate ...A dual-channel solar thermal storage wall system with eutectic phase change material is studied.The full-day cooling load in summer and heating load in winter can be both decreased by this novel system.To investigate the airflow in the dual channel,mixed area assumptions based on the experimental results are summarized.Dynamic mathematical models of the system under four work modes are established and verified by the experimental results.The average RMSD(root mean square deviation)value is 0.35%in summer and 0.95% in winter.By analyzing the heat flux,the combination of dual channel and PCM is proven to decrease and delay cooling load both in the daytime and nighttime of summer.In winter's daytime,the thermal efficiency is promoted by the dual channel.And in winter’s nighttime,the system is able to heat the room constantly by the PCM boards.Based on parameter researches,the optimum phase change temperature range and the optimum thickness of the PCM are 26-30℃,1.5 cm in summer and 16-22℃,0.6 cm in winter respectively.To reach the optimum annual thermal performance,the coverage area is 2 m^(2) for this system.展开更多
In this paper,a multi-objective optimization model is established for the investment plan and operation management of a hybrid distributed energy system. Considering both economic and environmental benefits, the overa...In this paper,a multi-objective optimization model is established for the investment plan and operation management of a hybrid distributed energy system. Considering both economic and environmental benefits, the overall annual cost and emissions of CO2 equivalents are selected as the objective functions to be minimized.In addition,relevant constraints are included to guarantee that the optimized system is reliable to satisfy the energy demands.To solve the optimization model,the non-dominated sorting generic algorithm Ⅱ (NSGA-Ⅱ)is employed to derive a set of non-dominated Pareto solutions.The diversity of Pareto solutions is conserved by a crowding distance operator,and the best compromised Pareto solution is determined based on the fuzzy set theory. As an illustrative example,a hotel building is selected for study to verify the effectiveness of the optimization model and the solving algorithm.The results obtained from the numerical study indicate that the NSGA-Ⅱ results in more diversified Pareto solutions and the fuzzy set theory picks out a better combination of device capacities with reason-able operating strategies.展开更多
Aiming at improving the capture performance of internal vortex electrostatic cyclone precipitator(ECP),a theoretical model with mechanics-electric-magnetic coupling was established,the collection efficiency of magneti...Aiming at improving the capture performance of internal vortex electrostatic cyclone precipitator(ECP),a theoretical model with mechanics-electric-magnetic coupling was established,the collection efficiency of magnetic confinement ECP under different working voltages was simulated,and the influence of magnetic flux intensity on the removal performance of submicron particles was explored.Results show that the number of particles escaped from the cyclone is greatly reduced after the introduction of magnetic field and electric field,indicating that charging effect and magnetic confinement are more conductive to trap submicron particles in the internal vortex ECP.The lower the working voltage is,the worse the charging lifting effect is,but the stronger the magnetic confinement characteristics are.Furthermore,the contributions of charging effect to collection efficiency and magnetic confinement characteristics are more obvious at a weaker magnetic flux density.The research results can provide a practical new idea for the innovative design of ECP.展开更多
Mechanically pumped two-phase loop(MPTL)which is a prominent two-phase heat transfer technology presents a promising prospect in thermal control for space payload.However,transient behavior of MPTL caused by phase-cha...Mechanically pumped two-phase loop(MPTL)which is a prominent two-phase heat transfer technology presents a promising prospect in thermal control for space payload.However,transient behavior of MPTL caused by phase-change and heat sources load-on/off in simulated space environment is rarely reported.In the present study,one MPTL setup was designed and constructed,and experimentally studied.Particularly,a novel two-phase thermally-controlled accumulator integrated with passive cooling measure and three capillary structures was designed as the temperature-control device.Dynamic behavior of the start-up,temperature control,and temperature adjustment were monitored;meanwhile,thermodynamic behavior within the proposed accumulator,the operating behavior as well as the heat and mass transfer behavior between the main loop and the accumulator were revealed.The results show that the fluid management function of the capillary structures for the novel accumulator is verified.The working point of the MPTL system can be adjusted by changing the temperature control point of the accumulator and it is little influenced by external heat flux and heat sources on/off.Pressure-drop oscillations which are manifested as fluctuations of temperature and pressure can be observed after phase changing due to the compressible volume within the accumulator and the negative-slope portion of the internal pressure.展开更多
Highly efficient photocatalytic reduction of CO2 is essential for solving the greenhouse effect and energy crisis.In this paper,the Sm-TiO2 nanocomposites were successfully prepared via sol-gel method.The CO2 photored...Highly efficient photocatalytic reduction of CO2 is essential for solving the greenhouse effect and energy crisis.In this paper,the Sm-TiO2 nanocomposites were successfully prepared via sol-gel method.The CO2 photoreduction activities of synthesized samples were tested under irradiation for 6 h and the results indicate that the 0.5% Sm-TiO2 catalyst has superior performance and stability.The CO and CH4 yields of0.5% Sm-TiO2 catalyst are 55.47 and 3.82 μmol/g·cat respectively,which are 5.02 and 2.67 times the yield of TiO2.The possible mechanism of Sm doped TiO2 was investigated through comprehensive characterization and photoetectrochemical analysis,After the Sm doping,the photo-generated electrons in TiO2 could migrate to Sm 4 f,and some of them can be captured by reducing Sm3+ o Sm2+,which can lower the recombination rate of electron and hole pairs.Therefore,the enhanced photocatalytic performance could be ascribed to large specific surface area,fast separation rate of electron-hole pairs and high visible light response.This report provides some meaningful attempts in researching the CO2 photocatalytic reduction.展开更多
基金supported by Shanghai Rising-Star Program(No.22QA1403900)the National Natural Science Foundation of China(No.71804106)the Noncarbon Energy Conversion and Utilization Institute under the Shanghai Class IV Peak Disciplinary Development Program.
文摘Cascading faults have been identified as the primary cause of multiple power outages in recent years.With the emergence of integrated energy systems(IES),the conventional approach to analyzing power grid cascading faults is no longer appropriate.A cascading fault analysis method considering multi-energy coupling characteristics is of vital importance.In this study,an innovative analysis method for cascading faults in integrated heat and electricity systems(IHES)is proposed.It considers the degradation characteristics of transmission and energy supply com-ponents in the system to address the impact of component aging on cascading faults.Firstly,degradation models for the current carrying capacity of transmission lines,the water carrying capacity and insulation performance of thermal pipelines,as well as the performance of energy supply equipment during aging,are developed.Secondly,a simulation process for cascading faults in the IHES is proposed.It utilizes an overload-dominated development model to predict the propagation path of cascading faults while also considering network islanding,electric-heating rescheduling,and load shedding.The propagation of cascading faults is reflected in the form of fault chains.Finally,the results of cascading faults under different aging levels are analyzed through numerical examples,thereby verifying the effectiveness and rationality of the proposed model and method.
基金supported by National Innovation Talent Promotion Program(G2022013028L).
文摘Building energy consumption and building carbon emissions both account for more than 20%of their total national values in China.Building employing phase change material(PCM)for passive temperature control shows a promising prospect in meeting the comfort demand and reducing energy consumption simultaneously.However,there is a lack of more detailed research on the interaction between the location and thickness of PCM and indoor natural convection,as well as indoor temperature distribution.In this study,the numerical model of a passive temperature-controlled building integrating the developed PCM module is established with the help of ANSYS.In which,the actual weather condition of Beijing city is set as the boundary conditions and the indoor natural convection is simulated with the consideration of radiation model.The effects of PCM’s thickness and location on the internal temperature field are analyzed and discussed.The results show that the room could maintain within the human comfort temperature range with the longest ratio of 94.10%and the shortest ratio of 51.04%as integrating PCM.In comparison,the value is only 26.70%without PCM.The room’s maximum temperature fluctuation can also be improved;it could be lowered by 64.4%compared to the normal condition.When the quantity of PCM is sufficient,further increasing the PCM amount results in a temperature fluctuation reduction of less than 0.1°C and does not increase the comfort time.Placing PCM on the wall induces an apparent variation in indoor temperature along the vertical direction.Conversely,placing PCM on the roof can lead to a heat transfer rate difference of up to seven times.The optimal placement of PCM depends on the difference between the environmental and phase change temperatures.If the difference is positive,placing PCM on the roof is more effective;conversely,the opposite holds.According to the results over the entire cycle,PCM application on vertical walls yields better performance.The significant difference in natural convection caused by the same thickness of PCM but different application positions,coupled with the influence of air movement on the melting and solidification of PCM,further impacts indoor temperature fluctuations and comfort.This study can provide guidance for the application location and thickness of PCM,especially for scenarios where temperature regulation is required at a specific time.
基金This research is supported by the Scientific Problem Tackling Program of Science and Technology Commission of Shanghai Municipality(18DZ1202000)the Shanghai Local University Project“Research and Application of Key Technologies of New Efficient Micro Gas Turbine System”(No.19020500900).
文摘When a brazed plate heat exchanger is used as an evaporator,the working mass in the channel may undergo soli-dification,thereby hindering the refrigeration cycle.In this study the liquid solidification process and its optimi-zation in a brazed plate heat exchanger are investigated numerically for different inlet velocities;moreover,different levels of corrugation are considered.The results indicate that solidificationfirst occurs around the con-tacts,followed by the area behind the contacts.It is also shown that deadflow zones exist in the sharp areas and such areas are prone to liquid solidification.After optimization,the solidification area attains its smallest value when a corrugation spacingλ=4.2 mm is considered.
基金funded by two projects of Science and Technology Commission of Shanghai Municipality,Grant Nos.20DZ1206300,18DZ1203304,18DZ1203403.
文摘The temporal and spatial characteristics of seasonal hydrogen storage will play a very important role in the coupling of multi-energy systems.This essay believes that there are several key issues worth noting in the seasonal hydrogen storage coupled multi-energy system,namely,hydrogen storage methods,coupling models,and benefit evaluation.Through research,this article innovatively divides seasonal hydrogen storage into two types:space transfer hydrogen storage technology and time transfer physical property conversion hydrogen storage technology.Then sort out the two most typical seasonal hydrogen storage multi-energy system application scenarios and their hydrogen storage unit models.Finally,it is shown that hydrogen storage methods should be selected according to different periods of time and regions,and the benefits should be evaluated before they can be used in practice.This review study is applicable to the process of coupling seasonal hydrogen storage in multi-energy systems.Hydrogen energy is used as an intermediate energy link for the selection,evaluation and modeling of the optimal selection and rational utilization.
基金supported by research funds from Shanghai’s 2020 Annual Science and Technology Innovation Action Plan:Social development and Science&Technology Project(No.20dz1205302).
文摘Recovery of waste heat from boiler flue gas is an effective way to improve energy utilization efficiency.Taking a heating station heating project as an example,the existing heating system of this heating station was analyzed for its underutilized flue gas waste heat and low energy utilization rate.Rankine cycle is an effective waste heat recovery method,and a steam boiler organic Rankine cycle(ORC)cogeneration waste heat utilization method is proposed.The system model simulation is constructed and verified.First,a thermodynamic model was constructed in MATLAB and five suitable work gases were selected to analyze the effects of evaporation temperature and condensation temperature on the network and thermal efficiency of the waste heat cycle power system.Secondly,the ORC model is invoked in TRNSYS to construct the improved cogeneration system,and the rationality of the remaining heat utilization methods is determined by calculating and analyzing the thermal performance,economy,and environmental protection of the improved system.The simulation results show that the system can generate about 552,000 kWh of electricity per year,and improving the energy utilization rate from 0.72 to 0.78.
基金the Shanghai Science and Technology Development Fund,No.20dz1206300.
文摘Realization of CO_(2) resource utilization is the main development direction of CO_(2) reduction.The CO_(2) methana-tion technology based on microbial electrolysis cell(MEC)has the characteristics of ambient temperature and pressure,green and low-carbon,which meets the need of low-carbon energy transition.However,the lack of the system such as the change of applied voltage and the reactor amplification will affect the methane production efficiency.In this research,the efficiency of methane production with different applied voltages and different types of reactors was carried out.The results were concluded that the maximum methane production rate of the H-type two-chamber microbial electrolysis cells(MECs)at an applied voltage of 0.8 V was obtained to be 1.15 times higher than that of 0.5 V;under the same conditions of inoculated sludge,the reactor was amplified 2.5 times and the cumulative amount of methane production was 1.04 times higher than the original.This research can provide a theoretical basis and technical reference for the early industrial application of CO_(2) methanation tech-nology based on MEC.
基金This paper is supported by Shanghai Science and Technology Development Fund,China,No.19DZ1205604.
文摘Reducing CO_(2) to produce methane through microbial electrolytic cell(MEC)is one of the important methods of CO_(2) resource utilization.In view of the problem of low methanogenesis rate and weak CO_(2) conversion rate in the reduction process,theflowfield environment of the cathode chamber is changed by changing the upper gas cir-culation rate and the lower liquid circulation rate of the cathode chamber to explore the impact on the reactor startup and operation and products.The results showed that under certain conditions,the CO_(2) consumption and methane production rate could be increased by changing the upper gas recirculation rate alone,but the increase effect was not obvious,but the by-product hydrogen production decreased significantly.Changing the lower liquid circulation rate alone can effectively promote the growth of biofilm,and change the properties of biofilm at the later stage of the experiment,with the peak current density increased by 16%;The methanogenic rate decreased from the peak value of 0.561 to 0.3 mmol/d,and the CO_(2) consumption did not change signifi-cantly,which indicated that CO_(2) was converted into other organic substances instead of methane.The data after coupling the upper gas circulation rate with the lower liquid circulation rate is similar to that of only changing the lower liquid circulation rate,but changing the upper gas circulation rate can alleviate the decline of methane pro-duction rate caused by the change of biofilm properties,which not only improves the current density,but also increases the methane production rate by 0.05 mmol/d in the stable period.This study can provide theoretical and technical support for the industrial application scenario offlowfield regulation intervention of microbial elec-trolytic cell methanogenesis.
基金Funding Statement:This paper is supported by Shanghai Science and Technology Development Fund,China,No.19DZ1205604.
文摘Microbial Electrolytic Cell(MEC)is an electrochemical reaction device that uses electrical energy as an energy input and microorganisms as catalysts to produce fuels and chemicals.The regenerative electrochemical system is a MEC improvement system for methane gas produced by biological carbon sequestration technology using renewable energy sources to provide a voltage environment.In response to the influence of fluctuating disturbances of renewable electricity and the long system start-up time,this paper analyzes the characteristics of two strategies,regulating voltage parameter changes and activated sludge pretreatment,on the methane production efficiency of the renewable gas electrochemical system.In this system,the methane production rate of regenerative electrochemical system is increased by 1.4 times through intermittent boosting start-up strategy;based on intermittent boosting,the methane production rate of regenerative electrochemical system is increased by 2 times through sludge pyrolysis pretreatment start-up strategy,and the start-up time is reduced to 10 days.Meanwhile,according to the simulation test results of power input fluctuation and intermittency,the stability standard deviation of its system operation is 75%of the original one,and the recovery rate is about 1 times higher.This study can provide a theoretical basis and technical reference for the early industrial application of microbial CO_(2)methanation technology based on renewable energy.
基金the National Natural Science Foundation of China(No.51606114)Science and Technology Commission of Shanghai Municipality(Nos.19020500900,16020500700)to this study are acknowledged and highly appreciated.
文摘In order to comprehensively evaluate the flow and heat transfer performance of a large-size annular combustion chamber of a heavy-duty gas turbine,we carried out numerical computation and analyses on the velocity,temperature and pressure fields in the chamber with double swirlers.The mathematical model of the coupling combustion,gas flow,and heat transfer process was established.The influences of the inlet swirling strength,fuel-air ratio and temperature of the premixed gas on the multi-field characteristics and synergy were investigated on the basis of field synergy theory.The results showed that the central recirculation zone induced by the inlet swirling flow grows downstream in the combustion chamber.The velocity and temperature in the outlet section of the chamber tend to be uniform due to the upstream improved synergy.The outer swirl number of the premixed gas flow has a great influence on the comprehensive flow and heat transfer performance of the combustion chamber.The synergy angles change towards benefiting the synergy between velocity and temperature fields with the increasing swirl numbers and inlet gas temperature while the velocity-pressure synergy becomes poor.The increasing fuel-air ratio of premixed gas leads to different trends of the velocity-temperature synergy and velocity-pressure synergy.The comprehensive synergy representing the low-resistance heat transfer performance is evidently dominated mainly by the velocity-temperature synergy.
基金supported by the National Natural Science Foundation of China(No.51606114)the Science and Technology Commission of Shanghai Municipality(No.18020501000).
文摘The earth to fluid pipe(ETFP)system has been widely applied to various energy engineering.The numerical model of the heat transfer process in the ETFP system with a shallow-buried horizontal or a deep-buried vertical U-shape pipe adopted in practical engineering was established and the model distinctions were pointed out.The comparison of the thermal performance between the two types of ETFP system under various schemes was conducted on the basis of numerical prediction.The results showed that the thermal parameters of the ETFP system with a shallow-buried horizontal pipe were influenced by the inlet velocity and ground temperature obviously.The variation of the fluid temperature was smooth and the thermal influence zone was limited under the fixed conditions.The proper intermittent operation scheme reduced 53.1%outlet fluid temperature rising.By contrast,the fluid temperature in the ETFP system with a deep-buried vertical U-shape pipe varied dramatically with the operation conditions.The intermittent operation scheme with a relatively short interval led to a less temperature fluctuation of soil around the pipe.The intermittent scheme is beneficial to the recovery of the thermal condition of soil around the U-shape pipe.These results indicated a stark difference in thermal performance between the two types of system.The study can provide guidance for the selection and operation of ETFP system in practical heat exchange engineering.
基金financially supported by the Research Project of China Guodian Corporation (No.D11T22)
文摘SO2 poisoning and regeneration of Mn-Ce/TiO2 catalyst prepared by a novel co-precipitation method for low temperature selective catalytic reduction (SCR) of NOx with ammonia were investigated in this study. When 700 ppm SO2 was fed in, the Mn-Ce/TiO2 catalyst had good resistance to SO2, but the deactivation of Mn-Ce/TiO2 poisoned by SO2 still occurred. The NO conversion of Mn-Ce/TiO2 (the molar ra-tio of Ce to Ti is 0.075) catalyst decreased from 92.5% to 34.6% in 13 h. Characterizations of fresh and SO2-poisoned Mn-Ce/TiO2 catalysts were carried out by Brunauer-Emmett-Teller method (BET), ion chromatography (IC), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The characterized results indicated that the deposition of sulfates and nitrates on the surface made the catalyst deactivated. Water washing, thermal regeneration and reductive regeneration were used to regenerate the deactivated Mn-Ce/TiO2. And water washing showed best performance on the regeneration of poisoned catalysts, especially with ultrasonic vibration. The Mn-Ce/TiO2 catalyst showed high stability under a series of deactivation-regeneration experiments for ten cycles.
基金supported by the National Natural Science Foundation of China(No.51878636,No.51908527)the Jiangxi Provincial Key Technology R&D Program,China(No.20202BBEL53033)+3 种基金the Key Research and Development Project of Anhui Province,China(201904a07020014)Young and Middle-aged Teacher Education Research Project 2020(Science and Technology)the Education Department of Fujian Province(No.JAT200284)Research Start-Up Fund of Jimei University(ZQ2020016).
文摘A dual-channel solar thermal storage wall system with eutectic phase change material is studied.The full-day cooling load in summer and heating load in winter can be both decreased by this novel system.To investigate the airflow in the dual channel,mixed area assumptions based on the experimental results are summarized.Dynamic mathematical models of the system under four work modes are established and verified by the experimental results.The average RMSD(root mean square deviation)value is 0.35%in summer and 0.95% in winter.By analyzing the heat flux,the combination of dual channel and PCM is proven to decrease and delay cooling load both in the daytime and nighttime of summer.In winter's daytime,the thermal efficiency is promoted by the dual channel.And in winter’s nighttime,the system is able to heat the room constantly by the PCM boards.Based on parameter researches,the optimum phase change temperature range and the optimum thickness of the PCM are 26-30℃,1.5 cm in summer and 16-22℃,0.6 cm in winter respectively.To reach the optimum annual thermal performance,the coverage area is 2 m^(2) for this system.
基金the National Natural Science Foundation of China (Grant No.71804106)Shanghai Sailing Program (No.17YF1406800)+1 种基金Shanghai Chenguang Program (No. 17CG57)The Key Fund of Shanghai Science Technology Committee (No.16020500900).
文摘In this paper,a multi-objective optimization model is established for the investment plan and operation management of a hybrid distributed energy system. Considering both economic and environmental benefits, the overall annual cost and emissions of CO2 equivalents are selected as the objective functions to be minimized.In addition,relevant constraints are included to guarantee that the optimized system is reliable to satisfy the energy demands.To solve the optimization model,the non-dominated sorting generic algorithm Ⅱ (NSGA-Ⅱ)is employed to derive a set of non-dominated Pareto solutions.The diversity of Pareto solutions is conserved by a crowding distance operator,and the best compromised Pareto solution is determined based on the fuzzy set theory. As an illustrative example,a hotel building is selected for study to verify the effectiveness of the optimization model and the solving algorithm.The results obtained from the numerical study indicate that the NSGA-Ⅱ results in more diversified Pareto solutions and the fuzzy set theory picks out a better combination of device capacities with reason-able operating strategies.
基金sponsored by National Natural Science Foundation of China (Grant numbers 12172228,11572187)Natural Science Foundation of Shanghai (Grant number 22ZR1444400).
文摘Aiming at improving the capture performance of internal vortex electrostatic cyclone precipitator(ECP),a theoretical model with mechanics-electric-magnetic coupling was established,the collection efficiency of magnetic confinement ECP under different working voltages was simulated,and the influence of magnetic flux intensity on the removal performance of submicron particles was explored.Results show that the number of particles escaped from the cyclone is greatly reduced after the introduction of magnetic field and electric field,indicating that charging effect and magnetic confinement are more conductive to trap submicron particles in the internal vortex ECP.The lower the working voltage is,the worse the charging lifting effect is,but the stronger the magnetic confinement characteristics are.Furthermore,the contributions of charging effect to collection efficiency and magnetic confinement characteristics are more obvious at a weaker magnetic flux density.The research results can provide a practical new idea for the innovative design of ECP.
基金supported by the National Natural Science Foundation of China(No.51806010)Shanghai Sailing Program,China(No.18YF1409100).
文摘Mechanically pumped two-phase loop(MPTL)which is a prominent two-phase heat transfer technology presents a promising prospect in thermal control for space payload.However,transient behavior of MPTL caused by phase-change and heat sources load-on/off in simulated space environment is rarely reported.In the present study,one MPTL setup was designed and constructed,and experimentally studied.Particularly,a novel two-phase thermally-controlled accumulator integrated with passive cooling measure and three capillary structures was designed as the temperature-control device.Dynamic behavior of the start-up,temperature control,and temperature adjustment were monitored;meanwhile,thermodynamic behavior within the proposed accumulator,the operating behavior as well as the heat and mass transfer behavior between the main loop and the accumulator were revealed.The results show that the fluid management function of the capillary structures for the novel accumulator is verified.The working point of the MPTL system can be adjusted by changing the temperature control point of the accumulator and it is little influenced by external heat flux and heat sources on/off.Pressure-drop oscillations which are manifested as fluctuations of temperature and pressure can be observed after phase changing due to the compressible volume within the accumulator and the negative-slope portion of the internal pressure.
基金Project supported by the National Key R&D Program of China(2018YFB0605002)the National Natural Science Foundation of Shanghai(14ZR1417800)。
文摘Highly efficient photocatalytic reduction of CO2 is essential for solving the greenhouse effect and energy crisis.In this paper,the Sm-TiO2 nanocomposites were successfully prepared via sol-gel method.The CO2 photoreduction activities of synthesized samples were tested under irradiation for 6 h and the results indicate that the 0.5% Sm-TiO2 catalyst has superior performance and stability.The CO and CH4 yields of0.5% Sm-TiO2 catalyst are 55.47 and 3.82 μmol/g·cat respectively,which are 5.02 and 2.67 times the yield of TiO2.The possible mechanism of Sm doped TiO2 was investigated through comprehensive characterization and photoetectrochemical analysis,After the Sm doping,the photo-generated electrons in TiO2 could migrate to Sm 4 f,and some of them can be captured by reducing Sm3+ o Sm2+,which can lower the recombination rate of electron and hole pairs.Therefore,the enhanced photocatalytic performance could be ascribed to large specific surface area,fast separation rate of electron-hole pairs and high visible light response.This report provides some meaningful attempts in researching the CO2 photocatalytic reduction.
