An actively water-cooled limiter has been designed for the long pulse operation of an HT-7 device, by adopting an integrated structure-doped graphite and a copper alloy heat sink with a super carbon sheet serving as a...An actively water-cooled limiter has been designed for the long pulse operation of an HT-7 device, by adopting an integrated structure-doped graphite and a copper alloy heat sink with a super carbon sheet serving as a compliant layer between them. The behaviors of the integrated structure were evaluated in an electron beam facility under different heat loads and cooling conditions. The surface temperature and bulk temperature distribution were carefully measured by optical pyrometers and thermocouples under a steady state heat flux of 1 to 5 MW/m^2 and a water flow rate of 3 m^3/h, 4.5 m^3/h and 6 m^3/h, respectively. It was found that the surface temperature increased rapidly with the heat flux rising, but decreased only slightly with the water flow rate rising. The surface temperature reached approximately 1200℃ at 5 MW/m^2 of heat flux and 6 m^3/h of water flow. The primary experimental results indicate that the integrated design meets the requirements for the heat expelling capacity of the HT-7 device. A set of numerical simulations was also completed, whose outcome was in good accord with the experimental results.展开更多
Many flight and icing conditions should be considered in order to design an efficient ice protection system to prevent ice accretion on the aircraft surface. The anti-icing heat load is the basic knowledge for the des...Many flight and icing conditions should be considered in order to design an efficient ice protection system to prevent ice accretion on the aircraft surface. The anti-icing heat load is the basic knowledge for the design of a thermal anti-icing system. In order to help the design of the thermal anti-icing system and save the design time, a fast and efficiency method for prediction the anti-icing heat load is investigated. The computation fluid dynamics (CFD) solver and the Messinger model are applied to obtain the snapshots. Examples for the calculation of the anti-icing heat load using the proper orthogonal decomposition (POD) method are presented and compared with the CFD simulation results. It is shown that the heat loads predicted by POD method are in agreement with the CFD computation results. Moreover, it is obviously to see that the POD method is time-saving and can meet the requirement of real-time prediction.展开更多
The next-generation heating systems,crucial for rational heat distribution and refined management,rely heavily on accurate zone-specific heat load predictions.This paper introduces a method for rapid zone-specific hea...The next-generation heating systems,crucial for rational heat distribution and refined management,rely heavily on accurate zone-specific heat load predictions.This paper introduces a method for rapid zone-specific heat load prediction based on heat consumption allocation and data-driven techniques.The approach involves predicting the overall heat load of the building and then redistributing the total heat according to a heat consumption matrix.This eliminates the need for real-time data collection from each room,resulting in cost savings on hardware and improved computational efficiency.The overall building heat load data is obtained through a data-driven algorithm,while the heat consumption matrix is constructed through energy software simulation analysis.Using Building 2 in the Baotou Industrial Park,China,as a case study,the paper analyzes the differences between actual measurements and room estimates.Experimental results indicate an average error of 7.02%for the proposed estimation method.Although not achieving high precision(>95%)in heat load prediction,this level of accuracy is deemed sufficient to meet the requirements of feedforward control.展开更多
This paper establishes a two-layer data-driven robust scheduling method to deal with the significant computational complexity and uncertainties in scheduling industrial heat loads.First,a two-layer deterministic sched...This paper establishes a two-layer data-driven robust scheduling method to deal with the significant computational complexity and uncertainties in scheduling industrial heat loads.First,a two-layer deterministic scheduling model is proposed to address the computational burden of utilizing flexibility from a large number of bitumen tanks(BTs).The key feature of this model is the capability to reduce the number of control variables through analyzing and modeling the clustered temperature transfer of BTs.Second,to tackle the uncertainties in the scheduling problem,historical data regarding BTs are collected and analyzed,and a data-driven piecewise linear Kernelbased support vector clustering technique is employed to construct the uncertainty set with convex boundaries and adjustable conservatism,based on which robust optimization can be conducted.The case results indicate that the proposed method enables the utilization of flexibility in BTs,improving the level of onsite photovoltaic consumption and reducing the aggregated load fluctuation.展开更多
This paper introduces a thermodynamically grounded framework that replaces conventional energy-centric building simulation with a heat-based reconstruction method,enabling the use of standard-year weather data without...This paper introduces a thermodynamically grounded framework that replaces conventional energy-centric building simulation with a heat-based reconstruction method,enabling the use of standard-year weather data without bespoke weather files.High-accuracy predictive models are developed to estimate seasonal heating and cooling loads and to derive convective heat transfer coefficients for transitional seasons.Models are calibrated against extended AMeDAS records for Kurume,Fukuoka Prefecture,demonstrating improved capture of local climatic variability compared with standard practice.Methodologically,the study establishes time-series regression relationships linking outdoor air temperature,incident solar radiation,and wind speed to instantaneous thermal demand and surface convective rates.These empirical relations feed a reconstruction algorithm that adjusts simulation outputs to standardized climatic conditions by rescaling heat flows and convective parameters rather than altering meteorological inputs.Results indicate that reframing simulation inputs in terms of heat enhances reliability and transferability of performance predictions and reduces uncertainty associated with variable weather.The paper examines essential assumptions affecting applicability,including the assumed linearity of convective correlations,representativeness of the reference building envelope,and the use of virtual walls for parameter identification.It further proposes a novel procedure to compute a physical adjustment coefficient for the convective heat transfer coefficient,addressing a parameter gap in macro-scale models while acknowledging challenges for conventional comparative validation.The authors recommend future work on automated calibration routines and on extending the method to tropical and arid climates to broaden applicability and support foundational reform of building energy simulation.展开更多
A new trajectory generation for heat load test is proposed based on gauss pseudospectral method within limit range. Firstly,with multiple path constraints and flight task requirements taken into consideration, heat lo...A new trajectory generation for heat load test is proposed based on gauss pseudospectral method within limit range. Firstly,with multiple path constraints and flight task requirements taken into consideration, heat load parameters are introduced into the dynamics equations. In order to solve the problem of generating such a trajectory within limit range rapidly, the dynamics equations have been normalized by Earth related parameters. Secondly, since the gauss pseudospectral method is just employed to solve the discrete nonlinear programming problem, transformations are developed, which can relate the Lagrange multipliers of the discrete nonlinear programming problem to the costates of the continuous optimal control problem. In addtion, another approach of trajectory generation by tracking the given heat rate is also presented. Finally, simulation results with common aero vehicle(CAV-H) show that the trajectories obtained by both methods can well perform the heat load test with high stagnation heating rate and the large total aeroheating amount; meanwhile, gauss pseudospectral method is better than the compared one in the given range. Furthermore, the 3-D trajectory states and control variables, angle of attack and bank, which are generated by gauss pseudospectral method, can change smoothly.展开更多
A great deal of effort has been made over the last decades to develop a better polarized electron source for high energy physics. Several laboratories operate DC guns with a gallium arsenide photocathode, which yield ...A great deal of effort has been made over the last decades to develop a better polarized electron source for high energy physics. Several laboratories operate DC guns with a gallium arsenide photocathode, which yield a highly polarized electron beam. However, the beam’s emittance might well be improved by using a superconducting radio frequency （SRF） electron gun, which delivers beams of a higher brightness than that from DC guns because the field gradient at the cathode is higher. SRF guns with metal and CsTe cathodes have been tested successfully. To produce polarized electrons, a Gallium-Arsenide photo-cathode must be used： an experiment to do so in a superconducting RF gun is under way at BNL. Since a bulk gallium arsenide （GaAs） photocathode is normal conducting, a problem arises from the heat load stemming from the cathode. We present our measurements of the electrical resistance of GaAs at cryogenic temperatures, a prediction of the heat load and verification by measuring the quality factor of the gun with and without the cathode at 2 K. We simulate heat generation and flow from the GaAs cathode using the ANSYS program. By following the findings with the heat load model, we designed and fabricated a new cathode holder （plug） to decrease the heat load from GaAs.展开更多
Technology advancement has ensured a better means of livelihood essentially in certain parts of West Africa, specifically Nigeria, where the climate is predominantly hot in most parts throughout the year. Air-conditio...Technology advancement has ensured a better means of livelihood essentially in certain parts of West Africa, specifically Nigeria, where the climate is predominantly hot in most parts throughout the year. Air-conditioning has reduced the harshness of indoor discomforts to the barest minimum. It is no more uncommon to find it regularly in use in most homes and offices. Currently, the economy has the centrality of its power supply hinged on generator plants. The enigma of the current situation is how this alternative problem has catastrophic after effects on the environment. This and many more add up to the greatest of all the threats now evading our environment and the world -- Global warming. The threat of Global warming is real and the need to find less environmentally destructive sources of energy cannot be overemphasized. This paper is a contribution towards energy saving in buildings through the reduction of solar radiation incident on buildings. Sustainable Building calls for an integrated planning approach for operating buildings economically, substantially reducing their impact on the environment by reducing energy/power consumption, amongst others, and enhancing the well-being of their inhabitants. Only buildings that reconcile all of the above factors are fit for the future. A case study of the CMS （Catholic Mission School） Book Shop house in Lagos was carried out. The methodology involved the use of a solar chart and shadow angle protractor to determine the overheated periods represented by the shading masks and data collected. From this analysis, it was decided to accept the use of external sun shading and preliminary designs and specifications were prepared by the architects. The use of external solar screens made a saving of up to 75% of the energy input which would otherwise have been required by air-conditioning.展开更多
Since loading complexand dynamic heat source is a difficult job during welding simulation process, methods are studied to add the load automatically. Firstly, an expert module for selecting welding heat source model i...Since loading complexand dynamic heat source is a difficult job during welding simulation process, methods are studied to add the load automatically. Firstly, an expert module for selecting welding heat source model is founded based on simulation knowledge and experienc Secondly, a method named as ＂High order routine＂ is presented, which creates subroutines of 3D dynamic heat source m＇od, el for user. Then an automated tool is presented to load the welding heat source boundary based on Marc software. The tool uses Marc command file to robustly achieve the process. At last, an electron beam welding heat model is presented to express the ＂toading method.展开更多
Since programing complex and dynamic heat source model for welding simulation is a complex job,the parametric methods are studied in this paper.Firstly,an overall flow to achieve automatically modeling welding was int...Since programing complex and dynamic heat source model for welding simulation is a complex job,the parametric methods are studied in this paper.Firstly,an overall flow to achieve automatically modeling welding was introduced.Secondly,an expert module rule for selecting welding heat source model was founded,which is based on simulation knowledge and experiences.Thirdly,a modularity routine method was investigated using writing with C++programing,which automatically creates subroutines of 3D dynamic heat source model for user.To realize the dynamic weld path,the local weld path coordinate system was moved in the global coordinate system and it is used to model the direction of weld gun,welding path and welding pose.The weld path data file was prepared by the automatic tool for the welding heat source subroutines.All above functions were integrated in the user interface and the connection with architecture was introduced.At last,a laser beam welding heat source modeling was automatically modeled and the weld pool geometry was compared with the reported literature.It demonstrated that the automated tool is valid for welding simulation.Since modeling became convenient for welding simulation using the tool proposed,it could be easy and useful for welding engineers to acquire the needed information.展开更多
The acoustic emission（AE） characteristics of C/SiC composite component under various conditions were compared, with the purpose of identifying the possible damage and failure mechanism. During the process of the sin...The acoustic emission（AE） characteristics of C/SiC composite component under various conditions were compared, with the purpose of identifying the possible damage and failure mechanism. During the process of the single mechanical loading, the highest amplitude of the AE signal was less than 85 dB and the main damage forms of matrix cracking and interface debonding were involved. For the heating process, high-energy AE signals with an amplitude more than 85 dB were detected and fiber fracture mechanism was determined as well due to the thermal stress caused by the mismatch of the thermal expansion coefficient between the reinforced fiber and matrix. During the combination process of the heating and mechanical loading, it was concluded that the degree of damage was much severer than the simple superposition of damage produced by the individual mechanical loading and the individual heating process.展开更多
The energy saving performance of energy efficient windows has strong dependence on window direction. Transmitted insolation level definitely affected the cooling and heating load. Simple simulation on the decrement of...The energy saving performance of energy efficient windows has strong dependence on window direction. Transmitted insolation level definitely affected the cooling and heating load. Simple simulation on the decrement of cooling load and the increment of heating load of a shading window compared with those of a transparent window show the prospect of energy saving effect clearly.From southeastward to southwestward, shading window even enlarges total heating and cooling loads when the thermal transmission is the same. However, if the shading coefficient of window is switched between summer and winter, total cooling and heating load can be reduced. This result clarifies the importance of ＂smart window＂.展开更多
In district heating(DH) system with gas-fired peak load regulating boiler in the secondary network,by prolonging run time of base load plants under rated condition,the mean energy efficiency could be increased. The fu...In district heating(DH) system with gas-fired peak load regulating boiler in the secondary network,by prolonging run time of base load plants under rated condition,the mean energy efficiency could be increased. The fuels of the system,including coal and gas,would cause different environmental impacts. Meanwhile,the reliability of the heating networks would be changed because the peak load regulating boiler could work as a standby heat source. A model for assessment of heating system was established by value analysis to optimize this kind of system. Energy consumption,greenhouse gas emission,pollution emission and system reliability were selected as functional assessment indexes in the model. Weights of each function were determined by analytical hierarchy process (AHP) and experts consultation. Life cycle cost was used as the cost in the model. A real case as an example was discussed to obtain the optimal base load ratio. The result shows that the optimal base load ratio of the case is 0.77.展开更多
In this paper, a case study of an electrothermal film heating community in Tianjin is carried out, in which the winter load characteristic and electricity use law are analyzed. In this community, every household insta...In this paper, a case study of an electrothermal film heating community in Tianjin is carried out, in which the winter load characteristic and electricity use law are analyzed. In this community, every household installs two watt-hour meters, one of which is only used to measure the electrothermal heating power, so the interference factors are eliminated. The main factors influencing the residents’ power consumption are summarized, and a method for estimating the thermal load of the residents is given. The conclusions can provide important reference to generalize the electric heating technology.展开更多
The response and failure of brass H62 specimens subjected to different levels of pre-loaded stresses and heating rates were investigated using a Gleeble-1500 thermal-mechanical material testing system. The metallograp...The response and failure of brass H62 specimens subjected to different levels of pre-loaded stresses and heating rates were investigated using a Gleeble-1500 thermal-mechanical material testing system. The metallographs of the tested material were also observed and analyzed. It is found that the increase of either pre-loaded stress or heating-rate decreases the failure temperature. Metallographic analysis shows that high heating-rate may cause stronger local thermal inconsistency(LTI) and remarkably increase the microdefects in the material,which may markedly degrade the macroscopic mechanical properties of the material.展开更多
As the existing heating load forecasting methods are almostly point forecasting,an interval forecasting approach based on Support Vector Regression (SVR) and interval estimation of relative error is proposed in this p...As the existing heating load forecasting methods are almostly point forecasting,an interval forecasting approach based on Support Vector Regression (SVR) and interval estimation of relative error is proposed in this paper.The forecasting output can be defined as energy saving control setting value of heating supply substation;meanwhile,it can also provide a practical basis for heating dispatching and peak load regulating operation.By means of the proposed approach,SVR model is used to point forecasting and the error interval can be gained by using nonparametric kernel estimation to the forecast error,which avoid the distributional assumptions.Combining the point forecasting results and error interval,the forecast confidence interval is obtained.Finally,the proposed model is performed through simulations by applying it to the data from a heating supply network in Harbin,and the results show that the method can meet the demands of energy saving control and heating dispatching.展开更多
为提高热负荷预测的精度,提升基于负荷预测的供热系统调控效果,提出一种基于特征融合的供热系统预测调控方法。首先,采用偏自相关函数(partial autocorrelation function,PACF)、Pearson相关系数和最大信息系数(maximum information coe...为提高热负荷预测的精度,提升基于负荷预测的供热系统调控效果,提出一种基于特征融合的供热系统预测调控方法。首先,采用偏自相关函数(partial autocorrelation function,PACF)、Pearson相关系数和最大信息系数(maximum information coefficient,MIC)相结合的特征选择方法来确定预测模型的基本特征;然后,使用线性回归融合、指数融合和主成分分析融合对基本特征进行融合,应用递归MLR预测确定最佳融合方法,进一步对比在最佳融合策略下递归MLR、PSO-SVR、CNN和XGBoost中效果最优的预测方法;最后,将辨识出的融合方法和预测模型方法用于实际热力站调控。结果显示,基于线性回归融合的XGboost预测方法效果最好,可以提升训练精度并减少计算时间,同时可以有效指导调控,节热率达到4%以上。展开更多
以电采暖为代表的新兴负荷灵活运行能力强,利用其可调能力提升中高压配电网运行安全水平成为“源荷互动”在配电网场景下的重要需求。面对中高压配电网安全运行中网络参数辨识困难与源荷协同复杂度高的双重挑战,提出一种基于数据挖掘的...以电采暖为代表的新兴负荷灵活运行能力强,利用其可调能力提升中高压配电网运行安全水平成为“源荷互动”在配电网场景下的重要需求。面对中高压配电网安全运行中网络参数辨识困难与源荷协同复杂度高的双重挑战,提出一种基于数据挖掘的电采暖负荷优化调度方法。首先,建立融合设备热动态特性和用户舒适度约束的电采暖负荷精细化调节模型,量化分析其调控成本;其次,构建计及光伏出力时序特性和网络潮流安全约束的多时段协同优化模型,实现源荷双侧资源的动态匹配;进而,提出基于历史运行数据挖掘的功率转移分布因子(power transfer distribution factor,PTDF)矩阵在线辨识算法,突破传统物理建模对网络参数精度的依赖;最后,设计基于二次规划的高效求解策略,生成兼顾电网安全和用户需求的最优调控方案。基于IEEE 30系统的仿真结果表明:所提方法可有效避免关键线路和变压器重过载,同时可在不影响用户供暖情况下尽量降低调节代价,实现源网荷高效互动协同。展开更多
基金The project partially supported by National Natural Science Foundation of China (No. 10275069)
文摘An actively water-cooled limiter has been designed for the long pulse operation of an HT-7 device, by adopting an integrated structure-doped graphite and a copper alloy heat sink with a super carbon sheet serving as a compliant layer between them. The behaviors of the integrated structure were evaluated in an electron beam facility under different heat loads and cooling conditions. The surface temperature and bulk temperature distribution were carefully measured by optical pyrometers and thermocouples under a steady state heat flux of 1 to 5 MW/m^2 and a water flow rate of 3 m^3/h, 4.5 m^3/h and 6 m^3/h, respectively. It was found that the surface temperature increased rapidly with the heat flux rising, but decreased only slightly with the water flow rate rising. The surface temperature reached approximately 1200℃ at 5 MW/m^2 of heat flux and 6 m^3/h of water flow. The primary experimental results indicate that the integrated design meets the requirements for the heat expelling capacity of the HT-7 device. A set of numerical simulations was also completed, whose outcome was in good accord with the experimental results.
文摘Many flight and icing conditions should be considered in order to design an efficient ice protection system to prevent ice accretion on the aircraft surface. The anti-icing heat load is the basic knowledge for the design of a thermal anti-icing system. In order to help the design of the thermal anti-icing system and save the design time, a fast and efficiency method for prediction the anti-icing heat load is investigated. The computation fluid dynamics (CFD) solver and the Messinger model are applied to obtain the snapshots. Examples for the calculation of the anti-icing heat load using the proper orthogonal decomposition (POD) method are presented and compared with the CFD simulation results. It is shown that the heat loads predicted by POD method are in agreement with the CFD computation results. Moreover, it is obviously to see that the POD method is time-saving and can meet the requirement of real-time prediction.
基金supported by the National Natural Science Foundation of China,61765012Natural Science Foundation of Inner Mongolia Autonomous Region,2023MS05047Basic research funds for universities directly under the Inner Mongolia Autonomous Region(2023RCTD011,2023YXXS012)。
文摘The next-generation heating systems,crucial for rational heat distribution and refined management,rely heavily on accurate zone-specific heat load predictions.This paper introduces a method for rapid zone-specific heat load prediction based on heat consumption allocation and data-driven techniques.The approach involves predicting the overall heat load of the building and then redistributing the total heat according to a heat consumption matrix.This eliminates the need for real-time data collection from each room,resulting in cost savings on hardware and improved computational efficiency.The overall building heat load data is obtained through a data-driven algorithm,while the heat consumption matrix is constructed through energy software simulation analysis.Using Building 2 in the Baotou Industrial Park,China,as a case study,the paper analyzes the differences between actual measurements and room estimates.Experimental results indicate an average error of 7.02%for the proposed estimation method.Although not achieving high precision(>95%)in heat load prediction,this level of accuracy is deemed sufficient to meet the requirements of feedforward control.
基金supported in part by the European Regional Development Fund through the Welsh Government(No.80835)(Flexible Integrated Energy Systems West)the Engineering and Physical Sciences Research Council(No.EP/W028573/1,No.EP/T022795/1)。
文摘This paper establishes a two-layer data-driven robust scheduling method to deal with the significant computational complexity and uncertainties in scheduling industrial heat loads.First,a two-layer deterministic scheduling model is proposed to address the computational burden of utilizing flexibility from a large number of bitumen tanks(BTs).The key feature of this model is the capability to reduce the number of control variables through analyzing and modeling the clustered temperature transfer of BTs.Second,to tackle the uncertainties in the scheduling problem,historical data regarding BTs are collected and analyzed,and a data-driven piecewise linear Kernelbased support vector clustering technique is employed to construct the uncertainty set with convex boundaries and adjustable conservatism,based on which robust optimization can be conducted.The case results indicate that the proposed method enables the utilization of flexibility in BTs,improving the level of onsite photovoltaic consumption and reducing the aggregated load fluctuation.
文摘This paper introduces a thermodynamically grounded framework that replaces conventional energy-centric building simulation with a heat-based reconstruction method,enabling the use of standard-year weather data without bespoke weather files.High-accuracy predictive models are developed to estimate seasonal heating and cooling loads and to derive convective heat transfer coefficients for transitional seasons.Models are calibrated against extended AMeDAS records for Kurume,Fukuoka Prefecture,demonstrating improved capture of local climatic variability compared with standard practice.Methodologically,the study establishes time-series regression relationships linking outdoor air temperature,incident solar radiation,and wind speed to instantaneous thermal demand and surface convective rates.These empirical relations feed a reconstruction algorithm that adjusts simulation outputs to standardized climatic conditions by rescaling heat flows and convective parameters rather than altering meteorological inputs.Results indicate that reframing simulation inputs in terms of heat enhances reliability and transferability of performance predictions and reduces uncertainty associated with variable weather.The paper examines essential assumptions affecting applicability,including the assumed linearity of convective correlations,representativeness of the reference building envelope,and the use of virtual walls for parameter identification.It further proposes a novel procedure to compute a physical adjustment coefficient for the convective heat transfer coefficient,addressing a parameter gap in macro-scale models while acknowledging challenges for conventional comparative validation.The authors recommend future work on automated calibration routines and on extending the method to tropical and arid climates to broaden applicability and support foundational reform of building energy simulation.
文摘A new trajectory generation for heat load test is proposed based on gauss pseudospectral method within limit range. Firstly,with multiple path constraints and flight task requirements taken into consideration, heat load parameters are introduced into the dynamics equations. In order to solve the problem of generating such a trajectory within limit range rapidly, the dynamics equations have been normalized by Earth related parameters. Secondly, since the gauss pseudospectral method is just employed to solve the discrete nonlinear programming problem, transformations are developed, which can relate the Lagrange multipliers of the discrete nonlinear programming problem to the costates of the continuous optimal control problem. In addtion, another approach of trajectory generation by tracking the given heat rate is also presented. Finally, simulation results with common aero vehicle(CAV-H) show that the trajectories obtained by both methods can well perform the heat load test with high stagnation heating rate and the large total aeroheating amount; meanwhile, gauss pseudospectral method is better than the compared one in the given range. Furthermore, the 3-D trajectory states and control variables, angle of attack and bank, which are generated by gauss pseudospectral method, can change smoothly.
基金Supported by China Scholarship Council, Brookhaven Science Associates, LLC (DE-AC02-98CH10886) with the U.S. DOE
文摘A great deal of effort has been made over the last decades to develop a better polarized electron source for high energy physics. Several laboratories operate DC guns with a gallium arsenide photocathode, which yield a highly polarized electron beam. However, the beam’s emittance might well be improved by using a superconducting radio frequency （SRF） electron gun, which delivers beams of a higher brightness than that from DC guns because the field gradient at the cathode is higher. SRF guns with metal and CsTe cathodes have been tested successfully. To produce polarized electrons, a Gallium-Arsenide photo-cathode must be used： an experiment to do so in a superconducting RF gun is under way at BNL. Since a bulk gallium arsenide （GaAs） photocathode is normal conducting, a problem arises from the heat load stemming from the cathode. We present our measurements of the electrical resistance of GaAs at cryogenic temperatures, a prediction of the heat load and verification by measuring the quality factor of the gun with and without the cathode at 2 K. We simulate heat generation and flow from the GaAs cathode using the ANSYS program. By following the findings with the heat load model, we designed and fabricated a new cathode holder （plug） to decrease the heat load from GaAs.
文摘Technology advancement has ensured a better means of livelihood essentially in certain parts of West Africa, specifically Nigeria, where the climate is predominantly hot in most parts throughout the year. Air-conditioning has reduced the harshness of indoor discomforts to the barest minimum. It is no more uncommon to find it regularly in use in most homes and offices. Currently, the economy has the centrality of its power supply hinged on generator plants. The enigma of the current situation is how this alternative problem has catastrophic after effects on the environment. This and many more add up to the greatest of all the threats now evading our environment and the world -- Global warming. The threat of Global warming is real and the need to find less environmentally destructive sources of energy cannot be overemphasized. This paper is a contribution towards energy saving in buildings through the reduction of solar radiation incident on buildings. Sustainable Building calls for an integrated planning approach for operating buildings economically, substantially reducing their impact on the environment by reducing energy/power consumption, amongst others, and enhancing the well-being of their inhabitants. Only buildings that reconcile all of the above factors are fit for the future. A case study of the CMS （Catholic Mission School） Book Shop house in Lagos was carried out. The methodology involved the use of a solar chart and shadow angle protractor to determine the overheated periods represented by the shading masks and data collected. From this analysis, it was decided to accept the use of external sun shading and preliminary designs and specifications were prepared by the architects. The use of external solar screens made a saving of up to 75% of the energy input which would otherwise have been required by air-conditioning.
基金This work is supported by the National Natural Science Foundation of China under contract 50904038.
文摘Since loading complexand dynamic heat source is a difficult job during welding simulation process, methods are studied to add the load automatically. Firstly, an expert module for selecting welding heat source model is founded based on simulation knowledge and experienc Secondly, a method named as ＂High order routine＂ is presented, which creates subroutines of 3D dynamic heat source m＇od, el for user. Then an automated tool is presented to load the welding heat source boundary based on Marc software. The tool uses Marc command file to robustly achieve the process. At last, an electron beam welding heat model is presented to express the ＂toading method.
基金supported by Young Innovative Talents Training Plan of Heilongjiang(UNPYSCT-2018133).
文摘Since programing complex and dynamic heat source model for welding simulation is a complex job,the parametric methods are studied in this paper.Firstly,an overall flow to achieve automatically modeling welding was introduced.Secondly,an expert module rule for selecting welding heat source model was founded,which is based on simulation knowledge and experiences.Thirdly,a modularity routine method was investigated using writing with C++programing,which automatically creates subroutines of 3D dynamic heat source model for user.To realize the dynamic weld path,the local weld path coordinate system was moved in the global coordinate system and it is used to model the direction of weld gun,welding path and welding pose.The weld path data file was prepared by the automatic tool for the welding heat source subroutines.All above functions were integrated in the user interface and the connection with architecture was introduced.At last,a laser beam welding heat source modeling was automatically modeled and the weld pool geometry was compared with the reported literature.It demonstrated that the automated tool is valid for welding simulation.Since modeling became convenient for welding simulation using the tool proposed,it could be easy and useful for welding engineers to acquire the needed information.
基金supported by the National Scientific Instrument and Equipment Development Project under Grant No.2011YQ14014504
文摘The acoustic emission（AE） characteristics of C/SiC composite component under various conditions were compared, with the purpose of identifying the possible damage and failure mechanism. During the process of the single mechanical loading, the highest amplitude of the AE signal was less than 85 dB and the main damage forms of matrix cracking and interface debonding were involved. For the heating process, high-energy AE signals with an amplitude more than 85 dB were detected and fiber fracture mechanism was determined as well due to the thermal stress caused by the mismatch of the thermal expansion coefficient between the reinforced fiber and matrix. During the combination process of the heating and mechanical loading, it was concluded that the degree of damage was much severer than the simple superposition of damage produced by the individual mechanical loading and the individual heating process.
文摘The energy saving performance of energy efficient windows has strong dependence on window direction. Transmitted insolation level definitely affected the cooling and heating load. Simple simulation on the decrement of cooling load and the increment of heating load of a shading window compared with those of a transparent window show the prospect of energy saving effect clearly.From southeastward to southwestward, shading window even enlarges total heating and cooling loads when the thermal transmission is the same. However, if the shading coefficient of window is switched between summer and winter, total cooling and heating load can be reduced. This result clarifies the importance of ＂smart window＂.
文摘In district heating(DH) system with gas-fired peak load regulating boiler in the secondary network,by prolonging run time of base load plants under rated condition,the mean energy efficiency could be increased. The fuels of the system,including coal and gas,would cause different environmental impacts. Meanwhile,the reliability of the heating networks would be changed because the peak load regulating boiler could work as a standby heat source. A model for assessment of heating system was established by value analysis to optimize this kind of system. Energy consumption,greenhouse gas emission,pollution emission and system reliability were selected as functional assessment indexes in the model. Weights of each function were determined by analytical hierarchy process (AHP) and experts consultation. Life cycle cost was used as the cost in the model. A real case as an example was discussed to obtain the optimal base load ratio. The result shows that the optimal base load ratio of the case is 0.77.
文摘In this paper, a case study of an electrothermal film heating community in Tianjin is carried out, in which the winter load characteristic and electricity use law are analyzed. In this community, every household installs two watt-hour meters, one of which is only used to measure the electrothermal heating power, so the interference factors are eliminated. The main factors influencing the residents’ power consumption are summarized, and a method for estimating the thermal load of the residents is given. The conclusions can provide important reference to generalize the electric heating technology.
基金Projects (10572157, 10272119) supported by the National Natural Science Foundation of China
文摘The response and failure of brass H62 specimens subjected to different levels of pre-loaded stresses and heating rates were investigated using a Gleeble-1500 thermal-mechanical material testing system. The metallographs of the tested material were also observed and analyzed. It is found that the increase of either pre-loaded stress or heating-rate decreases the failure temperature. Metallographic analysis shows that high heating-rate may cause stronger local thermal inconsistency(LTI) and remarkably increase the microdefects in the material,which may markedly degrade the macroscopic mechanical properties of the material.
基金Sponsored by the National 11th 5-year Plan Key Project of Ministry of Science and Technology of China (Grant No.2006BAJ01A04)
文摘As the existing heating load forecasting methods are almostly point forecasting,an interval forecasting approach based on Support Vector Regression (SVR) and interval estimation of relative error is proposed in this paper.The forecasting output can be defined as energy saving control setting value of heating supply substation;meanwhile,it can also provide a practical basis for heating dispatching and peak load regulating operation.By means of the proposed approach,SVR model is used to point forecasting and the error interval can be gained by using nonparametric kernel estimation to the forecast error,which avoid the distributional assumptions.Combining the point forecasting results and error interval,the forecast confidence interval is obtained.Finally,the proposed model is performed through simulations by applying it to the data from a heating supply network in Harbin,and the results show that the method can meet the demands of energy saving control and heating dispatching.
文摘为提高热负荷预测的精度,提升基于负荷预测的供热系统调控效果,提出一种基于特征融合的供热系统预测调控方法。首先,采用偏自相关函数(partial autocorrelation function,PACF)、Pearson相关系数和最大信息系数(maximum information coefficient,MIC)相结合的特征选择方法来确定预测模型的基本特征;然后,使用线性回归融合、指数融合和主成分分析融合对基本特征进行融合,应用递归MLR预测确定最佳融合方法,进一步对比在最佳融合策略下递归MLR、PSO-SVR、CNN和XGBoost中效果最优的预测方法;最后,将辨识出的融合方法和预测模型方法用于实际热力站调控。结果显示,基于线性回归融合的XGboost预测方法效果最好,可以提升训练精度并减少计算时间,同时可以有效指导调控,节热率达到4%以上。
文摘以电采暖为代表的新兴负荷灵活运行能力强,利用其可调能力提升中高压配电网运行安全水平成为“源荷互动”在配电网场景下的重要需求。面对中高压配电网安全运行中网络参数辨识困难与源荷协同复杂度高的双重挑战,提出一种基于数据挖掘的电采暖负荷优化调度方法。首先,建立融合设备热动态特性和用户舒适度约束的电采暖负荷精细化调节模型,量化分析其调控成本;其次,构建计及光伏出力时序特性和网络潮流安全约束的多时段协同优化模型,实现源荷双侧资源的动态匹配;进而,提出基于历史运行数据挖掘的功率转移分布因子(power transfer distribution factor,PTDF)矩阵在线辨识算法,突破传统物理建模对网络参数精度的依赖;最后,设计基于二次规划的高效求解策略,生成兼顾电网安全和用户需求的最优调控方案。基于IEEE 30系统的仿真结果表明:所提方法可有效避免关键线路和变压器重过载,同时可在不影响用户供暖情况下尽量降低调节代价,实现源网荷高效互动协同。
