The water wall is an important part of the passive natural circulation residual heat removal system in a high temperature gas-cooled reactor. The maximum temperatures of the pressure shell and the water wall are calcu...The water wall is an important part of the passive natural circulation residual heat removal system in a high temperature gas-cooled reactor. The maximum temperatures of the pressure shell and the water wall are calcu- lated using annular vertical closed cavity model. Fine particles can deposit on the water wall due to the thermophore- sis effect. This deposit can affect heat transfer. The thermophoretic deposit efficiency is calculated by using Batch and Shen’s formula fitted for both laminar flow and turbulent flow. The calculated results indicate that natural convection is turbulent in the closed cavity. The transient thermophoretic deposit efficiency rises with the increase of the pressure shell’s temperature. Its maximum value is 14%.展开更多
Aiming at reducing the difficulty of cooling the interior of high-density motors,this study proposed the placement of a water cold plate cooling structure between the axial laminations of the motor stator.The effect o...Aiming at reducing the difficulty of cooling the interior of high-density motors,this study proposed the placement of a water cold plate cooling structure between the axial laminations of the motor stator.The effect of the cooling water flow,thickness of the plate,and motor loss density on the cooling effect of the water cold plate were studied.To compare the cooling performance of water cold plate and outer spiral water jacket cooling structures,a high-speed permanent magnet motor with a high loss density was used to establish two motor models with the two cooling structures.Consequently,the cooling effects of the two models were analyzed using the finite element method under the same loss density,coolant flow,and main dimensions.The results were as follows.(1)The maximum and average temperatures of the water cold plate structure were reduced by 25.5%and 30.5%,respectively,compared to that of the outer spiral water jacket motor;(2)Compared with the outer spiral water jacket structure,the water cold plate structure can reduce the overall mass and volume of the motor.Considering a 100 kW high-speed permanent magnet motor as an example,a water cold plate cooling system was designed,and the temperature distribution is analyzed,with the result indicating that the cooling structure satisfied the cooling requirements of the high loss density motor.展开更多
A finite element is established for analyzing the dynamical mechanics and deformation of steel frame at high temperature when it is rapidly cooled down by spray water in fire fighting, The simulation result shows that...A finite element is established for analyzing the dynamical mechanics and deformation of steel frame at high temperature when it is rapidly cooled down by spray water in fire fighting, The simulation result shows that remarkable mechanical coupling effects are produced in the process, and the sectional stress in rapid cooling down is found considerably larger than that in heating-up. Meanwhile, the stress and deformation of a beam mainly related to cooling rate and location are much larger than those of a column in rapid cooling, In fire fighting, the structure on the first or second floor was more dangerous than those on other floors in rapid cooling, These results could provide a theoretical reference for the design of steel structure and fire fighting.展开更多
Tests were carried out to study the strength deterioration of concrete cooled in air or by water after sub-high temperature at different level and varying with cycles. It is proved that the cross-shaped cracks turned ...Tests were carried out to study the strength deterioration of concrete cooled in air or by water after sub-high temperature at different level and varying with cycles. It is proved that the cross-shaped cracks turned up and extended little by little on the surface of specimen subjected to repeat sub-high temperature, the splitting failure is characterized by cross-shaped cracks after 30 cycles, the concrete strengths decrease rapidly at early stage and to be steady subsequently with the increase of the temperature cycles, the splitting-tensile strength is more sensitive to temperature cycles than the compressive strength, the decline of concrete strength is mainly controlled by the maximum temperature having reached, the ultrasonic velocity in concrete is also declined. On the basis of test results, the mechanisms of sub-high temperature to the strength deterioration of concrete are analyzed.The formulas for calculating the compressive and splitting-tensile strength of concrete relating to the variation of temperature are proposed.展开更多
为实现柔性直流(voltage sourced converter-high voltage direct current,VSC-HVDC)换流阀冷却系统入阀水温的智能预测,文中提出一种基于随机森林(random forest,RF)和双向长短时记忆(bi-directional long short-term memory,BiLSTM)...为实现柔性直流(voltage sourced converter-high voltage direct current,VSC-HVDC)换流阀冷却系统入阀水温的智能预测,文中提出一种基于随机森林(random forest,RF)和双向长短时记忆(bi-directional long short-term memory,BiLSTM)网络混合的柔直换流阀冷却系统入阀水温的预测模型,并以此为基础对柔直换流站阀冷系统的冷却能力进行评估。首先,采用RF算法对由阀冷系统监测变量组成的高维特征集进行重要性分析,筛选出影响入阀水温的重要特征,与历史入阀水温构成输入特征向量。然后,将特征向量输入到BiLSTM预测模型,对模型进行训练并实现对入阀水温的准确预测和冷却能力定量评估。最后,以广东电网某柔直换流站为实例对所提方法进行分析,验证了所提出的基于RF-BiLSTM的混合模型预测精度优于BiLSTM模型、RF模型、支持向量机(support vector machine,SVM)模型和自回归滑动平均模型(auto-regressive and moving average,ARMA)模型,并且实现了冷却能力的定量评估。结果表明该换流站冷却裕量达98%,存在过度冷却、能源浪费的问题,与换流站现场运行情况相符,验证了文中所提方法的有效性和准确性。展开更多
文章提出了一种利用高温热泵回收冷却水余热制备中、高温热水的方案。通过建立简化的热力学模型,分析冷、热源温度对热泵单位制热量、单位压缩功及COP(Coefficient of Performance,能效比)值的影响。并从经济节能和环境保护两个方面进...文章提出了一种利用高温热泵回收冷却水余热制备中、高温热水的方案。通过建立简化的热力学模型,分析冷、热源温度对热泵单位制热量、单位压缩功及COP(Coefficient of Performance,能效比)值的影响。并从经济节能和环境保护两个方面进行了效益分析,结果表明:与传统的蒸汽加热制备热水相比,高温热泵回收冷却水余热制备中、高温热水的方案具有经济效益和环境效益,更符合节能减排要求。展开更多
基金Supported by the Special Funds for Major State Basic Research Projects of China (No.2002CB211604) and the National Key Projects in the Ninth Five –Year Plan (96-G01-02-05).
文摘The water wall is an important part of the passive natural circulation residual heat removal system in a high temperature gas-cooled reactor. The maximum temperatures of the pressure shell and the water wall are calcu- lated using annular vertical closed cavity model. Fine particles can deposit on the water wall due to the thermophore- sis effect. This deposit can affect heat transfer. The thermophoretic deposit efficiency is calculated by using Batch and Shen’s formula fitted for both laminar flow and turbulent flow. The calculated results indicate that natural convection is turbulent in the closed cavity. The transient thermophoretic deposit efficiency rises with the increase of the pressure shell’s temperature. Its maximum value is 14%.
基金supported by the National Natural Science Foundation of China(51920105011)Natural Science Foundation of Liaoning Province(2021-YQ-09)Liaoning Bai Qian Wan Talents Program,China.
文摘Aiming at reducing the difficulty of cooling the interior of high-density motors,this study proposed the placement of a water cold plate cooling structure between the axial laminations of the motor stator.The effect of the cooling water flow,thickness of the plate,and motor loss density on the cooling effect of the water cold plate were studied.To compare the cooling performance of water cold plate and outer spiral water jacket cooling structures,a high-speed permanent magnet motor with a high loss density was used to establish two motor models with the two cooling structures.Consequently,the cooling effects of the two models were analyzed using the finite element method under the same loss density,coolant flow,and main dimensions.The results were as follows.(1)The maximum and average temperatures of the water cold plate structure were reduced by 25.5%and 30.5%,respectively,compared to that of the outer spiral water jacket motor;(2)Compared with the outer spiral water jacket structure,the water cold plate structure can reduce the overall mass and volume of the motor.Considering a 100 kW high-speed permanent magnet motor as an example,a water cold plate cooling system was designed,and the temperature distribution is analyzed,with the result indicating that the cooling structure satisfied the cooling requirements of the high loss density motor.
基金supported by the National Natural Science Foundation of China (51478002)
文摘A finite element is established for analyzing the dynamical mechanics and deformation of steel frame at high temperature when it is rapidly cooled down by spray water in fire fighting, The simulation result shows that remarkable mechanical coupling effects are produced in the process, and the sectional stress in rapid cooling down is found considerably larger than that in heating-up. Meanwhile, the stress and deformation of a beam mainly related to cooling rate and location are much larger than those of a column in rapid cooling, In fire fighting, the structure on the first or second floor was more dangerous than those on other floors in rapid cooling, These results could provide a theoretical reference for the design of steel structure and fire fighting.
基金Funded by Outstanding Youth Science Foundation of Henan Province of China (No. 04120002300)
文摘Tests were carried out to study the strength deterioration of concrete cooled in air or by water after sub-high temperature at different level and varying with cycles. It is proved that the cross-shaped cracks turned up and extended little by little on the surface of specimen subjected to repeat sub-high temperature, the splitting failure is characterized by cross-shaped cracks after 30 cycles, the concrete strengths decrease rapidly at early stage and to be steady subsequently with the increase of the temperature cycles, the splitting-tensile strength is more sensitive to temperature cycles than the compressive strength, the decline of concrete strength is mainly controlled by the maximum temperature having reached, the ultrasonic velocity in concrete is also declined. On the basis of test results, the mechanisms of sub-high temperature to the strength deterioration of concrete are analyzed.The formulas for calculating the compressive and splitting-tensile strength of concrete relating to the variation of temperature are proposed.
文摘为实现柔性直流(voltage sourced converter-high voltage direct current,VSC-HVDC)换流阀冷却系统入阀水温的智能预测,文中提出一种基于随机森林(random forest,RF)和双向长短时记忆(bi-directional long short-term memory,BiLSTM)网络混合的柔直换流阀冷却系统入阀水温的预测模型,并以此为基础对柔直换流站阀冷系统的冷却能力进行评估。首先,采用RF算法对由阀冷系统监测变量组成的高维特征集进行重要性分析,筛选出影响入阀水温的重要特征,与历史入阀水温构成输入特征向量。然后,将特征向量输入到BiLSTM预测模型,对模型进行训练并实现对入阀水温的准确预测和冷却能力定量评估。最后,以广东电网某柔直换流站为实例对所提方法进行分析,验证了所提出的基于RF-BiLSTM的混合模型预测精度优于BiLSTM模型、RF模型、支持向量机(support vector machine,SVM)模型和自回归滑动平均模型(auto-regressive and moving average,ARMA)模型,并且实现了冷却能力的定量评估。结果表明该换流站冷却裕量达98%,存在过度冷却、能源浪费的问题,与换流站现场运行情况相符,验证了文中所提方法的有效性和准确性。
文摘文章提出了一种利用高温热泵回收冷却水余热制备中、高温热水的方案。通过建立简化的热力学模型,分析冷、热源温度对热泵单位制热量、单位压缩功及COP(Coefficient of Performance,能效比)值的影响。并从经济节能和环境保护两个方面进行了效益分析,结果表明:与传统的蒸汽加热制备热水相比,高温热泵回收冷却水余热制备中、高温热水的方案具有经济效益和环境效益,更符合节能减排要求。
