The geometry of a heat generating volume cooled by forced convection is optimized by applying the entransy dissipation extremum principle and constructal theory, while the optimal spacing between the adjacent tubes an...The geometry of a heat generating volume cooled by forced convection is optimized by applying the entransy dissipation extremum principle and constructal theory, while the optimal spacing between the adjacent tubes and the optimal diameter of each tube are obtained based on entransy dissipation rate minimization. The results of this work show that the optimal constructs based on entransy dissipation rate minimization and maximum temperature difference minimization, respectively, are clearly different. For the former, the porosity of the volume of channels allocated to the heat generating volume is 1/2; while for the latter, the larger the porosity is, the better the performance will be. The optimal construct of the former greatly decreases the mean thermal resistance and improves the global heat transfer performance of the system compared with the optimal construct of the latter. This is identical to the essential requirement of the entransy dissipation extremum principle that the required heat transfer temperature difference is minimal with the same heat transfer rate (the given amount of heat generated in the heat generating volume) based on the entransy dissipation extremum principle.展开更多
As for the factors affecting the heat transfer performance of complex and nonlinear oscillating heat pipe (OHP),grey relational analysis (GRA) was used to deal with the relationship between heat transfer rate of a loo...As for the factors affecting the heat transfer performance of complex and nonlinear oscillating heat pipe (OHP),grey relational analysis (GRA) was used to deal with the relationship between heat transfer rate of a looped copper-water OHP and charging ratio,inner diameter,inclination angel,heat input,number of turns,and the main influencing factors were defined.Then,forecasting model was obtained by using main influencing factors (such as charging ratio,interior diameter,and inclination angel) as the inputs of function chain neural network.The results show that the relative average error between the predicted and actual value is 4%,which illustrates that the function chain neural network can be applied to predict the performance of OHP accurately.展开更多
IEC 61850标准可以为配电网自动化提供标准化、统一化的信息模型和信息交换模型,能有效解决终端的互操作性问题,但是仅仅解决了配电网自动化信息的描述问题,而相应的传输协议尚未得到统一规范,不同协议的传输性能缺乏定量化的分析手段...IEC 61850标准可以为配电网自动化提供标准化、统一化的信息模型和信息交换模型,能有效解决终端的互操作性问题,但是仅仅解决了配电网自动化信息的描述问题,而相应的传输协议尚未得到统一规范,不同协议的传输性能缺乏定量化的分析手段。此外,随着IP网络在配电网自动化通信领域的不断推广,大量的配电网自动化信息可否在IP网络上进行传输也需要经过定量化的论证。针对这些问题,基于OPNET仿真平台,对配电网自动化业务进行精细的建模,探讨了IEC 60870-5-104和MMS+GOOSE等不同传输协议应用于配电网自动化信息传输的可行性,最后定量化地分析了不同传输协议下配电网自动化信息在IP网络中的传输性能。仿真结果表明,在IP网络中,IEC 60870-5-104、MMS+GOOSE over TCP以及MMS+GOOSE over UDP三种传输协议的最大传输延时都在10 ms以内,均能满足配电网自动化信息传输的实时性要求,但在遥测/遥信数据发送时间间隔较小的情况下,MMS+GOOSE over UDP的丢包率明显小于其余两种传输协议。展开更多
基金supported by the National Natural Science Foundation of China (10905093)the Program for New Century Excellent Talents in University of China (NCET-04-1006)the Foundation for Authors of National Excellent Doctoral Dissertations of China (200136)
文摘The geometry of a heat generating volume cooled by forced convection is optimized by applying the entransy dissipation extremum principle and constructal theory, while the optimal spacing between the adjacent tubes and the optimal diameter of each tube are obtained based on entransy dissipation rate minimization. The results of this work show that the optimal constructs based on entransy dissipation rate minimization and maximum temperature difference minimization, respectively, are clearly different. For the former, the porosity of the volume of channels allocated to the heat generating volume is 1/2; while for the latter, the larger the porosity is, the better the performance will be. The optimal construct of the former greatly decreases the mean thermal resistance and improves the global heat transfer performance of the system compared with the optimal construct of the latter. This is identical to the essential requirement of the entransy dissipation extremum principle that the required heat transfer temperature difference is minimal with the same heat transfer rate (the given amount of heat generated in the heat generating volume) based on the entransy dissipation extremum principle.
基金Project(531107040300) supported by the Fundamental Research Funds for the Central Universities in ChinaProject(2006BAJ04B04) supported by the National Science and Technology Pillar Program during the Eleventh Five-year Plan Period of China
文摘As for the factors affecting the heat transfer performance of complex and nonlinear oscillating heat pipe (OHP),grey relational analysis (GRA) was used to deal with the relationship between heat transfer rate of a looped copper-water OHP and charging ratio,inner diameter,inclination angel,heat input,number of turns,and the main influencing factors were defined.Then,forecasting model was obtained by using main influencing factors (such as charging ratio,interior diameter,and inclination angel) as the inputs of function chain neural network.The results show that the relative average error between the predicted and actual value is 4%,which illustrates that the function chain neural network can be applied to predict the performance of OHP accurately.
文摘IEC 61850标准可以为配电网自动化提供标准化、统一化的信息模型和信息交换模型,能有效解决终端的互操作性问题,但是仅仅解决了配电网自动化信息的描述问题,而相应的传输协议尚未得到统一规范,不同协议的传输性能缺乏定量化的分析手段。此外,随着IP网络在配电网自动化通信领域的不断推广,大量的配电网自动化信息可否在IP网络上进行传输也需要经过定量化的论证。针对这些问题,基于OPNET仿真平台,对配电网自动化业务进行精细的建模,探讨了IEC 60870-5-104和MMS+GOOSE等不同传输协议应用于配电网自动化信息传输的可行性,最后定量化地分析了不同传输协议下配电网自动化信息在IP网络中的传输性能。仿真结果表明,在IP网络中,IEC 60870-5-104、MMS+GOOSE over TCP以及MMS+GOOSE over UDP三种传输协议的最大传输延时都在10 ms以内,均能满足配电网自动化信息传输的实时性要求,但在遥测/遥信数据发送时间间隔较小的情况下,MMS+GOOSE over UDP的丢包率明显小于其余两种传输协议。
