Coal mine fires,which can cause heavy casualties,environmental damages and a waste of coal resources,have become a worldwide problem.Aiming at overcoming the drawbacks,such as a low analysis efficiency,poor stability ...Coal mine fires,which can cause heavy casualties,environmental damages and a waste of coal resources,have become a worldwide problem.Aiming at overcoming the drawbacks,such as a low analysis efficiency,poor stability and large monitoring error,of the existing underground coal fire monitoring technology,a novel monitoring system based on non-dispersive infrared(NDIR)spectroscopy is developed.In this study,first,the measurement principle of NDIR sensor,the gas concentration calculation and its temperature compensation algorithms were expounded.Next,taking CO and CH_(4) as examples,the liner correlation coefficients of absorbance and the temperature correction factors of the two indicator gases were calculated,and then the errors of concentration measurement for CO,CO_(2),CH_(4) and C_(2)H_(4) were further analyzed.The results disclose that the designed NDIR sensors can satisfy the requirements of industrial standards for monitoring the indicator gases for coal fire hazards.For the established NDIR-based monitoring system,the NDIRbased spectrum analyzer and its auxiliary equipment boast intrinsically safe and explosion-proof performances and can achieve real-time and in-situ detection of indicator gases when installed close to the coal fire risk area underground.Furthermore,a field application of the NDIR-based monitoring system in a coal mine shows that the NDIR-based spectrum analyzer has a permissible difference from the chromatography in measuring the concentrations of various indicator gases.Besides,the advantages of high accuracy,quick analysis and excellent security of the NDIR-based monitoring system have promoted its application in many coal mines.展开更多
Elastic heat transfer tube bundles are widely used in the field of flow-induced vibration heat transfer enhancement. Two types of mainly used tube bundles, the planar elastic tube bundle and the conical spiral tube bu...Elastic heat transfer tube bundles are widely used in the field of flow-induced vibration heat transfer enhancement. Two types of mainly used tube bundles, the planar elastic tube bundle and the conical spiral tube bundle were comprehensively compared in the condition of the same shell side diameter. The natural mode characteristics, the effect of fluid-structure interaction, the stress distribution, the comprehensive heat transfer performance and the secondary fluid flow of the two elastic tube bundles were all concluded and compared. The results show that the natural frequency and the critical velocity of vibration buckling of the planar elastic tube bundle are larger than those of the conical spiral tube bundle, while the stress distribution and the comprehensive heat transfer performance of the conical spiral tube bundle are relatively better.展开更多
The effect of the radial heat conduction on the effective thermal conductivity of carbon nanotube(CNT) bundles is studied by the nonequilibrium molecular dynamics(NEMD) method. The hexagonal CNT bundle consists of sev...The effect of the radial heat conduction on the effective thermal conductivity of carbon nanotube(CNT) bundles is studied by the nonequilibrium molecular dynamics(NEMD) method. The hexagonal CNT bundle consists of seven(10, 10) single-walled carbon nanotubes(SWCNTs). The radial heat conduction is induced by creating the vacancy defects in some segments of the constituent CNTs. Combined with the temperature differences and the inter-tube thermal resistances at the different segments,the radial heat flow in the CNT bundle is calculated. The maximum percentage of the radial heat flow is less than 7% with the presence of four defective CNTs, while the resultant decrement of the effective thermal conductivity of the bundle is about 18%.The present results indicate that the radial heat flow can significantly diminish the axial heat conduction in the CNT bundles,which probably explains the smaller effective thermal conductivity in the CNT assemblies compared to that of the individual CNTs.展开更多
In order to clarify the effect of condensate inundation on steam condensation in a large tube bundle, condensation heat transfer and the condensate flow pattern in the tube bundle have been experimentally investigated...In order to clarify the effect of condensate inundation on steam condensation in a large tube bundle, condensation heat transfer and the condensate flow pattern in the tube bundle have been experimentally investigated. Test tube bundle consists of 36 cooling tubes, 12 condensate supply tubes and 24 un-cooled dummy tubes. Cooling test tubes are made of copper and have an outer diameter of 19.1 mm and condensing length of 150 mm, Steam flows horizontally through the test tube bundle at gap velocities 15-27 m/s at pressures of 8.8 kPa. In this study, experimental data about condensate flow pattern and condensation heat transfer in a tube bundle were collected for the optimization of tube arrangement in large power plant condensers.展开更多
In this paper, a bank of tubes containing a flowing fluid which is immersed in a cross flow second medium of fluid with different temperature has been studied numerically using computational fluid dynamics. Laminar st...In this paper, a bank of tubes containing a flowing fluid which is immersed in a cross flow second medium of fluid with different temperature has been studied numerically using computational fluid dynamics. Laminar steady flow with a low Reynolds number has been studied in this work. Inlet mass flow rate and the bulk temperature are known and numerical method has been implemented to study the convective heat transfer to investigate the temperature and flow fields. Effects of different inlet bulk temperatures and mass flow rates have been investigated on temperature and pressure variations.展开更多
基金Project(2021MD703848) supported by the China Postdoctoral Science FoundationProjects(52174229, 52174230)supported by the National Natural Science Foundation of China+1 种基金Project(2021-KF-23-04) supported by the Natural Science Foundation of Liaoning Province,ChinaProject(2020CXNL10) supported by the Fundamental Research Funds for the Central Universities,China。
文摘Coal mine fires,which can cause heavy casualties,environmental damages and a waste of coal resources,have become a worldwide problem.Aiming at overcoming the drawbacks,such as a low analysis efficiency,poor stability and large monitoring error,of the existing underground coal fire monitoring technology,a novel monitoring system based on non-dispersive infrared(NDIR)spectroscopy is developed.In this study,first,the measurement principle of NDIR sensor,the gas concentration calculation and its temperature compensation algorithms were expounded.Next,taking CO and CH_(4) as examples,the liner correlation coefficients of absorbance and the temperature correction factors of the two indicator gases were calculated,and then the errors of concentration measurement for CO,CO_(2),CH_(4) and C_(2)H_(4) were further analyzed.The results disclose that the designed NDIR sensors can satisfy the requirements of industrial standards for monitoring the indicator gases for coal fire hazards.For the established NDIR-based monitoring system,the NDIRbased spectrum analyzer and its auxiliary equipment boast intrinsically safe and explosion-proof performances and can achieve real-time and in-situ detection of indicator gases when installed close to the coal fire risk area underground.Furthermore,a field application of the NDIR-based monitoring system in a coal mine shows that the NDIR-based spectrum analyzer has a permissible difference from the chromatography in measuring the concentrations of various indicator gases.Besides,the advantages of high accuracy,quick analysis and excellent security of the NDIR-based monitoring system have promoted its application in many coal mines.
基金Projects(xjj2013104,08143063)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2011CB706606)supported by the National Basic Research Program of China
文摘Elastic heat transfer tube bundles are widely used in the field of flow-induced vibration heat transfer enhancement. Two types of mainly used tube bundles, the planar elastic tube bundle and the conical spiral tube bundle were comprehensively compared in the condition of the same shell side diameter. The natural mode characteristics, the effect of fluid-structure interaction, the stress distribution, the comprehensive heat transfer performance and the secondary fluid flow of the two elastic tube bundles were all concluded and compared. The results show that the natural frequency and the critical velocity of vibration buckling of the planar elastic tube bundle are larger than those of the conical spiral tube bundle, while the stress distribution and the comprehensive heat transfer performance of the conical spiral tube bundle are relatively better.
基金supported by National Natural Science Foundation of China(Grant Nos.51476033,51376094)the Key Laboratory of Hydraulic Machinery Transients(Wuhan University)of Ministry of Educationthe Tianjin Key Laboratory of Advanced Functional Porous Materials
文摘The effect of the radial heat conduction on the effective thermal conductivity of carbon nanotube(CNT) bundles is studied by the nonequilibrium molecular dynamics(NEMD) method. The hexagonal CNT bundle consists of seven(10, 10) single-walled carbon nanotubes(SWCNTs). The radial heat conduction is induced by creating the vacancy defects in some segments of the constituent CNTs. Combined with the temperature differences and the inter-tube thermal resistances at the different segments,the radial heat flow in the CNT bundle is calculated. The maximum percentage of the radial heat flow is less than 7% with the presence of four defective CNTs, while the resultant decrement of the effective thermal conductivity of the bundle is about 18%.The present results indicate that the radial heat flow can significantly diminish the axial heat conduction in the CNT bundles,which probably explains the smaller effective thermal conductivity in the CNT assemblies compared to that of the individual CNTs.
文摘In order to clarify the effect of condensate inundation on steam condensation in a large tube bundle, condensation heat transfer and the condensate flow pattern in the tube bundle have been experimentally investigated. Test tube bundle consists of 36 cooling tubes, 12 condensate supply tubes and 24 un-cooled dummy tubes. Cooling test tubes are made of copper and have an outer diameter of 19.1 mm and condensing length of 150 mm, Steam flows horizontally through the test tube bundle at gap velocities 15-27 m/s at pressures of 8.8 kPa. In this study, experimental data about condensate flow pattern and condensation heat transfer in a tube bundle were collected for the optimization of tube arrangement in large power plant condensers.
文摘In this paper, a bank of tubes containing a flowing fluid which is immersed in a cross flow second medium of fluid with different temperature has been studied numerically using computational fluid dynamics. Laminar steady flow with a low Reynolds number has been studied in this work. Inlet mass flow rate and the bulk temperature are known and numerical method has been implemented to study the convective heat transfer to investigate the temperature and flow fields. Effects of different inlet bulk temperatures and mass flow rates have been investigated on temperature and pressure variations.
