We study an initial boundary value problem for the Navier-Stokes equations of compressible viscous heat-conductive fluids in a 2-D periodic domain or the unit square domain. We establish a blow-up criterion for the lo...We study an initial boundary value problem for the Navier-Stokes equations of compressible viscous heat-conductive fluids in a 2-D periodic domain or the unit square domain. We establish a blow-up criterion for the local strong solutions in terms of the gradient of the velocity only, which coincides with the famous Beale-Kato-Majda criterion for ideal incompressible flows.展开更多
Terrestrial heat flow is an important physical parameter in the study of heat transfer and thermal structure of the earth and it has great significance in the genesis and development and utilization potential of regio...Terrestrial heat flow is an important physical parameter in the study of heat transfer and thermal structure of the earth and it has great significance in the genesis and development and utilization potential of regional geothermal resources.Although several breakthroughs in geothermal exploration have been made in Guizhou Province.The terrestrial heat flow in this area has not been properly measured,restricting the development of geothermal resources in the province.For this reason,the terrestrial heat flow in Guizhou was measured in this study,during which the characteristics of heat flow were determined using borehole thermometry,geothermal monitoring and thermal property testing.Moreover,the influencing factors of the terrestrial heat flow were analyzed.The results show that the thermal conductivity of rocks ranges from 2.0W/(m·K)to 5.0 W/(m·K),with an average of 3.399 W/(m·K);the heat flow varies from 30.27 mW/m^(2) to 157.55 mW/m^(2),with an average of 65.26±20.93 mW/m^(2),which is slightly higher than that of the average heat flow in entire land area in China.The heat flow in Guizhou generally follows a dumbbell-shaped distribution,with high values present in the east and west and low values occurring in the north and south.The terrestrial heat flow is related to the burial depths of the Moho and Curie surface.The basaltic eruptions in the Emeishan led to a thinner lithosphere,thicker crust and lateral emplacement,which dominated the basic pattern of heat flow distribution in Guizhou.In addition,the dichotomous structure of regional active faults and concealed deep faults jointly control the heat transfer channels and thus influence the terrestrial heat flow.展开更多
In this paper,we prove a blow-up criterion of strong solutions to the 3-D viscous and non-resistive magnetohydrodynamic equations for compressible heat-conducting flows with initial vacuum.This blow-up criterion depen...In this paper,we prove a blow-up criterion of strong solutions to the 3-D viscous and non-resistive magnetohydrodynamic equations for compressible heat-conducting flows with initial vacuum.This blow-up criterion depends only on the gradient of velocity and the temperature,which is similar to the one for compressible Navier-Stokes equations.展开更多
This work addresses the problem of Magnetohydrodynamic laminar unsteady flow of an incompressible electrically conducting fluid past an infinite vertical porous plate. It investigates how joule heating affects the vel...This work addresses the problem of Magnetohydrodynamic laminar unsteady flow of an incompressible electrically conducting fluid past an infinite vertical porous plate. It investigates how joule heating affects the velocity and temperature profiles of the fluid flow subjected to transverse magnetic field. The research examines specific equations of MHD flow which are solved numerically by finite difference approximations, using computer programme. The numerical results of this study reveal that an increase in joules heating parameter causes an increase in the velocity and temperature profiles uniformly near the plate but remain constantly distributed away from the plate, implying that the flow field of the MHD free convective flow is influenced substantially by the strength of Joules heating near the wall of the plate and at the mainstream.展开更多
The operating range of the flow rate or flow velocity for the micro-jet flame is quite wide,which can be used as the heat source.In order to optimize the micro-jet tube combustor in terms of the solid material,the pre...The operating range of the flow rate or flow velocity for the micro-jet flame is quite wide,which can be used as the heat source.In order to optimize the micro-jet tube combustor in terms of the solid material,the present paper numerically investigates the impact of thermal conductivity(λs)on the operating limit of micro-jet flame.Unexpectedly,the non-monotonic blow-off limits with the increase ofλs is found,and the corresponding generation mechanisms are analyzed in terms of the thermal coupling effect,flow field,and strain effect.At first,the lower preheating temperature of the fuel and larger heat loss amount to the environment lead to a larger blow-off limit at a largerλs.After that,the smaller local flow velocity in the vicinity of flame root and smaller strain effect slightly increase the blow-off limit with the continuously increasingλs.Therefore,it is deduced that the applied performance of micro-jet combustor with a smaller thermal conductivity is better in terms of the blow-off limit.展开更多
Thermal performance of a loop heat pipe with two evaporators and two condensers was examined using a lumped network model analysis. Thermosyphon-type vertical loop heat pipe and capillary-pump-type horizontal loop hea...Thermal performance of a loop heat pipe with two evaporators and two condensers was examined using a lumped network model analysis. Thermosyphon-type vertical loop heat pipe and capillary-pump-type horizontal loop heat pipe were calculated by examining the change of heating rate of two evaporators. Calculation results showed that the vapor and liquid flow rates in the loop heat pipe and the thermal conductance of the heat pipe changed significantly depending on the distribution ratio of the heating rate of the multiple evaporators. The thermal performance of the vertical loop heat pipe with two evaporators was also examined and experimental results of flow direction and thermal conductance of the heat pipe agreed with the analytical results. The lumped network model analysis is therefore considered accurate and preferable for the practical design of a loop heat pipe with multiple evaporators.展开更多
Information on geothermal gradient and heat flow within the subsurface is critical in the quest for geothermal energy exploration. In a bid to ascertain the thermal potential of Nigeria sector of the Chad Basin for en...Information on geothermal gradient and heat flow within the subsurface is critical in the quest for geothermal energy exploration. In a bid to ascertain the thermal potential of Nigeria sector of the Chad Basin for energy generation, subsurface temperature information from 19 oil wells, 24 water boreholes drilled to depths beyond 100 metres and atmospheric temperature from the Chad basin were utilized in calculating geothermal gradient of the area. Selected ditch cuttings from the wells were subjected to thermal conductivity test using Thermal Conductivity Scanner (TCS) at the Polish Geological Institute Laboratory in Warsaw. The terrestrial heat flow was calculated according to the Fourier’s law as a simple product of the geothermal gradient and the mean thermal conductivity. Results obtained indicated geothermal gradient range of 2.81<sup> °</sup>C/100 m to 5.88<sup> °</sup>C/100 m with an average of 3.71<sup> °</sup>C/100 m. The thermal conductivity values from the different representative samples range from 0.58 W/m*K to 4.207 W/m*K with an average of 1.626 W/m*K. The work presented a heat flow value ranging from 45 mW/m<sup>2</sup> to about 90 mW/m<sup>2</sup> in the Nigerian sector of the Chad Basin.展开更多
The dynamics of unsteady magnetohydrodynamic convective fluid flow with radiation and thermophoresis of particles past a vertical porous plate moving through a binary mixture in an optically thin environment is invest...The dynamics of unsteady magnetohydrodynamic convective fluid flow with radiation and thermophoresis of particles past a vertical porous plate moving through a binary mixture in an optically thin environment is investigated. The approximate form of the radiative heat flux is considered as the fourth power of temperature. Chemical reaction that occurs as the chemically reacting fluid flow through binary mixture is accounted for in energy and species concentration equations. Exponential space dependent heat source is introduced to generate additional heat energy across the fluid domain. The corresponding influence of heat energy is properly accounted for. It is assumed that viscosity and thermal conductivity vary as a linear function of temperature. The governing boundary layer equations are converted to nonlinear ordinary differential equations using similarity variables. A novel method of obtaining root finding starting with three guesses in shooting techniques is presented. The corresponding nonlinear coupled ordinary differential equations is solved numerically by shooting technique along with quadratic interpolation scheme. Graphical results of the dimensionless velocity, temperature and concentration distributions are shown for certain pertinent parameters controlling the fluid flow. The quadratic interpolation method is found to produce better estimated values of , which satisfy the degree of accuracy and proportional to the physical quantities.展开更多
A carbon-nanotube-atom fixed and activated scheme of non-equilibrium molecular dynamics simulations is put forward to extract the thermal conductivity of carbon nanotubes （CNTs） embedded in solid argon. Though a 6.5...A carbon-nanotube-atom fixed and activated scheme of non-equilibrium molecular dynamics simulations is put forward to extract the thermal conductivity of carbon nanotubes （CNTs） embedded in solid argon. Though a 6.5% volume fraction of CNTs increases the composite thermal conductivity to about twice as much as that of the pure basal material, the thermal conductivity of CNTs embedded in solids is found to be decreased by 1/8-1/5 with reference to that of pure ones. The decrease of the intrinsic thermal conductivity of the solid-embedded CNTs and the thermal interface resistance are demonstrated to be responsible for the results.展开更多
基金supported by the China Postdoctoral Science Foundation (20090450333)supported by the National Basic Research Program (2005CB321700)NSFC (40890154)
文摘We study an initial boundary value problem for the Navier-Stokes equations of compressible viscous heat-conductive fluids in a 2-D periodic domain or the unit square domain. We establish a blow-up criterion for the local strong solutions in terms of the gradient of the velocity only, which coincides with the famous Beale-Kato-Majda criterion for ideal incompressible flows.
基金supported by the China Geological Survey Project(Grant No.DD20190128Grant No.DD20221676)Basic Research Operations Project of the Institute of Hydrogeology and Environmental Geology,Chinese Academy of Geological Sciences(SK202212)。
文摘Terrestrial heat flow is an important physical parameter in the study of heat transfer and thermal structure of the earth and it has great significance in the genesis and development and utilization potential of regional geothermal resources.Although several breakthroughs in geothermal exploration have been made in Guizhou Province.The terrestrial heat flow in this area has not been properly measured,restricting the development of geothermal resources in the province.For this reason,the terrestrial heat flow in Guizhou was measured in this study,during which the characteristics of heat flow were determined using borehole thermometry,geothermal monitoring and thermal property testing.Moreover,the influencing factors of the terrestrial heat flow were analyzed.The results show that the thermal conductivity of rocks ranges from 2.0W/(m·K)to 5.0 W/(m·K),with an average of 3.399 W/(m·K);the heat flow varies from 30.27 mW/m^(2) to 157.55 mW/m^(2),with an average of 65.26±20.93 mW/m^(2),which is slightly higher than that of the average heat flow in entire land area in China.The heat flow in Guizhou generally follows a dumbbell-shaped distribution,with high values present in the east and west and low values occurring in the north and south.The terrestrial heat flow is related to the burial depths of the Moho and Curie surface.The basaltic eruptions in the Emeishan led to a thinner lithosphere,thicker crust and lateral emplacement,which dominated the basic pattern of heat flow distribution in Guizhou.In addition,the dichotomous structure of regional active faults and concealed deep faults jointly control the heat transfer channels and thus influence the terrestrial heat flow.
基金supported by NSFC (11171228,10801111,10971171)the fundamental Research Funds for the Central University (2010121006)the Natural Science Foundation of Fujian Province of China (2010J05011)
文摘In this paper,we prove a blow-up criterion of strong solutions to the 3-D viscous and non-resistive magnetohydrodynamic equations for compressible heat-conducting flows with initial vacuum.This blow-up criterion depends only on the gradient of velocity and the temperature,which is similar to the one for compressible Navier-Stokes equations.
文摘This work addresses the problem of Magnetohydrodynamic laminar unsteady flow of an incompressible electrically conducting fluid past an infinite vertical porous plate. It investigates how joule heating affects the velocity and temperature profiles of the fluid flow subjected to transverse magnetic field. The research examines specific equations of MHD flow which are solved numerically by finite difference approximations, using computer programme. The numerical results of this study reveal that an increase in joules heating parameter causes an increase in the velocity and temperature profiles uniformly near the plate but remain constantly distributed away from the plate, implying that the flow field of the MHD free convective flow is influenced substantially by the strength of Joules heating near the wall of the plate and at the mainstream.
文摘The operating range of the flow rate or flow velocity for the micro-jet flame is quite wide,which can be used as the heat source.In order to optimize the micro-jet tube combustor in terms of the solid material,the present paper numerically investigates the impact of thermal conductivity(λs)on the operating limit of micro-jet flame.Unexpectedly,the non-monotonic blow-off limits with the increase ofλs is found,and the corresponding generation mechanisms are analyzed in terms of the thermal coupling effect,flow field,and strain effect.At first,the lower preheating temperature of the fuel and larger heat loss amount to the environment lead to a larger blow-off limit at a largerλs.After that,the smaller local flow velocity in the vicinity of flame root and smaller strain effect slightly increase the blow-off limit with the continuously increasingλs.Therefore,it is deduced that the applied performance of micro-jet combustor with a smaller thermal conductivity is better in terms of the blow-off limit.
文摘Thermal performance of a loop heat pipe with two evaporators and two condensers was examined using a lumped network model analysis. Thermosyphon-type vertical loop heat pipe and capillary-pump-type horizontal loop heat pipe were calculated by examining the change of heating rate of two evaporators. Calculation results showed that the vapor and liquid flow rates in the loop heat pipe and the thermal conductance of the heat pipe changed significantly depending on the distribution ratio of the heating rate of the multiple evaporators. The thermal performance of the vertical loop heat pipe with two evaporators was also examined and experimental results of flow direction and thermal conductance of the heat pipe agreed with the analytical results. The lumped network model analysis is therefore considered accurate and preferable for the practical design of a loop heat pipe with multiple evaporators.
文摘Information on geothermal gradient and heat flow within the subsurface is critical in the quest for geothermal energy exploration. In a bid to ascertain the thermal potential of Nigeria sector of the Chad Basin for energy generation, subsurface temperature information from 19 oil wells, 24 water boreholes drilled to depths beyond 100 metres and atmospheric temperature from the Chad basin were utilized in calculating geothermal gradient of the area. Selected ditch cuttings from the wells were subjected to thermal conductivity test using Thermal Conductivity Scanner (TCS) at the Polish Geological Institute Laboratory in Warsaw. The terrestrial heat flow was calculated according to the Fourier’s law as a simple product of the geothermal gradient and the mean thermal conductivity. Results obtained indicated geothermal gradient range of 2.81<sup> °</sup>C/100 m to 5.88<sup> °</sup>C/100 m with an average of 3.71<sup> °</sup>C/100 m. The thermal conductivity values from the different representative samples range from 0.58 W/m*K to 4.207 W/m*K with an average of 1.626 W/m*K. The work presented a heat flow value ranging from 45 mW/m<sup>2</sup> to about 90 mW/m<sup>2</sup> in the Nigerian sector of the Chad Basin.
文摘The dynamics of unsteady magnetohydrodynamic convective fluid flow with radiation and thermophoresis of particles past a vertical porous plate moving through a binary mixture in an optically thin environment is investigated. The approximate form of the radiative heat flux is considered as the fourth power of temperature. Chemical reaction that occurs as the chemically reacting fluid flow through binary mixture is accounted for in energy and species concentration equations. Exponential space dependent heat source is introduced to generate additional heat energy across the fluid domain. The corresponding influence of heat energy is properly accounted for. It is assumed that viscosity and thermal conductivity vary as a linear function of temperature. The governing boundary layer equations are converted to nonlinear ordinary differential equations using similarity variables. A novel method of obtaining root finding starting with three guesses in shooting techniques is presented. The corresponding nonlinear coupled ordinary differential equations is solved numerically by shooting technique along with quadratic interpolation scheme. Graphical results of the dimensionless velocity, temperature and concentration distributions are shown for certain pertinent parameters controlling the fluid flow. The quadratic interpolation method is found to produce better estimated values of , which satisfy the degree of accuracy and proportional to the physical quantities.
基金Supported by the National Natural Science Foundation of China under Grant No 50606018, and Tsinghua National Laboratory for Information Science and Technology of China.
文摘A carbon-nanotube-atom fixed and activated scheme of non-equilibrium molecular dynamics simulations is put forward to extract the thermal conductivity of carbon nanotubes （CNTs） embedded in solid argon. Though a 6.5% volume fraction of CNTs increases the composite thermal conductivity to about twice as much as that of the pure basal material, the thermal conductivity of CNTs embedded in solids is found to be decreased by 1/8-1/5 with reference to that of pure ones. The decrease of the intrinsic thermal conductivity of the solid-embedded CNTs and the thermal interface resistance are demonstrated to be responsible for the results.
