High speed and high efficiency synchronized electric motors are favored in the automotive industry and turbo machinery industry worldwide because of the demands placed on efficiency. Herein an electric motor thermal c...High speed and high efficiency synchronized electric motors are favored in the automotive industry and turbo machinery industry worldwide because of the demands placed on efficiency. Herein an electric motor thermal control system using cooling air which enters from the drive end of the motor and exits from the non-drive end of the motor as the rotor experiences dissipates heat is addressed using CFD. Analyses using CFD can help to find the appropriate mass flow rate and windage losses while satisfying temperature requirements on the motor. Here, the air flow through a small annular gap is fed at 620 L/min (0.011 kg/sec) as the rotor spins at 100,000 rpm (10,472 rad/sec) and the rotor dissipates 200 W. The CFD results are compared with experimental results. Based upon the CFD findings, a novel heat transfer correlation suitable for large axial Reynolds number, large Taylor number, small annular gap Taylor-Couette flows subject to axial cross-flow is proposed herein.展开更多
The objective of this work is to evaluate the feasibility of moderate resolution satellite data estimating the surface heat balance in a tropical hydroelectric reservoir. Each component of the heat flux balance was co...The objective of this work is to evaluate the feasibility of moderate resolution satellite data estimating the surface heat balance in a tropical hydroelectric reservoir. Each component of the heat flux balance was computed using the MODIS (Moderate Resolution Imaging Spectroradiometer) water surface temperature (WST) level 2, 1 km nominal resolution data (MOD11L2, version 5) from 2003 to 2008. The consequence of the heat flux exchange in the water column thermal structure is also investigated. The passage of cold front over a region decreases the atmospheric pressure and air temperature, enhancing the relative humidity. The sensible flux presents a small variability but an increase occurs due to a convective turbulence caused by front passage. The latent flux decrease but insufficiently to cause a condensation, just the evaporation decreases. The upwelling events are the responsible to maintain the loss of heat after the cold front pas- sage.展开更多
Forced and mixed convection heat and mass transfer are studied numerically for water containingmetallic corrosion products in a heated or cooled vertical tube with variable thermophysical propertiesat super-critical p...Forced and mixed convection heat and mass transfer are studied numerically for water containingmetallic corrosion products in a heated or cooled vertical tube with variable thermophysical propertiesat super-critical pressures. The fouling mechanisms and fouling models are presented. The influenceof variable properties at super-critical pressures on forced or mixed convection has been analyzed.The differences between heat and mass transfer under heating and cooling conditions are discussed. Itis found that variable properties, especially buoyancy, greatly influence the fluid flow and heat masstransfer.展开更多
The question posed in the title concerns the explanation of a well-practised technique in ECR ion sources for increasing the output of the highest charge states of the ions of interest.For a long time the most accepte...The question posed in the title concerns the explanation of a well-practised technique in ECR ion sources for increasing the output of the highest charge states of the ions of interest.For a long time the most accepted model was that of ion cooling,being a‘single-particle’effect.Two recent papers,likely inspired on earlier work,are proposing a‘collective’effect due to non-linear plasma-wave interaction,giving rise to turbulent heating.The mixing gas will in that picture reduce the heating.A few experiments are suggested to help unravel the problem of stating which effect is dominating.展开更多
文摘High speed and high efficiency synchronized electric motors are favored in the automotive industry and turbo machinery industry worldwide because of the demands placed on efficiency. Herein an electric motor thermal control system using cooling air which enters from the drive end of the motor and exits from the non-drive end of the motor as the rotor experiences dissipates heat is addressed using CFD. Analyses using CFD can help to find the appropriate mass flow rate and windage losses while satisfying temperature requirements on the motor. Here, the air flow through a small annular gap is fed at 620 L/min (0.011 kg/sec) as the rotor spins at 100,000 rpm (10,472 rad/sec) and the rotor dissipates 200 W. The CFD results are compared with experimental results. Based upon the CFD findings, a novel heat transfer correlation suitable for large axial Reynolds number, large Taylor number, small annular gap Taylor-Couette flows subject to axial cross-flow is proposed herein.
文摘The objective of this work is to evaluate the feasibility of moderate resolution satellite data estimating the surface heat balance in a tropical hydroelectric reservoir. Each component of the heat flux balance was computed using the MODIS (Moderate Resolution Imaging Spectroradiometer) water surface temperature (WST) level 2, 1 km nominal resolution data (MOD11L2, version 5) from 2003 to 2008. The consequence of the heat flux exchange in the water column thermal structure is also investigated. The passage of cold front over a region decreases the atmospheric pressure and air temperature, enhancing the relative humidity. The sensible flux presents a small variability but an increase occurs due to a convective turbulence caused by front passage. The latent flux decrease but insufficiently to cause a condensation, just the evaporation decreases. The upwelling events are the responsible to maintain the loss of heat after the cold front pas- sage.
文摘Forced and mixed convection heat and mass transfer are studied numerically for water containingmetallic corrosion products in a heated or cooled vertical tube with variable thermophysical propertiesat super-critical pressures. The fouling mechanisms and fouling models are presented. The influenceof variable properties at super-critical pressures on forced or mixed convection has been analyzed.The differences between heat and mass transfer under heating and cooling conditions are discussed. Itis found that variable properties, especially buoyancy, greatly influence the fluid flow and heat masstransfer.
文摘The question posed in the title concerns the explanation of a well-practised technique in ECR ion sources for increasing the output of the highest charge states of the ions of interest.For a long time the most accepted model was that of ion cooling,being a‘single-particle’effect.Two recent papers,likely inspired on earlier work,are proposing a‘collective’effect due to non-linear plasma-wave interaction,giving rise to turbulent heating.The mixing gas will in that picture reduce the heating.A few experiments are suggested to help unravel the problem of stating which effect is dominating.
