Losses in channel flows are usually determined using a frictional head loss parameter. Fluid friction is however not the only source of loss in channel flows with heat transfer. For such flow problems, thermal energy ...Losses in channel flows are usually determined using a frictional head loss parameter. Fluid friction is however not the only source of loss in channel flows with heat transfer. For such flow problems, thermal energy degradation, in addition to mechanical energy degradation, add to the total loss in thermodynamic head. To assess the total loss in a channel with combined convection and radiation heat transfer, the conventional frictional head loss parameter is extended in this study. The analysis is applied to a 3D turbulent channel flow and identifies the critical locations in the flow domain where the losses are concentrated. The influence of Boltzmann number is discussed, and the best channel geometry for flows with combined heat transfer modes is also determined.展开更多
The use of resistance spot welding（RSW）technology for joining Ti40Zr25Ni3Cu12Be20 metallic glass was investigated.The microstructure obtained from the welded BMG sample was studied.Joint without precipitates was pre...The use of resistance spot welding（RSW）technology for joining Ti40Zr25Ni3Cu12Be20 metallic glass was investigated.The microstructure obtained from the welded BMG sample was studied.Joint without precipitates was prepared with welding current of 5.0 kA for 2cycles.A fully coupled thermal-electrical-mechanical finite element model（FEM） was developed to complement the experimental study.The simulated results agree well with the measurements.The effects of key process parameters such as welding current and welding time on the evolvement and microstructure of the weldment were determined and discussed.Moreover,the critical cooling rate for preserving the amorphous state in the weld fusion zone is determined to be approximately 1×10^3 K·s^-1.展开更多
文摘Losses in channel flows are usually determined using a frictional head loss parameter. Fluid friction is however not the only source of loss in channel flows with heat transfer. For such flow problems, thermal energy degradation, in addition to mechanical energy degradation, add to the total loss in thermodynamic head. To assess the total loss in a channel with combined convection and radiation heat transfer, the conventional frictional head loss parameter is extended in this study. The analysis is applied to a 3D turbulent channel flow and identifies the critical locations in the flow domain where the losses are concentrated. The influence of Boltzmann number is discussed, and the best channel geometry for flows with combined heat transfer modes is also determined.
基金financially supported by the National Natural Science Foundation of China (No.50904021)the Naural Science Foundation of the Education Department of Anhui Province (No.KJ2014A023)the Scientific Research Starting Foundation of Anhui Polytechnic University (No.2012YQQ006)
文摘The use of resistance spot welding（RSW）technology for joining Ti40Zr25Ni3Cu12Be20 metallic glass was investigated.The microstructure obtained from the welded BMG sample was studied.Joint without precipitates was prepared with welding current of 5.0 kA for 2cycles.A fully coupled thermal-electrical-mechanical finite element model（FEM） was developed to complement the experimental study.The simulated results agree well with the measurements.The effects of key process parameters such as welding current and welding time on the evolvement and microstructure of the weldment were determined and discussed.Moreover,the critical cooling rate for preserving the amorphous state in the weld fusion zone is determined to be approximately 1×10^3 K·s^-1.
