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
墙体是建筑的主要组成部分之一,其热损失占据了冬季供暖能耗的一大部分,因此降低墙体热损失是建筑节能领域的研究重点.热管置入式墙体(wall implanted with heat pipes,WIHP)是一种新型的太阳能被动式利用技术.通过TRNSYS软件建立了一...墙体是建筑的主要组成部分之一,其热损失占据了冬季供暖能耗的一大部分,因此降低墙体热损失是建筑节能领域的研究重点.热管置入式墙体(wall implanted with heat pipes,WIHP)是一种新型的太阳能被动式利用技术.通过TRNSYS软件建立了一个新的WIHP传热部件,并通过实验测试进行模型验证.对WIHP不同方向的传热性能进行分析,并提出两种WIHP的优化方式.结果表明,在工作期间,南向WIHP、西向WIHP和东向WIHP均可以提高内表面温度,减少墙体热损失,节能效果显著.展开更多
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
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.
文摘墙体是建筑的主要组成部分之一,其热损失占据了冬季供暖能耗的一大部分,因此降低墙体热损失是建筑节能领域的研究重点.热管置入式墙体(wall implanted with heat pipes,WIHP)是一种新型的太阳能被动式利用技术.通过TRNSYS软件建立了一个新的WIHP传热部件,并通过实验测试进行模型验证.对WIHP不同方向的传热性能进行分析,并提出两种WIHP的优化方式.结果表明,在工作期间,南向WIHP、西向WIHP和东向WIHP均可以提高内表面温度,减少墙体热损失,节能效果显著.
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.
