毛细管束中层流粘性振荡流强化传热的若干问题

本文是作者从事振荡管流换热研究的总结。研究结果表明:流体在管内作轴向振荡运动时,可以极大地强化轴向的传热。本文给出了计及管壁效应的振荡管流换热的精确解析解,公布了变Pr数的实验结果。在此基础上,讨论了影响振荡管流轴向换热的6个无因次参数的物理含义,并指出其中的某些无因次参数在物理本质上就是傅里叶数的倒数的平方根,这将有利于理解振荡管流换热这种非定常换热过程。由本文的精确解析解,经过简化,可以得到国内外已公布的近似解。实验数据和解析解预言的基本规律符合很好。

SOME ASPECTS OF ENHANCED HEAT TRANSFER IN LAMINAR OSCILLATORY VISCOUS FLOWS WITHIN CAPILLARY BUNDLE

Heat transfer between two fluid reservoirs maintained at different temperatures and connected to each other via a capillary bundle is examined when the fluid within the capillaries is oscillated axially. It is found that very large effective axial heat conduction rates are achievable. Experimental measurements using water as the working fluid show equivalent thermal diffusivities up to 105 times of those existing in the absence of oscillations. Experimental data with variable Prandtle numbers are presented first of all. Based on governing equations of oscillatory pipe flow,exact analytical solution is obtained. The physical meanings of the six non-dimensional parameters which influence the axial enhanced heat transfer of oscillatory pipe flow are discussed, based on the analytical solutions and the experimental data with various Pr numbers. It is noted that to express these non-dimensional parameters in terms of Fourier number with some proper definitions will be helpful to comprehend the physical phenomena of the enhanced heat transfer of oscillatory pipe flow. All approximate results presented are obtained from this exact solution. The agreements between experimental data and analytical solution are very good.