Heat Transport by Inverse- Piezoelectric Driven Dream Pipe

摘要

A novel type of so-called dream pipe is introduced hoping for the high-efficiency heat removal. Unlike traditional types with mechanical shaker, this one fits up an inverse-piezoelectric-cells embedded thin disk coupled with ac power to cause oscillatory pipe flows. A theoretical approach is adopted to comprehensively describe thermal characteristics of that new device. With a view to obtaining more practical expressions than accepted before, the Galerkin method based on the variational principle is used to solve governing partial differential equations. The induced tidal displacement and the relative increase of thermal diffusivity are expressed in reduced algebraic form. Also presented are design formulas defining the specific driving power and the specific number of required tubes. Concerning the effective thermal diffusivity, the author's predictions are fairly well consistent with exact ones deduced from Watson's expression. Ratios of the two are linearly regressed to a cubic equation applicable to the frequency range from 0.5 Hz to 6.0 Hz. Recommendable coefficient values are listed in the table. Possible combinations of four fluids of interest and seven levels of the applied ac voltage are considered in a parametric study. Numerical results are graphically shown in the figures for discussion on the feasibility.