VAPOR AND LIQUID FLOW IN AN ASYMMETRICAL FLAT-PLATE HEAT-PIPE - A 3-DIMENSIONAL ANALYTICAL AND NUMERICAL INVESTIGATION

In this work, an analytical and numerical study was carried out for th e steady incompressible vapor and liquid flow in an asymmetrical flat plate heat pipe. The pseudo-three-dimensional analytical model employs the boundary layer approximation to describe the vapor flow under con ditions including strong flow reversal and the method of matched asymp totic expansions to incorporate the non-Darcian effects for the liquid flow through the porous wicks. The coupling of the liquid flow in the top, bottom and Vertical wicks is also included in the model. In the numerical study, a finite element scheme based on the Galerkin method of weighted residuals was used to solve the full-st of nonlinear diffe rential elliptical equations of motion and the continuity equation for the three-dimensional vapor flow. The analytical and numerical result s for various injection Reynolds numbers are presented. The three-dime nsional effects are discussed and the results show that a three-dimens ional analysis is necessary if the vapor channel width-to-height ratio is less than 2.5. Very good agreement was found between the analytica l and the numerical results. While showing, qualitatively and quantita tively, the pertinence and the effects of various physical parameters, the analytical results are quite useful for practical engineering pur poses by providing an effective and rapid prediction method for the fl at plate heat pipe operation. (C) 1997 Elsevier Science Ltd.