NUMERICAL AND ANALYTICAL INVESTIGATION OF VAPOR FLOW IN A DISK-SHAPEDHEAT-PIPE INCORPORATING SECONDARY FLOW

This paper presents a three-dimensional numerical analysis and a pseud o-three-dimensional analytical modeling of the steady incompressible v apor flow in an asymmetrical disk-shaped heat pipe heated from the top center area. The nonlinear differential elliptical equations of motio n and the continuity equation were solved numerically over the entire vapor flow domain. Discretization of the governing equations was achie ved using a finite element scheme based on the Galerkin method of weig hted residuals. The analytical model involves the use of the boundary layer approximation and the bifurcation of the flow field on the r-y p lane to describe the velocity profile under conditions including stron g flow reversal. For both numerical and analytical studies, backflow w as observed at the top entrance of the condensation zone for injection Reynolds number of 50 and higher. The three-dimensional effects and t he effects of the secondary flow formation are discussed in this work. The numerical and analytical results establish that the pressure vari ations in the angular and transverse directions for a typical disk-sha ped heat pipe are small and can be neglected. A very good agreement wa s found between the numerical results and the analytical results. The analytical model saves tremendous computer time compared with the nume rical simulation, which requires CPU times five orders of magnitude la rger than those for the analytical model. (C) 1997 Elsevier Science Lt d.