Numerical analysis of laminar flow in a double-walled annular heat pipe

The parabolic and elliptic representations of the governing equations of fluid motion for steady two-dimensional laminar flow in a double-walled annular heat pipe with various distributions of heating and cooling loads have been analyzed numerically. The results show that the flow reverses at very high condensation rates and that the parabolic representation provides a sufficiently accurate picture of the vapor pressure variations at both low and high evaporation and condensation rates. An approximate analytical method is also presented that can predict the pressure drop and velocity variation accurately along the double-walled annular heat pipe, as well as the location at which the flow reverses in the condenser zone.