A two-dimensional, transient mathematical model that accounts for diffusion and variable properties on the operation of a heat pipe is presented. The major advantage over previous models is that this model treats the noncondensable gas as a separate entity, which is described by mass transport phenomena. Also, the energy transport through the wall is coupled to the transient operation of the heat pipe through the use of a conjugate solution technique. The complete behavior of the heat pipe, along with the location and two-dimensional shape of the noncondensable gas front, are modeled from the initial continuum flow, liquid state startup to steady-state conditions. The proposed model predicted the existing experimental data for the operation of high-temperature heat pipes with and without noncondensable gases.
Heat-Pipe Development for Advanced Energy Transport Concepts Final Report Covering the Period January 1999 through September 2001