An improved algorithm for the modeling of vapor flow in heat pipes
Abstract
A heat pipe vapor flow algorithm suitable for use in codes on microcomputers is presented. The incompressible heat pipe vapor flow studies of Busse are extended to incorporate compressibility effects. The Busse velocity profile factor is treated as a function of temperature and pressure. The assumption of a uniform saturated vapor temperature determined by the local pressure at each cross section of the pipe is not made. Instead, a mean vapor temperature, defined by an energy integral, is determined in the course of the solution in addition to the pressure, saturation temperature at the wall, and the Busse velocity profile factor. For alkali metal working fluids, local species equilibrium is assumed. Temperature and pressure profiles are presented for several cases involving sodium heat pipes. An example for a heat pipe with an adiabatic section and two evaporators in sequence illustrates the ability to handle axially varying heat input. A sonic limit plot for a short evaporator falls between curves for the Busse and Levy inviscid sonic limits.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 December 1989
 Bibcode:
 1989STIN...9013748T
 Keywords:

 Algorithms;
 Computer Programs;
 Heat Pipes;
 Mathematical Models;
 Pipe Flow;
 Spacecraft Radiators;
 Evaporators;
 Incompressible Flow;
 Pressure Distribution;
 Temperature Profiles;
 Velocity Distribution;
 Working Fluids;
 Fluid Mechanics and Heat Transfer