Analytical Model for a Cylindrical Heat Pipe

The paper presents analytical and experimental temperature measurements for an axially grooved cylindrical heat pipe used in a spacecraft. The analytical framework is developed based on a proposed thermodynamic model for a heat pipe. The representative thermodynamic states at various locations in the heat pipe are derived from experimental temperature measurements reported in the paper. Experiments are performed on a 1.4-meter-long double cavity axially grooved heat pipe with ammonia as the working fluid. The evaporator and condenser sections are isolated by insulating the central portion of the heat pipe to create the adiabatic zone. Steady state temperatures are recorded at various locations in the evaporator, condenser and adiabatic sections for a range of heat loads. In addition to the steady state thermodynamic model, a transport model has also been developed to understand the heat and mass transfer rates within the wick structure and annular core of the adiabatic section. The two models (thermodynamic and transport)are coupled with suitable interface and boundary conditions to predict the overall performance of the heat pipe. The wall temperature predictions obtained from the analytical model for various heat loads are found to be in good agreement with the experimental measurements.