Design and Analysis Code for Radiators of Stirling Power Systems With General Purpose (GPHS) Heat Sources

An efficient finite difference (FD) computational code has been developed for the analysis and design of circular sector radiators for linear alternator output “Free Piston Stirling Engine” space power systems utilizing a radioisotope Pu-238 General Purpose (GPHS) heat source. The code calls on a subroutine developed by the author to solve the second order, fourth degree, ordinary differential equation (ODE) of a fin (extended heat transfer surface) radiating to the space environment. Although the code was originally written for a rectangular coordinates system, it was transcribed into polar (cylindrical) coordinates for the present application. The circular sector radiator panel analyzed has an embedded heat pipe at an arbitrary radial location conducting cycle reject heat from the Stirling engine cold end to the radiator. For a required radiator heat load and a given set of geometrical and thermo-physical properties of the radiator sector, the code will compute the required radiator surface area and mass, surface temperature and heat flux profiles and also the optimum radial location for the heat pipe. A novel second subroutine is also used to determine equilibrium space sink temperatures anywhere within the Solar System. Since this non-zero sink temperature is included in the FD iterative solution of the non-linear ODE, the code has been useful in analyzing radiator temperatures of spacecraft with a perihelion well inside the orbit of Venus, as planned for some deep space missions.