Parametric Analysis of Heat Transfer on Multistage Cryogenic Radiator

A theoretical and experimental parametric study of the heat-transfer phenomena on a multistage passive cryogenic radiator is presented. This investigation was performed in the frame of a cooperative effort between Clemson University and the Federal University of Santa Catarina. Passive cryogenic radiator technology is under development at the Satellite Thermal Control Laboratory at the Federal University of Santa Catarina, where two experimental prototypes have been built and ground tested. The mathematical model, developed to predict the temperature distribution on the radiator stages, was used to study the sensitivity coefficients with respect to the design parameters. The design parameters considered are the radiator stage's surface emissivity, the multilayer insulation effective emissivity, the radiator support's global conductance, and the thermal load over the radiator stages. This sensitivity analysis showed that the thermal joint conductance between the stages and the support structure (aluminum-Teflon) plays an important role in the temperature distribution of the radiator. An experimental study was conducted within the Mechanical Engineering Department of Clemson University to gather thermal conductance data for comparison with the theoretical results. The thermal conductance data were incorporated into an analytical model developed for the prediction of the transient temperature behavior of a multistage cryogenic radiator for spacecraft applications. The data were also compared with the recently developed model for the prediction of thermal conductance of polymer and metal joints. Ultimately, conclusions are presented about the importance of the thermal conductance between the polymer support structure and the passive cryogenic radiator stages in the temperature distribution of the radiator.