System Mass Variation and Entropy Generation in 100‐kWe Closed‐Brayton‐Cycle Space Power Systems

Abstract

State‐of‐the‐art closed‐Brayton‐cycle (CBC) space power systems were modeled to study performance trends in a trade space characteristic of interplanetary orbiters. For working‐fluid molar masses of 48.6, 39.9 and 11.9 kg/kmol, peak system pressures of 1.38 and 3.0 MPa and compressor pressure ratios ranging from 1.6 to 2.4, total system masses were estimated. System mass increased as peak operating pressure increased for all compressor pressure ratios and molar mass values examined. Minimum mass point comparison between 72% He at 1.38 MPa peak and 94% He at 3.0 MPa peak showed an increase in system mass of 14%. Converter flow loop entropy generation rates were calculated for 1.38 and 3.0 MPa peak pressure cases. Physical system behavior was approximated using a pedigreed NASA‐Glenn modeling code, Closed Cycle Engine Program (CCEP), which included realistic performance prediction for heat exchangers, radiators and turbomachinery. © 2004 American Institute of Physics