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This paper discusses a method of significantly reducing geometric math model (GMM) passive radiator node count while maintaining accurate temperature responses from thermal math model (TMM) runs. Multiple GMM/TMMs are combined into larger models to predict the integrated system response. GMM reduction is often necessary because the central processing unit (CPU) time required to run large models typically increases exponentially with increasing node count. The result of using this technique is that GMM node count is greatly reduced while maintaining accurate temperature responses and saving CPU time. The methodology uses sink temperatures, computed during the TMM run, to serve as boundary conditions for detailed radiator grid thermal nodes.

This paper discusses two types of sink temperatures as approved by the Space Station Freedom (SSF) project. The two types of sink temperatures are the “black body sink temperature”, and the “gray body sink temperature”. These sink temperatures apply to both individual nodes and a group of nodes (component). Computation of these sink temperatures are discussed as well as their applicability in differential equations. Included with the derivation of the sink temperature equations are the assumptions made for defining each formula. Both sink temperature methods described yield identical surface temperature results when applied with the correct radiation conductors. Black body sink temperatures are the recommended method of computing sink temperatures because applying them in thermal analysis is straightforward.