Analysis of close-paced brush-fiber interfaces for spacecraft thermal management

Abstract

A new interpenetrating-brush thermal interface is analyzed and evaluated for application to space-based thermal management. The interface consists of fibers attached to oppositely facing substrates. Each fiber is attached to one or the other substrate but not both. Heat transfer occurs through conduction and radiant exchange between interpenetrating fibers of opposite substrates. Linearization of the radiation terms results in an analytical temperature distribution along the fibers. The thermal performance of the interface is expressed in terms of a thermal effectiveness and an effective conductance-length ratio, both of which depend on the radiation/conduction number. For thin enough fibers, the heat transfer approaches that of the case in which all fibers are attached to both substrates. A fiber length (parameter-dependent) for optimum heat transfer is identified and agrees with previously published results. Such interfaces offer both high thermal effectiveness and compliance and are well suited for internal and external spacecraft applications. Nomenclature A = total jc-sectional area of fibers on one side, m2 Ah = base (substrate) area, m2 a = single fiber (fin) cross-sectional area, m2 d = fiber diameter, m £ = effectiveness factor F = view factor T = transfer function h = unit surface conductance, W/m2 • K K '= thermal conductance, kA/Ld, W/K