Thermochromic infrared surfaces have temperature-dependent emissivity spectra that enable radiators to passively respond to changes in the thermal environment. For spacecraft thermal-control applications, these surfaces transition between a high and low thermal emissivity to radiate heat when hot and retain heat when cold. This enhanced temperature-regulation functionality is derived from the intrinsic temperature-dependence of the thermochromic material but introduces complications in thermo-optic characterization and thermal system models. Variable emissivity materials (VEMs) necessitate a new set of thermo-optic characteristics to comprehensively describe the thermal emissivity as a function of both the instantaneous surface temperature and its time history. This research examines the methods of characterizing the thermal emissivity of VEMs using both spectroscopy (an indirect measurement) and radiative calorimetry (a direct measurement). The data are fit to a reduced-order logistic model that captures the primary design features, including the asymptotic emissivity levels and the transition temperature, as well as nonidealities such as transition rates and hysteresis. Together, these tools guide the design of novel VEMs, introduce a standardized set of material descriptors, and enable the representation of VEMs in thermal system models.


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    Title :

    Variable Emissivity Materials for Thermal Radiators: Methods for Characterizing Thermochromic Infrared Surfaces


    Contributors:


    Publication date :

    2024-10-01




    Type of media :

    Conference paper , Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English






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