Thermal Analysis of Foil Heaters for Estimation of Maximum Heat Flux for Space Applications

ABSTRACT

The thermal control system for satellites uses different thermal control elements, both passive and active. Among them, the heaters are widely used to actively control the temperature of the subsystem so that they are maintained always above the lower temperature limit of the acceptance range. Generally the space availability and temperature uniformity dictates the design of the heaters. There are two types of heaters namely the tape heater and the foil heater. The tape heaters are used where the mounting area availability is large and there is restriction on the allowable temperature differential in the area where it has to be mounted. Foil heaters are used where the space availability is less and where there is a need for localized heating.

This paper focuses on the study of foil heaters for space applications. Foil heater consists of a heating element that is sandwiched between two layers of polyamide sheets using suitable adhesive. The heat flux that can be handled by the foil heater is limited by the maximum operational temperature of the adhesive. Generally the adhesives used can withstand temperatures up to 150°–200°C without losing their properties. In addition, the spacecraft panels onto which the heaters are mounted have a similar temperature limitation of 70°C for the adhesive used in the bonding of face sheet and the honeycomb core. Both the peak temperature of the heater element and the temperature drop across the heater and the panel are constraints in designing the maximum heat flux that can be handled by the foil heaters for spacecraft applications. Hence detailed thermal analysis was carried out to arrive at the maximum heat flux value under various boundary conditions.

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