EXPERIMENTAL ANALYSIS OF UNIFORMITY AND MEASUREMENT OF ABSORBED THERMAL LOADS IMPOSED BY A TUNGSTEN FILAMENT LAMP ON A RADIOMETER PLATE

摘要

This paper deals with the development and manufacturing of a radiometer plate to be used in space simulation tests of space systems to measure and verify the uniformity of absorbed heat flux imposed by a Tungsten Filament Lamp. The radiometer plate is composed of an aluminum plate (670x550 mm), on which 49 radiometers are placed, black painted square copper plates (39x39x0.6 mm). On each radiometer a thermocouple was installed on the opposite surface to that being measured and these were isolated from the aluminum plate by nylon strands (Φ 0.20 mm) MLI (isolating shrouds). In order to install the lamp a vertical rod was placed at the center of one of the extremities of the aluminum plate and to this rod a horizontal rod was connected which made it possible to place the lamp in central position. Preliminary checks of flux and uniformity were carried out at environmental conditions in the Laboratory. The principal results were obtained in a high vacuum environment (≈ 10~(-7) Torr) in a 1x1 m thermal vacuum chamber. To guarantee that the thermal loads emanated only from the lamp, the chamber was kept at a temperature of -180℃. Several tests were carried out which varied the height of the lamp to the plate as well as the wattage (125, 250, 375, 450, 500 W). The Laboratory's data acquisition system was used to obtain the temperature data of each radiometer. This system handles 500 measuring channels with acquisition at 30 seconds intervals. From this information the heat fluxes are calculated and presented in the form of graphs. From the results obtained it was possible to evaluate which wattage and position of the lamp provided the best distribution of absorbed heat flux by a space system thermal control surface.