Measurement and prediction of dynamic temperatures in unsymmetrically cooled glass windows

Semitransparent materials such as glass have many applications in high-temperature environments such as supersonic aircraft canopies and spacecraft windows. At elevated temperatures, the energy transfer within semitransparent materials is dominated by radiation, making both the prediction and measurement of internal temperatures substantially more difficult than for opaque substances. Experimental measurement of the dynamic internal temperature distribution in soda-lime glass plates cooling from an initial temperature of about 550 C was carried out. The boundary conditions on the plates were established using the laboratory ambient for the front surface and employing a radiant heater at the rear surface. The surface and internal plate temperatures were measured using thermocouples fused in the glass. The temperature data are compared to predictions obtained from the solution of the transient energy equation where the internal radiative transfer has been accounted for using rigorous radiative transfer theory. The predicted and measured temperatures, the experimental method, the process used to fuse the thermocouples in the test plates, and the formulation of the energy equation for semitransparent materials are discussed. 18 refs.