MEASUREMENT OF HEAT-FLOW THROUGH VACUUM GLAZING AT ELEVATED-TEMPERATURE

A method is described for measuring the radiative and gas conductance of vacuum glazing while at room or elevated temperatures. Such measure ments are used to determine the residual gas pressure, permitting stud ies to be made of the accelerated degradation of vacuum glazing. The h eat flows associated with this method have been analysed using a detai led finite element model and the technique has been calibrated against both high accuracy measurements on a guarded hot plate apparatus, and calculations of the thermal conductance due to radiative heat transfe r. The technique is reasonably accurate-total uncertainties are less t han about +/- 5% and measurements are reproducible to about +/-2%, for temperatures over the range 20-200 degrees C. Copyright (C) 1996 Else vier Science Ltd.