Heat conduction through the support pillars in vacuum glazing

Vacuum glazing consists of two glass sheets with a narrow internal evacuate d space. The separation of the sheets under the influence of atmospheric pr essure is maintained by an array of small support pillars. The thermal resi stances associated with the heat flow through individual pillars, and throu gh the pillar array, are calculated using a simple analytic method, and by more complex finite element models. The results of both approaches are in v ery good agreement, and are validated by comparison with experimental data. It is shown that, for many purposes, the amount of heat which flows throug h the pillars can be determined without incurring significant errors by ass uming that the heat flow is uniformly distributed over the area of the glas s. Finite element modelling, and a superposition method, are used to determ ine the temperature distribution on the external surfaces of the glass shee ts due to pillar conduction. Again the results obtained with both approache s are in very good agreement. An approximate method is described for calcul ating the magnitude of these temperature non- uniformities for all practica l glazing parameters. (C) 1998 Elsevier Science Ltd. All rights reserved.