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A modified pump-out technique, incorporating a novel pump-out hole sealing process, has been developed that enables a high level of vacuum to be achieved between the panes of a vacuum glazing. The modified pump-out method provides several potential opportunities for the fabrication of a vacuum glazing with improved thermal performance. In particular, improved flexibility for production of a wide range of glazing sizes may allow a lower cost of manufacture to be achieved by avoiding the expense of a high vacuum oven which would otherwise be required for commercial production of high performance, large-scale vacuum glazings. The thermal performance of the vacuum glazing fabricated using the pump-out technique was characterized using a guarded hotbox calorimeter and theoretically analyzed using a finite volume model. The excellent experimentally determined thermal performance of the fabricated vacuum glazing was in good agreement with that predicted theoretically. Keywords: Vacuum glazing; Pump-out; Thermal performance

Flat evacuated glazing consists of two plane glass panes separated by a narrow internal evacuated space. Separation in the space is maintained by an array of support pillars typically 0.32 mm in diameter and 0.12 mm high arranged on a regular square grid with an inter-pillar separation of up to 40 mm. A detailed three-dimensional finite volume model has been employed to determine the variation of thermal performance of an evacuated glazing as a function of glass pane thickness. It was predicted that for evacuated glazing of dimensions of 0.3 m by 0.3 m and 0.5 m by 0.5 m, reducing glass pane thickness gave improved thermal performance. For evacuated glazings with dimensions of 1 m by 1 m, the opposite was predicted. Keywords. Evacuated glazing; Thermal performance; Glass thickness; Finite volume model

The thermal performances of vacuum glazings employing coatings with emittance between 0.02 and 0.16 were simulated using a three-dimensional finite volume model. Physical samples of vacuum glazings with hard and soft coatings with emittance of 0.04, 0.12 and 0.16 were fabricated and their thermal performance characterised experimentally using a guarded hot box calorimeter. Good agreement was found between experimental and theoretical thermal performances for both a vacuum glazing with a soft coating (emittance 0.04) and those with hard coatings (emittance 0.12 and 0.16). Simulations showed that for a low value of emittance (e.g. 0.02), the use of two low-emittance coatings gives limited improvement in thermal performance of the glazing system. The use of a single high performance low-emittance coating in a vacuum glazing has been shown to provide excellent performance. Keywords: Vacuum glazing; Low-emittance coating; Thermal performance; Insolation

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2005.04.002 Byline: Yueping Fang (a), Philip C. Eames (a), Brian Norton (b), Trevor J. Hyde (a) Keywords: Vacuum glazing; Guarded hot box calorimeter; Overall heat transfer coefficient Abstract: Flat vacuum glazings consisting of a narrow evacuated space between two glass panes separated by an array of small support pillars have been fabricated. A guarded hot box calorimeter was designed and constructed to measure their heat transfer coefficients. Experimental measurements of temperatures and rates of heat transfer were found to be in very good agreement with those predicted using a developed finite element model. A method for determining the heat transfer coefficient of the evacuated gap has been established and comparisons are made between the measured and predicted glass surface temperature profiles of the exposed glass area and the heat transfer coefficients of the total glazing system in order to validated the model. Author Affiliation: (a) Centre for Sustainable Technologies, School of the Built Environment, University of Ulster, Newtownabbey, BT37 0QB, N. Ireland, UK (b) Dublin Institute of Technology, Aungier Street, Dublin 2, Ireland Article History: Received 2 January 2004; Revised 24 November 2004; Accepted 4 April 2005 Article Note: (miscellaneous) Communicated by: Associate Editor Gabriela Alvarez-Garcia

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2004.11.009 Byline: Yueping Fang (a), Philip C. Eames (a), Trevor J. Hyde (a), Brian Norton (b) Keywords: Complex multimaterial frame; Evacuated glazing; Finite element model Abstract: The thermal performance of a complex multimaterial frame consisting of an exoskeleton framework and cavities filled with insulant materials enclosing an evacuated glazing was simulated using a two-dimensional finite element model and the results were validated experimentally using a guarded hot box calorimeter. The analysed 0.5m by 0.5m evacuated glazing consisted of two low-emittance film coated glass panes supported by an array of 0.32mm diameter pillars spaced 25mm apart, contiguously sealed by a 10mm wide metal edge seal. Thermal performance of windows employing evacuated glazing set in various complex multimaterial frames were analysed in detail. Very good agreement was found between simulations and experimental measurements of surface temperatures of the evacuated glazing window system. The heat loss from a window with an evacuated glazing and a complex multimaterial frame is about 80% of that for a window comprised of an evacuated glazing set in a single material solid frame. Author Affiliation: (a) Centre for Sustainable Technologies, School of the Built Environment, University of Ulster, Newtownabbey, N. Ireland BT37 0QB, UK (b) Dublin Institute of Technology, Aungier Street, Dublin 2, Ireland Article History: Received 5 December 2003; Revised 8 October 2004; Accepted 24 November 2004 Article Note: (miscellaneous) Communicated by: Associate Editor Gabriela Alvarez-Garcia