Evacuated glazing with tempered glass

The application of tempered glass has made it possible to significantly reduce the support pillar number within evacuated glazing (EG) since tempered glass (T-glass) is four to ten times mechanically stronger than annealed glass (A-glass). The thermal transmittance (U-value) of 0.4 m by 0.4 m double evacuated glazing (DEG) with 4 mm thick T-glass and A-glass panes with emittance of 0.03 were determined to be 0.3 Wm−2K−1 and 0.57 Wm−2K−1, respectively (47.4% improvement) using previously experimentally validated finite volume model. The thermal transmittance (U-value) of 0.4 m by 0.4 m triple evacuated glazing (TEG) with 4 mm thick T-glass and A-glass panes with emittance of 0.03 were determined to be 0.11 Wm−2K−1 and 0.28 Wm−2K−1, respectively (60.7% improvement). The improvement in the U-value of EG with T-glass is due to a reduction in support pillar number, leading to reduction in heat conduction through pillar array. The impact of tempered glass on the thermal transmittance for TEG is greater than that of DEG since radiative heat transfer in TEG is much lower than that in DEG, thus the reduction in heat conduction resulted from the reduction of support pillar number in TEG is much larger than that in DE

The influence of low-temperature surface induction on evacuation, pump-out hole sealing and thermal performance of composite edge-sealed vacuum insulated glazing

Hermeticity of vacuum edge-sealing materials are one of the paramount requirements, specifically, to the evolution of energy-efficient smart windows and solar thermal evacuated flat plate collectors. This study reports the design, construction and performance of high-vacuum glazing fabrication system and vacuum insulated glazing (VIG). Experimental and theoretical investigations for the development of vacuum edgeseal made of Sn-Pb-Zn-Sb-AlTiSiCu composite in the proportion ratio of 56:39:3:1:1 by % (CS-186) are presented. Experimental investigations of the seven constructed VIG samples, each of size 300mm·300mm·4 mm, showed that increasing the hot-plate surface temperatures improved the cavity vacuum pressure whilst expediting the pump-out hole sealing process but also increases temperature induced stresses. Successful pump-out hole sealing process of VIG attained at the hot-plate set point temperature of 50˚C and the approximate cavity pressure of 0.042 Pa was achieved. An experimentally and theoretically validated finite volume model (FVM) was utilised. The centre-of-pane and total thermal transmittance values are calculated to be 0.91 Wm-2K-1 and 1.05 Wm-2K-1, respectively for the VIG. FVM results predicted that by reducing the width of vacuum edge seal and emissivity of coatings the thermal performance of the VIG is improved

Optimising the Thermal Performance of Triple Vacuum Glazing with Low-emittance Coatings

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.The thermal performance of the triple vacuum glazing with one to four internal glass surfaces coated with a low-e (emittance) coating was simulated using a finite volume model. The simulated triple vacuum glazing comprises three, 4 mm thick glass panes with two vacuum gaps, sealed with indium metal and separated by an array of stainless steel pillars, 0.2 mm high, 0.3 mm diameter and spaced at 25 mm. The simulation results show that decreasing the emittance of the four low-e coatings from 0.18 to 0.03 decreases the heat transmission U-values at the centre-of-glazing area from 0.41 W.m-2.K-1 to 0.22 W.m-2.K-1 for a 0.4 m by 0.4 m TVG rebated by 10 mm within a solid wood frame. When using three low-e coatings in the TVG in a heating dominated climate, the vacuum gap with two low-e coatings should be set facing the warm environment, while the vacuum gap with one coating should face the cold environment. When using two low-e coatings with emittance of 0.03, the U-values at the centre-of-glazing area with one coating in both vacuum gaps is 0.25 W.m-2.K-1; that with two coatings in the cold facing environment vacuum gap is 0.50 W.m-2.K-1 and that with two low-e coatings in the warm facing environment vacuum gap is 0.33 W.m-2.K-1. Thus setting one low-e coating in both vacuum gaps is better than setting two coatings in the same vacuum gap. The thermal performance of fabricated 0.4 m by 0.4 m TVGs with two and three low-e coatings were experimentally characterised and were found to be in very good agreement with simulation results.dc201