The Influence of Emittance of Low-Emittance Coating on the Thermal Performance of Triple Vacuum Glazing

Y. Fang, T.J. Hyde, and N. Hewitt (UK)

Keywords

Triple vacuum glazing, low-emittance coating, thermal performance, finite volume model

Abstract

The thermal performance of the triple vacuum glazing was simulated using a finite volume model. The simulated triple vacuum glazing comprises three 4 mm thick glass panes with two vacuum gaps, with one to four internal glass surfaces coated with a low emittance (low-e) coating. The two vacuum gaps are sealed by an indium based sealant and separated by an array of stainless steel pillars with a height of 0.12 mm and a diameter of 0.3 mm spaced at 25 mm. The simulation results show that increasing the emittance of the low-e coatings from 0.03 to 0.18 increases the total glazing heat transmission U value by 50% for a 0.5 m by 0.5 m triple vacuum glazing; while for 1 m by 1m triple vacuum glazing, the U-value is increased by 36%. The centre-of-glazing U-value for both sizes is increased by 134.6%. The simulation results indicate that when using three low-e coatings in the triple vacuum glazing, the vacuum gap with two low-e coatings should be set to the direction facing the hot side environment, while the vacuum gap with one coating should face the cold environment. When using two low-e coatings in the triple vacuum glazing, the U-value of the total triple vacuum glazing with one low-e coatings in each of the vacuum gaps is 10.3% less than that with two low-e coatings in the outdoor side vacuum gap and 3.47% less than that with two low-e coatings in the indoor side vacuum gap. One coating should be set in both vacuum gaps rather than both coatings in the same vacuum gap.

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