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

摘要

The thermal performance of the triple vacuumglazing with one to four internal glass surfaces coated witha low-e (emittance) coating was simulated using a finitevolume model. The simulated triple vacuum glazingcomprises three, 4 mm thick glass panes with two vacuumgaps, sealed with indium metal and separated by an arrayof stainless steel pillars, 0.2 mm high, 0.3 mm diameterand spaced at 25 mm. The simulation results show thatdecreasing the emittance of the four low-e coatings from0.18 to 0.03 decreases the heat transmission U-values atthe centre-of-glazing area from 0.41 W.m-2.K-1to 0.22W.m-2.K-1for a 0.4 m by 0.4 m TVG rebated by 10 mmwithin a solid wood frame. When using three low-ecoatings in the TVG in a heating dominated climate, thevacuum gap with two low-e coatings should be set facingthe warm environment, while the vacuum gap with onecoating should face the cold environment. When using twolow-e coatings with emittance of 0.03, the U-values at thecentre-of-glazing area with one coating in both vacuumgaps is 0.25 W.m-2.K-1; that with two coatings in the coldfacing environment vacuum gap is 0.50 W.m-2.K-1and thatwith two low-e coatings in the warm facing environmentvacuum gap is 0.33 W.m-2.K-1. Thus setting one low-ecoating in both vacuum gaps is better than setting twocoatings in the same vacuum gap. The thermalperformance of fabricated 0.4 m by 0.4 m TVGs with twoand three low-e coatings were experimentallycharacterised and were found to be in very goodagreement with simulation results.