Effect of Cavity Vacuum Pressure Diminution on Thermal Performance of Triple Vacuum Glazing

Saim Memon,Farukh Farukh,Karthikeyan Kandan

doi:10.3390/app8091705

Saim Memon, Farukh Farukh + Show 1 more

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https://doi.org/10.3390/app8091705

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Abstract

Long-term durability of the vacuum edge seal plays a significant part in retrofitting triple vacuum glazing (TVG) to existing buildings in achieving progress towards a zero-energy building (ZEB) target. Vacuum pressure decrement with respect to time between panes affects the thermal efficiency of TVG. This study reports a 3D finite element model, with validated mathematical methods and comparison, for the assessment of the influence of vacuum pressure diminution on the thermal transmittance (U value) of TVG. The centre-of-pane and total U values of TVG are calculated to be 0.28 Wm−2 K−1 and 0.94 Wm−2 K−1 at the cavity vacuum pressure of 0.001 Pa. The results suggest that a rise in cavity pressure from 0.001 Pa to 100 kPa increases the centre-of-pane and total U values from 0.28 Wm−2 K−1 and 0.94 Wm−2 K−1 to 2.4 Wm−2 K−1 and 2.58 Wm−2 K−1, respectively. The temperature descent on the surfaces of TVG between hot and cold sides increases by decreasing the cavity vacuum pressure from 50 kPa to 0.001 Pa. Nonevaporable getters will maintain the cavity vacuum pressure of 0.001 Pa for over 20 years of life span in the cavity of 10-mm wide edge-sealed triple vacuum glazing, and enable the long-term durability of TVG.

Highlights

Climate change is a global challenge due to an increase of average global annual temperature of0.99 ◦ C, with CO2 levels reaching 400 ppm, breaking the 1950s’ level threshold of 300 ppm [1].In buildings, the thermal transmittance (U value) is the combination of thermal conductance and the thermal transfer coefficients
The Uc and Ut values of 0.28 Wm−2 K−1 and 0.94 Wm−2 K−1 were simulated for the triple vacuum glazing at the cavity vacuum pressure of 0.001 Pa, and the solar heat gain coefficient (G value) was predicted to be 0.7
A 3D finite element model with validated mathematical methods was utilised for the assessment of the influence of vacuum pressure diminution on the thermal performance of a 10-mm wide edge-sealed triple vacuum glazing

Summary

Introduction

Climate change is a global challenge due to an increase of average global annual temperature of0.99 ◦ C, with CO2 levels reaching 400 ppm, breaking the 1950s’ level threshold of 300 ppm [1].In buildings, the thermal transmittance (U value) is the combination of thermal conductance (i.e., the rate of heat flow between the higher-temperature area and lower-temperature area) and the thermal transfer coefficients.

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Results

Conclusion