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RESEARCH PAPERS

# Experimental Characterization and Detailed Performance Prediction of a Vacuum Glazing System Fabricated With a Low Temperature Metal Edge Seal, Using a Validated Computer Model

[+] Author and Article Information
Philip W. Griffiths1

Centre for Sustainable Technologies, University of Ulster, Newtownabbey, Northern Ireland BT37 0QBp.griffiths@ulster.ac.uk

Philip C. Eames, Trevor J. Hyde, Yueping Fang

Centre for Sustainable Technologies, University of Ulster, Newtownabbey, Northern Ireland BT37 0QB

Brian Norton

Dublin Institute of Technology, Dublin, Republic of Ireland

1

Corresponding author.

J. Sol. Energy Eng 128(2), 199-203 (Nov 10, 2005) (5 pages) doi:10.1115/1.2188529 History: Received May 13, 2004; Revised November 10, 2005

## Abstract

Current multi-pane windows have a very low heat loss but their solar transmittance is low resulting in a loss of daylight and solar gains. Multi-pane windows also require framing arrangements that are difficult to retrofit to existing apertures in many existing buildings. A contiguously sealed evacuated double-glazing with low long-wave radiative emittance coatings on its internal surfaces, no heavier than conventional double-glazing, with good visual transmittance suitable for retrofitting to existing buildings, has been analyzed experimentally. Measured heat transfer coefficients and visual transmittances of laboratory fabricated evacuated glazing samples, along with theoretical predictions of center of glazing thermal conductance are presented.

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## Figures

Figure 1

Schematic diagram of a metal-based edge sealed evacuated glazing

Figure 2

Performance of vacuum glazing where (a) both panes have the same low-emittance coating, and (b) where the exterior pane only has a low-emittance coating with an inner pane emissivity of 0.9. The internal and external temperatures were set at 21.1 and −17.8°C while the internal and external heat transfer coefficients were set at 8.3 and 30Wm−2K−1, respectively. The pillar spacing was 40mm and the pillar diameter was 0.32mm.

Figure 3

Schematic of the model used to determine the thermal performance of vacuum glazing with varying pillar separation and pillar radius

Figure 4

Thermal performance of the center pane U-value of vacuum glazing with varying pillar radius and pillar separation. The emissivities of the vacuum gap glass surfaces were set to 0.9 for the outside sheet and 0.04 for the internal sheet. The external and internal temperatures were set at −17.8 and 21.1°C while the external and internal heat transfer coefficients were set at 30 and 8.3Wm−2K−1 respectively.

Figure 5

Variation of temperature with distance from the pillar on the vacuum faces of the two glass sheets for three scenarios; (a) with pillars and radiative heat transfer; (b) a pillar but without radiative heat transfer; and (c) without a pillar but with radiative heat transfer. The emissivities of the vacuum gap glass surfaces for simulations with radiative heat transfer were set to 0.9 for the outside sheet and 0.04 for the inner sheet. The external and internal temperatures were set at −17.8 and 21.1°C while the external and internal heat transfer coefficients were set at 30 and 8.3Wm−2K−1, respectively.

Figure 6

Variation of radiative heat transfer with distance from the pillar center for two scenarios, (a) with a pillar, (b) a pillar with no thermal conductivity

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