Richard Collins's research works | The University of Sydney and other places

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Calculated (lines) and experimental (points) COG U-values (Centre-Of-Glazing) for a VIG specimen measured with buffer plates of resistance 0.26 m² K W⁻¹ and 0.103 m² K W⁻¹, and thickness 10 mm and 6 mm, respectively, as a function of distance of the measuring area from an edge seal

Analytic modelling data for the proportional error Δhv/hv\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\Delta h_{v} /h_{v}$$\end{document} in the thermal conductance due to heat flow through both edges of a VIG specimen for several VIG and buffer plate parameters

Heat flux along the diagonal of a unit cell for a pillar separation of 20 mm, glass sheets of different thickness, and no buffer plates

Heat flux along the diagonal of a unit cell for a pillar separation of 20 mm, glass sheets of 3 mm and 7 mm thickness, and a 10 mm thick buffer plate with different values of resistance

Heat flux along the diagonal of a unit cell for a pillar separation of 20 mm, 3 mm thick glass sheets, and different values of thickness for a buffer plate of resistance 0.1 m² K W⁻¹

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Measurement of heat flow through vacuum insulating glass part 2: measurement area separated from glass sheets with buffer plates

July 2022

96 Reads

2 Citations

Glass Structures and Engineering

[...]

This is the second of two papers concerning errors in the measurement of the thermal insulating properties of Vacuum Insulating Glass (VIG) due to non-uniformities in the heat flow due to the support pillars. Part 1 deals with the situation where the measurement area is in direct thermal contact with the glass sheets. This paper discusses how the non-uniformities and associated measurement errors can be reduced using thermally insulating buffer plates on each side of the specimen. A single parameter is developed that characterises the maximum error for measurement areas of all sizes. Values of this parameter are given for all practically relevant designs of the VIG and properties of the buffer plates. Methods are developed for selecting measurement conditions that lead to acceptable tradeoffs between reducing the errors associated with non-uniformities in the heat flow and errors due to heat flow through the edges of the specimen.

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Schematic diagram of a vacuum insulating glass unit

Thermal equivalent circuits representing heat flow through VIG remote from the edges

Two different large area guarded measurement configurations: a Guarded hot plate, b Heat flow meter

Schematic diagram of a large area configuration for measuring the thermal insulating properties of VIG

a Illustration of the unit cell; b image of the typical mesh layout at a 0.5 mm diameter pillar used in the FEM simulations

Measurement of heat flow through vacuum insulating glass part 1: measurement area in direct thermal contact with specimen

July 2022

166 Reads

Glass Structures and Engineering

[...]

Non-uniformities in the heat flow through the support pillars in vacuum insulating glass (VIG) can lead to significant errors in the measurement of the thermal insulating properties of these devices. This paper discusses these errors in instruments for which the measurement area is in direct thermal contact with the glass sheets. The spatial non-uniformities of the heat flow in different VIG designs are modelled using the finite element method. For measuring areas with large dimension compared with the separation of the support pillars, the errors are unacceptably large for all practical designs of VIG when using guarded hot plate instruments. These errors are less for heat flow meter instruments due to the construction of the heat flux transducer.

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... Given the above, the precise determination of internal pressure in the cavity is critical for the design of IGUs. This may be related to the possible loss of integrity of an IGU due to secondary sealing failure or premature glass failure caused by the combination of high mechanical stresses in glass resulting from high internal pressure and thermal stresses, which may be superimposed in certain areas [12]. Experiments, analytical and numerical studies on the performance of flat IGUs have been the subject of many studies [13][14][15][16][17][18][19][20][21][22][23] and engineering approaches were included in standards (eg [24]). ...
Reference:
Influence of curvature and geometrical parameters on internal pressure in cylindrical Insulating Glass Units

Measurement of heat flow through vacuum insulating glass part 2: measurement area separated from glass sheets with buffer plates

Citing Article
Full-text available
July 2022

Glass Structures and Engineering

[...]

Richard Collins’s research while affiliated with The University of Sydney and other places

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