Low-Iron Annealed Glass Spandrel Panel Thermal Stress
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Solution Overview
Problem
Spandrel panels in building glazing systems face thermal stress issues due to high heat absorption, leading to potential thermal breakage, especially when using highly absorbing coatings and glass with high iron oxide content, which can cause temperature gradients and fractures.
Innovation Solution
A laminated spandrel panel design featuring a first ply of annealed glass with reduced iron oxide content and a light-absorbing multilayer coating on the surface, which faces the interlayer, reducing visible light transmission and heat absorption, thereby minimizing thermal stress without the need for toughening the glass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a highly absorbing coating is applied to glass to reduce visible light transmission, then the spandrel panel achieves low light transmission and aesthetic properties, but the glass absorbs excessive heat causing thermal stress and potential thermal breakage
Solution Approach 1:
The patent changes the chemical composition parameter of the glass by reducing iron oxide content from typical levels (around 0.1-0.2%) to less than 0.01%, which fundamentally alters the glass's heat absorption characteristics. This parameter change allows the glass to work effectively with light-absorbing coatings without suffering from excessive heat buildup and thermal stress
Solution Approach 2:
The patent creates a composite system combining low-iron glass with light-absorbing coatings (such as ceramic frits, metals, or organic pigments). This composite material achieves the desired low visible light transmission while the low-iron glass component prevents excessive heat absorption, resolving the contradiction between aesthetic requirements and thermal stability
2Strength
If glass with high iron oxide content is used in spandrel panels, then the glass provides structural strength and cost-effectiveness, but it absorbs excessive heat leading to temperature gradients and thermal fractures
Solution Approach 1:
The patent modifies the iron oxide content parameter to less than 0.01%, which changes the glass's thermal properties while maintaining adequate structural strength. The reduced iron content decreases heat absorption coefficients, preventing the temperature gradients that cause thermal fractures in conventional high-iron glass
Solution Approach 2:
The patent applies different properties to different components of the spandrel panel system: the glass substrate is optimized for thermal stability (low iron content), while the coating provides the necessary aesthetic appearance and additional light absorption. This local optimization allows each component to address specific requirements without compromising the other
3Length of stationary object
If annealed glass is used instead of toughened glass in spandrel panels, then the glass can be manufactured in larger sizes without spontaneous breakage risk, but it is more susceptible to thermal stress from heat absorption
Solution Approach 1:
The patent changes the glass composition parameter (iron oxide content < 0.01%) to improve thermal stress resistance, enabling the use of annealed glass in large panel sizes. This compositional modification increases the glass's tolerance to thermal gradients, allowing larger dimensions without the spontaneous breakage risks associated with toughened glass
Solution Approach 2:
The patent extracts the thermal stress vulnerability from the glass by removing iron oxide impurities. This purification process eliminates the primary cause of excessive heat absorption, allowing annealed glass to achieve both large size and high reliability against thermal stress that would normally be contradictory requirements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a spandrel panel with low visible light transmittance and reduced heat absorption, preventing thermal breakage and allowing for larger panel sizes without the risk of spontaneous breakage, while maintaining aesthetic and functional properties.
Implementation Method 1
the first ply of glazing material without the light transmission reducing means has lower heat absorption than an equivalent ply of clear float glass
Implementation Method 2
the coating is a light absorbing multilayer coating comprising at least one metal layer
Implementation Method 3
The aluminium laminate is an effective heat absorber and is able to even out any temperature gradients developed in the glass
Data Source
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AI summary
A laminated spandrel panel comprising a first ply of glazing material and a second ply of glazing material with a ply of interlayer material in between the first and second plies of glazing material is described. The spandrel panel comprises light transmission reducing means, such as light absorbing multilayer coating deposited on a major surface of the first ply of glazing material, for providing the spandrel panel with suitably low visible light transmittance. The first ply of glazing material without the light transmission reducing means has lower heat absorption than an equivalent ply of clear float glass. A method of producing such a laminated spandrel panel is also described.