Vacuum insulating glass is a type of glass that provides protection from external heat. It can be used for a wide range of applications including air conditioning systems, cooling towers, and solar collectors. The benefits of vacuum insulating glass include low energy consumption and high levels of thermal performance.
First Practical Sample Made In 1989
The first practical vacuum insulating glass was made in 1989, the latest in a string of technological advancements by the Nippon Sheet Glass Group. Hideo Kawahara, former Director of the company’s Architectural Glass R&D division, led the charge, and the results have been spectacular. Despite some early hiccups, NSG has successfully completed two pilot projects. Using the NSG’s own patented acetate process, a series of vacuum insulating glass products have been produced, and are ready to be rolled out to the market.
Unlike its predecessor, the aforementioned acetate glass, the VIG has a hermetic seal, and no pump out tube. In fact, this technology has the potential to reduce the cost of a glazing application in the long run. Its benefits include reduced radiant heat flow, lower thermal losses, and increased occupant comfort. Considering the popularity of window treatments in both commercial and residential settings, this is an important technology for architects and manufacturers alike.
Heat Flux Non-Uniformities
Vacuum insulating glass (VIG) is a thermally insulating glazing containing two sheets of glass separated by a grid of small support pillars. Depending on the thickness of the glass sheets, and the separation between pillars, the heat flux through the VIG can vary significantly. It is critical to accurately measure the thermal insulation properties of VIGs. This article discusses methods of determining the magnitude of non-uniformities in the heat flow between the measuring area and the VIG.
The non-uniformities in the heat flux are modelled by the finite element method. These models are used to determine the average heat flow through the VIG. Various parameters are included in the model, including the diameter of the pillar, the thickness of the glass sheets, and the number of support pillars.
Heat Flow Through The Support Pillars
Vacuum insulating glass is a type of thermally insulating glazing consisting of two sheets of glass separated by an array of support pillars. The pillars are 0.5 mm in diameter and made of materials with a thermal conductivity of 20 W m-1 K-1.
Various measurements have been undertaken to characterize the heat flow through VIG. Specimens of different sizes have been tested using a custom built guarded hot plate instrument. Various non-uniformities in the local heat flux have been modelled using finite element method.
A model for the pillar array incorporates a high density of elements that allows good convergence. Finite element simulations accurately describe the thermal resistance of the pillar. It also includes radiation between the glass sheets that contributes to the heat flow.
Heat Flow Through The Edge Seal
The University of Sydney’s Vacuum Insulating Glass (VIG) research program has been investigating heat flow through VIG specimens since 1989. A custom built guarded hot plate instrument is used to characterise the overall heat transport rate through vacuum glazing.
Heat flux is measured in W m-2 at various distances from the edge of a VIG unit. Analytic and finite element modelling approaches provide independent estimates of the glass sheet temperature at the edge of the unit. These results are presented in this article.
The analytic model was developed using Simko et al. 1995. It accounts for the contributions of all four edges of a VIG specimen. In addition, the model calculates the exponential decrease in temperature with distance from the edge. This is consistent with previous modelling data.
Tri-Vacuum Glazing Must Withstand Different Climates And Temperatures
Vacuum glazing is an emerging technology aimed at meeting the thermal performance requirements of net-zero energy windows. It involves vacuuming two rigidly held panes of glass together, which creates a vacuum between them. This compare between vacuum glass and insulated glass is then sealed with a hermetic seal. A wide range of processes are involved in the transport of heat through a vacuum glazing system. The overall rate of heat transport through the system has been measured in guarded hot box instruments.
These measurements have been used to develop a finite element model that simulates the flow of heat through the system. It was discovered that the overall heat transport rate through a vacuum glazing system was relatively low. An important effect of this study was the analysis of the influence of the edge area on the thermal transmittance of the system. Specifically, a wider edge seal has a greater influence on the spread of temperature loss.
Conclusion
Vacuum insulated glass is an innovative glazing technology that has been developed to improve thermal insulation, acoustic insulation and soundproofing. The insulating properties of vacuum glass make it a suitable alternative to conventional glass for applications such as windows, facades and skylights.
