Conventional Glazing Research Articles

New pink ceramic pigment based on chromium (IV)-doped lutetium gallium garnet

Lutetium gallium garnet codoped with chromium and calcium (Ca,Cr:LGG) and lutetium gallium garnet with chromium as single dopant (Cr:LGG) have been studied. Samples with Ca x Cr x Lu 3−2 x Ga 5O 12 ( x = 0, 0.05, 0.10, 0.15, 0.2, 0.4, 0.6,) and Cr x Lu 3− x Ga 5O 12 ( x = 0.15 and 0.6) compositions were prepared by solid state reaction and the fired samples (1250 °C/6 h) were characterised by XRD, lattice parameters determination, UV–vis–NIR spectroscopy, CIE L* a* b* measurements and SEM/EDX. Moreover, the samples with calcium were tested as ceramic pigments in a conventional glaze matrix. In the Ca,Cr:LGG system solid solutions incorporating both Cr(III) and Cr(IV) ions were obtained. Cr(IV) occupies basically dodecahedral sites substituting for Lu (III) and is the predominant oxidation state up to x = 0.20 composition, giving a pink colouration in the ceramic glaze matrix. In the Cr:LGG system, only Cr(III) enters in solid solution occupying octahedral positions and producing green shades.

Tubular guidance systems for daylight: Achieved and predicted installation performances

Tubular daylight-guidance systems are linear devices that channel daylight into the core of a building. The development, over the last decade, of materials with high specular reflectance has led to a large number of passive zenithal systems; the most commercially successful type of daylight guidance being installed in many parts of the world. The rapid change in technology has not been matched by the development of either reliable and standardised design methods or design criteria against which the systems may be evaluated. This paper presents the results of several surveys of daylight guidance systems in 13 working buildings. These give an indication of the conditions created, which are used as the bases of suggested design criteria. A critical review of existing performance prediction methods notes that these lag far behind comparable methods for electric lighting and conventional glazing. A number of improved methods of prediction, currently under consideration by the CIE Technical Committee TC3-38, are presented and each is tested against measured data from the installation surveys.

Effect of some additives on the development of spinel-based glass-ceramic glazes for floor-tiles

The feasibility of developing spinel-based glass-ceramic glazes from a glass with composition in the system ZnO–MgO–B 2O 3–Al 2O 3–SiO 2 was examined. To do it additional fluxes and/or nucleants were added to a parent glass before melting. Pressed pellets of powdered glasses were submitted to standard thermal treatments up to 1200 °C. The crystallization path and the microstructural development at several temperatures were followed by several experimental techniques. The results showed that additions of TiO 2 as nucleant or additional B 2O 3 as flux to the chosen glass favored the crystallization of cordierite or mullite as main crystalline phase. Glasses which also contained minor amounts of Na 2O and K 2O, as additional fluxes, crystallized rapidly to spinel (Mg,Zn)Al 2O 4 using a single relatively fast heating ramp without a previous nucleating heat treatment step. Microstructural examination revealed that a uniform, fine-scale phase separation preceded crystallization. Very small, well-shaped crystals of spinel with octahedral morphology were formed. Slips of these glasses on conventional tile supports thermally treated under single heating ramps developed similar microstructures that the ones raised from pellets. This feature allows to suggesting these spinel-based glass-ceramic glazes as good candidates to improve the mechanical properties of conventional glazes.

Experimental investigation of cold draft induced by two different types of glazing panels in metal curtain walls

Metal curtain walls typically have a large portion of continuous glazing area. In cold climate, the cold draft induced by the large cold glazing surface may cause discomfort to occupants seated in the perimeter zone. This paper presents the experimental investigation of the characteristics of the cold draft induced by two different types of glazing panels and its effect on the occupant's local thermal sensation. A large-scale (3.8 m×6.7 m) metal curtain wall specimen consisting of two different wall systems was tested in an Environmental Chamber. The effect of the thermal performance of glazing units, the frame projection, and the mechanical ventilator on the cold draft was studied. The measurements indicate that the better-insulated glazing unit reduces the cold draft considerably compared to the conventional glazing unit, thus increasing the comfort level of the occupants. The frame projection deflects the cold flow from the wall surface and causes mixing of the cold air with the room air thus elevating the temperature and decreasing the momentum of the cold air before it penetrates into the occupied zone. The mechanical ventilator, located at the end of the room side, simulates the design of moving the heating supply away from the exterior wall. The measurements show that the resultant air movement from the ventilator increases the draft risks at ankle level for the occupants, and the ASHRAE requirements cannot be met until the occupants seat 2 m away from the wall. The analysis shows that, for the test conditions of this study, the glazing surface temperature of both wall systems needs to be raised, through perimeter heating or ventilation system for example, in order to provide a comfortable indoor climate, the need for the better-insulated system being less than the conventional system.

Experimental investigation of corner-supported architectural glazing under pulse pressure loading

City centre bombings demonstrate the vulnerability of buildings to the effects of an explosion. Glazing panels on buildings, which shatter in the blast, are the main cause of injury due to the high-velocity fragments produced. A special test facility recently developed in the University of Liverpool Impact Research Centre has been used to investigate the dynamic behaviour of glazing components under pulse pressure loading. The type of glazing system studied in this work is supported at discrete points, unlike conventional glazing systems, which are usually supported along all edges. Novel experimental techniques have been used successfully to apply dynamic pressure pulses to full-size, 1 m by 1 m by 10mm thick glazing panels supported at four corner points under controlled laboratory conditions.

Large-area smart glass and integrated photovoltaics

The field of switchable materials is ever expanding, with many types of new market and the technology [1, 2, 3, 4]. Switchable windows can be used for many applications including architectural and vehicle windows, aircraft windows, skylights and sunroofs. Related to glazing are applications for low-information-content displays for the presentation of information. Switchable windows rely on a variety of processes and materials. Several companies through out the world are developing dynamic glazing. University and National Laboratory groups are researching new materials and processes to improve these products. Switchable glazing for building and vehicle application is very attractive. Conventional glazing only offers fixed transmittance and control of energy passing through it. Given the wide range of illumination conditions and glare, dynamic glazing with adjustable transmittance offers the best solution.

The use of transparent insulation materials and optical switching layers in window systems

The new class of transparent insulation materials is classified and characterisation methods are summarised. An overview on available materials and a comparison of these new materials with conventional glazing systems is given. The high potential of these materials in collector systems is briefly discussed. In the final section an overview on new optical switching materials is given, which may help to achieve economically interesting system costs.

Transparent insulation of building facades—Steps from research to commercial applications

Transparent insulation materials (TIM) represent a class of new materials for application in solar thermal conversion systems. A U-value below 1 W/(m 2 K) and an energy transmittance greater than 70% characterize TI materials. With these physical properties TI materials outperform all conventional glazing systems and further increase the efficiency of thermal conversion of solar radiation. In winter, low elevation solar irradiance on vertical surfaces can be used effectively. Experiments, simulation calculations and results from demonstration projects have shown the space heating potential of transparently insulated walls. A properly built passive TI element on a sun-facing massive building facade can save heating energy by up to 200 kWh/(m 2 yr) each annual heating period. The paper describes the transparent insulation of building facades from the basic idea to the satisfying results of demonstration projects. Fundamental considerations for TIM and wall parameters, a list of projects, exact descriptions of TI wall constructions, the reduction of space heating demand and future developments from part of this paper. It is a summary of the work done in this specific field in the past 10 years giving examples of the dynamic developments in solar energy from the basic ideas to commercial systems. A Self-Sufficient Solar House, which is almost totally heated with transparently insulated walls, is an outstanding culmination of TI research and TI application.

A theoretical study of sound transmission through aerogel glazing systems

In view of the potential of aerogels for use in double-glazed window systems, sound transmission loss (STL) of aerogel-based glazing systems has been theoretically computed using the wave impedance approach and the results compared with corresponding values for conventional glazing. The results show a significant change in the double-leaf resonance frequencies caused by the aerogel layers and suggest that by selecting suitable material properties, aerogel glazing systems can be made acoustically superior to equivalent conventional glazing in a chosen frequency rage. The STL values for the glazing systems with aerogel of the highest density studied (285 kg/m 3) were found to be significantly better than those of air-based glazing systems.

A comparison of HVAC and HVDC contamination performance of station post insulators

Results of HVAC and HVDC (high-voltage alternating current and direct current) artificial contamination tests on station post insulators are reported. The tests were conducted using the clean fog method at various severity levels. The contamination behavior of station post insulators with semiconductive glaze was also evaluated and compared with the performance of post insulators with conventional glaze. For the latter type of insulator, different shed shapes were tested to study the effects of geometry on performance. The findings included the following: the critical flashover voltage (CFO) of the posts with conventional glaze, for a given minimum shed spacing, tends to increase as the specific leakage distance increases for both HVDC and HVAC tests. The ratio of the AC CFO (RMS) to the DC CFO also linearly increases as the specific leakage distance increases. The CFO per unit leakage distance decreases more rapidly with specific leakage distance for HVDC than for HVAC. Semiconductive glaze post insulators offer significantly improved contamination performance for both HVDC and HVAC.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The Design and Testing of a Highly Insulating Glazing System for Use With Conventional Window Systems

In most areas of the United States, windows are by far the poorest insulating material used in buildings. As a result, approximately 3 percent of the nation’s energy use is used to offset heat lost through windows. Under cold conditions, conventional double glazings create uncomfortable spaces and collect condensation. However, with the recent introduction of low-emissivity (low-E) coatings and low/conductivity gas filling to respectively reduce radiative and conductive/convective heat transfer between glazing layers, some manufacturers are beginning to offer windows with R-values (resistance to heat transfer) of 4 hr-ft2-F/Btu (0.70 m2-C/W). This papers presents designs for and analysis and test results of an insulated glass unit with a center-of-glass R-value of 8-10; approximately twice as good as gas-filled low-E units, and four times that of conventional double glazing. This high-R design starts with a conventional insulated-glass unit and adds two low-emissivity coatings, a thin glass middle glazing layer, and a Krypton or Krypton/Argon gas fill. The unit’s overall width is 1 in. (25 mm) or less, consistent with most manufacturers’ frame and sash design requirements. Using state-of-the-art low-emissivity coatings does not significantly degrade the solar heat gain potential or visible transmittance of the window. Work to date has substantiated this concept of a high-R window although specific components require further research and engineering development. Demonstration projects, in conjunction with utilities and several major window manufacturers, are planned. This high-R window design is the subject of a DOE patent application.

A Comparison of HVAC and HVDC Contamination Performance of Station Post Insulators

Results of HVAC and HVDC (high-voltage alternating current and direct current) artificial contamination tests on station post insulators are reported. The tests were conducted using the clean fog method at various severity levels. The contamination behavior of station post insulators with semiconductive glaze was also evaluated and compared with the performance of post insulators with conventional glaze. For the latter type of insulator, different shed shapes were tested to study the effects of geometry on performance. The findings included the following: the critical flashover voltage (CFO) of the posts with conventional glaze, for a given minimum shed spacing, tends to increase as the specific leakage distance increases for both HVDC and HVAC tests. The ratio of the AC CFO (RMS) to the DC CFO also linearly increases as the specific leakage distance increases. The CFO per unit leakage distance decreases more rapidly with specific leakage distance for HVDC than for HVAC. Semiconductive glaze post insulators offer significantly improved contamination performance for both HVDC and HVAC. >