Browsing by Author "Gläser, Hans Joachim"
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- ItemCondensation on the outer surface of window glazings - Causes, effect on heat loss and method for prevention(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1997) Gläser, Hans JoachimFogging on the outside surfaces of window glazings increases if the thermal insulation of the glazing is improved, i.e., the k value is decreased as realized in the heat-insulating glasses currently on the market. The main reason for this is the radiation exchange with the open sky. The most endangered Windows for fogging are the sky lights and glazings in the skin of buildings, e. g. structural glazing facades, because they are exposed to the largest portion of the open sky. The conditions of fogging are investigated and discussed, as well as its influence on the heat loss of glazings is demonstrated. By radiation exchange with the open sky, the heat loss of window glazings can be increased by more than a factor 2 in comparison to the standardized k value. However, fogging reduces heat losses in dependence on the outside air humidity. Fogging and heat loss can be considerably reduced by a low-emissive coating on the outer surface of glazings. The demands on such a coating are discussed. Also a method of double coating consisting of a low-emissive subcoating and a hydrophobic and anti-sticking top-coating is presented, which has a self-cleaning effect. Lowemissive and, at the same time, self-cleaning coatings, deposited on the outer surface of glazings are a new function of flat glass and may be a challenge to the glass industry in the next years.
- ItemLow-emissive coatings on the outer surface of heat-insulating glasses - a challenge to the flat glass industry(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2002) Gläser, Hans JoachimThe influence of low-emissive coatings on the outer surface of window glazings is reported.They reduce the heat radiation exchange with the open sky respectively the surroundings. However, they are effective and without disadvantages only on the outdoor surface of heat-insulating glasses. Here they diminish the risk of dewing on this surface and the heat loss through the window is not only decreased but it becomes also independent of the inclination of the glazing in the facade. The low-emissivity of coatings is camouflaged by wetting during rain, however, because in this case the sky is overcast, the heat loss is only insignificantly increased. It is known that the covering of dirt by weathering significantly decrease solar transmittance for all kinds of glazings. But surprisingly it has shown that these coverings only insignificantly influence the emissivity of coatings beneath. This proves that the function of heat-insulating glasses with low-emissive coatings on the outdoor surfaces is not impaired by weathering if the coatings have sufficient ageing resistance to environmental attacks.Today, there are low-emissive coatings on the base of SnO2 on the market with high solar transmittance developed forposition 3 of double heat-insulating glasses as well as coatings with reduced solar transmittance for position 2 of solar control glasses. Because the chemical and abrasive resistance of both types of coatings is better than that of untreated float glass, they can also be applied on outdoor surfaces. With these coatings on position 1 a new generation of heat-insulating and solar control glasses with improved functions can be created. In combination with the developing of coatings more advantageous than those on the base of SnO2 this may be a challenge to the flat glass industry in the future.
- ItemWeathering of tin oxide coated glass with low IR emissivity(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2002) Rädlein, Edda; Buksak, Anna; Heide, Gerhard; Gläser, Hans Joachim; Frischat, Günther HeinzThe weathering of K-glass has been studied by measuring transmission and reflection in the visible (VIS), near infrared (NIR) and infrared (IR) wavelength ranges, by chemical depth profiling with secondary neutral mass spectrometry (SNMS) and by atomic force microscopy (AFM) imaging. K-glass is a commercial tin oxide coated glass with low IR emissivity. The SnO2:F-coated side has been exposed to atmospheric conditions for up to 32 weeks and for up to two years. It could be shown that the optical properties are only affected in the VIS range, but the visible contamination does not influence the high IR reflection. This means that the heat-insulating properties of window glazings with the K-glass coating on the surface do not degrade under atmospheric conditions. Chemical depth profiles did not reveal major changes, except for an increase in the signals of minor elements on the surface, namely sodium, carbon and silicon. AFM showed that after 32 weeks the deep valleys of the rather rough crystalline SnO2:F are partially filled up. The high transmission of new K-glass can be regained since contamination or corrosion products can be removed by washing. The coating itself is chemically stable.