Heat transfer and flow characteristics of the cooling system of an industrial glass tempering unit

Monnoyer, F.; Lochegnies, Dominique

doi:10.1016/j.applthermaleng.2007.12.014

Cited by 36 publications

(14 citation statements)

References 15 publications

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“…[14] and Monnoyer et al. [18] have also observed this inhomogeneity by studying the variation of the residual stress along one line under the cooling jets in tempered glass. Higher compressive values are observed for σ x in the dark red zones in the centre and in the four corners of the analysis zone corresponding to the locations in the glass sample under the cooling jets (Figure 2A).…”

Section: D Residual Surface Stress Mapping For the Glass Sample Temmentioning

confidence: 98%

Measuring the 2D Residual Surface Stress Mapping in Tempered Glass under the Cooling Jets: the Influence of Process Parameters on the Stress Homogeneity and Isotropy

Chen

Lochegnies

Defontaine

et al. 2012

Strain

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In glass products, thermally tempered on industrial lines for automotive and architectural industries, the distribution of residual stress is highly inhomogeneous and, in certain situations, can produce optical defects that are more visible in sunlight because of the impact of the cooling jets on the hot glass during the tempering process. To analyse the influence of the process parameters on stress inhomogeneity, flat square glass samples were tempered with PRELCO tempering production unit without oscillation and with oscillation under cooling jets, thus reproducing the current industrial practice for the latter. To measure the residual stress distributions in the tempered glass samples, we developed a fully automatic system that combines the scattered light polariscope (SCALP) and a four‐axis machine, with three linear axes and one rotational one. Using the SCALP manually with the dedicated software makes it possible to access the glass surface at the laser beam’s entering point. With a four‐axis Computer Numerical Control (CNC) machine, we determined the 2D residual stress distribution under the cooling jets and analysed the influence of the cooling rate and oscillation on the homogeneity and the isotropy of the residual surface stress in the tempered glass samples.

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Section: D Residual Surface Stress Mapping For the Glass Sample Temmentioning

confidence: 98%

Measuring the 2D Residual Surface Stress Mapping in Tempered Glass under the Cooling Jets: the Influence of Process Parameters on the Stress Homogeneity and Isotropy

Chen

Lochegnies

Defontaine

et al. 2012

Strain

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“…Thus, it is important to have a good knowledge of the heat transfer which occurs to predict correctly the residual stresses at the end of the cooling phase. Thermal tempering of glass products has been modeled in the last twenty years using commercial software and packages …”

Section: Introductionmentioning

confidence: 99%

“…Thermal tempering of glass products has been modeled in the last twenty years using commercial software and packages. [3][4][5][6] Glass is a semitransparent material. The specificity of such material is that thermal radiation is simultaneously emitted and reabsorbed inside the glass for wavelength of the semitransparent domain.…”

Section: Introductionmentioning

confidence: 99%

Influence of radiative heat transfer model on the computation of residual stresses in glass tempering process

Agboka

Béchet

Siedow

et al. 2017

Int J of Appl Glass Sci

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During glass tempering, residual stresses are caused by the temperature gradient appearing between the surface and the core of the glass. It is therefore necessary to have an accurate knowledge of the heat transfer occurring during the process to obtain an accurate estimation of the residual stresses. Since glass is a semitransparent material, radiative heat transfer takes place inside the glass in addition to the conductive heat transfer. In this paper, we implemented 1‐D thermomechanical models using different methods for the computation of the radiative effects inside the glass: Rosseland approximation, P1 approximation and back ray tracing. Thermal and residual stresses results are compared to experimental results available in the literature to investigate the effects of the different methods on the heat transfer and mechanical behavior. We found that P1 approximation and back ray tracing are in good agreement with the experimental results. Finally, a numerical investigation is done by changing different parameters for which the experimental results are not available.

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“…The quality of the tempered glass is dependent on the efficiency of the heat transfer coefficient and the homogeneous distribution of the strengthening residual stresses. Air circulation is essential for heat transfer and distribution and modern numerical simulation has assisted in reducing waste products 4 …”

Section: Introductionmentioning

confidence: 99%

“…Air circulation is essential for heat transfer and distribution and modern numerical simulation has assisted in reducing waste products. 4 Glass breakage during the cooling period has always been a problem for glass processors. 5 This has been addressed and modeled theoretically by Shutov et al 6 using a model derived by L. M. Kachanov, presented in Equation 2…”

Section: Introductionmentioning

confidence: 99%

Metal Corrosion and its Impact on Glass Tempering Furnace Design

Tiernan

Naughton

2009

Int J Applied Ceramic Tech

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A reliable well‐designed tempering furnace is considered to be the cornerstone of any modern glass‐processing facility. This paper addresses a series of engineering anomalies encountered during the commissioning of such a glass‐processing furnace. Following the installation of a furnace in a European facility, small black deposits were noticed on both the silica‐fused rollers used to transport the glass through the hearth of the furnace and on the processed glass surface itself. EDAX and scanning electron microscopy investigations indicated conclusively that the deposits were primarily constituted of sodium sulfate and trace elements consistent with stainless steel (chromium, iron, and nickel). Traditionally, high‐density glass fiber was used to insulate the roof walls and side walls of tempering furnaces; however, it was noticed in this particular case that rolled stainless steel sheeting (SS316) was used. Chemical and X‐ray diffraction analyses were used to pinpoint the origin of the deposits. It was determined that poor material selection choices taken during the design stage of the furnace in question were at fault. The combination of stainless steel and sulfur dioxide (SO2 is used as a lubricant to prevent scuffing) at elevated temperatures (>650°C) generated droplets of sodium sulfate, which condensed due to the convectional flow of the heat currents within the oven. These droplets scorched the glass surface and destroyed the fused silica rollers. As a recommendation, the usage of stainless steel and other nonrefractory metals should be avoided in the design of any future glass tempering furnaces.

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Heat transfer and flow characteristics of the cooling system of an industrial glass tempering unit

Cited by 36 publications

References 15 publications

Measuring the 2D Residual Surface Stress Mapping in Tempered Glass under the Cooling Jets: the Influence of Process Parameters on the Stress Homogeneity and Isotropy

Measuring the 2D Residual Surface Stress Mapping in Tempered Glass under the Cooling Jets: the Influence of Process Parameters on the Stress Homogeneity and Isotropy

Influence of radiative heat transfer model on the computation of residual stresses in glass tempering process

Metal Corrosion and its Impact on Glass Tempering Furnace Design

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