Cooktop panel

Fig. 5. Relative change in length with temperature of P-quartz glass-ceramics designed for A, precision optics and B, cooktop panels. Curves for C, fused...

Range Hood. Range hoods come in a variety of widths (30,36, and 48 in). Controls for the range hood may be located on the lower front panel of the hood to decrease the reach-range requirements for operation. However, it is recommended that these controls he located on the cooktop panel or in nearby base cabinets just below the counter top. 

Since the beginning of the development of cooking systems with glass ceramic hobs in the late 1960s, several millions of cooktop panels have been sold worldwide. 

The combination of these advantages in design/appearance and in function was made possible by the special properties of the Ceran cooktop panel, (incorporated in the Ceran-Top-System ) based on the Li20-Al203-Si02 glass ceramic exclusively developed for this application by Schott Glaswerke. 

In addition to the colour shade and decoration, design requests are satisfied by the various geometric types of cooktop panels for built-in or freestanding cookers rectangular, oval-shaped, circular, square, with and without holes for control devices. These are advantages in design that no other cooking system can offer, and it is the properties of this product which make them possible. 

Smooth cooktop panel cookware can be pushed aside, easy-to-use... 

Low-expansion glass ceramics are widely used as precision parts (see Chap. 4), cooktop panels, stove windows, and cookware. In this section we will focus on the development of transparent glass ceramics used as stove windows (colourless) and cooktop panels (tinted) glass ceramics for cookware are also briefly discussed within this section. 

Property Field of application Cooktop panel Stove window Cookware... 

Depending on the application of low-expansion glass ceramics - we are now focussing on tinted cooktop panels and colourless stove windows - further physical and chemical properties are required from both the production and the user side. To lower production costs, fast and effective processing is required, for example, tank melting, on-line hot forming of panels, as well as fast nucleation rates and crystal growing are absolutely necessary. Moreover, the application of decoration, which, for example, indicates the hot zones of a final cooktop panel, should be performed at the same time as ceramization takes place, without any influence on the production quality. 

Furthermore, the glass ceramic used as a cooktop panel has to meet transmission specifications it has to be nearly opaque in the visible spectrum to avoid a direct view to the electric heating elements of the cooktop assembly. On the other hand, the glass ceramic should have a high transmission for infrared radiation to support the overall heating performance. 

As mentioned before, glass ceramics used as cooktop panels have, furthermore, to meet specific transmission specifications in the visible (nearly opaque) and in the near IR (transparent) spectral regions. Different well-... 

The decoration of cooktop panels is often performed at the same time as their ceramization. In this case the temperature-dependent properties of glazes have to be matched to the ceramization process as well. 

The physical and chemical properties of a typical glass ceramic produced in that way and used as a cooktop panel are summarized in Table 3.3 [3.22]. 

The manufacturing process for Ceran cooktop panels can be divided into two fundamentally different partial processes. The first process, the produc-... 

In Sect. 3.1 on the Ceran-Top-System our approach to the development and optimization of cooking systems was described. Schott always takes a system-approach to help create the optimum appliance for a satisfied end user in collaboration with suppliers of components and our customers, the appliance manufacturers. In this way the appliance is commercially very successful and with it also the component we supply the Ceran cooktop panel. 

The thermal expansion of many glass ceramic materials shows a non-linear temperature dependence. As indicated in Fig. 3.23, Ceran glass ceramic cooktop panels exhibit a parabolic function. 

To be able to take into consideration the non-linear curve of thermal expansion of Ceran glass ceramic cooktop panels with the temperature in our calculation, we introduce, instead of the coefficient of thermal expansion a, assumed as being constant in (3.5) to (3.7), the thermal expansion e. It is thus... 

With the temperature distributions in Fig. 3.25 at different times of the warming-up period, and with the curve of thermal expansion of Ceran glass ceramic cooktop panels with the termperature in Fig. 3.23, the stress distributions can be figured out. The temperature distributions in Fig. 3.25 were determined experimentally. 

For doing so, we used a square cooktop panel whose lateral length conin-cided with the diameter of the circular disk of our cooking-area model. 

We could use a square plate for the determination of the temperature distributions during the warming-up period, because the temperature distributions are rotationally symmetric also with this geometry, which is due to the poor heat conduction of Ceran glass ceramic cooktop panels (1.6 W/mK). The distortion of the temperature field by the heat dissipation into the corners of the square is negligible, regardless of the heating duration. 

As compared to glass and glass ceramics in which a is constant and positive, the following peculiarities turn up with the Ceran glass ceramic cooktop panels. 

Ceran cooktop panels are especially designed for small thermal expansions in the temperature range from 20 to 750 C. The thermal treatments during their production are optimized to reduce the compaction to a minimum. Thus, the level of stresses due to thermal expansion and compaction is low compared to the bending strength of the Ceran cooktops, which are not endangered by thermal and compaction stresses. 

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