Steady-state glass

For certain products, skill is required to estimate a product s performance under steady-state heat-flow conditions, especially those made of RPs (Fig. 7-19). The method and repeatability of the processing technique can have a significant effect. In general, thermal conductivity is low for plastics and the plastic s structure does not alter its value significantly. To increase it the usual approach is to add metallic fillers, glass fibers, or electrically insulating fillers such as alumina. Foaming can be used to decrease thermal conductivity. 

The sensor is an ammonium ion-selective electrode surrounded by a gel impregnated with the enzyme mease (Figme 6-11) (22). The generated ammonium ions are detected after 30-60 s to reach a steady-state potential. Alternately, the changes in the proton concentration can be probed with glass pH or other pH-sensitive electrodes. As expected for potentiometric probes, the potential is a linear function of the logarithm of the urea concentration in the sample solution. 

A comparison of the measured mean relative size with the model in Eq. (101) is shown in Fig. 28. The material was monosize glass beads. The data fit the model quite well, with the exception of fine 0.038-mm powder. It is evident that the steady-state size distribution is a function of the liquid content, and consequently, as shown by Sherrington (S9), there is an optimal granulating liquid for maximum granulation efficiency, that is, percentage of the product-grade material. 

There is no general correlation available to date to predict the steady state attrition rates for various materials. Zenz and Kelleher (1980) gave a simple correlation to predict steady-state attrition rates for FCC catalyst and glass beads. This is an empirical dimensional equation as given by ... 

FIG. 35 Percentage relative humidities of common foods at room temperature and typical steady-state moisture contents plotted as a universal sorption isotherm with portions of three glass curves (relatively positioned) for sorbitol, for a nonnetworked biopolymer, and for a permanent network [reproduced with permission from Slade and Levine (2003)]. 

---