INDEX problems/criticisms

Step 6. Apply the active constraint strategy to the flexibility index (F) at the stage of structure (without the energy recovery constraint). The form of this flexibility index problem is described in a later section, (a) If F a 1, then the HEN is operable in the specified uncertainty range. Stop, (b) If F< 1, then add the critical point for operability as another period of operation and return to step 5. 

Solving the indexing problem becomes a matter of identifying the differences that result in whole numbers when divided by a common divisor and c, respectively). The expected whole numbers are shown in Table 5.14 through Table 5.16 for several small h, k and /. It only makes sense to consider these small values because successful indexing is critically dependent on the availability of low Bragg angle peaks, which usually have small values of indices. 

During regional scale ozone episodes, elevated concentrations become widespread across Europe [20]. Transboundary transport is an important feature of the problem. The concentrations exceed air quality guidelines set to protect human health [22] and critical levels set to protect crops and trees firom ozone damage. To illustrate the approach, the target ecosystem is taken to be human health so that the sensitive ecosystems can be located in the major urban centres of London, Paris, Brussels, Bonn, Amsterdam, Copenhagen, Stockholm and Oslo. For these ecosystems, the maximum hourly mean in a worst-case episode is the most appropriate index of harm. 

Neat HOPE 9, used at 23% of the total HDPE in the formulation, had exceptionally low critical shear rate (100 s ) and the power-law index (0.34). It apparently should make the processing window narrower compared to a normal run. Regrinds 4 (Table 17.27), 5, and 6 were within norm and could hardly create serious problems. Probably, the HDPE materials were culprits in the respective runs (see HDPE 9 in Table 17.28 with a very low critical shear rate of 100 s ). Regrind 7 also showed very low critical shear rate (100 s ) and power-law index (0.33) and could create problems with run stability and output. 

Overcoming Problem 4. Another rotary furnace problem is the positioning of rounds on the hearth. Some operators index all the load pieces to one stop on the inlet roller table, which sets the pieces at a common point near the inner wall of the furnace. Others index the pieces to straddle the hearth centerline. In either case, short pieces may be 1 to 4 ft (0.3-1.3 m) from the outer wall of the furnace. One negative result of this is use of less hearth for heating loads. A second and critical problem is that the T-sensors will be farther away from the loads, causing the sensor to be less and less reflective of the pieces temperature and more of a representation of furnace temperature. This problem is especially critical in the final zones where very responsive temperature control is needed. 

Although this approach of Metzner and Otto [1957] has gained wide acceptance [Doraiswamy et al., 1994], it has come imder some criticism. For instance, Skelland [1967] and Mitsuishi and Hirai [1969] argued that this approach does not always yield a imique power curve for a wide range of the flow behaviour index, n. Despite this deficiency, it is safe to conclude that this method predicts power consiunption with an accuracy of 25-30%. Furthermore, Godfrey [1992] has asserted that the constant kg is independent of equipment size, and thus there are no scale-up problems. 

---