Design criteria approaches

Before suggesting an approach for predicting the minimum number of shells for an entire network, a more convenient method for determining the number of shells in a single unit must first be found. Adopting the design criterion given by Eq. (7.13) as the basis, then any need for trial and error can be eliminated, since an explicit... 

The various approaches to discriminate between models and to test a given model s adequacies have been treated above, and focus is given here on the design criterion A simple approach can be followed to determine the maximum divergence between model predictions Based on statistical considerations for two models, a simple expression was derived to measure the divergence D(x ) at the experimental settings x of the experimental grid... 

Bayesian methods have often proved useful for design of experiments, especially in situations in which the optimal design depends on unknown quantities. Certainly, to identify a design for optimal estimation of /3, the correct subset of active effects must be identified. Bayesian approaches that express uncertainty about the correct subset enable construction of optimality criteria that account for this uncertainty. Such approaches typically find a design that optimizes a criterion which is averaged over many possible subsets. DuMouchel and Jones (1994) exploited this idea with a formulation in which some effects have uncertainty associated with whether they are active. Meyer et al. (1996) extended the prior distributions of Box and Meyer (1993) and constructed a model discrimination design criterion. The criterion is based on a Kullback-Leibler measure of dissimilarity between... 

As shown in Fig. 13.4, the difference in the overall conversion is the consequence of a lower conversion rate at the reactor inlet, as expected. Although the characteristic mixing time corresponds to a distance of 0.24 m, the reaction rate (slope of the conversion profile) of the unmixed feed case approaches that of the premixed feed case by 0.1 m, or 10% of the total reactor volume. Furthermore, the predicted conversion for the immixed and premixed feeds is 25.1% and 25.7%, respectively. This corresponds to a relative difference of 2%, an acceptable level of error that will only decrease as the reactor residence time increases. This analysis validates the reactor design criterion that the characteristic mixing time based on... 

For the specific jacket-cooled CSTR process considered in this section and the next, a simple heuristic approach can be used to incorporate quantitatively the limitations of controllability into the steady-state design. The idea is to specify a design criterion that ensures good controllability. In the reactor temperature control problem we use the criterion of a specified ratio of the maximum heat removal rate to the heat removal rate at design conditions. This simple approach is easily understood by designers and operators, and it requires no dynamic simulation or control analysis. We illustrate its usefulness in the following section to determine the besf reactor operating temperature. 

In order to facilitate the implementation of this nuclear safety design criterion DOE 5480.28, NATURAL PHENOMENA HAZARDS MITIGATION, specifies the requirements for each new and existing DOE facility. The evaluation criteria for this DOE Order are built around a graded approach. DOE 5480.28 specifies that an NPH analysis will be performed for all new and existing dOE faciI ities. Specifically ... 

An Annex to this ISO document provides a design criterion for adhesive bonding. In order to determine the bonded area, a simplified approach based on shear loading is proposed. Shear stresses should be limited to 20% of the nominal bond shear strength, that is, a safety factor of 5. This factor is intended to account for both stress concentrations in real joints and the viscoelastic (time and temperature dependent) nature of adhesives. Shear data values, to be used if test values are not available, are provided, O Table 48.3. 

Clearly, in designs different from those in Figs. 16.13 and 16.14 when streams are split to satisfy the CP inequality, this might create a problem with the number of streams at the pinch such that Eqs. (16.3) and (16.4) are no longer satisfied. This would then require further stream splits to satisfy the stream number criterion. Figure 16.15 presents algorithms for the overall approach. ... 

The design methods de.scribed above rely on correlations of the overall reactor average quantities obtained from experimental tanks of different scales. The most important deficiency of these methods is that local effects are not taken into consideration, while these might be responsible for the overall reactor performance. Accordingly, if none of the above scale-up criteria is found satisfactory (see e.g. data of Middleton et ai, 1986) a more fundamental approach must be applied, although not necessarily as complex as the one presented in Section 5.4.S.2. Such an approach was presented by Paul et al. (1971) who found that the yield of the desired intermediate in a system of consecutive reactions (iodination of L-tjrosine) correlates reasonably with fluctuations of the velocity, So, these fluctuations could be chosen as a criterion for scale-up of the reactor. The average value for u in the upper part of the tank was evaluated from ... 

Wet-weather processes are subject to high variability. A simple deterministic model result in terms of the impacts on the water quality is out of scope. From a modeling point of view, a stochastic description is a realistic solution for producing relevant results. Furthermore, an approach based on a historical rainfall series as model input is needed to establish extreme event statistics for a critical CSO impact that can be compared to a water quality criterion. In terms of CSO design including water quality, this approach is a key point. 

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