Wire Problem

When a catalytic reaction takes place on a nonporous metal surface the coupling between the exothermic chemical reaction and the transport effects may also give rise to multiple steady states. Apparently, in the realm of chemical reaction engineering the first experimental observation of multiple steady states was done just for the catalytic wire problem [see Tamman (29), Davies (30), and Buben (5/)]. Catalytic gauzes consisting of wire screens or layers of metal pills (e.g., the silver crystals) are used for a number of industrially important catalytic reactions as, e.g., synthesis of 

After rewriting the Frank-Kamenetskii (32), Cardoso and Luss (33), and Aris (2) results the conditions governing the multiplicity phenomena are  

Condition 1 The necessary and suflcient condition for the occurrence of one steady state is y/3 4Nu/Sh. 

Condition 2 The necessary condition for multiple steady states is given by y/3 4Nu/Sh. 

Recently Ray (34) has shown that the periodic activity caused by thermal effects is impossible because of high thermal capacity of the metal catalysts. 

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Wiring problems were found in the electrical panel supplying the computers, such as with the neutral wires in the ground terminal and ground wires in the neutral terminal. This configuration caused a portion of the neutral return current of the load... 

Joking aside, the wiring problem, although probably the most serious omission to date in the molecular chip designer s toolkit, is being pursued actively in many laboratories worldwide. Currently, there are four main trains of thought as to how the future molecular computer will be wired. 

As with any instrument, calibration is important for thermocouples. Although manufacturers supply accuracy data for typical thermocouples, calibration can be used to check that these data apply to the specific instrument being used in an experiment. The accuracy can be improved by calibrating the specific thermocouple being used. More importantly, a thermocouple calibrator (see Figure 5.5) can be used to check for any wiring problems or any setup mistakes in the data acquisition system. A thermocouple that has been wired and connected to the data acquisition system can be inserted into the calibrator to check for problems. For example, if a Type R thermocouple is actually being used but it... 

Figure 8.5 Possible steady states for the single wire problem. (Cordoso and Luss 1969 reprinted with permission from Chemical Engineering Science. Copyright by Pergamon Press.)...

First, a single wire problem will be considered as an introduction. It brings out essential features of the stability problem and is similar in many respects to the more familiar stability problem with a CSTR. A simple and yet realistic case of negligible internal heat transfer and external mass transfer resistances will also be treated. The general problem will then be analyzed in a limited form for the case of unit Lewis number (Le) appearing in Eq. 8.27. This considerably simplifies the problem and yet the result can be extended to a certain extent to the general case of arbitrary Lewis numbers. Readers interested in more details on stability can refer to the book by Aris (1975) and the review by Luss (1977), from which the subsequent sections are derived. 

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