Water network

Tapia and Eklund (1986) carried out a Monte Carlo simulation of the substrate channel of liver alcohol dehydrogenase, based on the X-ray diffraction structure for this enzyme. The addition of substrate and the associated conformation change induce an order—disorder transition for the solvent in the channel. A solvent network, connecting the active-site zinc ion and the protein surface, may provide the basis for a proton relay system. A molecular dynamics simulation of carbonic anhydrase showed two proton relay networks connecting the active-site zinc atom to the surrounding solvent (Vedani et ai, 1989). They remain intact when the substrate, HCOf, is bound. 

Mackay and Wilson (1986) suggested that single-file waters in channel structures, like that studied in gramicidin A, may provide for long-range transfer of information, by a spatial (translational) response to a perturbation or by the correlated reorientation of water dipoles. 

Threads, clusters, or networks of water molecules have been detected by crystallographic, thermodynamic, and dynamic measurements. They appear to be a common feature of the protein—water interface, which should not be surprising, in view of the extensive hydrogen bonding of the bulk water. Moreover, the water of the interface differs from 

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Investigate the effect of the pressure surge on adjacent equipment per the 1997 edition of API RP-521. The design pressure of adjacent equipment and piping may be exceeded during a tube rupture. This is of special concern in cooling water networks. Dynamic simulation can assess the impact of a tube rupture on adjacent equipment and identify corrective measures. 

Mutations in Amino Acids Linked to Ca through a Water Network ... 

Figure 24.13 Flowsheet of cooling water network with maximum reuse of cooling water. (From Kim J-K and Smith R, 2001, Chem Eng Sci, 56 3641, reproduced by permission of Elsevier Ltd.)... 

Alternatively, air-cooled heat exchangers can be installed within the cooling water network to replace cooling water coolers. This has the effect of reducing the cooling load on the cooling tower and, in principle, allows the flowrate of cooling water to be decreased. 

Situations are often encountered when cooling water networks need to increase the heat load of individual coolers, which requires investment in new cooling tower capacity. Such situations demand a more complete analysis of the whole cooling water system. 

A cooling tower supplies water to a cooling water network at 25°C. The maximum inlet and outlet temperatures for the three cooling duties together with their flowrates are given in Table 24.6. 

Rather than reconfigure the cooling water network in Exercise 4, what other options might have been considered to accommodate the new cooling duty without having to invest in a new cooling tower ... 

This simple example illustrates the basic principles of water network design for maximum reuse for a single contaminant. A number of issues need to be considered that would apply to more complex examples. Consider Figure 26.25 involving three water mains and three operations. Operation 2 above the pinch terminates at a concentration less than the concentration for the high concentration water main. The outlet of Operation 2 must not be fed directly into this final water main. The basis of the mass balance from Figure 26.17 dictates that all streams must achieve the concentration of the water mains into... 

Figure 26.23 Water network without the intermediate water main.

Figure 26.36 Water network design based on the optimization...

A water network produces the 6 effluent streams in Table 26.17. The environmental discharge limit for the contaminant concentration is 50 ppm. There are two treatment processes available on the site, which are capable of reducing... 

Table 26.21 lists the limiting data for a water network. 

Polley GT and Polley HL (2000) Design Better Water Networks, Chem Eng Prog, Feb 47. 

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