For coils

Cracking reactions are endothermic, 1.6—2.8 MJ/kg (700—1200 BTU/lb) of hydrocarbon converted, with heat supplied by firing fuel gas and/or fuel oil in side-wall or floor burners. Side-wall burners usually give uniform heat distribution, but the capacity of each burner is limited (0.1—1 MW) and hence 40 to 200 burners are required in a single furnace. With modem floor burners, also called hearth burners, uniform heat flux distribution can be obtained for coils as high as 10 m, and these are extensively used in newer designs. The capacity of these burners vary considerably (1—10 MW), and hence only a few burners are required. The selection of burners depends on the type of fuel (gas and/or liquid), source of combustion air (ambient, preheated, or gas turbine exhaust), and required NO levels. 

TABLE 11-2 Overall Heat-Transfer Coefficients for Coils Immersed in Liquids... 

A wide variety of configurations exists for coils in agitated vessels. Correlations of data for heat transfer to helical coils have been of two forms, of which the following are representative ... 

WA Lim, A Hodel, RT Sauer, FM Richards. The crystal structure of a mutant protein with altered but improved hydrophobic core packing. Proc Natl Acad Sci USA 91 423-427, 1994. PB Harbury, B Tidor, PS Kim. Repacking proteins cores with backbone freedom Structure prediction for coiled coils. Pi oc Natl Acad Sci USA 92 8408-8412, 1995. 

There is some confusion in using Bayes rule on what are sometimes called explanatory variables. As an example, we can try to use Bayesian statistics to derive the probabilities of each secondary structure type for each amino acid type, that is p( x r), where J. is a, P, or Y (for coil) secondary strucmres and r is one of the 20 amino acids. It is tempting to writep( x r) = p(r x)p( x)lp(r) using Bayes rule. This expression is, of course, correct and can be used on PDB data to relate these probabilities. But this is not Bayesian statistics, which relate parameters that represent underlying properties with (limited) data that are manifestations of those parameters in some way. In this case, the parameters we are after are 0 i(r) = p( x r). The data from the PDB are in the form of counts for y i(r), the number of amino acids of type r in the PDB that have secondary structure J.. There are 60 such numbers (20 amino acid types X 3 secondary structure types). We then have for each amino acid type a Bayesian expression for the posterior distribution for the values of xiiry. 

Figure 10. Graph of Variance against Flow Rate for Coiled and Serpentine Tubes...

In order for coils included in any of the above systems to operate efficiently, they must be designed to have a uniform air velocity across the whole of the heater s face area. This is of prime importance, and the manufacturer s specifications regarding the maximum and minimum air velocities must be met. 

Table 5-8 gives the order of magnitude for coil-in-tank heat transfer. 

When silica levels increase, hydroxide alkalinity measurements become increasingly important to ensure maximum silica solubilization and the reduction of risk of silica deposition. This is especially so for coil boilers because, more than any other boiler type, the use of hydroxide is critical in keeping the waterside surface of the coiled tube clean and deposit free. 

NOTE Refer to Table 12.14 (BS 2486 1997 Table 6) for starting point recommendations for OH alkalinity and silica limit ratios for coil boilers. 

BSI recommended water characteristics for coil boilers note that it is imperative that the oxygen scavenger used in coil boilers remove all the oxygen in the FW, so the use of a proportionally dosed, fully catalyzed chemical scavenger is essential. Sulfite may decompose at pressures higher than 50 bar and produce hydrogen sulfide or sul-fure dioxide in the steam. 

This technique bus been applied by Rhodes and Younger(107) to obtain the values of h0 for condensation of a number of organic vapours, by Pratt(92) to obtain the inside coefficient for coiled tubes, and by Coulson and Mehta(i08) to obtain the coefficient for... 

R. C. Navarrete and S. N. Shah. New biopolymer for coiled tubing applications. In Proceedings Volume. SPE/Int Coiled Tubing Assoc Coiled Tubing Roundtable (Houston, TX, 3/7-3/8), 2(X)1. 

Roll coating of paint is the final process in a coil coating line. Roll coating is an economical method to paint large areas of metal with a variety of finishes and to produce a uniform and high-quality coating. The reverse roll procedure for coils is used by the coil coating industry, and allows both sides of the coil to be painted simultaneously. 

A major application of data base in our laboratories is in the tracking of coatings test exposure data. The two types of exposure records currently implemented are for exterior hardboard siding coatings, and for coil coatings. While these two classes of substrates and the coatings used for them are quite different, the basic structure of the data and reporting requirements are not. 

Figure 12.2 Profiles for coil temperature (Tc) and heat transfer rate (Q) for an isothermal batch reactor (Example 12-4)...

The coil heat transfer coefficient had a value of 0.1159 and a x2 statistic of 27.8. This value suggests that a gross error is present. Some clues can be found from examination of the residuals of the balances. They are presented in Table 7. There appears to be a problem with the balances for coils 2 and 3 their residuals are different from the others (especially coil 2). The reconciled value for the coil 2 cracking temperature is also significantly different from the measured value, thus suggesting an abnormal situation associated with both coils 2 and 3. 

These results would be satisfactory, but for the arbitrary nature of the adjustment to the coil 2 cracking temperature. The gross error could also be eliminated by adjusting either the flow rates through the coil 2 and 3 or the inlet temperature to the radiant zone (crossover temperature) for coil 2. As it happens, the best reduction in... 

Interesting results are obtained if 160 kg/h is deducted from the measured hydrocarbon flow for coil 2, and 210 kg/h added to the hydrocarbon flow for coil 3. The anomaly between the coil heat transfer coefficients for coils 2 and 3 has disappeared. Figure 7 shows the effect that the adjustment to the coil flow has on the crossover... 

One unifying rule accounting for block copolymer micelle morphology has been proposed by Discher and Eisenberg [239]. This rule should be considered for coil-coil block copolymer readily soluble in the selective solvent and is expressed as a function of the mass fraction of the hydrophilic block to total mass of the copolymer (/hydrophilic)-... 

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