Coil-shaped condenser

The shape of the coohng and warming curves in coiled-tube heat exchangers is affected by the pressure drop in both the tube and shell-sides of the heat exchanger. This is particularly important for two-phase flows of multicomponent systems. For example, an increase in pressure drop on the shellside causes boiling to occur at a higher temperature, while an increase in pressure drop on the tubeside will cause condensation to occur at a lower temperature. The net result is both a decrease in the effective temperature difference between the two streams and a requirement for additional heat transfer area to compensate for these losses. 

The shape of a vessel determines how well it drains (Figure 53.7). If the outlet is not at the very lowest point process liquid may be left inside. This will concentrate by evaporation unless cleaned out, and it will probably become more corrosive. This also applies to horizontal pipe runs and steam or cooling coils attached to vessels. Steam heating coils that do not drain adequately collect condensate. This is very often contaminated by chloride ions, which are soon concentrated to high enough levels (10-100 ppm) to pose serious pitting and stress corrosion cracking risks for 300-series austenitic stainless steel vessels and steam coils. 

The filament shape commonly used in resistively heated pyrolysers is either a ribbon or a coil. The sample can be put directly on the filament or in a silica tube that fits in the piatinum coil. A silica (quartz) tube used as a sample container can be extremely useful in accommodating for pyrolysis of a wide variety of samples. Flowever, when a silica tube is used, the TRT times are increased due to the larger mass that needs to be heated. The filament, the silica tube (if present), and the sample are maintained in a stream of inert gas and inside a heated housing as described in Section 4.1. This secondary heating is necessary as mentioned before to avoid the condensation of the pyrolysate. The stream of gas inside the heated chamber can be used further as a... 

As in the Eq. (64) X value has no effect on the distribution P (N), then the indicated relationship supposes three basic parameters influencing on distribution P (N) d, b and ty. Each of the indicated parameters characterizes a certain feature of the poly condensation process. The exponent d is thus essentially defined by the macromolecular coil stmcture, that directly follows from the Eq. (63). The value b characterizes the type and intensity of the destructive processes. Parameter is determined by the stochastic contribution to a polycondensation process and it is possible to assume dependence on comonomers initial concentration c the greater C(, the higher the probability of random collisions. This postulate is particularly important for the mode of interfacial polycondensation, where synthesis proceeds not in all reactive vessel volume, but only in the interfacial layer, for which enhanced in comparison with average value the magnitude c is expected. All experimental MWD curves have the unimodal shape that supposes low mobility for coils in solution or < 2/3 [101]. 

The authors [87-89] used for DMDAACh MWD curves theoretical description and determination of the factors influencing their shape, the model [48], successfully applied above for the similar curves description in case of polyarylates, obtained by different poly condensation modes (see section 1.2). As it has been noted above, since in the Eq. (64) of Chapter 1 the value X does not influence on the distribution P CN), then the indicated relationship assmnes three main parameters, influencing on the distribntion P CN) a , b and o. Each from the indicated parameters expresses the certain feature of polymerization process. So, the exponent a is defined as a matter of fact by macromolecnlar coil stmcture, that follows directly from the Eq. (63) of Chapter 1. The valne b characterizes a type and intensity of destraction processes. The parameter is defined by the stochastic contribntion in polymerization process and the dependence of on c, can be as-... 

An early form of sublimation apparatus of which the above arrangements are derivatives (Figure 3) included a means of cooling the surface on which the sublimate condenses. Cooling can be achieved in a number of ways, for example, using filter papers moistened with cool water, or in the case of the upturned funnel, a suitably shaped coil of circulating coolant liquid can be placed around the surface. 

As it is known [8], macromolecular coils in 0-solvent and in the condensed state of polymers possess the same shape as that expressed by approximately eqnal mean-square distance between the ends of a macromolecule. Boyer [59] has schematically shown that this circumstance does not prevent formation of local order domains. More strictly this conclusion is proved in paper [99]. It is obvions that this experimentally proved condition should also be true for a cluster model. For estimation in polymer clusters, Forsman [82] has proposed the following equation ... 

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