Coiled open tubes

U.D. Neue, H. Engelhardt, Reaction detector with three-dimensional coiled open tubes in HPLC, Chromatographia 15 (1982) 403. 

HaMsz, I., Mass transfer in ideal and geometrically deformed open tubes II Potential application of ideal and coiled open tubes in liquid chromatography. 

Open tubes with optimal geometric orientation. 3) Open tubes with liquid or gas segmentation 4) Coiled open tubes... 

Coil condenser. An open tube, into which is sealed a glass coil or spiral through which water circulates. The tube is sometimes also surrounded by an outer cooling Jacket. A double coil condenser has two inner coils with circulating water. 

Open Tube Sections (Water cooled) Tubes require no shell, only end headers, usually long, water sprays over surface, sheds scales on outside tubes by expansion and contraction. Can also be used in water box. Condensing, relatively low heat loads on sensible transfer. Transfer coefficient is low, takes up less space than pipe coil. 0.8-1.1... 

The reactor can consist of a short packed tube or a length of coiled tube. Open tubes can give very serious band dispersion as already discussed and, if a tube is used for the reactor, it should be constructed of low-dispersion tubing. Low dispersion tubing will not only reduce band dispersion but will also produce highly efficient mixing and thus accelerate the reaction. 

The flow pattern is also modified when reactors other than straight open tubes are used. In coiled reactors, all fluid elements cannot be displaced on parallel trajectories, as the distances travelled are dependent on their relative positions. This results in split circulation of the fluid elements (Fig. 3.5), which is a consequence of the establishment of secondary flows [48]. The effect becomes more pronounced at higher flow rates. Its beneficial influence on mixing conditions, hence, on sample broadening and sampling rate, has often been emphasised [10,49]. An analogous but more pronounced effect is observed with knitted (or 3-D) reactors [50]. 

Figure 2.8. The microreactor geometries most frequently used in FIA A, straight open tube B, coiled tube C, mixing chamber D, single-bead string reactor (SBSR) and E, knitted reactor. (For an example of the imprinted meandering reactor, see Chapters 3 and 4.)...

An open-tube radiation temperature sensor at the furnace outlet has been found very useful by many operators. However, emissivity changes from coil to coil can erode confidence in strip temperature measurement. Their use inside the furnace may be even more variable. 

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