Adapters still and column heads

The Dimroth condenser and the Friedrichs screw condenser, which give k values of 1.5 and 1.25 respectively, can be considered to have a good efficiency. The effectiveness of the Jena condenser with undulating tubes is a result of its very large cooling area (1136 om ) its heat transfer coefficient, 0.575 cal/cm min. °C, is only moderate. 

Brezina [82] dealt thoroughly with Liebig condenser designs and efficiencies. He derived a new mathematical relation for the examination of the efficiency of this type of condenser and suggested a measuring device for condenser tests. 

By using formula (198) and the values of k listed in Table 66 the reader can carry out calculations for individual types of condenser it is, however, always advisable to allow a margin of 50% above the area so found. Purchased condensers as a rule have very liberal dimensions. 

However, heat exchangers for semi-technical and pilot plants have to be calculated exactly, the more so because the cooling surfaces are assem bled from standardized components. For this purpose, the manufacturers of glass components give the heat tr ansfer coefficients k as listed in Table 67. 

For the assembly of larger cooling surfaces a varietj of components, mostly in the fornr of coils with nominal widths from 40 to 450 mni, are commercially available. 

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The vapours evolved in a boiler are led away, their temperature is measured and they are finally condensed. In simple distillation the auxiliary components used for this purpose are adapters and still heads. In countercurrent distillation it is also necessary to return reflux to the column and to measure the reflux ratio. Special... 

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