Helical pipe coils types

FIG. H-24 Coil-type stab-in tank heater. This type heater is installed through a side entering tank nozzle, and differs from the bayonet type in that usually more pipes or tubes than one are used, requiring therefore a tubesheet and bonnet, or a continuous coil to allow for usually lower flow of heating medium such as heat transfer oils, diphenyl, etc. Rns are helical for natural convec tion. (Source Armstrong Engineering Associates.)... 

The flow through a helical coil is uniquely different from that through a straight pipe due to the secondary flow pattern induced by the imbalance in the radial direction between the outwards-directed centrifugal force and the inwards-directed pressure force acting on the fluid. Reviews by Berger et al. [34], Nandakumar and Masliyah [36], and Ito [40] summarize recent studies of curve pipe flows. Ali reported the pressure drop performance of different types of coiled tubes [41]. The literature review attempted here is not broad or deep, but focuses mainly on the pressure drop of fluid flow through horizontal conduits and curved pipes. 

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