Helical pipe coils pressure drop

Pressure drop in helical coils is dependent on whether the flow is laminar or turbulent. Typically flows are laminar at low fluid velocities and turbulent at high fluid velocities. In cuived pipes and coils a secondary circulation takes plac e called the double eddy or Dean Effect. VVliile this circulation increases the friction loss, it also tends to stabilize laminar flow, thus increasing the critical Reynolds number. 

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. 

Initially he conducted the experiment on water flow through horizontal pipe (same PVC pipe for both cases) to find the roughness values (Venkatesan et al. [62], He compared the experimental friction factor for coil with the values obtained from smooth coil equation and observed that the experimental friction factor was higher than that of smooth coil. He found that as coil diameter increased the friction factor decreased (Figure 2). He presented a generalized correlation for predicting the frictional pressure drop across the rough helical coils as... 

Typical experimental setup used by Das [122] is shown in Figure 3. The experimental apparatus consisted of a water storage tank, a centrifugal pump, a test section, control and measuring systems for the flow rate, and pressure drop. The pipes were wound round a wooden cylindrical frame of known diameter to form a helical coil. The coil diameter could be varied by changing the diameter of the... 

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