Abstract
The paper presents the results of an investigation on hydraulics of a low-speed coil pump for transport of liquids. One of the pump’s advantages is its wide range of potential inclination angles for its rotating shaft, from the horizontal to an almost vertical position. A simplified hydraulic model was developed based on kinematic and geometrical considerations to determine the pump capacity. The model was verified under laboratory conditions using a low-speed coil pump composed of transparent PVC tube (15 mm outer diameter) wound around a cylindrical drum (104 mm external diameter; 550 mm long). Laboratory tests were performed for three angles of inclination of the axis of rotation (20°, 40°, and 60°) and four rotational speeds (10, 20, 30, and 40 rpm). The results of the tests showed satisfactory agreement with the hydraulic model predictions. Energetic efficiency was estimated on the base of electric power measurements and difference of water levels in the two arms of rotating transparent torus, partly filled with water. The hydraulic efficiency of the coil pump is increasing with decreasing rotational speed.
Highlights
The Archimedean screw is one of the oldest devices for water raising
With the increase of rotational speed, a decrease in efficiency can be observed, which results from the linear increase in shear stress along with the increase of fluid velocity
In the case of centrifugal pumps the hydraulic efficiency decreases with rotational speed [34,35,36]
Summary
The Archimedean screw is one of the oldest devices for water raising. It was described, not necessarily invented by Archimedes [1]. A coil pump is based on the same principle as the spiral pump, but the tube is wound around either a conical drum or a cylindrical drum, as a result creating a helix. Inclining the axis of rotation allows elimination of the rotating seal, since the coiled tube and the inclined force main are joined to form one component This means that the force main may be used as the drive shaft, enabling the pump to be driven from dry land as an alternative to the drum being driven by the stream power. Where ψ is the inclination of the cylindrical helix to the pump baseline and β is the angle of inclination of the axis of rotation to the horizontal.
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