Numerical study of a coil pump and comparison with field measurement

Abstract

Rural irrigation could be challenging in regions without proper access to electricity. In many remote places of Nepal, where the irrigation takes place in the vicinity of a river stream, a river water pump or coil pump can be used to supply water from the lower river terrain to the field. Water powered coil pump is a reciprocating pump that operates by rotating a coiled tube, by harnessing the power of a flowing river. A comparison in performance of cylindrical and conical shaped coil pumps was done both experimentally as well as numerically in this work. Under the river velocity of 0.9m/s, the maximum discharge at zero lift condition for the conical pump was 11,500 liters/day while for the cylindrical pump it was 8,600 liters/day. However, the conical pump could not generate lift more than 6.5m while the cylindrical pump performed well even at 11m head. The Numerical study was also carried out in order to visualize the flow patterns and compare the performance of the pumps while varying different parameters. The 3D computation domain of the pump for four cases (two cases varying the number of turns and two cases with change in shape) were generated and numerically studied using OpenFOAM. The interaction, being a multiphase case, interFoam solver was used, and to simplify the simulation laminar turbulence model was taken. The pressure and water volume at the outlet in the simulation were measured and compared between different cases. It was observed that the pressure obtained while using a cylindrical pump was 2.52 % more than that while using the conical pump. The outlet pressure was found to be increasing by 35% while increasing the number of turns from 7 to 15 in cylindrical and 42.5% in case of conical coil pump. The volume flow rate was observed to be more frequent in the case of the conical pump. Due to constraints of computational conditions, the experimental setup could not be totally replicated. However, the outcome showed a similar trend as obtained in the experiment. It was found that the cylindrical pump was better for the higher head, whereas the conical pump had shown better results for higher discharge.