SEDIMENT REMOVAL EFFICIENCY OF VORTEX CHAMBER TYPE OF SEDIMENT EXTRACTOR

Abstract

Vortex chambers have been widely used as a device to extract sediment from sediment-laden flow efficiently and economically under the actions of gravity and vortex flow. The vortex chamber makes use of vortex flow in a chamber as a separation device. The sediment particles present in the flow move along a helicoidal path toward the orifice, thereby obtaining a long settling length compared to the rectangular settling basin. In a vortex chamber, a relatively higher velocity flow is introduced tangentially into it that causes a free vortex in the chamber along with a forced vortex in the center of the chamber. Understanding of the discharge characteristics of the vortex chamber orifice is required for the design of the chamber for sediment removal. Various empirical equations have been developed for the coefficient of discharge C, of the orifice and sediment removal efficiency 'l() which relates them with various configuration parameters of vortex chamber. Forced vortex in the core of the chamber is the prime cause of the settling of sediment in the vortex chamber, however, circulation or vorticity parameters have yet not been considered in developing relation for c'1 and 'Z(' In the present study, data related to discharge characteristics of the vortex chamber have been collected from the literature and experimental data for sediment removal efficiency has been analyzed for developing a relation for C1 relating it with circulation number. It is found that the C, has strong dependency on the circulation number compared to the other parameters. It decreases with an increase in circulation number. The developed relation for C, is a function of only circulation number. The predicted coefficient of discharge is in good agreement with the observed value. Since the effect of circulation number on G, was significant therefore this parameter was also considered for developing the new relationship for sediment removal efficiency. Data from the experiment and literature have been collected and analysed for developing a new relationship for estimating sediment removal efficiency without circulation parameter because there is no correlation exist between efficiency and circulation parameter as diverted discharge is already accounted into other parameters. The obtained relationship for sediment removal efficiency of vortex chamber type of sediment extractor with change of orifice diameter produces results with maximum error of ±30 % for all the data considered herein. Analysis of data reveals that circulation does not has significant effect on sediment removal efficiency of vortex chamber.