Published 6 issues per year
ISSN Print: 2152-5102
ISSN Online: 2152-5110
Indexed in
EFFECT OF FLOCCULATING AGENTS ON DRAG IN GRAVITY-DRIVEN FLOW SYSTEMS
ABSTRACT
Efflux time measurements are carried out for draining water from a large cylindrical tank through an exit piping system in the absence and presence of flocculating agents. The flocculating agents used are potash alum (certified as well as commercial) and ferric alum in the concentration range of 0–50 ppm. The desired concentration is achieved by two methods: (a) diluting the stock solution and (b) direct preparation of dilute solution. Two methods of preparation have been adopted. They are (i) water added to the flocculating agent and (ii) flocculating agent added to water. The experiments are repeated for two diameters of exit pipes while keeping the exit pipe length constant at 1 m. The experiments are also performed with different initial heights of liquid in the tank. In the case of potash alum (both certified and commercial), drag reduction is observed (i.e., reduction in efflux time) for 30 ppm as well as 40 ppm concentrations. The concentration at which efflux time is less is the same both for commercial alum and certified alum. Even though efflux time is influenced by the initial height of the liquid in the tank, the optimum concentration is not. Surface tension data suggest the lowest surface tension for 40 ppm potash alum solution (for both certified and commercial alum). In the case of ferric alum, the drag enhancement (increase in efflux time) takes place with a corresponding increase in surface tension.