Drag reduction of trimethylolethane hydrate slurries treated with surfactants.

Drag reduction characteristics of trimethylolethane hydrate slurries treated with surfactants have been investigated. The effects of the surfactant concentration and hydrate fraction of the slurry on drag reduction behaviours were focused on in this paper. The friction coefficient in a pipe flow of hydrate slurries treated with surfactants and the relaxation time of trimethylolethane solution with surfactants were measured. From the results, it was found that the effective drag reduction appears in the cases of high surfactant concentration and of high hydrate fraction. This behaviour was supported by the viscosity shear-thickening occurrence reported in the previous study. However, the effective drag reduction disappears in the case of low surfactant concentration in spite of the shear-thickening occurrence. On this discrepancy, the relaxation time of the solution was measured. It is found that the critical concentration determined from the relaxation time disappearance well corresponds to the limitation of effective drag reduction occurrence.