Drag reduction due to nonionic-type surfactants in turbulent pipe flow of ethylene glycol aqueous solution

The drag-reducing effects of two nonionic-type surfactants, oleyl-N, N-dimethylamine N-oxide (ODMAO) and octadecyl-N, N-bis(2-hydroxyethyl)amine N-oxide (C18BAO), in ethylene glycol (EG) aqueous solution were comprehensively investigated at various surfactant concentrations of up to 2000 ppm by weight at various solution temperatures ranging from −5 to 80 °C in turbulent pipe flows. In EG aqueous solution (30% by weight), the mixture of ODMAO with salicylic acid with a molar ratio of 0.2 could effectively reduce the turbulent drag in the low-temperature range (up to 40 °C), whereas the effect of C18BAO was more notable at a temperature higher than 40 °C. Furthermore, the mixture of ODMAO and C18BAO in EG aqueous solution exhibited a high drag reduction ratio of more than 60% in a considerably wider range of solution temperatures (from 20 to 60 °C), while the drag reduction performance deteriorated below 0 °C and beyond 60 °C.