Study on formation mechanism of the flow drag and heat transfer reduction effect of the organic brine with surfactant

Recently, thermal energy transport systems using the flow drag and heat transfer reduction effect have attracted a great deal of interest for reduction of flowing pump power and heat loss. The surfactant is the most important additive for practical use. However, there have been few studies on the flow drag reduction effect of organic brine with surfactant below 0°C. In our previous work, we demonstrated the flow drag and heat transfer reduction effect of some organic brines with the nonionic surfactant, oleyl hydroxyethyl amine oxide (ODEAO). However, the mechanism underlying flow drag reduction of organic brine with surfactant is not fully understood. In addition, it is difficult to apply ODEAO for practical use because it is rare and very expensive. This study was performed to investigate different nonionic surfactants exhibiting flow drag and heat transfer reduction effect of 50 mass% EG solution below 0°C. In this study, a complex of oleyl dimethyl amine oxide (C18DMAO) and o-toluic acid was used as the flow drag surfactant additive. In addition, a vortex inhibition test was performed to determine a suitable molar concentration ratio between C18DMAO and o-toluic acid for 50 mass% EG solution. At this suitable surfactant concentration, dynamic light scattering analysis indicated that the size of rod-like micelles of C18DMAO was in the range of 79 - 142 nm. Finally, the flow drag and heat transfer reduction effect of 50 mass% EG solution with C18DMAO and o-toluic acid were confirmed experimentally at 0°C and -10°C.