Development of Practical Drag Reduction System for District Cooling Systems

In this report, results from the project, proposed in the original research plan are presented. 10 surfactant systems effective as drag reducing agents (DRA’s) in efficient district cooling, including four commercial cationic surfactants, one commercial and three novel synthesized zwitterionic surfactants, one commercial nonionic surfactant and one zwitterionic(synthesized)/anionic surfactant mixture were developed. The application of newly synthesized zwitterionic aminimide surfactants to drag reduction (DR) is a breakthrough of this little-known family of surfactants. In addition to 20% EG co-solvent added to pure water solvent, as proposed in the original plan, we also investigated the feasibility of replacing the 20% EG/W solvent with more environmentally friendly solvents such as 25% PG/W and 30% Gly/W. Surfactant micelle nanostructures in these unusual solvent systems have been identified with cryo-TEM techniques despite great technical difficulties. We conducted turbulence and rheological measurements of a commercial cationic surfactant-water DR solution and a novel synthesized zwitterionic surfactant (ZA)-20% EG solution in channel flow. Detailed analysis of DR behavior and numerical simulation and successfully developed a new model for the DR mechanism were also conducted. Techniques for enhancing heat transfer effectiveness in DR surfactant EG/W systems at low temperatures have been developed.