Abstract
Drag reduction caused by surfactant solutions is considered to be an effective way to reduce the running cost in closed-loop district heating and cooling systems. Many researches of drag reduction have been highly developed in recent years. It is known that the combine use of a cationic surfactant; Ethoquad O/12) and a counter ion; sodium salicylate shows significant drag reduction. However, there are few papers about the application of drag reduction. We have applied such additives for more than seventy practical air conditioning systems in Japan. Several problems encountered in the application are 1) changing rate of concentrations of surfactant and counter ion during long term use, 2) some corrosion inhibitors and oils blocked the drag reduction, and so on. It is also necessary to develop more effective additives, especially could be ns were examined experimentally and a suitable additive condition, which could expand effective temperature range of drag reduction, is proposed.
