Experimental study on turbulent drag-reducing performance of a long-term stable, high-temperature-resistant surfactant additive

Abstract

Adding drag reduction additives (DRAs) to district heating systems can effectively reduce pressure losses during the heat and fluid transport. However, there are remarkably limited choices on DRAs that can be stably applied under high-temperature conditions (≥100 °C) over extended periods. To achieve effective drag reduction (DR) at high temperature, this paper reports a long-term stable, high-temperature-resistant surfactant additive (Erucamide Propyl Trimethylammonium Chloride/Sodium Salicylate, EPTAC/NaSal), which shows efficient drag-reducing performance in a wide range of temperature. The detailed characteristics of EPTAC/NaSal solutions including their rheological properties, DR performance, efficiency in reducing pump power requirements and lifetime were experimentally evaluated under varying concentrations, temperatures, and counterion ratios. The effective DR temperature of EPTAC/NaSal and the starting drag-reducing Reynolds number (Re₁) both increase with the concentration. More counterions can increase the solution viscosity, extend its relaxation time, promote the formation of drag-reducing microstructures, and significantly raise the upper temperature limit for DR. EPTAC/NaSal solution exhibits excellent DR effects within the temperature range of 20∼110 °C, achieving DR rate of approximately 78 % at Reynolds number (Re) around 280,000, and reducing pump power consumption by 28 %. After continuous operation more than 3 months, the solution retains good DR efficiency with a decline of no more than 16 % compared to the initial value. In sum, the detailed experimental results imply the significant potential of EPTAC/NaSal in the long-distance transportation system under high-temperature.