Effect of polymer additives on the evaporation rate of water droplets

Wind tunnel experiments were carried out to study the effect of adding a drag-reducing polymer, sodium carboxymethylcellulose (CMC-7H), on the evaporation rate of water droplets. Experiments were carried out on a water droplet suspended in a stream of air. The dry bulb temperature, free stream velocity, droplet diameter, and CMC-7H concentration were varied during the present study. Experiments confirmed earlier studies that the evaporation loss rate increased with increasing dry bulb temperature and free stream velocity, and with decreasing drop size. The results confirm the expectation that polymer additives are capable of reducing evaporation. Reduction in the evaporation loss occurred when adding drag-reducing polymer solutions having concentrations of 20 and 50 PPMW (mg/kg). The percentage decrease in the evaporation loss becomes less effective with increasing CMC-7H concentration higher than 50 PPMW.